Dual lumen pigtail catheter and HOCM gradient catheter

Abstract

A pigtail catheter for measuring pressure gradients across a body narrowing is provided. The pigtail catheter may include a proximal shaft segment (102) and a distal shaft segment (104). The proximal shaft segment may include dual lumen tubing defining a proximal pressure lumen and a non-coaxial distal pressure lumen. In one example, the distal pressure lumen has a generally circular cross-sectional shape and the proximal pressure lumen has a generally crescent or kidney-shaped cross-sectional shape that partially wraps around the distal pressure lumen. The distal shaft segment may include at least one distal orifice (124) positionable distally relative to the body narrowing and at least one proximal orifice (122) positionable proximally relative to the body narrowing. Each orifice may have a diameter of at least about 0.46 mm, for example.

Description

[Technical field]

[0001] [Claim of priority] This application hereby claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 229,693, filed August 5, 2021, to Pedersen et al., entitled "Dual Lumen Pigtail Catheter and HOCM Gradient Catheter," which is incorporated by reference in its entirety.

[0002] This patent document relates to medical devices. More particularly, but not exclusively, this patent document relates to catheters. [Background technology]

[0003] Dual (or double) lumen pigtail catheters can be used in interventional procedures to measure pressure gradients across native or bioprosthetic valves of the heart, across stenoses in native vascular cavities of the body, or across other narrowings found in non-vascular cavities or tubular members of the body. To enable pressure gradient measurements across a stenosis or narrowing, a distal region of the pigtail catheter adapted to measure distal pressure can be placed distal to the stenosis or narrowing, and a proximal region of the pigtail catheter adapted to measure proximal pressure can be placed proximal to the stenosis or narrowing. Pressure gradient measurements across the aortic valve can be accomplished, for example, by positioning a distal region of the pigtail catheter in the left ventricle (LV) to measure LV pressure, and a more proximal region of the pigtail catheter in the ascending ventricle to measure aortic pressure. A high pressure gradient across the aortic valve is indicative of aortic valve stenosis, which can be treated through valvuloplasty, transcatheter aortic valve replacement, surgical valve replacement, drug therapy, or other treatment methods. Other stenoses can be treated, for example, through the placement of stents to widen stenoses found in the body's natural arteries, or in artificial conduits, or other non-vascular organ conduits.

[0004] Currently used dual lumen pigtail catheters are formed with catheter shafts that include coaxial lumens and are associated with drawbacks. Such catheters are prone to recording unreliable pressure signals, for example from the ascending aorta or left ventricle to a pressure transducer connected to the proximal end of the pigtail catheter. In many cases, the pigtail portion or adjacent distal region of the catheter shaft may be prone to kinking, which, combined with a smaller transmission lumen, may result in attenuation of signal transmission and lead to unreliable pressure gradients. The torque capability of the catheter shaft for distal positioning is also lacking.

[0005] The inventors have recognized that what is needed is a flat, dual lumen pigtail catheter that will accurately transmit pressure signals from both regions proximal and distal to the stenosis or narrowing to the proximal end of the catheter. For example, when using such a pigtail catheter for pressure gradient measurements across a stenotic aortic valve, the pigtail catheter must be able to simultaneously transmit highly accurate, undampened, frequency responsive pressure signals from the LV and ascending aorta to the proximal end of the catheter. The pigtail portion of the catheter should resist kinking, have excellent torque transmission to the distal catheter shaft, biased distal catheter shaft bending and / or optimal LV pigtail signal transmission. In some cases, the pigtail catheter must be able to be delivered to the LV over a flat cardiac diagnostic catheter that can be used, for example, to provide safer, less traumatic access across the stenotic aortic valve.

[0006] Measuring pressure gradients across stenotic LV intracavitary segments, such as in obstructive hypertrophic cardiomyopathy (HOCM), can be difficult to accurately localize and measure proximal and distal pressures. A hypertrophied region of myocardium, for example, can protrude from the proximal septal wall of the LV and extend into the left ventricular outflow tract (LVOT) adjacent to the anterior mitral leaflet. This protrusion can create a localized low pressure area that can cause blood to flow faster than normal through the LVOT, thereby pulling the anterior mitral leaflet toward the protrusion, resulting in even greater restriction to blood flow than caused by the protrusion alone. The result is a dynamic pressure drop across the LVOT narrowing.

[0007] Typically, the hypertrophied segments of the myocardium can be treated surgically or ablated by transcatheter alcohol ablation. Intra-LV pressure needs to be localized separately in the segments proximal and distal to the dynamic obstruction. This is often made difficult by the short distance between the aortic valve and the proximal segment of septal hypertrophy that needs to be localized for proximal pressure measurements. Localizing pressure proximal to the LVOT gradient is particularly relevant in patients with HOCM and aortic stenosis. In clinical scenarios where two distinct systolic gradients exist, they need to be quantified separately to determine the appropriate treatment strategy, such as HOCM septal ablation, TAVR, or both. In addition to this, patients with HOCM often have an enhanced LV systolic function that can result in systolic collapse of the distal cavity end that can act on the distal orifice and inhibit accurate pressure measurements.

[0008] The inventors have recognized that what is needed is a gradient catheter having a coil with a distal orifice or opening located distal to the obstruction, the coil having a small diameter and capable of being shaped to prevent impingement of the distal orifice or opening. The proximal orifice located proximal to the obstruction must be precisely positioned proximal to the LVOT and distal to the aortic valve. Proximal and distal pressures can be measured simultaneously to quantify dynamic stenosis. The baseline gradient will determine the severity of the obstruction. The pressure gradient can be measured from a location in the LV to a location just below or adjacent to the aortic valve in the LVOT. The catheter must be capable of placing the proximal orifice proximal to the stenotic aortic valve leaflet in the aorta, while maintaining the coil proximal to the dynamic obstructive segment in the LVOT without obstructing the orifice, thereby providing the ability to measure a separate end-systolic gradient across the stenotic aortic valve. Summary of the Invention [Means for solving the problem]

[0009] The present invention includes, for example, pigtail catheters formed from dual lumen extrusions that do not have a coaxial lumen. Dual lumen tubing can provide two lumens having separate axes that run parallel to one another but are not coaxial. It is believed that this dual lumen arrangement can provide a larger hydraulic diameter for each of the two lumens compared to dual lumen catheters having coaxial lumens, thereby providing improved pressure signal transmission from the distal shaft segment to a manifold located at the proximal end of the pigtail catheter.

[0010] The proximal shaft segment, including the dual lumen shaft tubing, can be braided to provide torque transmission characteristics to the distal shaft segment of the catheter. The catheter shaft can have shaft bending in the LV axial direction, allowing the catheter to extend into and most notably into the LV without hitting the septal segment, which could result in arrhythmic abnormalities that would provide an unreliable assessment of both pressure gradients and left ventricular systolic function. The distal shaft segment of the catheter adjacent to the pigtail coil can be supported by either braid or an elastic member that resists kinking and provides torque transmission to the distal shaft segment, while preserving flexibility for the coil to prevent trauma to accessory mitral valve structures and having less resistance to wire exchange.

[0011] The pigtail coil of the catheter embodiment may form a coil plane that is coplanar with the bending plane formed by the catheter shaft proximal and distal to the shaft bend, and the coil plane may be directed toward the left ventricular anterolateral side by applying a counterclockwise torque to the proximal portion of the catheter to optimize contrast opacification of the LV. In another embodiment, the pigtail catheter may form a coil plane that is not coplanar with the bending plane. The coil plane may be angled relative to the shaft bending plane to position the pigtail. In an embodiment, the distal pressure lumen may be sized and shaped to have a diameter that will aid in the delivery of straight-tip or other guidewires and allow the passage of a flattened cardiac diagnostic catheter that may be used to follow the diagnostic catheter from the aorta across the stenotic aortic valve to the LV. Such cardiac diagnostic catheters may include Amplatz Left (AL), multipurpose catheters, right Judkins catheters, and other catheter configurations, hereinafter referred to as cardiac diagnostic catheters. A less traumatic method can be provided by first retracting the straight-tip crossover wire back into the diagnostic catheter and then advancing the pigtail catheter over the cardiac diagnostic catheter, thereby using the diagnostic catheter as a rail for delivering the pigtail catheter without freely exposing the straight-tip guidewire to the LV apex.

[0012] The pigtail catheter may undergo some specific modifications to provide a catheter that accurately measures dynamic occlusion in the LV cavity present in the LVOT secondary to the hypertrophied segment of the proximal LV septum in obstructive hypertrophic cardiomyopathy (HOCM). The HOCM pigtail catheter may have any of the features described with respect to any of the embodiments of the cardiac pigtail catheter, including a braided shaft on various shaft regions to enhance torque capability and provide kink resistance characteristics, a dual lumen shaft to enhance pressure signal transmission through two lumens with appropriate hydraulic diameters in the dual lumens, a flexible coil positioned at the distal end of the pigtail catheter, an orifice positioned along a portion of the shaft or within the coil, a distal opening in the coil with an appropriate diameter to allow passage over a guidewire and provide an opening for pressure signal transmission from the body chamber to the shaft lumen, an orifice diameter that allows pressure signal transmission from the body chamber to the shaft lumen, and / or a shaft bend angle that positions the coil within the LV without inducing ectopic signals from the myocardium that would falsely indicate dynamic LVOT occlusion.

[0013] The HOCM pigtail catheter of the present invention can have an orifice and a distal opening that are protected from myocardial tissue impingement on the orifice or distal opening during systolic contraction of the heart. Such systolic contraction can cause the myocardial tissue to partially block the orifice or distal opening, resulting in attenuation of pressure signal transmission from the ventricle to the shaft lumen, leading to errors in pressure gradient measurements. The orifice can be protected by placing it at the innermost edge of a circular or elliptical shaped coil. The orifice can have an elliptical shape to increase the area of ​​the opening and make it less likely for myocardial tissue to block signal transmission. The distal opening can be protected by placing the distal opening at the end of the coil near or against the proximal adjacent catheter shaft, which can help keep the myocardial tissue away from the distal opening. Because the distance from the hypertrophied myocardium to the aortic valve is short, about 5 mm (range 2-10 mm), the proximal orifice area may contain only about one or two orifices so that the proximal orifice area can be precisely located below the aortic annulus and proximal to the hypertrophied septal segment. A radiopaque marker may be positioned, for example, about 1 mm proximal to the proximal orifice area to allow the operator to visualize the location of the proximal orifice area under fluoroscopy.

[0014] The coil diameter of the HOCM pigtail catheter can be even smaller, such as 5 mm in diameter (e.g., in the range of 3-10 mm). The smaller coil diameter can better localize the pressure distal to the LVOT occlusion within the more distal LV cavity during the enhanced systolic contraction commonly seen in HOCM patients. To better avoid closure of the distal orifice by myocardial tissue during systole, the post-bend region of the pigtail catheter can have a length of, for example, about 4 cm to keep the coil about 2-3 cm from the LV apex. A radiopaque marker positioned at the distal opening of the coil can assist in accurately fixing the catheter segment to measure the distal pressure distal to the occluded segment. Additionally, a radiopaque marker can be positioned near the proximal orifice, which is positioned adjacent to the aortic valve within the LVOT.

[0015] The dual lumen shaft of the present invention may alternatively be formed without a braid within its outer wall. In an alternative embodiment, a fiber or ribbon may be placed within the outer wall of the shaft during the extrusion process or through other processing methods, for example, near the center of the oval proximal pressure lumen. The presence of such a fiber or ribbon may allow and guide any bending the dual lumen shaft undergoes such that the minor diameter of the oval proximal pressure lumen does not decrease. Thus, the fidelity of the pressure signal delivered by the proximal pressure lumen may be maintained even when the catheter shaft is bent.

[0016] In another embodiment, the exterior surface of the dual lumen shaft can be formed with an oval shape. The outer major axis can be oriented along a line extending through the distal pressure lumen center and the proximal pressure lumen center. Such an oval exterior surface shape allows the proximal pressure lumen of the dual lumen shaft to have a larger minor diameter than can be achieved with a round dual lumen shaft of the same circumference, thereby keeping the circumference of the dual lumen exterior surface to a minimum. An oval dual lumen shaft can fit through a smaller introducer catheter than a round dual lumen shaft with the same minor diameter for the proximal pressure lumen. As a result, the dual lumen shaft can be passed through a smaller profile introducer sheath while still improving pressure signal fidelity.

[0017] Several factors can affect the fidelity of the pressure signal transmitted back to the pressure transducer located at or near the manifold. For example, flow resistance caused by the viscosity of the fluid moving through the small diameter proximal pressure lumen can reduce the magnitude of the pressure signal transmitted to the pressure transducer. Therefore, the hydraulic diameter of the proximal pressure lumen must be maintained at a size of at least about 0.018 inches to ensure faithful signal transmission performance. Long tubing can affect the inertia of the fluid moving through the catheter shaft, resulting in a phase delay of the pressure signal transmitted back to the pressure transducer. Tubing compliance can attenuate the pressure signal and cause a phase delay when it reaches the pressure transducer. Such variables can be mathematically considered and selected to optimize the fidelity of the signal transmitted from the proximal orifice of the dual lumen catheter of the present invention to the proximal pressure lumen and further to the pressure transducer located in the manifold.

[0018] These and other embodiments, features, and findings of the catheters and related methods of the present invention are recited, at least in part, in the Detailed Description below. This Summary is intended to provide non-limiting examples of the teachings of the present invention and is not intended to provide an exclusive or exhaustive description. The Detailed Description below is included to provide further information regarding the catheters and related methods of the present invention.

[0019] The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in this patent document. [Brief description of the drawings]

[0020] [Figure 1A] FIG. 1 is a plan view of a dual lumen pigtail catheter. [Figure 1B] FIG. 13 is a cross-sectional view of the braid pre-bend region. [Figure 1C] FIG. 2 is a plan view of a distal shaft segment of a dual lumen pigtail catheter. [Figure 1D] FIG. 13 is a cross-sectional view of the braid pre-bend region. [Figure 1E] FIG. 2 is a plan view of a pigtail catheter extending into the left ventricle of the heart. [Figure 1F] FIG. 1 is a plan view of a pigtail catheter with the coil apex extending into the nadir of the aortic valve cusp. [Diagram 2] FIG. 2 is a cross-sectional view of a dual lumen shaft. [Diagram 3] FIG. 1 is a cross-sectional view of a single lumen shaft. [Figure 4] FIG. 13 is a plan view of a distal shaft segment showing the pigtail coil plane. [Diagram 5] FIG. 13 is a plan view of the pigtail catheter extending into the left ventricle showing the shaft bending plane and the coil plane. [Figure 6] FIG. 2 is a plan view of a distal shaft segment. [Figure 7] FIG. 13 is a cross-sectional view through a single lumen shaft. [Figure 8]FIG. 13 is a plan view of an embodiment of a distal shaft segment. [Figure 9] FIG. 13 is a cross-sectional view of a dual lumen shaft with a collapsed oval outer wall. [Figure 10] FIG. 13 is a cross-sectional view of a single lumen shaft formed by reflowing a collapsed oval lumen. [Figure 11A] FIG. 1 is a plan view of a straight linear catheter used for pressure gradient measurements. [Figure 11B] FIG. 13 is a plan view of a distal shaft segment showing the shaft curvature. [Figure 11C] FIG. 2 is a cross-sectional view of a dual lumen shaft. [Figure 12] FIG. 2 is a plan view of a cardiac diagnostic catheter extending within the aorta. [Figure 13] FIG. 2 is a plan view of a dual lumen pigtail catheter extending within the aorta over a cardiac diagnostic catheter. [Figure 14] FIG. 2 is a semi-transparent view of a cardiac diagnostic catheter and a pigtail catheter advanced across the aortic valve and into the left ventricle. [Figure 15] FIG. 13 is a semi-perspective view of the pigtail catheter within the left ventricle after withdrawal of the cardiac diagnostic catheter. [Figure 16] FIG. 1 is a semi-transparent view of a pigtail catheter extending over a therapeutic guidewire within the left ventricle. [Figure 17A] FIG. 1 is a semi-transparent view of a pigtail catheter extending into the left ventricle to measure the pressure gradient across a stenosis caused by hypertrophied myocardium. [Figure 17B] FIG. 13 is a plan view of a coil with a distal end positioned near an inner surface. [Figure 17C] FIG. 1 is a plan view of a coil with orifices located along the inner surface of the coil. [Figure 17D] FIG. 13 is a plan view of a coil with its distal opening pressed against an opposing wall. [Figure 17E] FIG. 1 is a plan view of a coil having an oval orifice on its inner surface. [Figure 18]FIG. 1 is a semi-transparent view of a dual lumen pigtail catheter positioned with the distal opening in the left ventricle and the proximal orifice positioned in the aorta. [Figure 19] FIG. 13 is a cross-sectional view of a dual lumen shaft with wall fibers positioned on the outer wall. [Figure 20] FIG. 1 is a cross-sectional view of a dual lumen shaft having an oval outer surface. [Figure 21] FIG. 1 is a plan view of a component model showing the pressure signal from the heart, P(t), the inertia of the fluid within the pigtail catheter system, Lp, the resistance to fluid movement within the lumen of the pigtail catheter, Rp, and the total system compliance, Ct.

[0021] The drawings are not necessarily to scale: certain features and components may be shown exaggerated in scale or in schematic form and some details may not be shown for clarity and conciseness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Although the pigtail catheters of the present invention can be used to measure pressure gradients across narrowings within tubular members or chambers of the body, most of the following description will focus on cardiac pigtail catheters configured to measure pressure gradients across a stenotic aortic valve.

[0023] 1A-1F, 2, 3, and 5 show an embodiment of a pigtail catheter of the present invention. The proximal shaft segment may contain two lumens that transmit pressure signals from the distal catheter segment to the proximal catheter segment through a circular distal pressure lumen that may be approximately circular in cross section and a more oval proximal pressure lumen. The proximal shaft segment may extend from a manifold located outside the body during use into the vasculature of the body and reach a narrowing in a tubular or cardiovascular member of the body located a few centimeters (e.g., in the range of 5-140 cm) from the access site where the catheter enters the body. The distal catheter segment may contain a distal orifice and a distal opening that are in direct and immediate fluid communication with bodily fluids located distal to the narrowing. The distal catheter segment may also contain a proximal orifice that is in direct and immediate fluid communication with bodily fluids proximal to the narrowing. The distal orifice is in direct fluid communication with the distal pressure lumen and transmits distal pressure (from a location distal to the narrowing (e.g., a stenotic aortic valve or other body member)) to a distal pressure port located on a manifold at the proximal end of the catheter. The proximal orifice is in direct fluid communication with the proximal pressure lumen, which may be oval in cross-sectional shape, and transmits proximal pressure signals (from a location proximal to the narrowing of the body member) to a proximal pressure port located on a manifold at the proximal end of the catheter. The proximal and distal pressure ports of the manifold may be connected to pressure transducers for measuring and recording the pressure gradient across the narrowing of the tubular body member.

[0024] Additionally, the pressure ports on the catheter manifold can be alternately used for intravascular contrast injection, i.e., to provide opacification to define the structure and function of a lumen, chamber, or valve. Contrast can be injected into the proximal pressure port and pumped through the proximal pressure lumen to exit the proximal orifice into the vessel cavity or chamber proximal to the narrowing. Alternatively, contrast can be injected into the distal pressure port and pumped through the distal pressure lumen to exit through the distal orifice or distal opening into the vessel cavity or chamber proximal to the narrowing. It should be noted that when pumping contrast through the proximal or distal pressure port, back pressure generated through a syringe or other pressure generating device (to pump contrast under pressure) is required to create the appropriate flow of contrast to opacify a particular chamber. Back pressure can cause the pressure port to become dislodged from the pressure generating device if the pressure lumen diameter or orifice diameter is not of sufficient diameter or hydraulic diameter. The hydraulic diameter of the pressure lumen should in most instances be approximately 0.020 inches (eg, in the range of 0.018 to 0.038 inches) to ensure that the delivery of contrast does not create excessive backpressure.

[0025] For example, in an embodiment intended for pressure gradient measurements across a stenotic aortic valve, the distal shaft segment is configured to allow access into multiple arterial and venous access sites, such as a femoral artery access site, and reside within the aorta and LV such that the distal shaft segment extends across narrowings or stenoses found in tubular or chamber-like members of the body. The distal shaft segment can be conceptually divided into several regions: a proximal orifice region, a braid pre-bend region, a shaft bend, a braid post-bend region, a straight segment, and a coil region. The coil and adjacent flexible straight region contain only a single distal pressure lumen, which can transmit distal pressure signals from the body lumen distal to the narrowing to a distal pressure port located on the catheter manifold. The post-bend region extends from the shaft bend to the distal end of the pigtail catheter. Note that the proximal pressure lumen found in the proximal shaft segment can be easily removed from the distal shaft segment or not contained within the distal shaft segment; the oval side walls of the proximal pressure lumen can be scraped off, thermally removed, or otherwise rendered unable to transmit an accurate proximal pressure signal from the coil or flexible straight region of the distal shaft segment.

[0026] As shown in Figures 1A and 1B, the braided post-bend region and the braided pre-bend region can contain a single distal pressure lumen. Alternatively, as shown in Figures 1C and 1D, the braided post-bend region and the braided pre-bend region can contain both distal and proximal pressure lumens. The proximal pressure lumen does not necessarily have to be distal to the proximal orifice region, but may provide advantages in terms of manufacturability by extending the dual lumen shaft to a shaft junction located distal to the post-bend region (the shaft junction defining the change from a dual lumen shaft to a single lumen shaft), as shown in Figure 1C. As shown in FIG. 1E, a shaft bend of about 155 degrees thread angle (e.g., in the range of 145-160 degrees) at the distal shaft segment allows the distal shaft portion to extend approximately into the elongated LV cavity axis, which is angled or bent relative to the proximal aortic central axis, minimizing aggressive contact with wall segments (mainly the lower base segments of the LV) with the resulting potential for electrical arrhythmia or disruption of normal sequential contractions that are necessary to obtain accurate pressure waveforms and optimal contrast opacification to evaluate LV systolic function. A shaft bend of greater than 145 degrees allows the axis of the distal shaft segment to more closely coincide with the aortic central axis, allowing the coil apex positioned on the most distal bend of the coil to be placed within the nadir of the aortic valve non-coronary cusp to best view the nadir of the valve cusp via fluoroscopy or ultrasound, as shown in FIG. 1F. A radiopaque or other marker can be placed at the coil apex for visualization purposes, e.g., to provide the operator with the exact location of the aortic annulus and native leaflets, as well as potential locations for placement of a TAVR device. The coil can have an asymmetric shape with the coil apex having a radius of curvature of about 3 mm (e.g., in the range of 2-4 mm) that is smaller than the radius of curvature for the remainder of the coil, which has a radius of curvature of about 5 mm. This asymmetric coil can allow the coil apex to extend more completely to the nadir of the aortic leaflets, e.g., to more accurately localize the aortic annulus and more accurately place a TAVR device.

[0027] The shaft bend angle may not be required in other embodiments of the invention, such as a pigtail catheter used to measure pressure gradients across a narrowing in the vasculature or tubular member of the body except this narrowing (e.g., between the LV and the stenotic aorta across the aortic valve). The shaft bend forms a shaft bend plane with a braided pre-bend region and a braided post-bend region on each side of the shaft bend. The braided structure of the catheter shaft may extend 2.0 cm (e.g., in the range of 0.5-4 cm) distal to the shaft bend to reach the distal end of the braided structure, providing adequate torque transmission capability from the proximal shaft segment to the distal shaft segment. To avoid possible premature ventricular contractions (PVCs), the catheter shaft length distal to the shaft bend may not extend into the apex of the LV cavity.

[0028] The proximal shaft segment can have a braided structure applied to the lateral wall of the dual lumen tubing, the braided structure can have, for example, metal wires or polymer fibers having a diameter of about 0.004 inches. The braided structure can extend into various regions of the distal shaft segment to allow an operator to apply torque to the exteriorized catheter manifold and the proximal shaft segment and transmit the torque to the distal shaft segment including a region located distally relative to the shaft bend. Regions of the distal shaft segment that can be braided can include the proximal orifice region, pre-braid bend region, shaft bend, post-braid bend region, and distal orifice region as shown in FIGS. 1A and 1C, and in some embodiments, the braided structure is absent from the coil and is immediately proximal to the coil, 4-10 mm. The braided structure can extend the entire length of the distal shaft segment, but when the braided structure is in a flexible straight region at or near the coil, the braided structure in that region must be formed from very thin, easily bendable fibers so that it does not become entangled with the coil during removal or repositioning of the pigtail catheter within the heart, vascular, or non-vascular structure, causing, for example, fracture of the chordae tendineae. In many embodiments, the braided structure should not exceed a fiber diameter of about 0.010 inches in diameter, since crossings of the braided fibers could create an extreme profile on the catheter shaft, and the braided fibers or wires should preferably be less than about 0.005 inches in diameter. The profile of the proximal catheter shaft, consistent with its dimensions and pressure transmission capabilities, can have a low external profile of as little as 6 French (F) or less, although certain therapeutic procedures where a larger profile introducer sheath is required to deliver the therapeutic catheter, including, for example, some TAVR procedures, can tolerate larger profile dual lumen pigtail catheters in the range of 7F to 10F.

[0029] Approximately 3 cm proximal to the shaft bend (e.g., in the range of 2-8 cm), one or more proximal orifices positioned above the aortic root transition of the aorta provide fluid communication and aortic pressure transmission from the aorta to the oval proximal pressure lumen and further to a proximal pressure port positioned, for example, on the manifold. Positioning the proximal orifice above the aortic root transition and proximal to the shaft bend can avoid inaccurate measurement of the pressure gradient across the stenosis, which may result from a lack of pressure recovery downstream of the stenosis due to placement of the proximal orifice too close to the vena contracta jet associated with blood flow through the stenotic valve leaflets. Pressure transducers connected to the proximal and distal pressure ports of the manifold can simultaneously measure the pressure difference between the proximal and distal pressure ports, thereby measuring the pressure gradient across, for example, the narrowing of the aortic valve or a narrowing found in a ventricle or other vascular, non-vascular, or body chamber.

[0030] The proximal orifice holes can be positioned between the openings of the braided structure, which allows for spaced apart (between the fibers of the braided structure) individual braided fibers and about four (e.g., in the range of about 1-8) 0.020 inch diameter (e.g., in the range of 0.018-0.028 inch) proximal orifices in the proximal shaft portion. The proximal orifice holes can be in fluid communication with an oval proximal pressure lumen having a major axis of about 0.035 inch and a minor axis of about 0.016 inch, and the hydraulic diameter of the oval or elliptical proximal pressure lumen can be about 0.020 inch (e.g., in the range of 0.018-0.025 inch) to ensure fully accurate transmission of the pressure signal from the aorta and accurate determination of the pressure gradient across the aortic valve. The hydraulic diameter of the oval proximal pressure lumen is determined from the following formula: DH=(4BC(64-16E 2 )) / ((BC)(64-3E 4 )), where 2B is the major axis, 2C is the minor axis, DH is the hydraulic diameter, and E=(BC) / (B+C).

[0031] The dual lumen shaft can be made, for example, from polyurethane, Pebax (a block copolymer made up of hard polyamide blocks and soft polyether blocks, sold by Arkema), polyethylene, or other polymers found in medical catheter devices that are extrudable and thermally reshapeable, and should be resilient and preferably soft enough that the properties of the dual lumen shaft and the single lumen shaft can be obtained (but not necessarily) from single lumen shaft extrusion for both the dual lumen shaft and the single lumen shaft, possibly forming a single lumen shaft in a post-extrusion thermal step. The dual lumen shaft should be able to undergo at least a thermal or other combining step to combine the dual lumen shaft into a single lumen shaft, if necessary.

[0032] The dual lumen shaft extends to the shaft junction as shown in Figures 1A, 1C, and 3, and distal to the shaft junction, a single lumen shaft extends, housing a single distal pressure lumen (the only lumen capable of providing adequate pressure transmission capability) capable of providing adequate pressure transmission of the distal lumen pressure to a distal port located on the catheter manifold. The distal shaft segment can include a flexible straight region extending approximately 4 cm (e.g., in the range of 2-6 cm) and can be free of braided structures up to the pigtail coil of the distal shaft portion. The flexible straight region can provide a shaft region with intermediate torque transmission characteristics and intermediate bending stiffness between the braided post-bend region and the coil region that can extend into the LV without causing electrical disturbances due to interaction with certain LV wall segments. A distal orifice positioned proximally adjacent to the coil allows the distal pressure of the narrowing to be measured simultaneously with the proximal pressure of the narrowing measured through the proximal orifice, such simultaneous measurement of proximal and distal pressures indicating the absolute pressure gradient across the narrowing without risk of error that may result from the presence of a high velocity jet across the narrowing and the resulting reduction in local pressure readings near the jet. The coil can have a coil diameter of about 1 cm (e.g., in the range of 7 mm to 15 mm) and can have a distal opening that provides a passage for a guidewire, such as a 0.035 inch guidewire, and provides fluid communication with the distal pressure lumen to transmit a distal pressure signal from the LV to a distal pressure port positioned on the catheter manifold. The diameter of the distal opening, along with the diameter of the distal pressure lumen, can be made with a smaller diameter, for example, about 0.025-0.032 inches, to accommodate smaller diameter guidewires, allowing the present invention to have a flattening on the order of 5F-6F for applications that can accommodate guidewires with less support. The guidewire can extend proximally through the distal pressure port (or guidewire port) and throughout the distal pressure lumen, as well as distally through the distal opening of the pigtail catheter.

[0033] The flexible straight region can also have a distal shaft orifice located just proximal to the softer, more flexible pigtail coil and positioned on the single lumen shaft, the distal orifice extending axially over a length of about 1 cm (e.g., in the range of 5-20 mm) of the single lumen shaft. One or more distal orifices (about 4 orifices, e.g., in the range of about 1-6) can extend within the coil and extend adjacent and proximal to the coil up to about 2 cm (e.g., in the range of 1-4 cm) and can be positioned within the coil, with the orientation of the distal orifices being circumferential to the catheter shaft both proximal to the coil and within the coil. The distal orifice has a diameter of about 0.020 inches (e.g., in the range of 0.018-0.028 inches) to provide adequate transmission of the pressure signal from the LV to the distal pressure port positioned on the manifold. The single lumen shaft may be made from polyurethane, Pebax, polyethylene, or other polymers that can be extruded into a coiled shape and elastically retain that shape.

[0034] The distal coil must be soft enough to straighten the pigtail coil and distal shaft segment when passed over the guidewire, and must be able to recoil upon removal of the guidewire. The coil may be formed, for example, from a soft polymeric material that deploys with a force of about 25 grams or less so that the chordae tendineae are not stretched or torn when captured by the coil. The coil may have a round shape, as shown in Figures 1A and 1C, or may have an oval, elliptical, other geometric shape, or in some cases, the coil may be omitted from the catheter configuration and simply a straight distal shaft segment may be used rather than the presence of a coil. The oval shaped coil shown in Figure 1E has a small radius of curvature (i.e., smaller than the remainder of the coil) at the coil apex found at the most distal portion of the oval shaped curved coil, most preferably allowing the coil apex to be positioned at the lowest point of the native valve leaflet. With the pigtail catheter delivered into the LV, for example over a guidewire trapped within the distal pressure lumen, the guidewire is intended to be removed prior to measuring the LV pressure through the distal pressure lumen. The distal pressure lumen has a diameter that allows delivery of a guidewire, for example, 0.035 inches, and thus has a hydraulic diameter (hydraulic diameter equals the diameter of the circular lumen) of at least 0.035 inches, and preferably 0.002 to 0.004 inches larger in diameter than the guidewire to facilitate movement of the guidewire.

[0035] As shown in Figures 1C, 2, 3, and 4, the braided structure of the dual lumen shaft can terminate at or near the junction with the single lumen shaft. The single lumen shaft can be formed by grinding, cutting, or thermally removing the oval side wall of the proximal pressure lumen, thereby leaving the distal pressure lumen confined to the common wall and the lateral circular wall that creates the distal lumen of the distal shaft portion. The oval side wall can also be heat fused or otherwise attached to the common wall to form a single lumen shaft. A mandrel can be placed within the distal pressure lumen to retain the shape and dimensions of the distal pressure lumen during such a thermal reshaping process. A distal orifice can be formed through the wall of the single lumen shaft with an opening positioned in the distal orifice region on the inner curved surface, outer curved surface, and in-plane surface (see FIG. 4) positioned in the pigtail coil plane that extends circumferentially along the coil plane, minimizing the risk of kinking in the distal orifice region and providing unhindered flow of bodily fluids in direct contact with the open distal orifice, for example, to accurately represent pressure within the bodily fluid.

[0036] When using the pigtail catheter of the present invention to measure the pressure gradient across the aortic valve, for example as shown in FIG. 5, the coil can be positioned in the LV with the distal pressure orifice and the proximal pressure orifice can be positioned in the ascending aorta. The coil plane can be further angled in a second plane relative to the shaft bend plane to form a coil plane angle that is to the left of the interventricular septum when viewed forward from the frontal plane, with the angulation directed toward the anterolateral free wall of the LV. This coil plane angulation allows the coil to reside in the LV without impinging on the inferior or septal wall segments of the LV, minimizing ectopic ventricular activation and optimizing LV opacification during left ventricular imaging by injecting contrast at the mitral inflow rather than the left ventricular apex, which allows the LV to be more uniformly opacified with less contrast and allows for more optimal assessment of LV systolic function with this enhanced imaging. The angulation of the coil plane refers to the angular separation between the angle of the coil plane and the plane of the shaft bend, and the angulation of the coil plane can be approximately 30 degrees (eg, in the range of 5 to 45 degrees).

[0037] Alternatively, the braided structure found in the dual lumen shaft can extend into a portion of the single lumen shaft, for example to the location of the pigtail coil, as shown in Figures 6 and 7. The presence of such a braid in the single lumen shaft allows the single lumen shaft to resist kinking and better permits the operator to apply torque to the catheter shaft at the exposed proximal shaft segment and manifold to transmit torque to the coil. The coil should unravel with less than about 25 grams of force, for example, to avoid tearing or rupturing the chordae tendineae.

[0038] To form such a catheter shaft, the oval lateral wall of the oval proximal pressure lumen can be scraped off prior to placing the braid on both the dual lumen shaft and the single lumen shaft. The braided structure of the single lumen shaft is axially expanded, bringing the braided structure into intimate contact with the wall of the single lumen shaft. The braided catheter shaft can then be formed by thermally reflowing the braided material into the outer wall of the catheter shaft by applying heat and an outer shrink wrap that applies an inward force onto the braided structure, and by protecting the proximal and distal pressure lumens with a forming mandrel (that conforms to the shape of the lumens), such as a Teflon (a synthetic fluoropolymer of tetrafluoroethylene manufactured by Chemours) mandrel. The reflow of the polymer shaft material allows the braid to penetrate into the circular and oval lateral walls of the dual lumen shaft, allowing it to penetrate into the circular and common walls of the dual lumen shaft, as shown in FIG. 7. Alternative methods of forming the braided proximal and distal shaft portions are contemplated using reflow techniques known in the catheter manufacturing industry.

[0039] Alternatively, as shown in FIGS. 8-10, an elastic member can be inserted into the collapsed proximal pressure lumen just proximal to the shaft junction, which can extend into the heat reflowable collapsed oval lumen distal to the shaft junction and into the flexible straight region to the coil. The elastic member can be, for example, a flat ribbon of Nitinol, formed into the shape of the shaft within which it is placed. The elastic member can be a flat ribbon having a thickness of about 0.003 inches (e.g., in the range of 0.002-0.007 inches) and a width of about 0.5 mm (e.g., in the range of 0.1-2 mm). The elastic member can help prevent kinking at the junction. The coil is preferably formed of a soft polymeric plastic without the elastic member present, such that the coil can be uncoiled with less than 25 grams of force to protect the chordae from breakage.

[0040] To form this distal shaft portion, the braid can be positioned only within the dual lumen shaft, as shown in Figures 1C and 9. The elastic member can be slid into the distal oval opening and placed within the braided region of the dual lumen shaft and within the reflowable oval lumen of the single lumen shaft, overlapping the shaft junction by about 10 mm (e.g., in the range of about 5-25 mm). A portion of the dual lumen shaft can then be thermally reflowed distal to the shaft junction (or alternatively, also proximal to the shaft junction in the braid post-bend region) to collapse the oval proximal pressure lumen and encapsulate the elastic member, forming an attachment between the elastic member, the common wall, and the collapsed oval side wall, as shown in Figure 10, and the dual lumen shaft is now converted into a single lumen shaft distal to the shaft junction. The oval side wall can be thermally melted into contact with the common wall to form a single lumen shaft distal to the elastic member. Alternatively, the oval side wall can be milled away to form a single lumen shaft distal to the elastic member. A distal opening can be formed in the central lumen at a location that does not interfere with or be blocked by the presence of the elastic member.

[0041] 11A and 11B show another embodiment of the invention directed to pressure gradient measurements across narrowings in linear tubular members, chambers, or cavities of the body, as well as narrowings in cardiovascular or noncardiovascular anatomical structures of the body. In this embodiment, the distal shaft segment located across the narrowing can have a straight configuration, as shown in FIG. 11A, or alternatively, the distal shaft segment can have a shaft bend located near the distal end, as shown in FIG. 11B. The shaft bend can be helpful when traversing tortuous or curved paths or entering side branches of the tubular member. The proximal catheter shaft can be braided to facilitate torque transfer from the manifold to the distal shaft segment, for example, to aid in traversing the vasculature, and to provide pushability to the shaft without significantly affecting flexibility. The catheter can have a distal pressure lumen of 0.025 inches (e.g., in the range of 0.018-0.038 inches) that can provide a passageway for a guidewire to achieve transmission of an unattenuated pressure signal, and a smaller distal pressure lumen of 0.018 inches that can deliver an accurate, unattenuated pressure signal back to a distal pressure port located on the manifold. The distal orifice can have a diameter of about 0.020 inches (e.g., in the range of 0.018-0.028 inches). As shown in FIG. 11C, the proximal pressure lumen can have a major axis of about 0.028 inches and a minor axis of 0.016 inches to provide a hydraulic diameter of at least 0.018 inches to deliver a pressure signal back to a proximal pressure port on the manifold with sufficient accuracy. The proximal pressure orifice can have a diameter of about 0.020 inches (e.g., in the range of 0.018-0.028 inches). This catheter formed from the dual lumen construction described in the previous embodiment allows for improved pressure transmission signal along the catheter up to 140 cm from the distal shaft segment to the pressure port located on the manifold over current dual lumen catheters formed from concentric tubes. The catheter profile of this embodiment can be as small as 4.5F to 6F.

[0042] A standard procedure for advancing a straight-tip guidewire and a cardiac diagnostic catheter across a stenotic aortic valve is described with its limitations. One cardiac diagnostic catheter currently used to deliver a straight-tip guidewire from the aorta to the LV across a stenotic aortic valve is, for example, a single lumen Amplatz Left (AL) catheter as shown in FIG. 12, where the profile of such a catheter can range, for example, from 4F to 8F, and can be delivered over a guidewire with a diameter ranging from 0.025 inches to 0.038 inches. The distal portion of the cardiac diagnostic catheter can be positioned in the aortic root while the straight-tip guidewire is advanced in the through lumen under fluoroscopic guidance and advanced into the LV across the stenotic aortic annulus. The cardiac diagnostic catheter can then be advanced over the straight-tip guidewire and positioned in the LV. Once the straight-tip guidewire is removed, the cardiac diagnostic catheter can be used to provide a passage for delivery of a supportive special guidewire with a coiled configuration positioned in the distal LV to prevent LV perforation.

[0043] It should be noted that cardiac diagnostic catheters can have a distal tip configuration that points approximately at the LV apex. This configuration can result in a straight-tipped wire being inadvertently jetted into the LV apex as the cardiac diagnostic catheter is advanced into the LV, potentially resulting in perforation. The round lumen of the pigtail embodiment of the present invention can confine a low-profile cardiac diagnostic catheter, which can be used to exchange pigtail catheters and reduce the risk of exchanging a catheter only over a straight-tipped guidewire.

[0044] As shown in Figures 13-15, the dual lumen pigtail catheter of the present invention can be forward loaded over the exterior of the cardiac diagnostic catheter with the shaft of the cardiac diagnostic catheter residing in the distal lumen of the pigtail catheter. The distal portion of the cardiac diagnostic catheter can extend distally beyond the distal opening of the pigtail catheter by as much as 10 cm (e.g., in the range of 8-15 cm) so that the shape of the distal portion of the cardiac diagnostic catheter is not significantly affected by the shape of the distal opening of the pigtail catheter, and can effectively guide a straight-tip guidewire through the stenotic aortic valve leaflets, as shown in Figure 13. The cardiac diagnostic catheter can be advanced over the fixed guidewire and then partially retracted into the cardiac diagnostic catheter, as shown in Figure 14. When the guidewire is fully withdrawn, the cardiac diagnostic catheter can provide a less traumatic rail for threading the pigtail catheter over it and into the LV. When the cardiac diagnostic catheter is removed, the pigtail catheter can be positioned within the LV cavity, as shown in Figure 15.

[0045] The pigtail catheter can have a distal lumen diameter of, for example, 0.052 inches (range 0.045-0.060 inches) to accommodate the passage of a 4F cardiac diagnostic catheter (e.g., range 3.5F-4.5F), and the pigtail catheter can be formed with an overall profile of 8F while maintaining hydraulic diameters of the proximal and distal lumens greater than 0.018 inches to provide highly accurate pressure signal transmission. Alternatively, the pigtail catheter can have a distal lumen diameter of, for example, 0.069 inches (range 0.065-0.075 inches) to accommodate the passage of a 5F cardiac diagnostic catheter (e.g., range 4.5F-5.5F) that can track over a 0.032 inch guidewire, and the pigtail catheter can be formed with an overall profile of 9-10F while maintaining hydraulic diameters of the proximal and distal lumens greater than 0.018 inches to provide highly accurate pressure signal transmission. Alternatively, the pigtail catheter of the present invention provides a 7F-8F pigtail catheter profile and high precision pressure signal transmission, and can track directly over a 0.035 inch guidewire.

[0046] The J-tip guidewire can be advanced while guiding the cardiac diagnostic catheter through the vascular access sheath into the aortic root, and then the straight tip guidewire is exchanged for the J-tip guidewire and advanced across the stenotic aortic valve and into the LV.

[0047] FIG. 17A shows the distal shaft segment of a dual lumen pigtail catheter of the present invention placed in the LV of a patient with obstructive hypertrophic cardiomyopathy (HOCM). The HOCM pigtail catheter can have a braided shaft near the bend angle and in other parts of the proximal shaft segment to provide torque control of the distal shaft segment and prevent kinking of the catheter shaft. The flexible straight region of the coil and post-bend region generally may not be braided to provide a more flexible catheter shaft that may not cause damage to the chordae tendineae in the LV. A bend angle of 155 degrees (e.g., in the range of 145-165 degrees) allows the catheter to be delivered into the LV without making strong contact with the inferior basal wall of the LV, which may lead to ectopic excitation. The 155 degree bend angle also allows for straighter alignment of the distal catheter shaft with the ascending aorta and allows the coil apex and a radiopaque marker located at the coil apex to seat more completely at the nadir of the aortic valve cusp, allowing for more precise visualization of the location of the aortic valve cusp and aortic annulus for precise placement of a TAVR device, for example. The coil is provided with a radiopaque marker at its distal opening to allow precise identification of the location of distal pressure measurements.

[0048] The coil may have a coil diameter of about 5 cm (e.g., in the range of 3-8 cm), which is smaller than the coil diameters of other cardiac pigtail catheter coils of the present invention. The smaller coil diameter of 5 mm is more suitable for not impeding LV systolic contraction in HOCM patients who often experience direct contact of the LV opposing wall near the LV apex during systolic contraction. During systolic LV contraction, orifices located along the coil or distal openings found at the coil ends may be blocked by myocardial tissue. Typically, such distal openings may have a diameter of 0.038 inches (e.g., in the range of 0.025-0.040 inches) to allow passage of a guidewire and pressure signal transmission to the distal lumen of the pigtail catheter. Blockage of such orifices or distal openings may result in a reduction in the pressure signal that would normally be transmitted through the orifices or distal openings to the distal lumen of the pigtail catheter shaft. This reduced pressure signal may result in an inaccurate measurement of pressure within the LV. As shown in FIG. 17A, the distal opening can be positioned near (e.g., within 1 mm) or in direct contact with the catheter shaft in the flexible straight region of the post-bend shaft region. The proximity of the distal opening near the catheter shaft can prevent myocardial tissue from entering the distal opening during systolic contraction of the heart. A radiopaque marker can be positioned on the most distal surface of the coil to visualize the coil location within the LV, and the coil can be kept approximately 2-3 cm from the LV apex, where there is usually greater compression of the myocardium by the opposing wall, and the coil location of the HOCM pigtail catheter may be preferred to keep the coil at a constant distance from the LV apex.

[0049] Orifices can also be located at other locations along the coil of the HOCM pigtail catheter, as shown in Figures 17B-17E. As shown in Figure 17B, the orifices can be located along the inner surface of the coil at or near (within 1 mm) the distal opening. The orifices located along the inner surface of the coil can have an orifice diameter of 0.020 inches (e.g., in the range of 0.018-0.028 inches) so that the pressure signal from the pressurized blood in the LV is not attenuated as it is transmitted to the distal lumen of the HOCM pigtail catheter. Alternatively, a series of orifices (e.g., in the range of 2-5 orifices) can be located along the inner surface of the coil closest to the coil center, as shown in Figure 17C, with no orifices located on a plane (i.e., the face of the coil formed by a plane tangent along the entire coiled length of the coil) or on the outer surface of the coil. The presence of orifices on the planar or outer surface may allow myocardial tissue to enter such orifices and obstruct the distal lumen, resulting in inaccurate pressure signals being transmitted to the distal lumen. As shown in FIG. 17D, the coil may be folded inward to form a coil with a curvature of greater than 180 degrees. This may allow the distal opening to be protected by the inner surface of adjacent regions of the coil in addition to being protected by direct or near contact with the opposing walls of the coil, which may help prevent myocardial tissue from impinging on the distal opening. Furthermore, the cross-sectional shape of the orifice may be an oval opening in the coil wall, as shown in FIG. 17D, with the oval orifice having a major axis along the inner perimeter of the coil of about 0.030 inches (e.g., in the range of 0.020-0.035 inches) and a minor axis perpendicular to the major axis of about 0.020 inches (e.g., in the range of 0.018-0.025 inches), providing for accurate pressure signal transmission across the coil wall.

[0050] The profile of such a HOCM pigtail catheter having a distal lumen capable of tracking a 0.035 guidewire and providing proximal and distal pressure lumens with hydraulic diameters of at least 0.018 inches (to provide accurate pressure signal transmission through the proximal and distal pressure lumens) is approximately 6F to 7F.

[0051] Approximately one or two proximal orifices are placed at or about 1 mm below the location of the radiopaque marker located at the shaft bend along the distal shaft segment. The proximal orifices are intended to measure pressure between the aortic annulus (or stenotic aortic valve leaflets) and the hypertrophied myocardium, spaced no more than 5 mm apart (e.g., in the range of 3-8 mm). The one or two orifices positioned at this location cannot extend downstream past the stenotic native leaflets and upstream from the hypertrophied proximal muscle, so this proximal orifice area cannot extend more than 2 mm.

[0052] During measurement of the pressure gradient across the hypertrophied proximal muscle from the LV, the proximal orifice region can be positioned between the aortic valve and the hypertrophied myocardium, and the coil can be positioned approximately 2-3 cm into the LV cavity from the LV apex, which avoids excessive compression of the HOCM pigtail coil by systolic compression near the LV apex. The HOCM pigtail catheter can also be repositioned so that the proximal orifice region is located downstream of the aortic valve cusp that may be stenotic in the ascending aorta, as shown in FIG. 18. The coil can be positioned distal to the hypertrophied septal muscle such that the pressure gradient reflects the overall pressure gradient from the LV cavity to the aorta. The difference between the overall pressure gradient and the pressure gradient across the hypertrophied myocardium allows the pressure gradient across the stenotic aortic valve to be determined. Based on knowledge of the primary flow resistance, treatment of the stenotic aortic valve, for example by valve replacement, or treatment of the hypertrophied septal muscle, for example by alcohol cauterization, can be performed.

[0053] A second shaft bend can be placed within the pigtail catheter shaft to provide a proximal shaft bend with a proximal bend angle and a distal shaft bend with a distal bend angle, as shown in FIG. 18. The proximal and distal bend angles can both be about 165 degrees, and the proximal orifice region can be located just distal to the proximal orifice bend where the radiopaque marker is located. During global pressure gradient measurements, the proximal orifice region can be retracted into the ascending aorta, as shown in FIG. 18, and the distal shaft bend positions the coil away from the lower base wall of the LV. During pressure gradient measurements across the hypertrophied myocardium, the proximal orifice region can be positioned below the aortic annulus, and the combination of both the proximal and distal shaft bends helps position the coil away from the lower base wall of the LV.

[0054] 19 shows a dual lumen shaft of the present invention with no braided structure contained within the outer wall. The outer wall of this embodiment contains oval side wall fibers positioned in the oval side wall in line with the distal pressure lumen center and the proximal pressure lumen center. The oval side wall fibers can extend along the axial direction of the outer wall of the dual lumen shaft. The oval side wall fibers can be ribbons, rods, or fibers formed of materials that are easily bendable but do not stretch or expand due to their relatively high tensile strength, such materials include polymeric fibers such as polyethylene terephthalate, Dacron, Kevlar, and other high tensile polymers, and the oval side wall fiber materials also include metallic fibers such as stainless steel, nitinol, and other metals that can be formed into high tensile fibers for use in medical devices. The oval sidewall fibers should have a small thickness or radial dimension, about 0.002 inches (e.g., in the range of 0.0005 to 0.005 inches), radially within the shaft outer wall so that they can be molded into the polymeric sidewall of the dual lumen shaft during extrusion or during a thermal or adhesive-based post-processing step. The oval sidewall fibers can have a ribbon rectangular cross-sectional shape with a cross-sectional round or outer wall circumferential width of about 0.003 to 0.010 inches (e.g., in the range of 0.002 to 0.030 inches) to provide strength to prevent axial stretching, but still allow bending of the dual lumen shaft in a plane perpendicular to a line extending from the distal pressure lumen center to the proximal pressure lumen center. With a guidewire positioned within the distal pressure lumen, the dual lumen shaft can bend along a plane perpendicular to a line extending from the distal lumen center to the proximal lumen center. This bend direction ensures that the minor axis of the proximal pressure lumen does not decrease in dimension during bending, and tends to increase or widen during bending. The hydraulic radius of the proximal pressure lumen does not decrease due to shaft bends, and is maintained at a hydraulic diameter of at least 0.018 inches. This ensures that bending of the dual lumen shaft does not compromise the fidelity of the pressure signal transmission from the proximal orifice, through the proximal pressure lumen, to the pressure transducer located at or near the manifold.

[0055] In an alternative embodiment, in addition to the oval side wall fibers, circular side wall fibers can be placed within the circular side wall. The circular side wall fibers can be placed within the circular side wall in a location that is aligned with the distal pressure lumen center and the proximal pressure lumen center. The circular side wall fibers can be formed within the circular side wall during the extrusion process or can be formed by alternative post-processing methods. The circular side wall fibers can have the same material and dimensional properties as the oval side wall fibers. The presence of both the circular side wall fibers and the oval side wall fibers ensures that the dual lumen shaft will bend along a plane perpendicular to the line connecting the circular side wall fibers with the oval side wall fibers.

[0056] Other methods of placing either the oval or circular sidewall fibers are contemplated, and the oval sidewall fibers can be inserted into the proximal pressure lumen and attached at the desired location along the luminal surface of the proximal pressure lumen by adhesive, thermal bonding, or other attachment methods. Alternatively, the oval sidewall fibers can be attached along the outside of the outer wall to provide similar bending characteristics to the dual lumen shaft.

[0057] FIG. 20 illustrates another embodiment of a dual lumen shaft configuration with an oval dual lumen shaft. In this embodiment, the oval dual lumen shaft can be formed with an oval outer surface to have a major shaft diameter that is 20% (e.g., in the range of 10-30%) larger than the minor shaft diameter. The minor shaft diameter can be at least 10% smaller than the major shaft diameter. Reducing the minor shaft diameter by 20-25% can provide an oval dual lumen shaft that is 10-15% smaller in circumference than a circular dual lumen shaft and thus can be accommodated within an introducer catheter with a profile that is approximately 10-15% smaller. Alternatively, the oval dual lumen shaft allows for a larger diameter proximal pressure lumen with better signal transmission and can fit within a smaller introducer catheter profile than a round dual lumen shaft would allow.

[0058] An oval dual lumen shaft has a tendency to bend in a plane perpendicular to the long axis. A dual lumen shaft is often bent as it travels along a path in the body, and bending of the dual lumen shaft causes the proximal pressure lumen to expand in a direction along the proximal lumen short axis. Thus, the proximal pressure lumen can be formed with an oval shape in which the proximal lumen long axis is larger than the proximal lumen short axis that runs in line with the catheter shaft long axis. Bending of the dual lumen shaft then results in the proximal lumen short axis expanding, making the proximal pressure lumen more round, resulting in a larger hydraulic diameter, and thus improving the fidelity of the transmitted signal. To enhance the tendency of the dual lumen shaft to bend in a plane perpendicular to the shaft long axis, the presence of oval or circular sidewall fibers can be applied to the dual lumen shaft in locations as described for the round dual lumen shaft.

[0059] FIG. 21 shows a simplified elemental model of a system having a pressure signal transmitted through a proximal pressure lumen, where, for example, the transmission of the pressure signal is affected by several system characteristics. The model includes a pressure signal representing the pressure generated by a cardiac pressure pulse signal. The inertia of the fluid or blood trapped within the pressure lumen is L p and represents the mass per unit area for the fluid in the proximal pressure lumen. The resistance to fluid flow is R p and Poiseuille's law, i.e., R p =8uL / Pi×R 4 where u is the viscosity, L is the length of the tubing or, for example, a dual lumen shaft, and R is the hydraulic radius (i.e., 1 / 2 the hydraulic diameter) of the proximal lumen of, for example, a dual lumen shaft. The total compliance is C tand represents the sum of compliance due to the presence of an air bubble in the proximal pressure lumen, compliance of the pressure transducer diaphragm, compliance due to fluid such as blood trapped in the proximal pressure lumen, and compliance of the dual lumen shaft material. The dual lumen shaft may be constructed from polyethylene, nylon, Pebax, or other materials commonly used in catheter construction for transmitting pressure signals within the body, and the compliance of such materials describes the change in radius of the pressure lumen per change in pressure in the pressure lumen, such as the proximal pressure lumen. A dual lumen shaft constructed from a material with a greater elastic modulus will have a smaller compliance.

[0060] The equation describing the flow in the proximal pressure lumen as a function of time has two components, a natural component and a forced component that depends on the nature of the pressure signal generated by the heart. The natural component represents the natural frequency of the system that includes the dual lumen shaft, the compliance of the shaft, the length of the shaft, and the hydraulic diameter of the proximal lumen. The natural frequency of the system, fo, is described by: fo = (l / 2Pi)(R 2 -(4L / C) 1 / 2 In constructing the dual lumen shaft of the present invention, it is desirable for f0 to be greater than about 40 Hz. 2 If L / C > 4, the system becomes overdamped and the amplitude of the transmitted signal sent to the manifold is smaller than the actual signal, potentially missing high frequency signals generated by the heart. 2 For LC < 4, the system becomes underdamped and "ringing" occurs in the transmitted signal, potentially resulting in the transmission of signals associated with the natural frequency of the system rather than those generated by the heart. 2= 4L / C. The hydraulic diameter (i.e., twice R) is one of the most empirical factors that determine the ability of the dual lumen shaft of the present invention to transmit a signal accurately and faithfully to the pressure transducer located in the manifold. The hydraulic radius of the proximal pressure lumen is (4L / C) 1 / 2 is equal to.

[0061] The catheter design of the present invention offers advantages over existing designs. For example, in terms of safety, the two lumens enclosed within a single extrusion cannot be separated by high pressure injection forces. The design of the present invention offers the opportunity to eliminate the risk of elemental embolization. Also in terms of safety, the single extrusion design can reduce or eliminate dead space within the proximal shaft segment of the catheter, simplifying cleaning setups and reducing the risk of air embolization. In terms of efficacy, the relatively rigid single extrusion that confines the independent non-coaxial lumens overcomes the risk of either lumen becoming blocked due to the relative movement of one catheter component within the other. The non-coaxial lumen design also overcomes the high shear forces inherent in coaxial designs that affect both signal fidelity and injection flow rates.

[0062] Element Number Reference Guide In the drawings, like numerals may be used to describe like features and components throughout the several views.

[0063] (table) TIFF2024529662000002.tif225158 TIFF2024529662000003.tif232158 TIFF2024529662000004.tif151158

[0064] The above Detailed Description includes reference to the accompanying drawings, which form a part of the Detailed Description. The Detailed Description should be read with reference to the drawings. The drawings show, by way of example, certain embodiments in which the catheters and related methods of the present invention may be practiced. These embodiments are also referred to herein as "Examples." The use of "adapted to," "configured to," or similar phrases herein is intended to be open and inclusive, not excluding devices or components adapted or configured to perform additional functions. The use of "proximal" and "distal" herein refers to the relative location of the elongated minimally invasive device to the user, with "proximal" meaning relatively toward the user and "distal" meaning relatively away from the user. The headings, lists, and numbering contained herein are for ease of explanation only and are not intended to be limiting. All numerical values ​​are assumed to be modified by the term "about," whether expressly stated or not. The term "about" generally refers to a range of numbers that one of ordinary skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the term "about" may include numbers that are rounded to the nearest significant figure. The recitation of numerical ranges by endpoints includes all numbers and subranges within that range and delimiting that range (e.g., 1 to 4 includes 1, 1.5, 1.75, 2, 2.3, 2.6, 2.9, etc., as well as 1 to 1.5, 1 to 2, 1 to 3, 2 to 3.5, 2 to 4, 3 to 4, etc.).

[0065] The Detailed Description is intended to be illustrative and not limiting. For example, the above-described embodiments (or one or more features or components thereof) can be used in combination with each other. Other embodiments can be used by those of skill in the art upon review of the Detailed Description above. Similarly, various features or components may be combined or combined to streamline the disclosure of the invention. This should not be construed as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter resides in less than all features of a particular embodiment disclosed. That is, the following claimed examples are hereby incorporated into the Detailed Description, with each example standing on its own as a separate embodiment.

[0066] In example 1, a pigtail catheter configured to measure pressure proximal and distal to a narrowing can include a proximal shaft segment and a distal shaft segment. The proximal shaft segment can include dual lumen tubing defining a proximal pressure lumen and a non-coaxial distal pressure lumen. The distal shaft segment can be configured to be positioned partially across the narrowing, having a portion that includes the distal pressure lumen but does not include the proximal pressure lumen. The distal shaft segment can include at least one distal orifice positionable distal to the narrowing and having a diameter of at least about 0.018 inches, and at least one proximal orifice positionable proximally to the narrowing and having a diameter of at least about 0.018 inches.

[0067] In Example 2, the pigtail catheter of Example 1 can be optionally configured such that the distal pressure lumen has an approximately circular cross-sectional shape and the proximal pressure lumen has an approximately crescent or kidney-shaped cross-sectional shape that partially wraps around the distal pressure lumen.

[0068] In Example 3, the pigtail catheter of either Example 1 or 2 can optionally further comprise a manifold coupled to a proximal end of the proximal shaft segment. The manifold can include a proximal pressure port in fluid communication with the proximal pressure lumen and a distal pressure port in fluid communication with the distal pressure lumen.

[0069] In Example 4, the pigtail catheter of Example 3 can optionally be configured with a manifold configured to send proximal and distal pressure signals to a transducer to determine the pressure gradient across the narrowing.

[0070] In Example 5, the pigtail catheter of any one or any combination of Examples 1-5 is optionally configured such that the proximal shaft segment includes a braided structure confined within the outer wall of the dual lumen tubing.

[0071] In Example 6, the pigtail catheter of Example 5 is optionally configured such that the braided structure comprises metal or polymeric fibers spaced at least about 0.020 inches apart, allowing the proximal orifice to be positioned therebetween.

[0072] In Example 7, the pigtail catheter of either Example 5 or 6 is optionally configured such that the braided structure extends to a portion of the distal shaft segment.

[0073] In Example 8, the pigtail catheter of any one or any combination of Examples 1-7 is optionally configured such that the outer wall of the dual lumen tubing comprises a first wall fiber adjacent the proximal pressure lumen. The first wall fiber can extend axially and have a non-stretching property.

[0074] In Example 9, the pigtail catheter of Example 8 is optionally configured such that the outer wall of the dual lumen tubing comprises a second wall fiber adjacent to the distal pressure lumen, the second wall fiber extending axially and having a non-stretching property.

[0075] In Example 10, the pigtail catheter of any one or any combination of Examples 1 to 10 can optionally be configured such that the outer surface of the dual lumen tubing has an oval cross-sectional shape defining a shaft major axis and a shaft minor axis, and the distal pressure lumen center and the proximal pressure lumen center are positioned on the shaft major axis.

[0076] In Example 11, the pigtail catheter of Example 10 can optionally be configured with an outer surface having a minor shaft diameter that is at least ten percent (10%) smaller than the major shaft diameter.

[0077] In Example 12, the pigtail catheter of any one or any combination of Examples 1-11, optionally further comprising an elastic member positioned within the distal portion of the proximal pressure lumen and forming an attachment to the distal shaft segment.

[0078] In Example 13, the pigtail catheter of Example 12 is optionally configured with an elastic member extending along the length of the distal shaft segment that includes the pigtail coil at the end thereof.

[0079] In Example 14, the pigtail catheter of any one or any combination of Examples 1-13 is optionally configured such that the distal shaft segment includes a shaft bend distal to the at least one proximal orifice.

[0080] In Example 15, the pigtail catheter of Example 14 is configured so that the shaft bend portion forms a shaft bend angle in the range of about 145 degrees to about 165 degrees.

[0081] In Example 16, the pigtail catheter of any one or any combination of Examples 1-15 is configured such that the distal shaft segment includes a pigtail coil having a diameter of about 1.5 cm or less.

[0082] In Example 17, the pigtail catheter of Example 16 is optionally configured such that the plane of the pigtail coil is non-coplanar with the plane of a shaft bend positioned in the distal shaft segment distal to the at least one proximal orifice.

[0083] In Example 18, the pigtail catheter of Example 17 is optionally configured such that the plane of the pigtail coil forms an angle of about 5 degrees to about 45 degrees (including the endpoints) with respect to the plane of the shaft bend.

[0084] In Example 19, the pigtail catheter of any one or any combination of Examples 16-18 is optionally configured such that the pigtail coil includes a coil apex at a distal-most coil portion, the distal-most coil portion having a radius of curvature smaller than the radius of curvature of the remainder of the pigtail coil.

[0085] In Example 20, the pigtail catheter of any one or any combination of Examples 16-19 is optionally configured such that the pigtail coil includes a coil apex at the distal-most coil portion. A radiopaque marker can be positioned at the coil apex.

[0086] In Example 21, the pigtail catheter of any one or any combination of Examples 1-20 is optionally configured such that one or both of the proximal pressure lumen and the distal pressure lumen have a hydraulic diameter of at least about 0.018 inches.

[0087] In Example 22, the method may include inserting a pigtail catheter into the heart such that a distal shaft segment of the catheter is partially positioned within the left ventricle, and determining a pressure gradient across the aortic valve. The proximal shaft segment of the catheter may include a dual lumen tubing defining a distal pressure lumen having a generally circular cross-sectional shape and a proximal pressure lumen having a generally crescent or kidney-shaped cross-sectional shape that partially wraps around the distal pressure lumen. The distal shaft segment may include a portion that includes the distal pressure lumen but does not include the proximal pressure lumen, at least one proximal orifice positioned proximally relative to the aortic valve, and at least one distal orifice positioned distally relative to the aortic valve. Determining the pressure gradient across the aortic valve may include coupling a pressure transducer to a manifold of the pigtail catheter. The manifold may include a proximal pressure port in fluid communication with the proximal pressure lumen and a distal pressure port in fluid communication with the distal pressure lumen.

[0088] In Example 23, the method of Example 22 can optionally be configured such that the step of inserting the pigtail catheter into the heart includes inserting the pigtail catheter over a cardiac diagnostic catheter using the distal pressure lumen.

[0089] In Example 24, the method of Example 23 can optionally further comprise removing the cardiac diagnostic catheter from the distal pressure lumen.

[0090] In Example 25, the method of any one of Examples 22-24 can optionally be configured such that one or both of the proximal pressure lumen and the distal pressure lumen include a hydraulic diameter of at least about 0.018 inches.

[0091] The scope of the catheters and related methods of the present invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain English equivalents of the respective terms "comprisong" and "wherein." Also in the following claims, the terms "including" and "comprising" are open-ended, i.e., a catheter or method that includes features, components, or steps in addition to those recited after such term in a claim will still be deemed to be within the scope of that claim. Moreover, in the following claims, terms such as "first," "second," and "third" are used merely as labels, and such terms are not intended to impose numerical requirements on their subject matter.

[0092] The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. [Explanation of symbols]

[0093] 100 Dual Lumen Pigtail Catheter 102 Double Lumen Shaft 104 Single Lumen Shaft 114 Manifold 128 Braided structure 134 Shaft bend

Claims

1. A pigtail catheter configured to measure pressure proximal to a narrowing and to measure pressure distal to said narrowing, a proximal shaft segment including a dual lumen tubing defining a proximal pressure lumen and a non-coaxial distal pressure lumen; a distal shaft segment configured to be positioned across the narrowing, the distal shaft segment having a portion that includes the distal pressure lumen but does not include the proximal pressure lumen; at least one proximal orifice positioned along the outer catheter wall, in fluid communication with the proximal pressure lumen, and positionable proximally of the narrowing; at least one distal orifice positioned along the outer catheter wall, in fluid communication with the distal pressure lumen, and positionable distal to the narrowing; a shaft bend positioned between the at least one proximal orifice and the at least one distal orifice; a braided structure contained within the outer catheter wall and extending along the proximal shaft segment. Pigtail catheter.

2. the distal pressure lumen has a generally circular cross-sectional shape; the proximal pressure lumen has a generally crescent or kidney-shaped cross-sectional shape that partially wraps around the distal pressure lumen; The pigtail catheter of claim 1.

3. a manifold coupled to a proximal end of the proximal shaft segment; the manifold includes a proximal pressure port in fluid communication with the proximal pressure lumen and a distal pressure port in fluid communication with the distal pressure lumen; The pigtail catheter of claim 1.

4. A pigtail catheter as described in claim 3, wherein the proximal pressure port and the distal pressure port of the manifold are connectable to a transducer configured to measure a pressure gradient across the narrowing.

5. A pigtail catheter as described in claim 1, wherein the outer catheter wall has first wall fibers adjacent to the proximal pressure lumen, the first wall fibers extending axially and having non-stretching properties.

6. A pigtail catheter as described in claim 5, wherein the outer catheter wall has second wall fibers adjacent to the distal pressure lumen, the second wall fibers extending axially and having non-stretching properties.

7. an outer surface of the dual lumen tubing having an oval cross-sectional shape defining a shaft major axis and a shaft minor axis; a center of the distal pressure lumen and a center of the proximal pressure lumen are positioned on the shaft longitudinal axis; The pigtail catheter of claim 1.

8. 8. The pigtail catheter of claim 7, wherein the outer surface has a length of the shaft minor axis that is at least ten percent (10%) less than the length of the shaft major axis.

9. The pigtail catheter of claim 1 further comprising a resilient member positioned within a distal portion of the proximal pressure lumen and forming an attachment to the distal shaft segment.

10. 10. The pigtail catheter of claim 9, wherein the elastic member extends along the length of the distal shaft segment including a pigtail coil at the end of the distal shaft segment.

11. 10. The pigtail catheter of claim 1, wherein the shaft bend defines a shaft bend angle in the range of about 145 degrees to about 165 degrees, inclusive.

12. The pigtail catheter of claim 1 , wherein the distal shaft segment includes a pigtail coil having a diameter of about 1.5 cm or less.

13. The pigtail catheter of claim 12, wherein the plane of the pigtail coil is not coplanar with the plane of the shaft bend located in the distal shaft segment.

14. 14. The pigtail catheter of claim 13, wherein the plane of the pigtail coil forms an angle of about 5 degrees to about 45 degrees, inclusive, with the plane of the shaft bend.

15. 13. The pigtail catheter of claim 12, wherein the pigtail coil includes a coil apex at a distal-most coil portion, the distal-most coil portion having a radius of curvature that is smaller than the radius of curvature of the remainder of the pigtail coil.

16. the pigtail coil includes a coil apex at a distal-most coil portion; a radiopaque marker is positioned at the coil apex; The pigtail catheter of claim 12.

17. 10. The pigtail catheter of claim 1, wherein one or both of the proximal pressure lumen and the distal pressure lumen has a hydraulic diameter of at least about 0.018 inches.

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