Implantable heart assist system and method of applying same

Abstract

An extracardiac pumping for supplementing the circulation of blood, including the cardiac output, in a patient without any component thereof being connected to the patient's heart, and methods of using same. One embodiment of the intravascular extracardiac system comprises a pump with inflow and outflow conduits that are sized and configured to be implantable intravascularly through a non-primary vessel, whereby it may positioned where desired within the patient's vasculature. The system comprises a subcardiac pump that may be driven directly or electromagnetically from within or without the patient. The pump is configured to be operated continuously or in a pulsatile fashion, synchronous with the patient's heart, thereby potentially reducing the afterload of the heart. In another embodiment, the system is positioned extracorporeally, with the inflow conduit and outflow conduit applied percutaneously to a non-primary vessel for circulating blood to and from the non-primary vessel or between the non-primary vessel and another blood vessel within the patient's vasculature.

Description

RELATED APPLICATIONS [0001] This application is a continuation of U.S. application Ser. No. 10 / 878,592, filed Jun. 28, 2004, which is a continuation of U.S. application Ser. No. 10 / 408,926, filed Apr. 7, 2003, which is a continuation of U.S. application Ser. No. 10 / 078,260, filed on Feb. 15, 2002, now U.S. Pat. No. 6,610,004, all of which are incorporated herein by reference in their entirety.FIELD OF THE INVENTION [0002] The present invention relates generally to a system for assisting the heart and, in particular, to an extracardiac pumping system and a method for both supplementing the circulation of blood through the patient and for enhancing vascular blood mixing using a minimally invasive procedure. BACKGROUND OF THE INVENTION [0003] During the last decade, congestive heart failure (CHF) has burgeoned into the most important public health problem in cardiovascular medicine. As reported in Gilum, R. F., Epidemiology of Heart Failure in the U.S., 126 Am. Heart J. 1042 (1993), fo...

AI Technical Summary

Benefits of technology

[0026] An ancillary but important benefit of the present invention is the ability to apply the present invention in such a way as to also reduce the pumping load on the heart, thereby potentially permitting the heart to recover during use. With the present invention, no bulky pump, valves or oxygenator are required, and no thoracic invasion with major cardiac surgery is required. Indeed, a significant advantage of the present invention is its simplicity while achieving extraordinary results in improving the condition of a patient suffering from CHF. It is contemplated that the present invention be applied such that the heart experiences a reduced pressure at the aortic root during systole (afterload) and / or a reduced left ventricular end diastolic pressure (pre-load), thus reducing the hemodynamic burden or workload on the heart and, thus, permitting the heart to recover.

[0027] The extracardiac system of the present invention preferably comprises, in several embodiments, a rotary pump configured to pump blood through the patient at subcardiac rates; i.e., at a flow rate significantly below that of the patient's heart. Other types of pumps or flow generating mechanisms may be effective as well, including but not limited to rotating means, e.g., an Archimedes screw or impeller housed within an open or closed housing, either of which may be cable driven or shaft driven. Pumping the blood tends to revitalize the blood to a certain extent by imparting kinetic and potential energy to the blood discharged from the pump. Importantly, the preferred pump for the present invention pumping system is one that requires a relatively low amount of energy input, when compared to prior art pumps designed to pump at cardiac rates. The pump may be implanted corporeally or more specifically intravascularly, or it may be positioned extracorporeally, depending upon the capability, practicality, or need of the patient to be ambulatory.

[0028] The present invention also comprises, in several embodiments, an inflow conduit fluidly coupled to the pump, to direct blood to the pump from a first blood vessel, either the aorta or a first peripheral or non-primary vessel, either directly or indirectly through another blood vessel, wherein insertion of the pump and / or inflow conduit is through a non-primary blood vessel. The invention further comprises an outflow conduit fluidly coupled to the pump, to direct blood from the pump to a second blood vessel, either the aorta or a second peripheral or non-primary blood vessel, whether directly to the second vessel or indirectly through the first or other peripheral or non-primary blood vessel. The connection of the inflow and outflow conduits to the respective blood vessels is performed subcutaneously; not so deep as to involve major invasive surgery. In other words, minimally subdermal. This permits application of the connections in a minimally-invasive procedure. Preferably, the connections to the blood vessels are just below the skin or just below the first layer of muscle, depending upon the blood vessels at issue or the location of the connection, although slightly deeper penetrations may be necessary for some patients or for some applications.

[0029] In one embodiment, the present invention is configured so that it may be applied at a single cannulated site and comprises, for example, a multi-lumen catheter having at least one lumen as an inflow lumen and a second lumen as an outlet lumen. The multi-lumen catheter has an inflow port in fluid communication with the inflow lumen. With this embodiment, blood may be drawn into the inflow port of the first lumen from a first peripheral or non-primary blood vessel site, either the blood vessel into which the multi-lumen catheter is inserted or a different blood vessel. The output of the pump directs blood through a second (outlet) port at the distal end of the second lumen that may be located in a second peripheral or non-primary vessel site. This method accomplishes the same beneficial results achieved in the previously described embodiments, but requires only a single cannulated site, rather than two such sites. It should be appreciated that the multi-lumen catheter could be used in a manner where the outflow of the cannula is directed to the first vessel, while the inflow is drawn from the second vessel. Further still, it should be appreciated that in one application the inflow lumen could be positioned to draw blood from a peripheral or non-primary vessel at the site of entry into the patient while the outflow could be positioned in the aorta, proximate an arterial branch.

[0030] The pump of the present invention may be a continuous flow pump, a pulsatile pump, and / or a hybrid pump that is configured to generate flow in both a continuous and pulsatile format. The pump may be implantable and is used to fluidly connect two blood vessels, such as the femoral artery at the inflow and the left axillary artery at the outflow, although other peripheral or non-primary arterial and venous blood vessels are contemplated, as well as any singular and / or cumulative combination thereof. An alternative embodiment employs both a continuous flow and a pulsatile flow pump connected in parallel or in series and operating simultaneously or in an alternating fashion. Yet another alternative embodiment employs a rotary pump that is controllable in a synchronous copulsating or counterpulsating fashion, or in some out-of-phase intermediate thereof.

[0031] It is contemplated that, where the entire system of the present invention is implanted, that it be implanted subcutaneously without the need for major invasive surgery and, preferably, extrathoracically. For example, the pump may be implanted in the groin area, with the inflow conduit attached to the femoral or iliac artery proximate thereto and the outflow conduit attached to the axillary artery proximate the shoulder. It is contemplated that the outflow conduit be applied by tunneling it under the skin from the pump to the axillary artery. Alternatively, the pump and conduits may be applied intravascularly through a non-primary blood vessel in a subcutaneous application. In such an embodiment, the pump is sized and configured to be positioned within or pass through a non-primary vessel and introduced via a percutaneous insertion or a surgical cutdown with or without accompanying inflow and outflow conduits. The pump may be enclosed within a conduit through which blood may be directed, an open housing having a cage-like arrangement to shield the pump blades from damaging the endothelial lining, or a closed housing having an inlet and outlet to which inflow and outflow conduits may be respectively attached.

Problems solved by technology

Unfortunately, nearly 250,000 patients die of heart failure annually.

CHF manifests itself primarily by exertional dyspnea (difficult or labored breathing) and fatigue.

Under these circumstances, however, continuous flow may not be desired because the patient's arterial system is deprived of pulsatile wave flow, which is beneficial to certain parts of the patient.

If it is not operated in direct synchronization with the patient's heart, there is a risk that the pump might cause “carotid steal phenomenon” where blood is drawn away from the patient's brain through the carotid arteries when there is insufficient blood in the left ventricle.

Moreover, they do not operate as a continuous flow system, operating exclusively in pulsatile fashion.

Of course, with any system that includes an oxygenator, such as the conventional heart-lung machine, the patient cannot be ambulatory.

Inflation and deflation of the balloon, however, requires a pneumatic pump that is sufficiently large that it must be employed extracorporeally, thereby restricting the patient's movements and ability to carry out normal, daily activities.

IABP devices are, thus, limited to short term use, on the order of a few days to a few weeks.

With such systems, extreme pumping and large amounts of energy, volume, and heat dissipation are required.

Due to having one or more of these features, the prior art heart assist devices are limited in their effectiveness and / or practicality.

Noncompliance with what is often a complex drug regime may dramatically adversely affect the recovery of a CHF patient leading to the need for hospitalization and possibly morbidity and mortality.

In addition, ACE inhibitors and diurectics can cause hypotension, which leads to decreased organ perfusion or an increasing demand on the heart to pump more blood.

This leads to an inability, in many cases, to prescribe the most effective dosage of ACE inhibitors and a less than optimum outcome for the patient.

When blood flow through the coronary arteries falls below the level needed to provide the energy necessary to maintain myocardial function, due often to a blockage in the coronary arteries, a myocardial infarction or heart attack occurs.

The closer the blockage is to the coronary ostia, however, the more severe and life threatening the myocardial infarction.

The larger the area that dies due to the loss of oxygen, the more devastating the infarction.

Unloading the left ventricle decreases the energy requirements of the myocardium and increases the amount of time before irreversible damage occurs.

The disadvantage, however, is that each of these techniques can only be performed in an emergency room or hospital setting.

Unless the patient is already in the hospital when the myocardial infarction occurs, there is usually some level of irreversible damage and subsequent loss of myocardial function.

Images