Implantable device for monitoring aneurysm sac parameters

Abstract

A device for measuring physiological parameters within an aneurysm sac that has been excluded from blood flow by an endoprosthesis. The device is comprised of at least two sensors, one placed in the aneurysm sac and another in a systemic artery. A differential between the readings of the two sensors can then be calculated, making the device easily calibrated in vivo and insensitive to changes in atmospheric pressure.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Continuation of application Ser. No. 10 / 116,782, filed on Apr. 4, 2002, which claims benefit of provisional application No. 60 / 294,959, filed on May 31, 2001.BACKGROUND [0002] 1. Field of Invention [0003] The invention relates to a device for introduction into a human body for the purpose of measuring and / or monitoring physiological parameters such as pressure, pressure waveform, or fluid flow rate. This invention is particularly useful for chronic monitoring of physiological parameters within the sac of an aneurysm. [0004] 2. Description of Prior Art [0005] In the arteries of human bodies one of the major problems is the loss of strength of the wall of arteries, which can result in aneurysm formation. An aneurysm may endanger the health of a patient because of the risk of internal bleeding which often results in the death of the patient. Therefore, aneurysms are often treated before rupture occurs by minimally invasive implantation of ...

AI Technical Summary

Benefits of technology

"The present invention is a device that can be implanted in a patient to measure pressure, pressure waves, and blood flow within an aneurysm sac. The device has two sensors, one in the aneurysm sac and one in an artery subjected to systemic blood pressure and flow. The sensors are attached to an implantable housing assembly. The device can be chronically implanted without major surgery and can compensate for changes in atmospheric pressure. It also allows for calibration of multiple sensors in vivo."

Problems solved by technology

In the arteries of human bodies one of the major problems is the loss of strength of the wall of arteries, which can result in aneurysm formation.

An aneurysm may endanger the health of a patient because of the risk of internal bleeding which often results in the death of the patient.

Although the procedure can be safely performed now, endoleakage is still a major problem immediately following the operation as well as many months or years following the procedure.

Because the aneurysm sac is isolated from fluid conveyance by the endoprosthesis, inflowing blood has no exit path, resulting in a pressure build-up within the aneurysm sac.

These non-invasive methods require the patient to frequently return to a hospital or imaging center at substantial expense.

In addition, the patient may suffer from a ruptured aneurysm sac caused by an endoleak that develops or worsens between non-invasive monitoring periods.

Finally, because of limitations with these current non-invasive monitoring systems, failure to visualize an endoleak does not exclude the presence of such an endoleak.

Thus, without a visible endoleak, the aneurysm sac can still be under pressure with the danger of ultimate rupture and internal bleeding.

First, Baum is invasive and must be performed by a physician in a clinical setting.

However, van Bockel imposes several limitations:

Energizing the device in this fashion would require the patient with to charge it frequently from a fixed base station, this would be very inconvenient.

Second, if a battery were used, the small size van Bockel describes would severely limit the life of the device, requiring frequent battery replacement over the patient's lifetime.

Third, the small size of the van Bockel's device necessarily limits the memory capacity, the gain of the transducer, and the transmission strength of the transponder.

Fifth, because van Bockel's device is entrapped within the aneurysm sac, it cannot be removed or replaced if it malfunctions, becomes fouled with thrombus (clotted blood), or needs to be calibrated, without an open-abdomen surgical procedure.

Finally, the device disclosed by van Bockel has no means for compensating for changes in atmospheric pressure (so-called “zeroing” the transducer).

Since the pressure measurement in question may be on the order of 20 mm Hg (0.4 PSI or 2.67*103 Pa), failure to account for atmospheric pressure would make the error a large percentage of the pressure measurement.

However, both Cimochowski and Porat disclose devices with sensors placed within the blood flow, rather than within an aneurysm sac.

Thus, these devices would be of little use for monitoring aneurysm sac pressure.

Although useful in a laboratory setting in an animal model, the Brockway's device would suffer from several limitations if used to measure aneurysm sac pressure:

However, this would not be practical for pressure measurements in a human aneurysm sac because it would require placing the catheter between the endoprosthesis and the aorta, which itself would be a source of endoleak.

In a human patient, this would lead to loss of the lower portion of the ligated limb.

Third, the Brockway has no means of calibration to account for drift in the transducer except to surgically remove the transducer and replace it with a new transducer.

Therefore, while providing benefits over Brockway such as reduced diameter and kink resistance, Corl's device would not be suitable for chronic measurement of pressure within an aneurysm sac.

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