Surgery – Cardiac augmentation
Reexamination Certificate
2001-03-13
2003-10-14
Jastrzab, Jeffrey R. (Department: 3762)
Surgery
Cardiac augmentation
Reexamination Certificate
active
06632169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the field of mechanical cardiac pumping devices, and, more particularly, to a ventricular assist device (VAD) and a total artificial heart (TAH) device and method of using same. More specifically, this invention relates to a VAD and a TAH that are optimized by the new method to produce customized pulsatile blood flow mimicking that of the healthy native heart for each individual patient case.
2. Description of Related Art
Introduction:
Some medical studies indicate: a) 400,000 new cases of congestive heart failure are diagnosed annually in the United States; b) a mortality rate of 75 percent in men and 62 percent in women; c) standard medical therapies benefit only a limited percentage of patients with ventricular dysfunction; and d) from 17,000 to 66,000 patients per year, in the United States alone, may benefit from a permanent implantable blood pump. Presently, potential cardiac transplant recipients with hemodynamic compromise (inadequate perfusion of the systemic circulation by the native heart) sometimes receive temporary mechanical circulatory support as a “bridge” to permit them to survive until cardiac transplantation is possible. It is foreseen that some day mechanical blood pumps will provide a cost-effective alternative to either cardiac transplantation or long term medical management of patients. It is to this end that the devices and methods described herein have been developed.
It is to be understood that for purposes of this document a “ventricular-assist device (VAD)” is a mechanical blood pump that assists a diseased native heart to circulate blood in the body, and a “total artificial heart (TAH)” is another type of mechanical blood pump that replaces the native heart and provides all of the blood pumping action in the body.
In order for a VAD to function optimally, it must both complement the diseased native heart and make the combined output of the VAD and native diseased heart emulate the pumping action of the natural healthy human heart. That is, it should provide pulsatile flow similar to that of the healthy heart. In order for a TAH to function optimally, it must mimic the pulsatile pumping action of the natural healthy human heart. In either case, the device must be sized such that it fits within the required areas in the patient's body. In order to minimize the size of the power supply portion of the device, each device (VAD or TAH) must use as little energy and as little power as possible to accomplish the required function. Thus, there is a need for bio-emulating efficient pump (BEEP) systems for VAD and TAH applications.
It is known that VADs can be implanted to assist a functioning heart that does not have adequate pumping capability. Often, however, residual cardiac function is not taken into account in the design of such devices, resulting in less than optimal effects. What is needed is a bio-emulating efficient pump (BEEP) system, which works in concert with the native human heart. The new VAD device and system and optimization procedure described herein utilize patient specific information concerning residual cardiac output to optimize the pumping action provided for each individual patient, thereby providing such a BEEP system. The TAH device and optimization procedure described in this document optimize the pumping function provided for each individual patient, thereby providing such a BEEP system which is customized for each such patient. Known Heart Pump Devices:
Previously, a number of devices were developed for blood pumping. Highly specialized pumps have been used to completely replace a biological heart which has been surgically removed. Such known heart pumps may be temporary, or permanently implantable. Temporary heart pump devices usually involve either: 1) an attempt to augment a compromised native heart while it recovers from surgery or some other short-term problem; or 2) use of the device as a “bridge” to extend the life of a patient by temporarily replacing the native heart until a suitable donor heart can be found for cardiac transplantation.
Many types of permanently implantable heart pumps have been proposed and several have been developed. Because the left ventricle of the heart, which pumps blood to the entire body except for the lungs, becomes diseased far more commonly than the right ventricle (which pumps blood only to the lungs), most heart pumps have been developed to assist or replace the left ventricle. Fewer pumps have been proposed, tested, and used for bi-ventricular function (i.e. assisting both the left and right ventricles).
Known mechanical blood pumps can be roughly divided into three major categories: a. pulsatile sacks; b. reciprocating piston-type pumps; and c. pumps with axial or centrifugal impellers. Each category has distinct advantages and disadvantages.
a. Pulsatile Sacks
Pulsatile sack devices are the most widely tested and used implantable blood pumps. These devices employ flexible sacks or diaphragms which are compressed and released in a periodic manner to cause pulsatile flow of blood. Sack or diaphragm pumps are subject to fatigue failure of compliant elements. They are generally used as temporary heart-assist devices, and they are mechanically and functionally different from the present invention described hereafter.
The intra-aortic balloon (IAB) counter-pulsation device, a pulsatile sack device, is readily available. It is a catheter-mounted intra-vascular device designed to improve the balance between myocardial oxygen supply and demand. The first successful clinical application of the balloon was reported by Kantrowitz et al. in 1968. The IAB is positioned in the thoracic aorta and set to inflate at the dicrotic notch of the atrial pressure waveform when monitoring aortic pressure. The diastolic rise in aortic pressure augments coronary blood flow and myocardial oxygen supply. The IAB is deflated during the isovolumetric phase of left ventricular contraction. The reduction in the afterload component of cardiac work decreases peak left ventricular pressure and myocardial oxygen consumption. These units are not portable and are limited to in-hospital critical care use only. Use of the IAB is now a standard form of therapy for a variety of patients with cardiovascular disease, primarily reserved for patients with deteriorating heart function while awaiting revascularization procedure. In 1993, nearly 100,000 IABs were inserted in the United States alone.
Another example of a pulsatile sack device is the Abiomed™ BVS® device (Abiomed, Inc., Boston, Mass.). It is an externally placed dual-chamber device that is capable of providing short term univentricular or biventricular support. It has pneumatically driven polyurethane blood sacks and it is not intended for long-term support. Also, U.S. Pat. No. 4,888,011 to Kung and Singh discloses a hydraulically driven dual-sack system; and U.S. Pat. No. 5,743,845 to Runge discloses a sack-operated bi-ventricular assist device that balances the flow in the left and right side of the circulatory system.
b. Reciprocating Piston-Type Pumps
Several types of implantable blood pumps containing a piston-like member have been proposed to provide a mechanical device for augmenting or totally replacing the blood pumping action of a damaged or diseased heart. For example, the HeartMate® (Thermo Cardiosystems, Inc., Woburn, Mass.) is a pneumatically powered device that is implanted in the left upper quadrant of the abdomen. A pneumatic air hose exits from the lower half of the abdominal wall and is attached to a pneumatic power unit. Blood from the cannulated left ventricular apex empties into a pump, at which point an external control system triggers pumping. The blood chamber is pressurized by a pusher plate forcing a flexible plastic diaphragm upward. This motion propels the blood through an outflow conduit grafted into the aorta, the main artery supplying the body with blood. This device is unique in that the textured, blood-containing surface promotes the formation
Grandia Lonn
Korakianitis Theodosios
Blackwell Sanders Paper Martin LLP
Jastrzab Jeffrey R.
LTK Enterprises, L.L.C.
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