Surgery – Cardiac augmentation – Aortic balloon pumping
Reexamination Certificate
1999-02-05
2001-05-08
Schaetzle, Kennedy (Department: 3762)
Surgery
Cardiac augmentation
Aortic balloon pumping
C623S003100
Reexamination Certificate
active
06228018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a left ventricular assist device, and in particular to an apparatus and method for supporting the blood circulation when the heart is severely injured and is unable to maintain a systemic arterial pressure adequate to support the inside walls of patient's aorta. Still more particularly, the present invention relates to an apparatus and method for supporting and expanding the walls of the aorta from collapse during operation of the device, which might otherwise occur due to extremely low blood pressure and for providing diastole/systole-like cardiac function in a patient with a severely diseased or injured heart.
2. Description of the Prior Art
In the United States alone, 60,340,000 people have cardiovascular disease. Of these, over 2,000,000 have congestive heart failure, with more than 500,000 new cases diagnosed each year. In 1995, only 2,359 patients received heart transplants, the most permanent of treatments to date, while 770 patients who qualified for heart transplant died waiting. About 450,000 patients undergo open-heart surgery each year, and 2% of these cases require mechanical cardiac support after surgery at a cost of about $400,000 per survivor.
There are many different causes of heart failure, the most common of which are (1) acute myocardial infarction; (2) cardiomyopathy; (3) cardiac valvular dysfunction; (4) extensive cardiac surgery; and (5) uncontrolled cardiac arrhythmias. Heart failure, especially resulting from disease or damage to the left ventricle of the heart, can result in many problems.
Problems arising from left ventricle disfunction are particularly troublesome since the heart itself, as well as the rest of the body, depends on left ventricle function for oxygenated blood to maintain aerobic respiration. Heart failure results in ineffective emptying of the failing left ventricle during systole, which can result in (1) decreased cardiac output; and (2) elevated left atrial and pulmonary venous pressures, which cause pulmonary congestion and edema. Pulmonary congestion and edema, or tissue swelling, prevent effective oxygenation of the arterial blood, and coupled with reduced cardiac output, and can lead to tissue hypoxia. In the final stage of congestive heart failure, a vicious cycle leads to progressive systemic hypotension (low blood pressure), hypoxemia (oxygen depletion), tissue anoxia, further depression of cardiac function and cardiac arrhythmias, and ultimately, death.
Left ventricular assist devices (LVAD) are an alternative treatment for heart failure to transplantation or medical therapy. Patrick M. McCarthy et al., Cardiopulmonary Support and Physiology, 115 J. Thoracic Cardiovascular Surgery 904 (1998). LVADs that are presently available in clinical settings or being developed are of several types: (1) the heart-lung machine, providing cardiopulmonary bypass; (2) intra-aortic balloon pumps (IABP), which reduce resistance to left ventricular ejection and augment diastolic pressure; (3) pumps positioned in parallel with the left ventricle; and (4) complete artificial hearts. Of these, only the IABP devices can be implemented without surgically opening the chest and operating on the heart and/or major blood vessels. Further, after improvement of left ventricular function, only the IABP devices can be removed without opening the chest and operating on heart and blood vessels. Thus, this device has become, by far, the most commonly utilized LVAD. However, the application of present IABP devices is limited to less severecases, since the IABP can function effectively only if the left ventricle is able to eject an adequate output to maintain a mean systemic arterial pressure greater than 60 mmHg. This greatly limits the practical use of present IABPs.
When the heart is injured to the point that mean systemic arterial pressure is less than 60 mmHg, the aorta will collapse during the deflation phase of present IABPs. There are no prior art devices that can be used to support the walls of the aorta so that the IABP can effectively assist heart function. Some stent devices have been used to mechanically support smaller arteries, especially the coronary arteries. But these devices are permanently placed within smaller arteries, and are not designed to be used in conjunction with other devices placed within the artery that assist in increasing systemic arterial blood pressure. There is yet a need for a device that can be used to support the aorta, can be used in conjunction with IAPBs, and is removable. With such a device, blood can be sucked from the defective left ventricle and then pumped to the systemic circulation, essentially replacing the function of a severely injured heart.
Therefore, the present invention is directed towards a LVAD device that can act as a temporary replacement for the function of the left ventricle in a patient whose heart is severely diseased or injured and is unable to maintain a systemic arterial pressure adequate to support the aorta, as required for effective operation of present IABPs.
SUMMARY OF THE INVENTION
It is therefore one object of the present invention to provide an apparatus and method for temporarily replacing the function of the left ventricle in a patient who is suffering severe heart disease or trauma.
It is another object of the present invention to provide an apparatus and method for temporarily providing support to the inside aortic walls of a patient who is suffering from severe heart disease or trauma, such that the left ventricle is unable to maintain enough systemic arterial pressure to prevent the collapse of the walls of the aorta during use of an IABP.
Another object of the present invention is to expand the walls of the aorta during the ejection phase of the left ventricle, so as to enhance ejection of blood from the left ventricle into the aorta. This expansion of the aorta is synchronized with inflation of blocking balloons to prevent reflux of blood from arteries of the aortic arch and from the distal aorta and is also synchronized with deflation of a pumping balloon or blood flow control means positioned in the descending aorta.
It is another object of the present invention to provide an apparatus and method for creating an intermittent elevation of aortic blood pressure, so as to perfuse the systemic circulation with oxygenated blood in a patient who has suffered severe heart disease or trauma such that the left ventricle is not functioning or is functioning only minimally.
It is another object of the present invention to provide an apparatus and method for blocking the flow of blood to the aortic arch arteries during left ventricle systole and concomitant deflation of the device's pumping balloon, so that backflow of oxygenated blood from the aortic arch and from the distal aorta will not reduce the efficiency of the pumping-function of the device.
It is another object of the present invention to provide a cost-effective and easily operated LVAD and aortic support and expansion capabilities that can be placed within the aorta of a patient by insertion through a femoral artery, as would be accomplished with a typical intra-aortic catheter.
The foregoing objects are achieved through a ventricular assist device with aortic supporting and expanding capability and method comprising a removable, pressurizable support means positionable within the aorta of a patient, the pressurizable support means having an external profile which is expandable to fit firmly against the inside wall of the aorta of a patient and to intermittently expand the aorta during the ejection phase of the left ventricle. The external profile also presents a central opening that allows blood to flow through the aorta while a pumping balloon and distal blocking balloon are deflated. A pressure control port is coupled to the removable pressurizable support means which carries the pressurization gas from a pressurization control means external to the patient.
Other devices are placed within the central opening of th
Bian Xiaoming
Downey H. Fred
Gunter, Jr. Charles D.
My-Tech, Inc.
Schaetzle Kennedy
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