Surgery: kinesitherapy – Kinesitherapy – Exercising appliance
Reexamination Certificate
2001-01-29
2004-06-22
DeMille, Danton D. (Department: 3764)
Surgery: kinesitherapy
Kinesitherapy
Exercising appliance
Reexamination Certificate
active
06752771
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the medical field of cardiopulmonary assist treatment, and especially to cardiac assist methods using external body compression to improve the vascular blood flow and pressure in patients with weak or deteriorating hearts.
BACKGROUND OF THE INVENTION
I. Heart Failure—Need for Circulatory Assist
There is a need for medical equipment and methods for treatments that assist a beating heart of a patient suffering from heart disease or other weakened heart condition. When a heart becomes diseased or weak, the heart muscle deteriorates. The weakened heart muscle strains to pump sufficient amounts of blood through the patient's vascular system. The strain placed on the already-weak heart can lead to further deterioration and weakening of the heart. Treatments that assist a weakened heart to pump blood can be therapeutic by relieving some of the strain on a laboring, weakened heart.
The heart functions as two pumps in series. The right ventricle forces blood through the lungs into the left ventricle, and the left ventricle forces blood through the systemic circulation into the right ventricle. Small, but significant contributions to blood flow are also made by the skeletal muscle pump and the respiratory pump. In addition, the major periods of the cardiac cycle are diastole, during which the ventricles fill, and systole during which the ventricles eject blood.
To meet the demand for blood in a patient's vascular system, a weak heart increases its beat rate and devotes an increasing portion of its time and energy to pumping blood. The weak heart attempts to compensate for its weakness by working harder to pump blood through the vascular system. The straining heart diverts its time and energy away from sustaining itself with blood. In particular, the heart cuts short its rest stages during which blood normally flows into the heart muscle through the coronary arteries. When the rest stages become too short, the heart does not receive enough blood to sustain its already-weakened condition. By depriving itself of adequate amounts of blood, the heart contributes to its own deterioration. Accordingly, a weakened heart may deteriorate in a perilous cycle that increasingly strains the heart to pump blood and further reduces the blood supplied to the heart itself This cycle can result in rapid heart deterioration (within a few hours or days) that leads to the irreversible failure of vital organs including the heart itself and possibly death.
A method to treat heart disease and other conditions in which a beating heart is weakened or over-strained is to assist the heart in pumping blood to the vascular system of the patient. By assisting the flow of blood, the strain (also referred to as load) on the heart can be artificially reduced.
The heart ejects blood from its left ventricular LV chamber into the aorta which leads to the vascular system. The “load” on the heart is the power required by the heart to eject blood from the LV chamber and aorta. Cardiac assist treatments reduce the load on the heart. When a weakened heart ejects blood against a reduced load, the heart can successfully evacuate more blood from the LV chamber and heart than would be evacuated without an assist volume. During each heart ‘stroke’ the heart ejects more blood which leads to the increase of total blood flow, i.e., cardiac output, from the heart and through the vascular system.
In addition, by reducing some of the pumping load, the heart can devote more of its resources and time to providing blood to its own coronary arteries. Coronary arteries stem from the segment of the aorta that is closest to the heart and provide blood to the heart muscle. When the coronary arteries and muscle have sufficient blood flow, the heart has the ability to heal itself.
The heart often is prevented from healing itself when caught in the dangerous cycle of ever deteriorating and increasing strain. A cardiac assist treatment breaks this cycle by relieving the heart of some of its strain and reducing the load on the heart. Cardiac assist can treat a heart condition by relieving the load on the heart and allowing the heart to heal itself. Even if the heart is unable to heal itself, cardiac assist is beneficial because it prevents further deterioration and total heart failure, e.g., heart stoppage, until some other treatment, such as heart surgery, can be applied.
II. Existing Methods for Cardiac Assist
Ventricular Assistance has been attempted and, in some cases, accomplished by the following methods set forth in TABLE A:
TABLE A
Intra-aortic balloon Pump (IABP)
Heart bypass (Left Ventricular Assist Devices - LVAD and Right
Ventricular Assist Devices RVAD)
External upper body compression.
Cardiopulmonary bypass also known as heart-lung machine
Veno-arterial and Veno-venous bypass.
External Leg Counterpulsation.
Direct Mechanical Pressure on Heart.
Of all the methods listed in Table A, IABP is the method most commonly used as a clinical treatment. IABP counterpulsation is a method of providing temporary circulatory assistance to a failing and/or ischemic heart by providing reduced afterload and increased coronary perfusion pressure. In IABP, a balloon catheter is routed through the femoral artery, and positioned in the descending thoracic aorta with the tip of the catheter below the branches of the arteries that feed the heart (coronary) and brain (carotid).
The IABP device is synchronized with an ECG or arterial pulse tracing so that the balloon is rapidly inflated with an inert gas (helium) during the diastole phase of the heart cycle, and is rapidly deflated just before the onset of systole phase. The inflation of the balloon during diastole elevates the blood pressure in the aorta and drives blood into the heart muscle via the coronary arteries. As the balloon is rapidly deflated during systole, a low pressure zone is generated in the aorta. The aorta is, in effect, a large elastic vessel that stores a relatively large volume of oxygenated arterial blood between heartbeats. The elastic aorta expands, during each heart cycle, to accommodate the added volume of blood called ‘stroke volume’ ejected from the left ventricle and stored between heartbeats. The elasticity of the aorta resists expansion and, thus, the increased volume of blood pumped from the left ventricle. The resistance from the aorta is in proportion to the initial volume of the aorta, to which the ‘stroke volume’ is added. The power applied by the left ventricle as it ejects blood is, in part, used to overcome the elastic resistance of the aorta and to push out the stroke volume of blood left in the aorta from the prior heartbeat cycle.
The balloon catheter used with IABP assists the heart by relieving the heart of some of the work of moving the stroke volume of blood out of the aorta to receive a new stroke volume. IABP displaces some of the volume of blood in the aorta by inflating the balloon with compressed gas to displace the stroke volume blood. By collapsing the balloon just before the left ventricle starts to eject blood, IABP creates a ‘void’ in the aorta, which void is, at least partially, retained as a new stroke volume of blood is ejected from the left ventricle into the void left in the aorta. The void formed in the aorta by IABP reduces the tension of aortic walls and assists the left ventricle in its effort to eject blood by reducing the elastic resistance from the aorta to the stroke volume.
IABP has difficulty keeping up with the rapid heart rates associated with heart failure. When the cardiac cycle is shortened, the duration of diastole is reduced dramatically. The best modem IABP are believed to inflate the balloon in 120 ms minimum and deflate it in another 120 ms. These inflation and deflation rates are too slow to provide effective cardiac assist during each heartbeat cycle at high heart rates. IABP techniques may skip the inflation of the balloons during some heartbeats to facilitate synchronization with the heart cycle.
Other disadvantages of IABP balloon catheters are that they are inv
Burkhoff Daniel
Gelfand Mark
Rothman Neil S.
Weisfeldt Myron L.
Crockett & Crockett
Crockett, Esq. K. David
DeMille Danton D.
Revivant Corporation
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