Surgery – Cardiac augmentation – With condition responsive means
Reexamination Certificate
2000-07-18
2002-09-24
Bockelman, Mark (Department: 3762)
Surgery
Cardiac augmentation
With condition responsive means
C604S006110, C604S006140, C604S006130
Reexamination Certificate
active
06454697
ABSTRACT:
BACKGROUND
It is well known that if the blood supply to the heart is significantly compromised and the demand of the heart for blood supply remains unchanged or increases (so called supply demand mismatch), the muscle of the heart will be irreversibly damaged in a few minutes to a few hours, depending on the severity of the mismatch and other factors. This time limit of the survival of the heart in this condition—only minutes to hours—presents a major challenge to physicians and exposes patients to high mortality and morbidity during myocardial infarction (heart attack). Patients may not be able to survive the heart attack or, if they do, they may develop severe heart failure due to extensive injury to the heart. This imposes a huge social and financial burden on society.
In most situations, blood supply to the heart can not be improved immediately and, if the demand of the heart for blood supply can be decreased significantly, the heart may survive this insult much longer pending further treatment and may gain enough time to recover from the insult. This is conventionally accomplished in part by keeping the patient at rest, including the use of sedatives if necessary. Also, the patient is typically given supplemental oxygen to make enhanced use of the available cardiovascular function.
The heart works as a pump to maintain blood circulation. The function of circulation is to maintain blood pressure at a certain level to provide perfusion to the organs of the body. All the prior art inventions available to artificially support circulation are designed as left ventricular supportive devices with an assumption that the heart will continue to play a central role in maintaining blood circulation. They are designed to assist the heart when it can not work normally such as a left ventricular assistant device. Alternatively, the prior art devices are intended to replace the heart's function without considering coordination between the heart and the system, such as the cardiac-pulmonary bypass machine, which also requires a complicated procedure.
Previous inventions were designed to provide cardiac-pulmonary bypass as an assistance to the heart and allow the heart to work continuously even there is significant compromise of blood supply to the heart, or to replace the function of the heart when it fails to function. For example, U.S. Pat. No. 4,540,399 to Litzie discloses a cardiopulmonary bypass machine. It allows a physician to control the speed of the pump to maintain blood pressure at a certain level. U.S. Pat. No. 5,879,316 to Safar also discloses a cardiopulmonary bypass machine, which provides differential perfusion of different organs including the heart. It considers selective perfusion of the heart as a part of resuscitation and allows the heart to stop for one to two hours. However, it requires a complicated procedure.
A design of a pump was made public (Tokano H. et. al,
World J. Surgery
9:78-88, 1985), which has EKG gating and left arterial pressure feed back to control work load on the heart. The left arterial pressure is used to determine the work load on the heart and, therefore, to control pump activity for unloading volume from the left ventricle. It is also a left ventricular assistant device and allows the heart to continue to contract and to assume a central role in circulation.
A number of inventions have disclosed cardiopulmonary bypass machines for open-heart surgery. They require insertions of a catheter into the heart chambers and the great blood vessels surgically and extensive technical support.
SUMMARY OF THE INVENTION
If a machine can maintain blood pressure, a physician can put the heart into asystole, or near asystole, without significant compromise to the function of the organs. Patients can survive without the heart's functioning, and the heart survives until a definitive treatment takes place. The heart has enough time to recover from a transient myocardial insult.
The invention relates to a cardiac support system which can be used in conjunction with medication to render the heart in an asystolic or nearly asystolic status. It is a goal of the invention that the work load of the heart is minimized by coordination between the activities of the heart and of the system during induction and maintenance of the asystolic or nearly asystolic status and later the resumption of the normal activity of the heart.
Because the invention allows a physician to put an acutely diseased heart into an asystolic or nearly asystolic status, the physician has enough time to perform further diagnostic tests and therapeutic intervention, and to transfer the patient to a referral center for further treatment. The invention is designed with the concept that the heart needs to stop working if its blood supply is significantly compromised. It is also a consideration of the invention that the pump system disclosed herein is easy to use by most medical practitioners in most medical facilities throughout the world.
No previous invention has been designed with the concept of intentionally rendering the heart temporarily asystolic or nearly so in order to allow adequate time for the performance of diagnostic tests, therapeutic maneuvers, and recovery from the myocardial insult. To achieve this goal, the device and the heart need precisely coordinated activity. This may be achieved by a complex interaction between the electromechanical activity of the heart and the device. None of the prior art devices teaches adequate mechanisms for coordination between the heart and pump activity. It is important to have mechanisms of coordination between the cardiopulmonary pump and the heart when attempting purposeful induction and maintenance of an asystolic or nearly asystolic status.
For example, '399 does not take it into account that the heart needs to stop working. Neither '399 nor '316 teach intentional cessation of the heart as a primary treatment instead of as a resuscitation attempt or as a part of open heart surgery. Neither patent has a mechanism to sufficiently coordinate the contraction of the heart with the activity of the cardiopulmonary bypass machine, such as EKG gated pump activity with interaction between pressure control and EKG gating, although some of them did have EKG gated activity and pressure feedback. Although there are EKG gating and pressure control (only left atrial pressure feed back) devices known in the art, there is no interaction among EKG, arterial pressure, contraction of the heart and pump activity.
The invention provides a method of facilitating cardiac rest in a human comprising induction of a controlled asystolic state in the human and application of life support techniques while the human is in the asystolic state.
Typically, the induction includes administration of a medication or medications such as calcium channel blockers, beta adrengenic blockers, antiarrhythmics and potassium. These drugs are well known in the art. Examples of calcium channel blockers include verapamil and diltiazem. Examples of beta adrenergic blockers (or beta adrenergic receptor antagonists) include propranolol, esmolol and bretylium. Examples of antiarrhythmic agents include lidocaine, adenosine, procainamide and quinidine.
Some of the medications can be placed in more than one category. For instance, the beta blockers can be useful as antiarrhythmic agents. If potassium is used to slow or to stop the heart, intravenous potassium chloride is a preferred embodiment. For this purpose, the potassium is administered in a large vein or a central vein, such as the femoral, jugular or subclavian vein. Other drugs may be administered as is well known in the art. For example, pain killers and sedatives may be indicated. Examples include morphine, phenobarbital and diazepam.
Life support techniques of the invention include application of a closed extra-corporeal circulation system. Such a system typically includes a venous conduit, a gas exchanger, a pump for pumping at least a portion of the patient's blood, and an arterial conduit. Preferably, the arti
Bockelman Mark
Chan Albert Wai-Kit
Elkins Mark
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