Surgery – Cardiac augmentation – With condition responsive means
Reexamination Certificate
2001-05-16
2003-01-28
Evanisko, George R. (Department: 3762)
Surgery
Cardiac augmentation
With condition responsive means
C600S016000, C623S003280
Reexamination Certificate
active
06511413
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a ventricular-assist method and apparatus and, more particularly, to a ventricular-assist device (VAD, which utilizes only a single cannula and can assist both the acute and chronic failing heart. The device can be used as bridge to recovery of the failing heart, as a permanent implanted assist device or as a bridge to transplantation or as a bridge to other Cardiac Assist Devices. The invention also relates to a method of sustaining the failing heart utilizing a ventricular-assist device and an algorithm for operating a ventricular-assist device.
BACKGROUND OF THE INVENTION
The normal range of cardiac output, normalized to total body surface, is wide, 2.5 to 3.8 liter per minute per one square meter (1/min/m
2
). In general, cardiac assist is necessary whenever a patient's cardiac output drops below the adequate blood supply needed to sustain proper blood perfusion, which is around 2 1/min/m
2
. Failure of the cardiac ventricle to contract and to eject the blood out of the ventricle and thereby to supply adequate flow is defined as“systolic failure”. However, more than 50% of the patients over 60 display inadequate ventricle filling and tissue congestion, which is defined as “diastolic failure”. Cardiac assist is used to treat patients suffering from heart failure at a stage where conventional drug therapy proves ineffective.
Cardiovascular diseases (CVD) represent the leading cause of death in the industrialized world. CVD claimed 960,592 lives in the US in 1995 (41.5% of all deaths for that year).
Congestive Heart Failure (CHF) is a chronic disorder that develops over time, manifested clinically by an enlarged heart and symptoms and signs of low cardiac output and tissue congestion. The low cardiac output leads to decreased blood perfusion to vital organs (liver, kidney and brain). The CHF is also characterized by lung congestion (recurrent pulmonary edema), which threatens life and requires frequent hospitalization. CHF is associated with profound symptoms that limit daily activities, is a debilitating disease with poor quality of life. CHF is the most common cause of hospitalization of patients over 60 years of age.
According to the US National Heart Lung and Blood Institute (NHLBI) and the American Heart Association there are approximately 5 million patients who suffer from Congestive Heart Failure (CHF) in the US and between 400,000 and 500,000 newly diagnosed patients each year. Long-term survival rates are low and the 5 year mortality rate for patients with CHF is 75% in men and 62% in women, while in patients with decompensated heart failure the mortality rate is 60% per year.
CHF has various etiologies, including cardiovascular disease (diseases which affect blood flow to the myocardium), chronic hypertension (high blood pressure), incompetent valves, inflammation of the heart muscle or the valves, substance (amyloid) accumulation and congenital heart problems.
Patients suffering from Congestive Heart Failure (CHF) are initially treated with medication. While conventional drug therapy may delay the progress of CHF, it is not curative. Cardiologic intervention (such as Angioplasty and Stenting), surgery (Heart by-pass surgery, Cardiomyoplasty, Partial Ventriculectomy known as Batista's procedure), and mechanical devices are often considered when drug therapies prove ineffective or inadequate. Electrical disturbances of the heart that threaten or impair the quality of the patient's life have been treated effectively with pacemakers and implantable defibrillators. However, congestive heart failure has not been addressed effectively. Currently, the only available method of treating end-stage CHF is a heart transplant.
The demand for temporary and permanent cardiac-assist devices for the treatment of chronic heart failure is remarkably large; in 1993 between 40,000 to 70,000 patients needed life-sustaining assist devices or a total artificial heart, and an additional 80,000 to 200,00 patients needed quality of life improvements by surgery (Cardiomyoplasty or Heart Booster).
Ventricular-assist devices are needed for:
1. Bridge-to Transplantation—patients awaiting heart transplants and who are not scheduled and when the heart failure is unresponsive to medical treatment.
2. Bridge-to-Recovery—cardiac assist for patients whose heart has sustained serious injury, but can recover if adequately supported. This includes the use of a cardiac-assist device after open heart surgery in order to provide support until the heart regains its ability to pump, and severe myocardial infarction refractory to conventional treatment with medication. Temporary cardiac support is intended primarily to:
a) Prevent or reduce damage to vital organs (brain, kidneys) from cardiac failure and to support adequate blood circulation.
b) Allow the failing heart to recover, i.e. to provide adequate coronary perfusion to the heart itself.
c) Reduce the energy consumption of the failing heart and to improve the balance between energy supply and demands.
3. Permanent support for the failing heart, for patients that are not candidates for heart transplantation.
Existing temporary mechanical cardiac devices are divided into three groups:
1. Temporary cardiac assist for several hours, as the intra-aortic balloon that is frequently utilized for patients with heart failure after open-heart surgery, due to failure to wean from the cardiopulmonary bypass.
2. Long-term (days, weeks, months) Ventricular Assist Device (VAD), as a bridge to heart transplantation or a bridge to recovery.
3. Permanent support by permanent VAD or by Total Artificial Heart (TAH).
Intra Aortic Balloon Pump (IABP). The IABP has been in clinical use for over 30 years. The IABP consists of a balloon (30-50 ml) that is inserted into the descending aorta and is inflated during the diastole and deflated during the systole. The IABP increases the cardiac output by less than 0.5 1/min/m
2
. Consequently, although it was designed to assist a failing heart by improving blood perfusion, it requires a certain threshold level of cardiac output and cannot take over the pumping function of the heart. As a result, it can only be utilized in treatment of patients who require mild levels of mechanical assistance (unless there is a supplemental assisting heart device).
The main advantages of the IABP are that it increases the coronary flow and decreases the afterload (the work against which the ventricle works). Hence the device improves the energy supply to the myocard, reduces the energy consumption and allows the heart to recover. However, the IABP is used only for short-term circulatory assist due to high risk of severe thromboembolic complications.
Ventricular Assist Devices (VAD)—VADs take over the complete pumping function of one or both sides of a failing heart. They unload the assisted ventricle. Left Ventricular Assist Devices have been approved for use by the FDA as bridge-to-heart transplantation, to keep alive those awaiting a donor heart. These devices have also been approved by the FDA for use by patients whose hearts are in failure but may be able to recover by reducing the myocardial work (unloading), including patients in postsurgical life-threatening heart failure.
More than a dozen companies are developing devices, ranging from left-ventricular assist products to total artificial hearts, that offer CHF patients either longer-term support with an alleviation of symptoms, and/or an alternative to heart transplant. Some of these (Thermo CardioSystems, Thortec, Abiomed and Baxter Healthcare) have ventricular assist products on the U.S. market. Ventricular-assist devices are generally employed on a temporary basis, with treatment periods ranging from a few hours to a few weeks, or at most, a limited number of months. However, some devices have been designed for long-term use and can be considered lifetime support systems. However, to date, such lifetime support is still in developmental and experimental stages and has not been approved by the FDA.
The currently available a
Dubno Herbert
Evanisko George R.
Khan Omar
Levram Medical Devices, Ltd.
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