Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-12-22
2003-05-13
Wolfe, Willis R. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S129000
Reexamination Certificate
active
06564094
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a device and method for treating heart disease. More particularly, the present invention is directed to a method and device for treating congestive heart disease, intraventricular conductance delays, and related valvular dysfunction.
2. Description of the Prior Art
Congestive heart disease is a progressive and debilitating illness. The disease is characterized by a progressive enlargement of the heart.
As the heart enlarges, the heart is performing an increasing amount of work in order to pump blood each heart beat. In time, the heart becomes so enlarged the heart cannot adequately supply blood. An afflicted patient is fatigued, unable to perform even simple exerting tasks and experiences pain and discomfort. Further, as the heart enlarges, the internal heart valves cannot adequately close. This impairs the function of the valves and further reduces the heart's ability to supply blood.
Patients suffering from congestive heart disease are commonly grouped into four classes (i.e., Classes I, II, III and IV). In the early stages (e.g., Classes I and II), drug therapy is the commonly proscribed treatment. The only permanent treatment for congestive heart disease is heart transplant. To qualify, a patient must be in the later stage of the disease (e.g., Classes III and IV with Class IV patients given priority for transplant). Unfortunately, not enough hearts are available for transplant to meet the needs of congestive heart disease patients.
Not surprising, substantial effort has been made to find alternative treatments for congestive heart disease. Recently, a new surgical procedure has been developed. Referred to as the Batista procedure, the surgical technique includes dissecting and removing portions of the heart in order to reduce heart volume. This is a radical new and experimental procedure subject to substantial controversy. Furthermore, the procedure is highly invasive, risky and expensive and commonly includes other expensive procedures (such as a concurrent heart valve replacement). Also, the treatment is limited to Class IV patients and, accordingly, provides no hope to patients facing ineffective drug treatment prior to Class IV. Finally, if the procedure fails, emergency heart transplant is the only available option.
Cardiomyoplasty is a recently developed treatment for earlier stage congestive heart disease (e.g., as early as Class III dilated cardiomyopathy). In this procedure, the latissimus dorsi muscle (taken from the patient's shoulder) is wrapped around the heart and chronically paced synchronously with ventricular systole. Pacing of the muscle results in muscle contraction to assist the contraction of the heart during systole.
While cardiomyoplasty has resulted in symptomatic improvement, the nature of the improvement is not understood. For example, one study has suggested the benefits of cardiomyoplasty are derived less from active systolic assist than from remodeling, perhaps because of an external elastic constraint. The study suggests an elastic constraint (i.e., a non-stimulated muscle wrap or an artificial elastic sock placed around the heart) could provide similar benefits. Kass et al.,
Reverse Remodeling From Cardiomyoplasty In Human Heart Failure: External Constraint Versus Active Assist,
91
Circulation
2314-2318 (1995).
Even though cardiomyoplasty has demonstrated symptomatic improvement, studies suggest the procedure only minimally improves cardiac performance. The procedure is highly invasive requiring harvesting a patient's muscle and an open chest approach (i.e., sternotomy) to access the heart. Furthermore, the procedure is expensive—especially those using a paced muscle. Such procedures require costly implantable sources. The cardiomyoplasty procedure is complicated. For example, it is difficult to adequately wrap the muscle around the heart with a satisfactory fit. Also, if adequate blood flow is not maintained to the wrapped muscle, the muscle may necrose. The muscle may stretch after wrapping reducing its constraining benefits and is generally not susceptible to post-operative adjustment. Finally, the muscle may fibrose and adhere to the heart causing undesirable constraint on the contraction of the heart during systole.
In addition to cardiomyoplasty, mechanical assist devices have been developed as intermediate procedures for treating congestive heart disease. Such devices include left ventricular assist devices (“LVAD”) and total artificial hearts (“TAH”). An LVAD includes a mechanical pump for urging blood flow from the left ventricle and into the aorta. An example of such is shown in U.S. Pat. No. 4,995,857 to Arnold dated Feb. 26, 1991. LVAD surgeries are still in U.S. clinical trials and not generally available. Such surgeries are expensive. The devices are at risk of mechanical failure and frequently require external power supplies. TAH devices, such as the celebrated Jarvik heart, are used as temporary measures while a patient awaits a donor heart for transplant.
Other attempts at cardiac assist devices are found in U.S. Pat. No. 4,957,477 to Lundbäck dated Sep. 18, 1990, U.S. Pat. No. 5,131,905 to Grooters dated Jul. 21, 1992 and U.S. Pat. No. 5,256,132 to Snyders dated Oct. 26, 1993. Both of the Grooters and Snyders patents teach cardiac assist devices which pump fluid into chambers opposing the heart to assist systolic contractions of the heart. The Lundbäck patent teaches a double-walled jacket surrounding the heart. A fluid fills a chamber between the walls of the jacket. The inner wall is positioned against the heart and is pliable to move with the heart. Movement of the heart during beating displaces fluid within the jacket chamber.
Additionally, cardiac failure patients may suffer from long intraventricular conduction delays. Generally, such delays result in a slow uncoordinated contraction, resulting in poor ejection of blood from the ventricle. Inefficient ejection can lead to poor cardiac output and an increased end-diastolic volume. Increased end-diastolic volume can result in increased ventricular wall stress and stretching of the myocardium. This, in turn, may stimulate ventricular dilation and ventricular remodeling, starting a progressive heart failure spiral.
Pacing systems that stimulate heart muscle contraction with precisely timed discharges of electricity are available. Pacing has been used to resynchronize ventricular contraction, thereby increasing the efficiency of ventricular contraction, reducing end-diastolic volume and slowing the heart failure progression.
Pacing systems that pace the right ventricle (RV) and the left ventricle (LV) simultaneously via a transvenous lead introduced through the cardiac veins are available. Additionally, a left ventricular epicardial lead combined with a right ventricular lead has been used for biventricular pacing. However, when only a single point on the left ventricle is paced, delayed conduction in the left ventricle may result in a poorly synchronized contraction (i.e., part of the ventricle contracts while other portions are not contracting). This can result in a dyskinetic bulging in the non-contracting section.
Thus, selection of the left ventricular stimulation site is critical in achieving good clinical outcomes. Ideally several points on the left ventricular wall are paced to assure the most coordinated contraction. However, pacing from various or multiple sites on the left ventricle is difficult. Positioning one transvenous lead through the cardiac veins is difficult, much less positioning multiple leads. Additionally, current epicardial electrodes are screwed or sewn into or onto the epicardium. This may cause damage to the heart or create chronic exit block (high pacing energy required to simulate through the resultant scar tissue, ultimately energy greater than implantable source can apply so no stimulation occurs), particularly if multiple epicardial electrodes are used.
Commonly assigned U.S. Pat. No. 5,702,343 to Alferness dated Dec. 30, 1997 teaches
Alferness Clif
Girard Michael
Shapland J. Edward
Acorn Cardiovascular Inc.
Wolfe Willis R.
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