Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-09-24
2002-01-15
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S425000, C600S436000, C600S365000, C600S476000, C600S479000, C600S450000, C600S449000
Reexamination Certificate
active
06339716
ABSTRACT:
BACKGROUND OF THE INVENTION
In patients with ischemic heart disease, regions of the heart may be poorly perfused, dysfunctional, but still viable. Myocardial ischemia limits blood flow and therefore the available supply of oxygen. This limited availability of oxygen affects oxidative metabolism, which ultimately negatively affects the production of adenosine triphosphate (ATP), essential for maintenance of contractility and cellular integrity. Varied states of ischemia exist. However, either transient or chronic ischemia may result in partial reduction of myocardial ATP with subsequent impairment of contractile function, but not cell death.
Various diagnostic methods have been developed to aid in determining whether areas of myocardium are “hibernating,” “stunned,” or are non-viable. Hibernating myocardium is generally considered to be myocardium that has modulated its function and therefore energy requirements in response to chronic poor perfusion. Stunned myocardium denotes an acute, transient episode of poor perfusion due to coronary vasospasm, coronary artery disease or other maladies. This determination of viable, though poorly functioning mycardium, versus non-viable myocardium is essential to first, identify and second, to predict eventual clinical outcome following a revascular intervention. One newly developed therapy where, the distinguishing of viable versus non-viable myocardium is crucial for an optimal outcome, is the partial left ventriculectomy or remodeling procedure of Batista (R. Batista, Eur. J. Cardiothoracic Surg., (1999) Suppl. 1, pp. 512. See particularly the discussion on pp. 539-43.)
End stage heart disease is often treated by transplantation of a healthy donor heart. Approximately 2500 patients were listed and waiting for heart transplant in the United States in 1996, with an additional 300 new listings each month. The availability of donor hearts is limited and typically, about 20% of those on the list die before a suitable heart is available. (Jessup, Mariell: Cardiol. Rev. (1996) 4:5, 286-191.) The usual criteria for selection to this waiting list covers a wide spectrum of patients, from those in extremely critical condition, close to death, to others who could be well sustained on aggressive drug therapy for a time period, with potential improvement in cardiac status, if a more accurate assessment of vitality were possible. Clearly, the recipient evaluation process would benefit from the application of objective, quantifiable criteria needed for estimating either success of transplant or the determinants of survival without transplant.
Many techniques have been developed to measure blood flow and cardiac function in the various segments of the heart. Bax et al. published a review of currently available techniques, which include positron emission tomography with fluorine-18 fluorodeoxyglucose, thallium (T1)-201 stress- redistribution-reinjection, T1-201 rest-distribution, single photon emission tomography with technetium-99 m and low dose dobutamine echocardiography. (Bax et al J. Am. Coll. Cardiol. (1997) 30:1451-1460.)
Positron emission tomography (PET) scans have been considered to be the gold standard as a tool of diagnostic cardiology, however, newer computer-based techniques for acquisition and display of echocardiograms have generated increasing interest in the method for assessing the condition of the myocardium (Sawada et al. (1991) Circulation, 83: 1605-1614.) Measurement of ventricular wall thickness, segmental wall movement, ejection fraction and volume have been correlated with myocardial function. During echocardiography, a radar signal is sent through an esophageal or transthoracic probe, into the chest, and picked up by a monitor. A dobutamine infusion uncovers areas of reduced perfusion that were not apparent prior to using dobutamine. Studies have shown that segmental wall motion abnormalities can correlate with the distribution of at least one significantly diseased vessel in 93% of the patients with multivessel or main vessel disease.
The need remains for an improved method for distinguishing viable from non-viable myocardium as a diagnostic tool and for decision-making in subsequent therapy.
BRIEF SUMMARY OF THE INVENTION
It has been investigated and is here disclosed that the beneficial effects of D-ribose on ATP levels, in the presence of a vasodilator and/or inotropic agent, improves the identification of viable versus non-viable myocardium in patients with cardiovascular disease. The effect of D-Ribose on wall motion seen on echocardiography examination was studied in various populations suspected of having stunned or hibernating myocardium.
This invention provides an improved method to diagnose viability of myocardial segments which have the potential for functional recovery after revascularization. This invention further provides D-Ribose alone or preferably in combination with vasodilators and/or inotropic agents to increase the sensitivity of detection of viable, stunned or hibernating tissue.
DETAILED DESCRIPTION OF THE INVENTION
Myocardial hibernation and stunning define conditions in which tissue viability may be present but is hindered in the presence of reduced regional or global blood flow. The phenomenon of hibernating and stunned myocardium has been the subject of increasing interest with recognition that function may improve in these regions after restoration of adequate blood supply or treatment with newly available therapies such as the Batista procedure, in which the diastolic volume of the ventricle is surgically reduced by removal of non-viable or poorly viable tissue. The resulting ejection efficiency of the ventricle is improved with the patient usually experiencing a clinical benefit.
Among the techniques used to distinguish non-viable from viable myocardium, echocardiography is commonly used because of its direct measurement of contractile function, which is thought to be a better predictive indicium than blood-flow tracing with radionuclides. However, the sensitivity of this method, as with other methods such as thallium imaging and PET scan, may be limited in the presence of severe coronary artery disease (CAD). It has been previously found that the use of low dose dobutamine enhances the diagnosis of viable myocardium (Sawada et al, 1991). It has also been previously found that D-Ribose improves thallium imaging. (Angello et al, (1989) Am. J. Ar. Imag. 3:256-265.) It has now been discovered that the diagnosis is further enhanced by the combination of a vasodilator, inotropic agent and D-Ribose, leading to a more optimal clinical outcome.
Coronary artery bypass grafting (CABG) has become a routine procedure. During this procedure, blood flow is restored to regions of the heart served by stenotic coronary arteries. Identification of those areas that are hibernating or stunned rather than non-viable aids the surgeon in revascularizing those regions that are most capable of being revived and improved with reperfusion.
Once viability has been determined, various methods of revascularization may be considered by the medical personnel and offered to the patient. Ischemia may be viewed in the disease state as either acute or chronic, and decisions made according to the following Table:
TABLE I
Choice of Therapy for Coronary Artery Disease
ACUTE ISCHEMIA
(myocardial infarction or
CHRONIC ISCHEMIA
coronary arteriospasm)
(coronary artery occlusion)
CABG
CABG
coronary balloon angioplasty
coronary balloon angioplasty
coronary artery atherectomy
coronary artery atherectomy
transmyocardial revascularization
heart transplant
Each treatment carries its own risks and benefits. For example, angioplasty has a lower rate of long-term success than CABG due to the tendency of the vessel to reocclude ( “restenosis”), but because it is a simpler procedure with lower risks, it will be often indicated as a first course of action, when the patient has an amenable lesion. However, not all patients carry the same preoperative risk for each procedure. If the heart contains large areas of non-viable tissue with severely decrease
Cyr John St.
Johnson Clarence A.
Sawada Stephen G.
Bioenergy Inc.
James Talaya
Lateef Marvin M.
Schwegman Lundberg Woessner & Kluth P.A.
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