Treatment of Inoperable Coronary Disease and Refractory Angina: Spinal Stimulators, Epidurals, Gene Therapy, Transmyocardial Laser, and Counterpulsation

Abstract

Intractable angina from refractory coronary disease is a severe form of myocardial ischemia for which revascularization provides no prognostic benefit. Inoperable coronary disease is also accompanied by a “vicious cycle” of myocardial dystrophy from a chronic alteration of the cardiac sympathetic tone and sensitization of damaged cardiac tissues. Several adjunctive treatments have demonstrated efficacy when revascularization is either unsuccessful or contraindicated. Spinal cord stimulation modifies the neurologic input and output of the heart by delivering a very low dose of electrical current to the dorsal columns of the high thoracic spinal cord. Neural fibers then release CGRP and other endogenous peptides to the coronary circulation reducing myocardial oxygen demand and enhancing vasodilation of collaterals to improve the myocardial blood flow of the most diseased regions of the heart. Randomized study has shown the survival data at five years is comparable to bypass for high-risk patients. Transmyocardial laser revascularization creates small channels into ischemic myocardium in an effort to enhance flow though studies have shown no improvement in prognosis over medical therapy alone. Enhanced external counterpulsation uses noninvasive pneumatic compression of the legs to improve diastolic filling of the coronary vessels and promote development of collateral flow. The compressor regimen requires thirty-five hours of therapy over a seven-week treatment period. Therapeutic angiogenesis requires injection of cytokines to promote neovascularization and improve myocardial perfusion into the regions affected by chronic ischemia. Phase 3 trials are pending. High thoracic epidural blockade produces a rapid and potent sympatholysis, coronary vasodilation and reduced myocardial oxygen demand in refractory coronary disease. This technique can be used as an adjunct to bypass surgery or medical therapy in chronic or acute unstable angina. Epidurals are easy to perform and often available for outpatient or inpatient use. The rapid anti-ischemic effect may complement therapeutic angiogenesis or other interventions with delayed onset to clinical benefit. A new era for interventional and implant cardiology is beginning to emerge as more clinicians, including cardiologists, gradually learn new procedures to safely provide more therapeutic options for patients suffering refractory angina.