Extent of ischemic stimulus and plasma β-endorphin levels in silent myocardial ischemia

Abstract

Background β-Endorphin has been reported to play a role in the mechanism of silent myocardial ischemia. Objectives Plasma β-endorphin levels during coronary angioplasty–induced silent and symptomatic myocardial ischemia were compared with those during exercise-induced silent ischemia. Methods and Results The study population consisted of 40 nondiabetic patients with angioplasty-indicated coronary artery disease. All patients underwent exercise treadmill testing 2 to 4 days before angioplasty. Patients were divided into three groups: group 1, 10 patients with silent ischemia during exercise and angioplasty; group 2, 15 patients with silent ischemia during exercise and symptomatic ischemia during angioplasty; and group 3, 15 patients with symptomatic ischemia during both exercise and angioplasty. In group 1, plasma β-endorphin levels during balloon inflation were significantly higher than in groups 2 and 3 and also significantly higher than during exercise. In group 2, plasma β-endorphin levels were significantly elevated at exercise-induced silent myocardial ischemia and balloon-induced symptomatic myocardial ischemia, but the levels between exercise and balloon inflation were not significantly different. Conclusions For "silent" myocardial ischemia, it may be necessary for β-endorphin levels to increase to sufficiently high levels to suppress anginal symptoms in response to the degree of ischemic stimuli. (Am Heart J 1998;135:813-8.)