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Extent of ischemic stimulus and plasma beta-endorphin levels in silent myocardial ischemia
1First Department of Internal Medicine, National Defense Medical College, Saitama, Japan.
Background:
Beta-endorphin has been reported to play a role in the mechanism of silent myocardial ischemia.
Objectives:
Plasma beta-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 beta-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 beta-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 beta-endorphin levels to increase to sufficiently high levels to suppress anginal symptoms in response to the degree of ischemic stimuli.