Studies on Myocardial Metabolism during Atrial Pacing-induced Tachycardia : Special Reference to Myocardial Free Radical Metabolism

Abstract

Electrocardiogram and coronary angiography play an important role in the diagnosis of ischemic heart disease. However, ischemic heart disease should be evaluated intrinsically on the basis of myocardial metabolism for its diagnosis because it is the pathophysiological state of myocardial hypoxia. Although various metabolic indicators of myocardial hypoxia such as excess lactate and redox-potential etc. have been advocated so far by many investigators, a number It has been suggested that electron spin resonance (ESR) spectrometry was an useful method for detecting of the mechanism of biological reactions, particularly an involvement in enzymatic oxidation-reduction processes. Yamazaki examined pathophysiological state in oxidation-reduction system in ischemic myocardium by means of ESR spectrometry, and proposed a new metabolic indicator of myocardial hypoxia based on the myocardial free The left descending coronary artery distal to radical metabolism. Yamawoto reported myocardial free radical metabolism during coronary insufficiency induced by exercise, and observed an increase in the free radical of coronary sinus plasm after exercise. Exercise, the most physiological myocardial stress, has its own intrinsic direct effects on metabolism. It is therefore not always appropriate to the examination of myocardial metabolism. On the other hand, atrial pacing, which enables to apply a controllable stress to the heart, is a simple, repeatable and safe procedure without the hemodynamic and metabolic changes that accompany exercise. It has there-fore been employed in the study of pathological states during coronary insufficiency. The present study was undertaken to investigate alterations in coronary circulation and myocardial metabolism, especially free radical and lactate metabolism, during atrial pacing-induced tachycardia in dogs with experimental acute and chronic coronary insufficiency, and to define the clinical application of ESR spectrometry in combination with atrial pacing to the diagnosis of ischemic heart disease.