Sequential Alterations in Myocardial Lactate Metabolism, S-T Segments, and Left Ventricular Function During Angina Induced by Atrial Pacing

Myocardial lactate metabolism was monitored before, during, and after a period of atrial pacing with a continuous automated sampling technic. The electrocardiogram was recorded, and left ventricular function was evaluated by relating left ventricular end-diastolic pressure to left ventricular stroke work. Seventeen of 21 patients with coronary artery disease experienced angina during pacing, and 13 of these showed lactate pro-duction by the myocardium during angina. The abnormalities in lactate metabolism developed early in the pacing period, along with S-T segment depression and impair-ment of left ventricular function, all of which usually occurred before the onset of pain. In the patients with angina, the mean lactate extraction was 14.1 % during the control period and-15.1 % during the pacing period. Abnormalities in myocardial lactate metabolism have been demonstrated with greater regularity during pacing-induced an-gina than during angina precipitated by exercise or isoproterenol. This investigation has demonstrated the sequences of changes in lactate metabolism during and after a period of angina and their relation to electrocardiographic and hemodynamic events. Additional Indexing-Myocardial metabolis