Electrical Stability of Acutely Ischemic Myocardium

Abstract

Previous investigations have shown that a slower heart rate (HR) and myocardial ischemia independently diminish the electrical stability of the heart. It therefore was suggested that increasing heart rate during myocardial infarction might diminish the incidence of serious ventricular arrhythmias. However, since increased HR during experimental acute myocardial ischemia augments the degree of ischemia, an evaluation of the presumed "protective" effects of increased HR on the electrical stability of acutely ischemic myocardium was undertaken. The differences in refractory periods (RP) of eight contiguous areas of the left ventricle were determined as a function of HR. In nonischemic myocardium, the disparity of RP was less at an HR of 180 than 60. However, in ischemic myocardium the disparity increased in three of six animals as the HR was increased from 60 to 90, in seven of 10 animals as HR was increased from 60 to 120, and in all animals when the HR was increased from 60 to 180. The increased disparity ...