MODE OF QT CORRECTION FOR HEART-RATE - IMPLICATIONS FOR THE DETECTION OF INHOMOGENEOUS REPOLARIZATION AFTER MYOCARDIAL-INFARCTION

In 22 conscious, chronically instrumented dogs, the relationship between R-R interval and OT interval was better explained by linear regression than by nonlinear regression according to Bazett's formula. The correction formula QT(L) = QT-0.1*(RR-1000), which is based on the assumption of a linear relationship between OT and R-R interval, was then compared with Bazett's formula regarding its capability to detect inhomogeneous repolarization 5 to 7 days after temporary occlusion of the left anterior descending coronary artery. This comparison was performed only in those dogs exhibiting changes in QRS duration of less than 5 msec in response to myocardial infarction (n = 12). In these animals, myocardial infarction resulted in a significant dispersion of repolarization between the left ventricular normal zone and the infarct zone and a shift to the right of strength-interval curves of the infarct zone with respect to the normal zone, indicating local dispersion of refractoriness. As opposed to QT(C) (Bazett's formula), QT(L) WaS significantly (p = 0.04) prolonged after occlusion. Hence the adequacy of OT correction contributes significantly to the detection of inhomogeneous ventricular recovery after acute myocardial infarction.