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 QT interval was better explained by linear regression than by nonlinear regression according to Bazett's formula. The correction formula QTL = QT-0.1*(RR-1000), which is based on the assumption of a linear relationship between QT 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 QTc (Bazett's formula), QTL was significantly (p = 0.04) prolonged after occlusion. Hence the adequacy of QT correction contributes significantly to the detection of inhomogeneous ventricular recovery after acute myocardial infarction.
Todt
H
H
Department of Cardiovascular Pharmacology, University of Vienna, Austria.
Krumpl
G
G
Krejcy
K
K
Raberger
G
G
D000818:Animals; D003250:Constriction; D003331:Coronary Vessels; D004285:Dogs; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate; D008297:Male; D009203:Myocardial Infarction / Q000503:physiopathology*; D012044:Regression Analysis