EVALUATION OF VENTRICULAR REPOLARIZATION TIME IN PATIENTS WITH BUNDLE BRANCH BLOCK AND COMPARISON OF TWO FORMULAS FOR CORRECTION OF JT INTERVAL FOR HEART RATE

Objective To evaluate the effects of prolongation of the QRS time on QT interval and seek for a proper formula for correction of the JT interval for heart rate.Methods QRS and QT intervals were measured in 68 patients with bundle branch block (BBB) and 50 normal control subjects.The JT interval was derived by subtracting QRS from QT interval (JT= QT-QRS).The QTc was obtained by applying Bazett’s formula(QTc = QT/(RR)1/2).The JTc was obtained by using JTc = JT/(RR)1/2+ QRS/(RR)1/2-QRS ( F1 ) and JTC = JT/(RR)1/2(F2)respectively.Results The patients with BBB have a prolonged QTc interval but a normal JTc interval. The JTc obtained by applying F( was significantly different from that obtained by applying F2 ·The curve corresponding to F1 was parallel to the curve defined by Bazett’s formula, but the curve corresponding to F2 was not.Conclusion Formula JTc = JT/(RR)1/2+ QRS/(RR)1/2-QRS is a better equation than JTc = JT/(RR)1/2for correcting JT interval for heart rate corresponding