Effects of Myocardial Perfusion on QT Dispersion in Patients with Hypertrophic Cardiomyopathy

Background:In patients with hypertrophic cardiomyopathy (HCM), myocardial ischemia and myocardial fibrosis as well as ventricular tachyarrhythmia are frequently observed. An increase of heterogeneity of repolarization provided the development of ventricular tachyarrhythmia. The aims of the present study are to evaluate the influence of exercise-induced myocardial perfusion abnormalities on QT dispersion and to assess whether QT dispersion was involved in ventricular tachycardia (VT) in patients with HCM. Methods:Thirty-eight patients with HCM and 20 control subjects underwent an exercise stress test, and QT intervals were measured pre-exercise and at 3 minutes after peak exercise. All subjects underwent thallium (TI)-201 stress myocardial imaging, and their TI-201 defect score and exerciseinduced myocardial ischemia were evaluated. Results:Twelve patients (31%) revealed sustained or nonsustained VT. The pre-exercise QTc dispersion (QTcD) was significantly correlated with the Tl-201 defect score (r = 0.61, P < 0.0001). The QTcD at 3 minutes after peak exercise was significantly greater in patients with exerciseinduced myocardial ischemia than without exercise-induced myocardial ischemia (96 ± 36, 72 ± 24 ms1/2, P < 0.03). The QTcD at 3 minutes after peak exercise was significantly greater in patients with VT than without VT (111 ± 23, 64 ± 17 ms1/2, P < 0.0001). Conclusion:It is suggested that the degree of myocardial fibrosis influences the pre-exercise QTcD, and exercise-induced myocardial ischemia precipitates the increase in the QTcD at 3 minutes after peak exercise in patients with HCM. The increased QTcD at 3 minutes after peak exercise may play a role in identifying patients at a potentially higher risk. A.N.E. 2000;5(1):60–67