Abstract 3550: Long-Term Exercise Training Improves QT Dispersion in Metabolic Syndrome Patients With and Without Coronary Heart Disease
Background: Abnormal QT dispersion (QTd) is a marker of myocardial electrical instability and predicts arrhythmia, tachycardia and sudden death in cardiac patients. Patients with metabolic syndrome have been shown to present abnormal QTd, and exercise training (ET) has been shown to reduce QTd at rest in patients with coronary heart disease (CHD). The effect of ET on QTd in metabolic syndrome (MS) patients is unknown. The aim of this study was to assess the effect of a long-term (≥6 months) exercise-training program on QT parameters in MS patients with and without CHD.
Method: Fifteen CHD and 31 non-CHD patients with MS (mean age 63±7 vs. 54±9 years respectively) were identified at entry into identical ET programs, with a training frequency of approximately 3 times/week. MS was defined using Adult Treatment Panel III (ATP III) criteria. Ventricular repolarization (QT dispersion = QTd, standard deviation of QT = SDQT, relative dispersion of QT = RDQT, QT corrected dispersion = QTcd) and metabolic parameters were measured before and after ET. Additionally, QT dispersion was measured in a sedentary CHD control group with MS (n=8, mean age 65±6 years) at baseline and after 1 year.
Results: Program duration was over 9 months in both MS groups (312±25 vs. 284±18 days in CHD and non-CHD groups respectively, P=NS). The prevalence of MS as defined by ATP III criteria was reduced by 25% in CHD patients and by 22% in non-CHD patients. Exercise training resulted in a significant reduction in QTd in both MS groups (QTd after vs. before = 56 vs. 67 msec, P<0.01 in CHD group; 52 vs. 58 msec in non-CHD group, P≤0.01). Similarly, QTcd, SDQT, and RDQT all improved after ET in both groups (P≤0.0001). Measures of QT dispersion were unchanged in the sedentary MS control group.
Conclusion: Improvements in measures of QT dispersion accompany the improvement in metabolic profile witnessed after long-term exercise training in MS patients with and without CHD.