value of signal-averaged electrocardiogram and QT dispersion as predictors of arrhythmic vulnerability in patients with left ventricular hypertrophy

ABSTRACT

Left ventricular hypertrophy [LVH] predicts increased risk for ventricular arrhythmias [VAs] which probably accounts for the elevated risk of sudden cardiac death. To investigate the value of signal-averaged electrocardiogram [SAECG] and QT dispersion as noninvasive markers for ventricular arrhythmias in patients with LVH. We subjected 60 patients with LVH;30 hypertensive [group 1], 15 with hypertrophic cardiomyopathy [HCM] [group II] and 15 with valvular aortic stenosis [group III] to a complete echo-Doppler examination, 12-lead electrocardiogram and SAECG for estimation of left ventricular mass index [LVMI], detection of QT dispersion and late diastolic potentials [LDPs]. Ventricular arrhythmias were detected in 32% of patients with LVH. LDPs were detected in 17% of patients with LVH. All patients with LDPs had VAs. All VAs in patients with LDPs were of Lown grade [2] and [3], whereas most of VAs in patients without LDPs were of Lown grade [1]. Patients with LVH had significantly high QT dispersion, QTc dispersion and LVMI when compared to control subjects [P=0.04, 0.03 and 0.01, respectively]. Patients with HCM had significantly high QT dispersion, QTc dispersion and LVMI when compared to group I [P=0.02, 0.03 and 0.02, respectively] and group II [P=0.02, 0.02 and 0.04, respectively]. Significant correlation was found between LVMI and LDPs as well as QT and QTc dispersion [P=0.042 for LDPs, 0.036 for QT dispersion and 0.028 for QTc dispersion]. Of the many ECG and echocardiographic variables subjected to univariate and multivariate analysis, only three were identified as significant independent predictors of VAs QT, QTc dispersion, LVMI and LDPs [P=0.006 and 0.04 for QT dispersion; 0.008 and 0.043 for QTc dispersion, 0.008 and 0.033 for LVMI and 0.0001 and 0.0001 for LDPs]. QT dispersion, QTc dispersion, LVMI and LDPs may be a useful adjuncts to the noninvasive assessment of patients with LVH, particularly in the prediction of sudden death