933-94 Left Ventricular Hypertrophy in Hypertensives is Associated with an Increased QT Dispersion

Abstract

Hypertensive patients who develop left ventricular hypertrophy (LVH) are at much greater cardiovascular risk than those without and in particular their incidence of sudden death is several times higher. This may be mediated by an increase in ventricular arrhythmias. It has recently been suggested that QT dispersion may indicate arrhythmia risk by reflecting dispersion of recovery of ventricular excitability In order to test the hypothesis that left ventricular hypertrophy may be associated with an increase in QT dispersion 100 previously untreated subjects were studied. These consisted of 52 subjects with essential hypertension (BP > 160/90), 21 subjects with borderline hypertension (BP > 140/85) and 27 normotensives. Each underwent 2 dimensional and Doppler echocardiography to determine left ventricular mass index (LVMI), E/A ratio and isovolumic relaxation time (IVRT). Additionally from a 12-lead ECG examination QT length was measured for each lead and corrected for heart rate (QTc). QTc dispersion was determined as the difference between the maximum and minimum QTc interval. Maximum QTc was significantly correlated with LVMI (r = 0.41, p < 0.01), systolic BP(r = 0.43, p < 0.01), E/A ratio (r = -0.33, p < 0.01) IVRT (r = 0.35, p < 0.01) and age (r = 0.30, p < 0.01). QTc dispersion was similarly significantly correlated with LVMI (r = 0.30, p < 0.01), systolic BP (r = 0.30, p < 0.01, E/A ratio (r = -0.22, p = 0.02), IVRT (r = 0.31, p < 0.01) and age (r = 0.21, P < 0.04). The interdependence of these factors preclude multiple regression analysis. QT dispersion and maximum QT length are related to left ventricular structure and diastolic function. This may reflect an increase in dispersion of recovery of ventricular excitability occurring as a result of the myocardial structural changes that occur as a consequence of hypertension. This may in turn predispose to ventricular arrhythmias which could help explain the high incidence of sudden death in hypertensives with LVH.