Association of QT Dispersion with Left Ventricular Hypertrophy in Essential Hypertensives

ABSTRACT

BACKGROUND: Left ventricular hypertrophy(LVH) is a powerful indepedent risk factor of ventricular tachycardia and sudden death. Even though it is not clear the mechanism of sudden death in patients with LVH, inhomogenous ventricular repolarization is highly suggested. QT dispersion which reflecting regional inhomogeneity of repolarization is defined as interlead variation in QT intervals of 12 leads ECG. The purpose of this study was to assess whether QT dispersion is associated with LVH in hypertensive patients. METHODS: We assessed 23 untreated hypertensives with echocardiographic LVH and normal left ventricular systolic function. The criteria of 5th Joint National Committee stage I-III was used to define hypertension. Thirty four normotensives was assessed as controls. On a standard 12 lead ECG, the intervals between onset of QRS to end of T wave were measured(QT intervals) and corrected by heart rate(QTc). QT dispersion was calculated by the difference of maximal and minimal QTc. Left ventricular mass(LVM) was calculated from Devereux's formula using the parameters measured by the recommendation of American Society of Echocardiography. LVH was defined by LVM indices over 130 g/m2. RESULTS: LVM indices of hypertensive group were significantly greater than those of controls (162.2+/-39.3 g/m2 vs 84.2+/-16.1 g/m2, p<0.001). Maximal QT and QTc of hypertensive group were significantly prolonged than those of controls(maximal QT=401+/-31 ms vs 380+/-35 ms, p<0.05 ; maximal QTc=432+/-19 ms vs 414+/-17 ms, p<0.001). QT dispersions were significantly greater in hypertensive group than in controls(60.2+/-15.7 ms vs 33.2+/-11.7 ms, p<0.001). In hypertensive group, there was significant association between LVM index and QT dispersion(r=0.492, p=0.017). CONCLUSIONS: Hypertensives with LVH have a prolonged QT and QTc and increased QT dispersion in comparision with controls. QT dispersion in these patients correlates with degree of LVH.