Different actions of irbesartan and atenolol on cardiac repolarization in hypertensive patients with left ventricular hypertrophy

Abstract

Left ventricular hypertrophy (LVH) is associated with an increased risk for malignant arrhythmias and sudden death. A prolonged QT dispersion is predictive of such events. We evaluated 92 hypertensive patients with echocardiographically verified LVH (age 55±9 years, BP 162±20/104±8 mmHg, LVMI 148±32 g/m2) randomized double-blind to receive the AT1-receptor blocker irbesartan (n=44) or the beta1-receptor blocker atenolol (n=48) for 48 w. At w 0, 12 and 48 echocardiography was performed, and QT and QTc dispersion were calculated from a standard 12 lead ECG (50 mm/s). We also examined 37 age and gender matched hypertensive patients without LVH (BP 148±14/97±6 mmHg, LVMI 99±6 g/m2) once. Patients with LVH had increased QT and QTc dispersion, as compared to those without LVH (52 vs 41 ms, p=0.007, and 52 vs 44 ms, p=0.032, respectively). LVMI related to QT dispersion (r=0.34, p<0.001). By similar reductions in BP, the irbesartan group had a greater reduction in LVMI than the atenolol group (-27±29 vs -18±21 g/m2, p<0.031). With irbesartan QT dispersion decreased from 56±24 to 52±21 (12 w) and 44±20 ms (48w; p<0.001), and QTc dispersion decreased from 56±24 to 54±21 (12 w) and 44±19 ms (48 w; p<0.001). There was little influence of atenolol on QT dispersion (e.g., 48±20, 53±17 and 53±20 ms) and QTc dispersion. The changes in QT and QTc dispersion after 48 w were different (p=0.001 and p=0.011, respectively) between the irbesartan and atenolol groups. These significant differences remained when changes in LVMI, BP and heart rate were included in multivariate analyses. QT dispersion is related to LVMI. Irbesartan, but not atenolol, reduces QT and QTc dispersion, independent of changes in LVMI, BP or heart rate. We suggest that AT1-receptor blockade may induce both structural and electrical remodeling in a direction that reduces the risk of malignant arrythmias. A reduced QT dispersion by irbesartan may be important in preventing malignant arrhythmias and sudden cardiac death in high-risk hypertensive patients.