Restoration of Normal Ventricular Electrophysiology in Renovascular Hypertensive Rabbits after Treatment with Losartan

Left ventricular hypertrophy (LVH) is associated with abnormal ventricular electrophysiology. We have shown complete regression of LVH and normalization of ventricular electrophysiology in renovascular hypertensive rabbits treated with captopril. To determine if angiotensin II type 1 receptor (AT1) blockade produces the same benefit, we treated hypertensive rabbits with losartan for 3 months. LVH was evaluated by heart-to-body weight ratio (HW/BW). Vulnerability to ventricular arrhythmia was assessed by ventricular fibrillation threshold (VFT) and dispersion of effective refractory period (ERP). The electrical properties of single left ventricular myocytes were characterized by action potential duration at 90% repolarization (APD90) and inward rectifier K+ current (I(K1)) density. Hypertensive rabbits treated with vehicle (LVH/Vehicle) had higher mean arterial pressure (MAP, 81+/-2 vs. 60+/-2 mm Hg) and HW/BW (2.71+/-0.07 vs. 1.97+/-0.04 g/kg), lower VFT (20+/-1 vs. 39+/-2 mA), larger dispersion of ERP (34+/-3 vs. 14+/-3 ms), longer APD90 (187+/-6 vs. 162+/-6 ms) and lower I(K1) density compared with control rabbits. Hypertensive rabbits treated with losartan (LVH/Losartan) had HW/BW (2.36+/-0.06 g/kg) between those of LVH/Vehicle and control rabbits, whereas MAP (65+/-2 mm Hg), VFT (34+/-2 mA), dispersion of ERP (19+/-1 ms), APD90 (160+/-6 ms), and I(K1) density were significantly different from LVH/Vehicle but similar to control. We conclude that AT1 blockade in renovascular hypertensive rabbits normalizes ventricular electrophysiology.