Regression of Left Ventricular Hypertrophy With Captopril Restores Normal Ventricular Action Potential Duration, Dispersion of Refractoriness, and Vulnerability to Inducible Ventricular Fibrillation

Abstract

Background Left ventricular hypertrophy (LVH) is associated with multiple cellular electrophysiological abnormalities, susceptibility to ventricular arrhythmias, and an increased risk of sudden death. Several pharmacological therapies have been shown to produce regression of hypertrophy, but the value of regression is unclear. The present study examines whether pharmacological regression of LVH has effects on the susceptibility to ventricular arrhythmia or the cellular electrophysiological abnormalities of LVH. Methods and Results Rabbits underwent unilateral renal artery banding and contralateral nephrectomy to induce LVH or were placed in the control group. Both groups were studied 3 months later by in vivo and in vitro electrophysiological techniques. Banded rabbits had increased mean arterial pressure, increased left ventricular weight and wall thickness, increased dispersion of refractoriness, and lower ventricular fibrillation thresholds than control rabbits. Action potential duration and cell capacitance were also greater in the banded group. Additional rabbits were treated beginning 3 months after banding with either captopril (5 mg·kg −1 ·d −1 ) or vehicle added to their diet for an additional 3 months. These rabbits and age-matched controls were then studied by in vivo and in vitro electrophysiological techniques. In banded rabbits that received vehicle and were studied 6 months after banding, increased dispersion of refractoriness, a lower ventricular fibrillation threshold, and action potential prolongation persisted and were unchanged from animals studied 3 months after banding. Captopril, started 3 months after banding, caused regression of hypertrophy and normalization of the in vivo and in vitro electrophysiological abnormalities. Addition of captopril to the tissue bath during in vitro electrophysiological study showed no effect on cells from control or banded rabbits. Conclusions Pharmacological regression of LVH with captopril normalizes the in vivo and in vitro electrophysiological abnormalities of ventricular hypertrophy and reduces the vulnerability to ventricular fibrillation in a renovascular model of LVH.