The effect of chlorthalidone on ventricular ectopic activity in patients with isolated systolic hypertension. The SHEP Study Group.

In an ancillary study of the Systolic Hypertension in the Elderly Program (SHEP), the effects of diuretics on ventricular ectopic activity were investigated in 186 patients with isolated systolic hypertension. Ventricular premature complexes (VPCs) were examined as the number of VPCs/24 hours, presence of > or = 1 VPC, presence of > or = 10 VPCs/24 hours, and presence of VPC pairs or ventricular tachycardia. Significant changes in VPCs were not observed either in the 92 patients randomized to chlorthalidone stepped-care (12.5 and 25 mg/day) or in the 94 placebo-treated patients (p > 0.1 for all VPC definitions and both groups). Serum potassium decreased from 4.4 +/- 0.5 to 4.1 +/- 0.5 mEq/liter (p = 0.002) in the chlorthalidone group and did not change (4.4 +/- 0.5 to 4.5 +/- 0.4 mEq/liter) in the placebo group. Potassium was prescribed routinely for confirmed hypokalemia < 3.5 mEq/liter. A relation between serum potassium and VPC or change in serum potassium and change in VPC was not observed in the chlorthalidone group. In summary, in patients with isolated systolic hypertension, chlorthalidone in doses that are effective in decreasing stroke and cardiovascular event rates (12.5 or 25 mg/day), did not increase VPCs.