Diuretics, serum potassium and ventricular arrhythmias in the Multiple Risk Factor Intervention Trial.

To examine the relation between diuretic use and ventricular premature complexes (VPCs) in the Multiple Risk Factor Intervention Trial, data derived from the baseline and annual rest electrocardiograms were analyzed for men in the special-intervention (SI) and usual-care (UC) groups. At baseline, age, diuretic use and presence of other rest electrocardiographic abnormalities were significantly associated with the prevalence of VPCs. Among diuretic users at baseline, those with lower serum potassium levels were most likely to have VPCs. Over the follow-up period among nonhypertensive persons the relative risk (SI/UC) for the occurrence of VPCs during follow-up was 0.83, and for hypertensives this relative risk increased linearly from 1.08 to 1.42, with higher levels of diastolic blood pressure at entry (p less than 0.01 for linear trend of relative risk estimates). This was due to an increasing risk among the SI group, and the risk was independent of the presence or absence of rest electrocardiographic abnormalities at baseline. The relative risk estimate, diuretic vs no diuretic, for development of VPCs was approximately 1.2 (p = 0.04) for SI men and 1.1 (p = 0.35) for UC men. The reduction in serum potassium level was greater for those with VPCs, and regression analysis showed that low serum potassium levels were significantly associated with the incidence of VPCs in both study groups. These data confirm and quantify the relation between diuretic drugs and VPCs and suggest that at least 1 mechanism of diuretic-induced VPCs is potassium depletion.