DIURETIC THERAPY FOR HYPERTENSION AND THE RISK OF PRIMARY CARDIAC-ARREST

Background. The results of trials of the primary prevention of coronar y heart disease have suggested that treating hypertension with high do ses of thiazide diuretic drugs might increase the risk of sudden death from cardiac causes. In contrast, treatment with low doses of thiazid e reduces the risk of coronary heart disease. Methods. To examine the association between thiazide treatment for hypertension and the occurr ence of primary cardiac arrest, we conducted a population-based case-c ontrol study among enrollees of a health maintenance organization. The case patients were 114 persons with hypertension who had a primary ca rdiac arrest from 1977 through 1990. The control patients were a strat ified random sample of 535 persons with hypertension. The patients' tr eatment was assessed with the use of a computerized pharmacy data base . Records of their ambulatory care were reviewed to determine other cl inical characteristics. Results. The risk of primary cardiac arrest am ong patients receiving combined thiazide and potassium-sparing diureti c therapy was lower than that among patients treated with a thiazide w ithout potassium-sparing therapy (odds ratio, 0.3; 95 percent confiden ce interval, 0.1 to 0.7). As compared with low-dose thiazide therapy ( 25 mg daily), moderate-dose therapy (50 mg daily) was associated with a moderate increase in risk (odds ratio, 1.7; 95 percent confidence in terval, 0.7 to 4.5), and high-dose therapy (100 mg daily) was associat ed with a larger increase in risk (odds ratio, 3.6; 95 percent confide nce interval, 1.2 to 10.8) (P value for trend, 0.02). The addition of a potassium-sparing drug to low-dose thiazide therapy was associated w ith a reduced risk of cardiac arrest (odds ratio, 0.4; 95 percent conf idence interval, 0.1 to 1.5). Conclusions. Both the dose of thiazide d rugs and the addition of potassium-sparing drugs influence the risk of primary cardiac arrest. These results may explain the differences in the effect of antihypertensive therapy on mortality from coronary hear t disease in previous clinical trials.