To determine whether hypertensive patients with ECG abnormalities and receiving hydrochlorothiazide diuretics were at increased risk of sudden death.

BACKGROUND:

The Multiple Risk Factor Intervention Trial (MRFIT) revealed an unexpected subgroup finding: an association between diuretic therapy (especially with hydrochlorothiazide) and an increased rate of sudden death in hypertensive men with left ventricular hypertrophy and other ECG abnormalities. The Diuretics, Hypertension, and Arrhythmias Clinical Trial sought to determine whether the finding resulted from random variation or represented a serious toxic response to hydrochlorothiazide.

DESIGN NARRATIVE:

Randomized, double-blind. Following one month of withdrawal from all diuretics and repletion with oral potassium and magnesium, the study participants were randomized to two months of treatment with one of six treatment groups: hydrochlorothiazide; hydrochlorothiazide with oral potassium; hydrochlorothiazide with oral potassium and magnesium; hydrochlorothiazide and triamterene; chlorthalidone; or placebo. The main outcome measures were ventricular arrhythmias on 24-hour Holter monitoring and serum and intracellular potassium and magnesium levels.

Men, ages 35 to 70, with ECG abnormalities, diastolic blood pressure less than 95 mm Hg at entry.

Subjects had been treated for at least six months by their own physicians with hydrochlorothiazide (HCT), HCT and potassium supplementation, triamteren