Heart Failure in ALLHAT: Did Blood Pressure Medication at Study Entry Influence Outcome?

Lower heart failure (HF) rates in individuals taking chlorthalidone vs amlodipine, lisinopril, or doxazosin were unanticipated in the Antihypertensive and Lipid‐Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). HF differences appeared early, leading to questions about the possible influence of pre‐enrollment antihypertensive drugs. A post hoc study evaluated hospitalized HF events. During year 1479 individuals had HF, with pre‐entry antihypertensive medication data obtained on 301 patients (63%). Case‐only analysis examined interactive effects (interaction odds ratio [OR, ratio of ORs]) of previous medication and ALLHAT treatment on HF outcomes, eg, did treatment effect differ by pre‐entry antihypertensive class? Among cases, 39%, 37%, 17%, and 47% were taking pre‐entry diuretics, angiotensin‐converting enzyme inhibitors, β‐blockers, and calcium channel blockers, respectively. Interaction OR for year 1 HF for amlodipine vs chlorthalidone for patients taking vs not taking diuretics pre‐entry was 1.08 (95% confidence interval [CI], 0.53–2.21; P=.83); for lisinopril vs chlorthalidone, 1.33 (95% CI, 0.65–2.74; P=.44); and for doxazosin vs chlorthalidone, 1.13 (95% CI, 0.57–2.25; P=.73). Controlling for other pre‐entry antihypertensives yielded similar results. There was no significant evidence that pre‐entry drug type explained observed hospitalized HF differences by ALLHAT treatment.