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Background Hypertension is a known risk factor for heart failure (HF), possibly via the mechanism of cardiac remodeling and left ventricular hypertrophy (LVH). We studied the extent to which blood pressure (BP) change and evolving LVH contribute to the effect that lisinopril, doxazosin, and amlodipine have on HF compared with chlorthalidone. Methods and Results We conducted causal mediation analysis of ALLHAT (Antihypertensive and Lipid‐Lowering Treatment to Prevent Heart Attack Trial) data (1994‐2002; in‐trial follow‐up). ALLHAT participants with available serial ECGs and BP measurements were included (n=29 892; mean age 67±4 years; 32% black; 56% men): 11 008 were randomized to chlorthalidone, 5967 to doxazosin, 6593 to amlodipine, and 6324 to lisinopril. Evolving ECG LVH and BP lowering served as mediators. Incident symptomatic HF was the primary outcome. Linear regression (for mediator) and logistic regression (for outcome) models were adjusted for mediator‐outcome confounders (demographic and clinical characteristics known to be associated both with both LVH/hypertension and HF). A large majority of participants (96%) had ECG LVH status unchanged, but 4% developed evolving ECG LVH. On average, BP decreased by 11/7 mm Hg. In adjusted Cox regression analyses, progressing ECG LVH (hazard ratio [HR] 1.78 [95% CI 1.43‐2.22]), resolving ECG LVH (HR 1.33 [95% CI 1.03‐1.70]), and baseline ECG LVH (1.17 [95% CI 1.04‐1.31]) carried risk of incident HF. After full adjustment, evolving ECG LVH mediated 4% of the effect of doxazosin on HF. Systolic BP lowering mediated 12% of the effect of doxazosin, and diastolic BP lowering mediated 10% of the effect of doxazosin, 7% of the effect of amlodipine, and borderline 9% of the effect of lisinopril on HF. Conclusions Evolving ECG LVH and BP change account for 4% to 13% of the mechanism by which antihypertensive medications prevent HF. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000542. |
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