Chlorthalidone vs Hydrochlorothiazide for Hypertension Treatment After Myocardial Infarction or Stroke: A Secondary Analysis of a Randomized Clinical Trial.

Importance: Patients with prior myocardial infarction (MI) or stroke have a greater risk of recurrent cardiovascular (CV) events. Objective: To evaluate the association of chlorthalidone (CTD) vs hydrochlorothiazide (HCTZ) with CV outcomes and noncancer deaths in participants with and without prior MI or stroke. Design, Setting, and Participants: This was a prespecified secondary analysis of the Diuretic Comparison Project (DCP), a pragmatic randomized clinical trial conducted within 72 participating Veterans Affairs health care systems from June 2016 to June 2021, in which patients aged 65 years or older with hypertension taking HCTZ at baseline were randomized to continue HCTZ or switch to CTD at pharmacologically comparable doses. This secondary analysis was performed from January 3, 2023, to February 29, 2024. Exposures: Pharmacologically comparable daily dose of HCTZ or CTD and history of MI or stroke. Main Outcomes and Measures: Outcome ascertainment was performed from randomization to the end of the study. The primary outcome consisted of a composite of stroke, MI, urgent coronary revascularization because of unstable angina, acute heart failure hospitalization, or noncancer death. Additional outcomes included achieved blood pressure and hypokalemia (potassium level <3.1 mEq/L; to convert to mmol/L, multiply by 1.0). Results: The DCP randomized 13 523 participants to CTD or HCTZ, with a mean (SD) study duration of 2.4 (1.4) years. At baseline, median age was 72 years (IQR, 69-75 years), and 96.8% were male. Treatment effect was evaluated in subgroups of participants with (n = 1455) and without (n = 12 068) prior MI or stroke at baseline. There was a significant adjusted interaction between treatment group and history of MI or stroke. Participants with prior MI or stroke randomized to CTD had a lower risk of the primary outcome than those receiving HCTZ (105 of 733 [14.3%] vs 140 of 722 [19.4%]; hazard ratio [HR], 0.73; 95% CI, 0.57-0.94; P = .01) compared with participants without prior MI or stroke, among whom incidence of the primary outcome was slightly higher in the CTD arm compared with the HCTZ arm (597 of 6023 [9.9%] vs 535 of 6045 [8.9%]; HR, 1.12; 95% CI, 1.00-1.26; P = .054) (P = .01 for interaction). The incidence of a nadir potassium level less than 3.1 mEq/L and hospitalization for hypokalemia differed among those with and without prior MI or stroke when comparing those randomized to CTD vs HCTZ, with a difference only among those without prior MI or stroke (potassium level <3.1 mEq/L: prior MI or stroke, 43 of 733 [5.9%] vs 37 of 722 [5.1%] [P = .57]; no prior MI or stroke, 292 of 6023 [4.9%] vs 206 of 6045 [3.4%] [P < .001]; hospitalization for hypokalemia: prior MI or stroke, 14 of 733 [1.9%] vs 16 of 722 [2.2%] [P = .72]; no prior MI or stroke: 84 of 6023 [1.4%] vs 57 of 6045 [0.9%] [P = .02]). Conclusions and Relevance: Results of this secondary analysis of the DCP trial suggest that CTD may be associated with reduced major adverse CV events and noncancer deaths in patients with prior MI or stroke compared with HCTZ. Trial Registration: ClinicalTrials.gov Identifier: NCT02185417.