Role of Diuretics in Cardiovascular Events and Mortality in Systolic Blood Pressure Intervention Trial: A Post Hoc Analysis

Background: In a post hoc analysis, we examined whether postrandomization diuretics use can explain and/or mediate the beneficial effects of intensive systolic BP lowering on cardiovascular disease and all-cause mortality in the Systolic Blood Pressure Intervention Trial (SPRINT).

Methods: SPRINT was a randomized, controlled trial of 9361 participants comparing the effects of intensive (systolic BP target <120 mm Hg) versus standard (systolic BP target <140 mm Hg) BP control on a primary composite cardiovascular end point in participants aged 50 years or older with systolic BP of 130-180 mm Hg. In time-varying multivariable Cox analyses, we assessed hazard ratios (HRs) of cardiovascular end points and all-cause mortality in participants on thiazide type, loop and/or potassium (K) sparing, or no diuretics. We also conducted mediation analysis to formally assess the role of diuretics in the effects of intensive systolic BP lowering.

Results: At baseline, diuretics were prescribed in 46% and 48% of participants in standard and intensive systolic BP-lowering groups, respectively, and in 46% and 74% in the corresponding groups during the trial. The lower risk of cardiovascular end points in the intensive group (HR, 0.75; 95% confidence interval [CI], 0.64 to 0.89) persisted after adjustment for postrandomization time-varying diuretics use (HR, 0.74; 95% CI, 0.62 to 0.89). Across the entire study population, time-varying diuretics use was not associated with cardiovascular end points (compared with no diuretics, HR for thiazide type, 0.89; 95% CI, 0.73 to 1.10, and loop/K sparing, 1.29; 95% CI, 0.97 to 1.73). However, thiazide-type diuretics were associated with lower risk of cardiovascular end points in the intensive (HR, 0.62; 95% CI, 0.46 to 0.85) but not in the standard (HR, 1.07; 95% CI, 0.82 to 1.39) group. In mediation analysis, HRs for total effect, direct effect (not mediated through diuretics use), and indirect effect (mediated through diuretics) of the intervention on cardiovascular end points were 0.66 (95% CI, 0.54 to 0.79), 0.67 (95% CI, 0.54 to 0.81), and 0.98 (95% CI, 0.88 to 1.10), respectively. The results were largely similar for all-cause mortality.

Conclusions: The favorable effects of intensive systolic BP lowering on cardiovascular end points and all-cause mortality in SPRINT were independent of and not mediated by time-varying diuretics use. However, thiazide-type diuretics use associated with benefit if intensive systolic BP lowering was targeted.