Increased Spironolactone Dosing in Acute Heart Failure Alters Potassium Homeostasis but Does Not Enhance Decongestion.

ABSTRACT

BACKGROUND: The ATHENA-HF clinical trial found no improvements in natriuretic peptide levels or clinical congestion when spironolactone 100 mg/day for 96 hours was used in addition to usual treatment for acute heart failure. METHODS: We performed a post hoc analysis of ATHENA-HF to determine whether spironolactone treatment induced any detectable pharmacodynamic effect and whether patients with potentially greater aldosterone activity experienced additional decongestion. Trial subjects previously treated with spironolactone were excluded. We first examined for changes in renal potassium handling. Using the baseline serum potassium level as a surrogate marker of spironolactone activity, we then divided each treatment arm into tertiles of baseline serum potassium and explored for differences in laboratory and clinical congestion outcomes. RESULTS: Among spironolactone-naïve patients, the change in serum potassium did not differ after 24 hours or 48 hours but was significantly larger with spironolactone treatment compared to placebo at 72 hours (0.23±0.55 vs 0.03±0.60 mEq/L, P=0.042) and 96 hours (0.32±0.51 vs 0.13±0.72 mEq/L, P=0.046). While potassium supplementation was similar at treatment start and 24 hours, spironolactone-treated patients required substantially less potassium replacement at 48 hours (24% vs 36%; P=0.048), 72 hours (21% vs 37%; P=0.013), and 96 hours (11% vs 38%; P<0.001). When the treatment arms were divided into tertiles of baseline serum potassium, there were no differences in the 96-hour log N-terminal pro-B-type natriuretic peptide, net fluid loss, urine output, or dyspnea relief between any of the potassium groups, with no effect modification by treatment exposure. CONCLUSIONS: Spironolactone 100 mg/day for 96 hours in patients receiving intravenous loop diuresis for acute heart failure has no clear added decongestive ability but does meaningfully limit potassium wasting.