High- Versus Low-dose Losartan and Serum Potassium: An Analysis From HEAAL

Patients with heart failure (HF) experience frequent alterations of serum potassium. Despite the high risk of events associated with hypokalemia, hyperkalemia is feared by clinicians and often leads to interruption or discontinuation of renin-angiotensin-aldosterone system inhibitors. Data on serum potassium of patients treated with different doses of renin-angiotensin-aldosterone system inhibitors are scarce.The effects of high-dose vs low-dose losartan on clinical outcomes in patients with heart failure (HEAAL) trial randomized 3834 patients with HFrEF intolerant to angiotensin-converting enzyme inhibitors to losartan 150 mg/d (high dose) vs 50 mg/d (low dose). We studied the associations of serum potassium (baseline and time updated) with study outcomes and the effect of the randomized treatment on serum potassium. Patients with higher baseline potassium were older, had diabetes, poorer renal function, and used mineralocorticoid receptor antagonists more frequently. In time-updated models, hyperkalemia (>5.0 or ≥5.5 mmol/L) was not associated with cardiovascular death or the composite of cardiovascular death or HF hospitalization. Hypokalemia (serum potassium of ≤3.5 mmol/L, in particular) was associated with a higher risk of the composite of cardiovascular death or HF hospitalization (hazard ratio [HR] 1.58, 95% confidence interval [CI] 1.19-2.08), all-cause death (HR 1.68, 95% CI 1.26-2.24), and sudden cardiac death or resuscitated cardiac arrest (HR 1.74, 95% CI 1.11-2.73). High-dose losartan decreased the risk of hypokalemia (HR 0.77, 95% CI 0.63-0.92) and increased the risk of hyperkalemia (HR 1.21, 95% CI 1.05-1.39). High-dose losartan decreased the composite of cardiovascular death or HF hospitalizations consistently across the full spectrum of serum potassium at baseline (interaction P = .85).In patients with HF with reduced ejection fraction intolerant to angiotensin-converting enzyme inhibitors and treated with either high- or low-dose losartan, incident hypokalemia had a stronger association with poor outcomes than incident hyperkalemia. High-dose losartan reduced the incidence of hypokalemia, and its benefits were maintained across the full spectrum of serum potassium.