AIM: We investigated the association between potassium levels and 90-day all-cause mortality in atrial fibrillation or flutter (AF) patients co-treated with diuretics and rate- or rhythm-controlling drugs.

METHODS AND RESULTS: During 2000-2012, first-time AF patients treated with beta-blockers, amiodarone, sotalol, verapamil, and/or digoxin combined with any diuretic within 90 days post-AF discharge were included. Following co-treatment, a potassium measurement within 90 days after initiating diuretic treatment was required. Mortality risk associated with potassium <3.5, 3.5-3.7, 3.8-4.0, 4.5-4.7, 4.8-5.0, and >5.0 mmol/L (reference: 4.1-4.4 mmol/L) was assessed using Multivariable Cox regression. In total, 14,425 AF patients were included (median age: 78 years; women: 52%). Patients most often received beta-blocker monotherapy (29%), beta-blocker and digoxin combined (25%), digoxin monotherapy (24%), amiodarone monotherapy (3%), and verapamil monotherapy (3%). Increased 90-day mortality risk was associated with <3.5 mmol/L (HR 2.05, 95% CI: 1.68-2.50), 3.5-3.7 mmol/L (HR: 1.28, 95% CI 1.05-1.57), 4.5-4.7 mmol/L (HR: 1.20, 95% CI: 1.02-1.41), 4.8-5.0 mmol/L, (HR: 1.37, 95% CI: 1.14-1.66) and >5.0 mmol/L: (HR: 1.84, 95% CI: 1.53-2.21). Compared with beta-blocker monotherapy, rate- or rhythm-controlling drugs did not modify the association between potassium groups and mortality risk.

CONCLUSION: In addition to hypo- and hyperkalemia, low and high normal range potassium levels were associated with increased 90-day mortality risk in AF patients co-treated with diuretics and rate- or rhythm-controlling drugs. These associations were independent of rate- or rhythm-controlling drugs.