Long-Term Potassium Monitoring and Dynamics in Heart Failure and Risk of Mortality

• DOI: 10.1161/circulationaha.117.030576
• Publication Date: 2017-10-13T00:10:49Z
• Authors: Julio Núñez; Antoni Bayés-Genís; Faiez Zannad; Patrick Rossignol; Eduardo Núñez; Vicent Bodí; Gema Miñana; Enrique Santas; Francisco J. Chorro; Anna Mollar; Arturo Carratalá; Jorge Navarro; Jose Luis Górriz; Josep Lupón; Oliver Husser; Marco Metra; Juan Sanchis
• Keywords: Male; Risk; heart failure; Hypokalemia; 03 medical and health sciences; 0302 clinical medicine; cohort studies; Cause of Death; hypokalemia; longitudinal studies; Humans; Prospective Studies; Aged; Proportional Hazards Models; Aged, 80 and over; Heart Failure; potassium; Middle Aged; hyperkalemia; Prognosis; mortality; Survival Analysis; 3. Good health; Potassium; Potentiometry; Hyperkalemia; Female; acute heart failure; heart failure; hyperkalemia; hypokalemia; longitudinal cohort study; mortality; potassium; Glomerular Filtration Rate

Background: The prognostic value of long-term potassium monitoring and dynamics in heart failure has not been characterized completely. We sought to determine the association between serum potassium values collected at follow-up with all-cause mortality in a prospective and consecutive cohort of patients discharged from a previous acute heart failure admission.

Methods: Serum potassium was measured at every physician-patient encounter, including hospital admissions and ambulatory settings. The multivariable-adjusted association of serum potassium with mortality was assessed by using comprehensive state-of-the-art regression methods that can accommodate time-dependent exposure modeling.

Results:

The study sample included 2164 patients with a total of 16 116 potassium observations. Mean potassium at discharge was 4.3±0.48 mEq/L. Hypokalemia (<3.5 mEq/L), normokalemia (3.5–5.0 mEq/L), and hyperkalemia (>5 mEq/L) were observed at the index admission in 77 (3.6%), 1965 (90.8%), and 122 (5.6%) patients, respectively. At a median follow-up of 2.8 years (range, 0.03–12.8 years), 1090 patients died (50.4%). On a continuous scale, the multivariable-adjusted association of potassium values and mortality revealed a nonlinear association (U-shaped) with higher risk at both ends of its distribution (omnibus P =0.001). Likewise, the adjusted hazard ratios for hypokalemia and hyperkalemia, normokalemia as reference, were 2.35 (95% confidence interval, 1.40–3.93; P =0.001) and 1.55 (95% confidence interval, 1.11–2.16; P =0.011), respectively (omnibus P =0.0003). Furthermore, dynamic changes in potassium were independently associated with substantial differences in mortality risk. Potassium normalization was independently associated with lower mortality risk ( P =0.001).

Conclusions: Either modeled continuously or categorically, serum potassium levels during long-term monitoring were independently associated with mortality in patients with heart failure. Likewise, persistence of abnormal potassium levels was linked to a higher risk of death in comparison with patients who maintained or returned to normal values.