Serum Potassium Levels and Risk of Sudden Cardiac Death Among Patients With Chronic Kidney Disease and Significant Coronary Artery Disease

Abstract

Introduction: Chronic kidney disease (CKD) patients have increased risks of sudden cardiac arrest and sudden cardiac death (SCA/SCD) that are not explained by traditional risk factors. We examined associations between serum potassium and SCA/SCD in a large cohort of patients with coronary artery disease (CAD) and moderate CKD.

Methods: Among 22,009 patients who underwent cardiac catheterization at our institution between 1999 and 2011, 6181 patients had an estimated glomerular filtration rate of ≤60 ml/min per 1.73 m² and were not receiving renal replacement therapy. The risk of SCA/SCD and all-cause mortality associated with potassium concentration was evaluated at the time of cardiac catheterization (baseline) and most proximate to SCA/SCD events. Covariate-adjusted Cox models were used to examine relationships between baseline potassium measurements and outcomes. A propensity score-matched, case-control design was used to assess risk associations of potassium measurements obtained proximate to SCA events.

Results: In the baseline potassium analysis, compared with levels in the normal range, there was no significant risk association between hyperkalemia (>5 mEq/l) or hypokalemia (<3.5 mEq/l) and SCA/SCD or all-cause death after covariate adjustment. In the proximate potassium analysis, hyperkalemia occurred more frequently than hypokalemia (16.7% vs. 3%), and was associated with a doubling in SCA/SCD risk (adjusted odd ratio: 2.37; 95% confidence interval: 1.33-4.23) whereas there was no significant relationship between hypokalemia and outcome.

Discussion: Among CKD patients with significant CAD, elevated serum potassium levels >5.0 mEq/l are common and are associated with an increased short-term risk of SCA/SCD. Early detection and treatment of hyperkalemia may reduce the high risk of SCD among CKD patients.

Keywords: cardiac arrhythmias; cardiovascular disease; chronic kidney disease; hyperkalemia; hypokalemia; sudden death.

Figure 1

Study flow diagram. eGFR, estimated glomerular filtration rate.

Figure 2

Unadjusted cumulative incidence curves for sudden cardiac death/sudden cardiac arrest (SCD/SCA) according to baseline serum potassium categories. High: >5.0 mEq/l; normal: 3.5 to 5.0 mEq/l; low: <3.5 mEq/l.

Figure 3

Risk of sudden cardiac death/sudden cardiac arrest according to the last recorded serum potassium value before the event. Odds ratio estimates are shown with 95% confidence intervals (CI) within each serum potassium category. *Adjusted for ejection fraction, congestive heart failure severity, and proportion of patients who underwent coronary artery bypass grafting after catheterization.