Relationship between urinary potassium excretion, serum potassium levels, and cardiac injury in non-dialysis chronic kidney disease: KoreaN cohort study for Outcome in patients With Chronic Kidney Disease (KNOW-CKD).

Although the cardiovascular benefits of an increased urinary potassium excretion have been suggested, little is known about the potential cardiac association of urinary potassium excretion in patients with chronic kidney disease (CKD). In addition, whether the cardiac association of urinary potassium excretion was mediated by serum potassium levels has not been studied yet. We reviewed the data of 1,633 patients from a large-scale multicenter prospective Korean study (2011-2016). Spot urinary potassium to creatinine ratio was used as a surrogate for urinary potassium excretion. Cardiac injury was defined as a highly sensitive troponin T (hs-TnT) ≥ 14 ng/L. Odds ratios (ORs) and 95% confidence intervals (CIs) for cardiac injury were calculated using logistic regression analyses. Of 1,633 patients, the mean spot urinary potassium to creatinine ratio was 49.5 ± 22.6 mmol/g Cr and the overall prevalence of cardiac injury was 33.9%. Although serum potassium levels were not associated with cardiac injury, per 10 mmol/g Cr increase in the spot urinary potassium to creatinine ratio was associated with decreased odds of cardiac injury: OR (95% CI) of 0.917 95% CI (0.841-0.998, P = 0.047) in multivariate logistic regression analysis. In mediation analysis, approximately 6.4% of the relationship between spot urinary potassium to creatinine ratio and cardiac injury was mediated by serum potassium levels, which was not statistically significant ( P = 0.368). Higher urinary potassium excretion was associated with lower odds of cardiac injury, which was not mediated by serum potassium levels.