U-shaped association of serum potassium with all-cause mortality in patients with atrial fibrillation and chronic kidney disease: a retrospective cohort study

Given the frequent coexistence and bidirectional relationship of atrial fibrillation (AF) and chronic kidney disease (CKD), and the known cardiovascular risks of potassium abnormalities, the impact of serum potassium on mortality in this high-risk population was unclear. This retrospective cohort study investigated the association between serum potassium levels and all-cause mortality in 1703 patients diagnosed with AF and CKD in the First Affiliated Hospital of Shantou University Medical College between August 2018 and December 2023. Multivariate Cox proportional hazards models, restricted cubic spline (RCS), inflection point analysis, and subgroup analyses were used to assess mortality risk across potassium categories: <3.60, 3.60–3.80, 3.80-4.00, 4.00-4.20, 4.20–4.40 (reference: 4.40–4.60), 4.60–4.80, and > 4.80 mmol/L. With the nadir of risk at 4.55 mmol/L via RCS analysis, the results revealed a significant U-shaped association between serum potassium levels and all-cause mortality. Compared to the reference group (4.40–4.60 mmol/L), patients with the lowest potassium levels (< 3.60 mmol/L) had a significantly increased risk of all-cause mortality (HR = 1.55, 95% CI: 1.02–2.35). Similarly, patients with the highest potassium levels (> 4.80 mmol/L) also showed a significantly elevated risk (HR = 1.73; 95% CI, 1.12–2.66). No statistically significant increased mortality risk was observed for other potassium categories. The study concludes that both hypokalemia (< 3.60 mmol/L) and hyperkalemia (> 4.80 mmol/L) are independently associated with an increased risk of all-cause death in AF patients with CKD, demonstrating a U-shaped relationship. However, these results are hypothesis-generating and require prospective validation before clinical implementation. What was known: The prevalenceof AF in CKD is about two- to three-fold higher than that reported in the general population. Some guidelines currentlyrecommend a strict serum potassium management target in AF or CKD patients, which may help avoid adverse events. However, notreatment recommendations were provided for potassium management in AF patients with CKD. This study adds: In addition to hypokalemia and hyperkalemia, low-normal (< 3.60 mmol/L) and high-normal range potassium levels (> 4.80 mmol/L) wereassociated with increased mortality risk, which filled the evidence gap in AF patients with CKD. Potential impact: Among this high-risk population, management within a narrower serum potassium level may enhance the prognosis.