Association between serum alkaline phosphatase and cardiovascular events in patients with atrial fibrillation

High alkaline phosphatase (ALP) levels are reported to be associated with an increased risk of cardiovascular events in patients with chronic kidney disease (CKD). Given the pathological link with CKD, a similar relationship may exist in patients with atrial fibrillation (AF). We retrospectively evaluated 1,719 patients with AF and normal hepatic function who were registered in the Shinken Database between November 2011 and March 2017. Study patients were divided into three groups according to ALP value tertiles with cut-offs of 175 and 227 IU/L (normal range: 95-350 IU/L). Each group's incidence rate was recorded, and the risks of cardiovascular events and each component for patients in the middle and high ALP tertiles were compared with those in the low tertile and evaluated using Cox regression models. The additional predictive value of the high ALP tertile over the existing risk scores for the components of cardiovascular events was evaluated via receiver operating characteristic (ROC) curve analysis. During the median follow-up of 731 days (IQR: 444-1095 days), 137 cardiovascular events occurred, with incidence rates of 2.94%, 3.44%, and 6.19%/person-year for the low, middle, and high ALP tertiles, respectively. Of these cardiovascular events, heart failure had the highest incidence rates (1.34%, 1.89%, and 4.29%/person-year for the low, middle, and high ALP tertiles, respectively) and the incidence rates of the other components of cardiovascular event were similar in each ALP groups. Multivariate Cox regression analysis yielded hazard ratios of 1.22 (95% confidence interval [CI] 0.70-1.96) and 1.62 (95% CI 1.06-2.48) for cardiovascular events and 1.66 (95% CI 0.87-3.15) and 2.50 (95% CI 1.39-4.48) for heart failure admission in the middle and high ALP tertiles, respectively. By ROC curve analysis for heart failure admission showed that the high ALP tertile lacked significant additive predictive value over the existing risk scores. High serum ALP levels, even those in the normal range, were significantly associated with an increased risk of cardiovascular events, especially heart failure admission in patients with AF.