ABSTRACT: Background Thrombocytopenia is associated with increased mortality in the general population, but few data exist in patients with atrial fibrillation (AF) taking oral anticoagulants. We investigated factor determinants of thrombocytopenia in a large cohort of patients affected by AF and its association with total mortality. Methods and Results Multicenter prospective cohort study, including 5215 patients with AF from the START (Survey on Anticoagulated Patients Register) registry, 3877 (74.3%) and 1338 (25.7%) on vitamin K or non-vitamin K antagonist oral anticoagulants, respectively. Thrombocytopenia was defined by a platelet count <150×109/L. Determinants of thrombocytopenia were investigated, and all-cause mortality was the primary survival end point of the study. Thrombocytopenia was present in 592 patients (11.4%). At multivariable logistic regression analysis, chronic kidney disease (odds ratio [OR], 1.257; P=0.030), active cancer (OR, 2.065; P=0.001), liver cirrhosis (OR, 7.635; P<0.001), and the use of diuretics (OR, 1.234; P=0.046) were positively associated with thrombocytopenia, whereas female sex (OR, 0.387; P<0.001) and the use of calcium channel blockers (OR, 0.787; P=0.032) were negatively associated. During a median follow-up of 19.2 months (9942 patient-years), 391 deaths occurred (rate, 3.93%/year). Mortality rate increased from 3.8%/year to 9.9%/year in patients with normal platelet count and in those with moderate-severe thrombocytopenia, respectively (log-rank test, P=0.009). The association between moderate-severe thrombocytopenia and mortality persisted after adjustment for CHA2DS2 VASc score (hazard ratio, 2.431; 95% CI, 1.254-4.713; P=0.009), but not in the fully adjusted multivariable Cox regression analysis model. Conclusions Thrombocytopenia is common in patients with AF. Despite an increased incidence of mortality, thrombocytopenia was not associated with mortality at multivariable analysis. Thrombocytopenia may reflect the presence of comorbidities associated with poor survival in AF.
