Prognostic implication of monocytes in atrial fibrillation: The West Birmingham Atrial Fibrillation Project

BACKGROUND AND OBJECTIVES: High monocyte counts are related to adverse outcomes in cardiovascular disease. Their role in prognostication in patients with atrial fibrillation (AF) is unknown. We investigated whether monocyte counts are useful as a marker of prognosis in patients with AF.

METHODS: Monocyte counts were obtained from blood samples in 881 AF patients. Study outcomes were (i) all-cause death; (ii) major adverse cardiovascular events; (iii) stroke, TIA or other systemic embolism (SSE); and (iv) major bleeding.

RESULTS: Median follow up was 7.2 years; 44% of patients died, 48% developed MACE; 9% had SSE and 5% had major bleeding. On Cox regression, after adjustment for CHA2DS2-VASc score, the highest quartile of monocyte counts (i.e., ≥580 μL vs. other quartiles) was associated with increased risk of death (hazard ratio [HR] 1.64, 95% confidence interval [CI] 1.31-2.05, p<0.001) and MACE (HR 1.58, 95% CI 1.28-1.96, p<0.001). Persistent monocyte levels ≥580 per μL during follow up were associated with further increase in risk of death (HR 1.52, 95% CI 1.10-2.11, p = 0.01) and MACE (HR 1.54, 95% CI 1.13-2.09, p = 0.006). Persistent monocyte levels ≥580 per μL during were associated with a significant increase in major bleeding events (HR 2.77, 95% CI 1.36-5.67, p = 0.005, after adjustment for HAS-BLED score).

CONCLUSION: High monocyte counts independently predict the occurrence of MACE, major bleeding and mortality, but not SSE. Understanding the pathophysiological mechanisms involved would help understand the relationships between monocytes, and adverse thrombotic and bleeding outcomes in AF patients.