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Abstract
Introduction Exercise capacity is one of the strongest predictors of all cause morbidity and mortality in cardiovascular disease. Atrial fibrillation (AF) can be associated with limited peak exercise tolerance in patients with preserved left ventricular function. However, the contributing factors are poorly understood. The role of inflammation and indeed monocytes has been highlighted as a key mechanism in the adverse cardiac remodelling that takes place in AF.
Purpose To investigate whether total monocyte count, neutrophils, lymphocytes and white blood cell count along with other biomarkers as markers of inflammation affect exercise capacity in patients with permanent AF and preserved left ventricular function.
Methods We studied 225 patients with permanent AF (median (IQR) age 73 (68–78) years, 78% males) recruited from general practice and outpatient clinics. Exclusion criteria included age <50 years, ejection fraction <55%, recent CABG, severe airways disease, BP >160/90 mmHg, advanced renal dysfunction (table 1). White cell count, total monocyte count, neutrophil and lymphocyte counts were obtained from full blood count blood sample taken at the time of first clinic visit. Exercise capacity was evaluated using VO2 max from cardiopulmonary exercise testing (CPET). Potential predictors of exercise capacity were assessed using univariate and multivariate linear regression, adjustment for gender, weight, systolic and diastolic blood pressure, heart rate, history of diabetes, N-terminal pro brain natriuretic peptide (NT-pro-BNP) levels and E/E’ ratio.
Results Total monocyte count was predictive of maximum exercise capacity as measured by CPET on univariate and multivariate analysis (p=0.04 and 0.05 respectively) (table 2). Furthermore, gender, weight, diabetes and diastology were found to be predictive of peak VO2 in patients with AF and preserved left ventricular function. Neither total white blood cell count, neutrophils or lymphocytes were predictive of peak exercise capacity. Resting heart rate, systolic and diastolic blood pressure were not predictors of peak VO2 in this population of patients.
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Conclusion Total monocyte count is associated with peak exercise capacity in this population. The role of monocytes and indeed their contribution to adverse remodelling in patients with AF may be a potential therapeutic target.