Brain natriuretic peptide elevation and the development of atrial fibrillation following coronary artery bypass surgery.

The study was designed to determine whether the development of atrial fibrillation is associated with post-operative left ventricular dysfunction and subsequent left atrial stretch. We recruited 133 patients with well preserved pre-operative left ventricular function undergoing bypass surgery. Brain natriuretic peptide was measured at baseline, 24 and 48 h after the onset of cardiopulmonary bypass, and patients were monitored for 72 h after surgery. Atrial fibrillation occurred in 65 patients. Median 48 h brain natriuretic peptide levels were greater in the atrial fibrillation group (440 pg/ml (AF) and 319 pg/ml (non AF) P=0.001). As atrial fibrillation can cause an elevation in brain natriuretic peptide we divided the subjects into early atrial fibrillation (<48 h) and late (>48 h). In those with early atrial fibrillation there was no difference in the 24 h brain natriuretic peptide levels (381 pg/ml and 365 pg/ml P=0.73). In those with late atrial fibrillation the median 48 h brain natriuretic peptide level was greater than in the control group (405 pg/ml and 319 pg/ml, respectively, P=0.02). Brain natriuretic peptide levels rise significantly following bypass surgery. This increase was more evident in those who develop late atrial fibrillation which may suggest a role for atrial stretch in this arrhythmia.