Plasma B-type natriuretic peptide predicts atrial fibrillation during rehabilitation after cardiac surgery.

Sarzi Bragaet al.
European Journal of Cardiovascular Prevention & Rehabilitation

Special Author Introduction

Atrial fibrillation (AF) is a frequent complication of cardiac surgery, occurring, in the early postoperative period, in up to 65% of patients. Many factors, including valvular heart disease, male gender, atrial enlargement, chronic obstructive lung disease, electrolyte disarrangements, hypertension, and left ventricular hypertrophy, have been associated with postoperative AF, the most consistent being patient older age. Although this arrhythmia is benign and often self-limiting, it adds morbidity, prolongs hospital length of stay, and significantly increases costs.

B-type natriuretic peptide (BNP) is a hormone produced by cardiomyocytes with regulatory and modulatory activities on the cardiovascular system. Circulating levels of BNP are increased in conditions characterized by left ventricular dysfunction and volume overload. Some clinical studies have recently shown that BNP levels are also associated with AF and can predict AF occurrence short-term after cardiac surgery. In this context no information is available on the predictive potential of BNP levels at a later time point. Aim of the present study was to evaluate whether BNP levels predict post-cardiac surgery AF events occurring during rehabilitation program. AF impact on hospitalization length and rehabilitation program have also been evaluated.

One hundred and forty-nine patients (mean age 66 ± 10 yrs, 76% males, LVEF 56 ± 9%) who underwent cardiac surgery (coronary artery by-pass graft 64%, valve replacement 28%, combined surgery 8%) were monitored for ‘late' AF, defined as AF occurring during the rehabilitation period (20 ± 5 days) in contrast to ‘early' AF defined as AF documented in the surgical department soon after surgery.

At admission, 10 ± 5 days after cardiac surgery, blood samples for routine chemistry and plasma BNP were drawn, ECG and transthoracic echocardiography were performed, and history of AF occurred in the surgical department was collected by the hospital discharge summaries. Plasma BNP levels less than 100 pg/ml were considered as normal. The occurrence of the first documented AF episode during the rehabilitative hospitalization was the study endpoint.

Late AF was observed in 17% of patients. AF patients had higher BNP levels than event-free patients (459 ± 209 vs 401 ± 449 pg/ml, p = 0.01). Lower kaliemia values (p = 0.048), early AF (p < 0.001), and combined surgery (coronary artery by pass graft and valve replacement; p = 0.016) were also associated with late AF. At multivariate analysis, BNP levels more than 322 pg/ml (p = 0.02), and early AF (p = 0.003) showed an independent association with late AF occurrence, which did not interfere with the physical training program but prolonged hospitalization (22 ± 5 vs 20 ± 5 days, p = 0.062) and telemetry monitoring (6 ± 5 vs 1 ± 3 days, p < 0.001).

Our data demonstrate that high BNP plasma levels are independent predictors of postoperative AF that occurs late after cardiac surgery, during the rehabilitation period. At multivariate analysis, other than BNP levels, early postoperative AF was an independent predictor of late AF, increases medical and nurse time requirements and prolongs hospital stay. This may suggest a more aggressive prophylactic approach, either in the intra-operative phase, in example with the use of ablation techniques, and during the rehabilitation period, with the optimization of the medical treatment in high-risk patients.

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