NT-pro-BNP, but not C-reactive protein, is predictive of atrial fibrillation in patients undergoing coronary artery bypass surgery

Abstract

Objective: Atrial fibrillation (AF) remains the most commonly observed complication following myocardial revascularisation surgery. We aimed to evaluate the clinical utility of N-terminal fragment of the brain natriuretic peptide (NT-pro-BNP), troponin T, transcoronary lactate gradient (TCLG) and C-reactive protein (CRP) as predictors of AF in patients undergoing isolated coronary artery bypass surgery (CABG).

Methods: This study included 215 consecutive patients in sinus rhythm (SR) undergoing elective CABG between May 2007 and May 2008. The patients were grouped according to their respective postoperative rhythm into SR and AF groups. The data are presented as mean values+/-standard deviation, or medians with quartiles.

Results: Fifty-five patients developed AF (26%). The preoperative NT-pro-BNP values were 273+/-347 and 469+/-629 pg ml(-1) in the SR and AF groups, respectively (p<0.0001). The postoperative NT-pro-BNP values were 3110+/-3600 pg ml(-1) in the SR and 4625+/-5640 pg ml(-1) in the AF groups (p=0.027). The transcoronary lactate gradient rose from the pre-cardiopulmonary bypass values to those observed 5 min after revascularisation in both groups (-0.05+/-0.37 to 0.39+/-0.46 mmol l(-1) (p<0.0001) in the SR group and -0.01+/-0.27 to 0.43+/-0.46 mmol l(-1) (p<0.0001) in the AF group). The CRP values increased from 6+/-13 to 163+/-88 mg l(-1) (p<0.0001) in the SR group, and from 6+/-16 to 163+/-104 mg l(-1) (p<0.0001) in the AF group. The dynamics of TCLG and CRP did not differ between the groups (p=0.71, p=0.44, respectively). The troponin T values on postoperative day 1 were significantly higher in the AF than the SR group (0.86 (0.49-2.1) ng ml(-1) vs 0.67 (0.37-1.16) ng ml(-1), p=0.046). The duration of cardiopulmonary bypass (CPB) was 85+/-24 min in the SR and 93+/-30 min in the AF group (p=0.05). Patients who developed AF were older (66+/-7 years vs 60+/-9 years, p<0.0001) and had a higher EuroSCORE (3.9+/-2.7 vs 2.9+/-2.2, p=0.009). Multivariate analysis identified age (p=0.0043), preoperative NT-pro-BNP (p=0.019) and duration of CPB (p=0.035) as independent predictors of AF.

Conclusions: Preoperative and postoperative NT-pro-BNP as well as TnT values were significantly higher in patients who subsequently developed AF. TCLG and CRP were not useful in identifying patients at higher risk for AF. Multivariate analysis identified age, preoperative NT-pro-BNP and duration of CPB as independent correlates of AF.