Is NT-pro-BNP predictive of atrial fibrillation in patients undergoing coronary artery bypass surgery?

We read with interest the recent article by Gasparovic et al. [1] stating that NT-pro-brain natriuretic peptide (BNP) is predictive of atrial fibrillation (AF) in patients undergoing coronary artery bypass surgery (CABG). A total of 215 consecutive patients in sinus rhythm (SR) undergoing elective CABG were grouped according to their respective postoperative rhythm into SR and AF groups. Fifty-five patients whose preoperative and postoperative NT-pro-BNP were significantly higher developed AF (26%). However, can NT-pro-BNP be considered an independent predictor of AF? Both BNP and NT-pro-BNP levels increase with age [2,3], and there is a reduction in the natriuretic peptide clearance (NPR)-C clearance receptor with ageing [4]. In addition, there is an association between heart failure (HR) and elevated levels of BNP. In their article, the AF group was older, more symptomatic and had a higher risk profile (Euro SCORE). We think the higher preoperative NT-pro-BNP were caused by the older age and the inferior cardiac function in AF groups, so it is inappropriate to recognise preoperative NT-pro-BNP as an independent predictor of AF. Otherwise, NT-pro-BNP levels seem to rise in the setting of AF, including lone AF [5], so the higher postoperative NT-pro-BNP may be caused by AF. On the other hand, NT-pro-BNP is secreted from the ventricles. We think the left ventricular end-diastolic diameter (LVDd), which may have greater impact on the NT-pro-BNP than the left atrial diameter, should be included in preoperative patient characteristics.