Diagnostic accuracy of pre-operative NT-proBNP level in predicting short-term outcomes in coronary surgery: a pilot study.

BACKGROUND

B-type natriuretic peptides (BNP) are acknowledged markers of acute and chronic heart failure. Insufficient data exist, however, regarding their diagnostic usefulness in cardiac surgery, particularly in coronary patients.

AIM

To assess diagnostic accuracy of preoperative value of NT-proBNP level as a predictor of short-term postoperative complications in subjects undergoing coronary artery bypass grafting (CABG).

METHODS

This pilot study included 100 consecutive patients scheduled for elective CABG, including 24 females and 76 males (mean age 65.9 ± 9.1 years). Exclusion criteria were: significant valvular disorders, off-pump procedure, renal failure (GFR < 60 mL/min/1.73 m2), low ejection fraction (< 30%), intra-aortic balloon pump counterpulsation (IABP), use of inotropic agents, atrial fibrillation (AF), and implanted pacemaker or defibrillator. The NT-proBNP level was measured on the day of the surgery before induction of anaesthesia. We investigated short-term postoperative complications, defined as those occurring within 30 days or before hospital discharge.

RESULTS

Median NT-proBNP concentration was 526.0 pg/mL (IQR 156.0-1150.0). None of patients died postoperatively. Excessive drainage (> 850 mL) was found in 13 (13%) patients and 22 (22%) subjects required transfusions. Prolonged mechanical ventilation (> 12 h) was necessary in 15 (15%) patients and respiratory failure occurred in 2 (2%) of them. Postoperative AF was present in 34 (34%) subjects. Perioperative myocardial infarction was diagnosed in 2 (2%) persons. Low cardiac output was present in 9 (9%) patients. Haemodynamic support with the use of IABP was necessary in 7 (7%) patients and inotropic drugs were used in 61 (61%) subjects. Stroke or delirium was diagnosed in 1 (1%) subject. The NT-proBNP level correlated with the operative risk estimated by logistic and additive EuroSCORE: r = 0.558 (95% CI 0.406-0.680; p < 0.001) and r = 0.551 (95% CI 0.397-0.674; p < 0.001), respectively. The NT-proBNP level correlated significantly with the length of Intensive Care Unit (ICU) stay and hospital stay: r = 0.412 (95% CI 0.238-0.566; p < 0.001) and r = 0.547 (95% CI 0.393-0.672; p < 0.001), respectively. The NT-proBNP level was a predictor of postoperative prolonged mechanical ventilation, respiratory failure, AF, IABP use, inotropic support and postoperative platelet transfusions (p < 0.05 for all). However, good or very good diagnostic accuracy was found only in relation to mechanical ventilation (AUROC = 0.854), respiratory insufficiency (AUROC = 0.867), IABP use (AUROC = 0.889), and milrinone use (AUROC = 0.929).

CONCLUSIONS

Preoperative assessment of NT-proBNP level in CABG patients could be a valuable diagnostic method for predicting several postoperative complications, especially pulmonary outcomes and requirement for haemodynamic support, and it correlated with the length of ICU stay and hospital stay.