N-terminal pro B-type natriuretic peptide is an independent predictor of postoperative myocardial injury in patients undergoing major vascular surgery

The data for log-transformed N-terminal pro B-type natriuretic peptide (NT-pro-BNP) levels in patients who have myocardial injury after surgery, compared with those who do not, are shown in box and whisker plots. The horizontal line in the center of the box represents the median; the top and bottom borders of the box represent the interquartile range, and the whiskers mark the range. The y axis represents the log-transformed NT-pro-BNP, which was used in the power calculation. Patients who sustained postoperative myocardial injury had a significantly higher preoperative NT-pro-BNP value than those who did not (P = .003).

A receiver operating characteristic curve was calculated for the ability of the preoperative plasma N-terminal pro B-type natriuretic peptide level to predict postoperative cardiac events in the elective vascular surgical cohort. The horizontal axis represents the false-positive ratio (1 minus specificity), and the vertical axis represents the true-positive ratio (sensitivity). The area under curve, which measures discrimination (ie, the ability of the test to correctly classify those with and without myocardial injury), was 68% (95% confidence interval, 56%-78%, P = .005).