The interrelationship between preoperative anemia and N-terminal pro-B-type natriuretic peptide: the effect on predicting postoperative cardiac outcome in vascular surgery patients.

INTRODUCTION: N-terminal pro-B-type natriuretic peptide (NT-proBNP) predicts adverse cardiac outcome in patients undergoing vascular surgery. However, several conditions might influence this prognostic value, including anemia. In this study, we evaluated whether anemia confounds the prognostic value of NT-proBNP for predicting cardiac events in patients undergoing vascular surgery. METHODS: A detailed cardiac history, resting echocardiography, and hemoglobin and NT-proBNP levels were obtained in 666 patients before vascular surgery. Anemia was defined as serum hemoglobin <13 g/dL for men and <12 g/dL for women. Troponin T measurements and 12-lead electrocardiograms were performed on postoperative days 1, 3, 7, and 30 and whenever clinically indicated. The primary end point of the study was the composite of 30-day postoperative cardiovascular death, nonfatal myocardial infarction, and troponin T release. Receiver operating characteristic curve analysis was used to assess the optimal cutoff value of NT-proBNP for the prediction of the composite end point. Multivariable regression analysis was used to assess the additional value of NT-proBNP for the prediction of postoperative cardiac events in nonanemic and anemic patients. RESULTS: Anemia was present in 206 patients (31%) before surgery. Hemoglobin level was inversely related with the NT-proBNP levels (beta coefficient = -2.242; P = 0.025). The optimal predictive cutoff value of NT-proBNP for predicting the composite cardiovascular outcome was 350 pg/mL. After adjustment for clinical cardiac risk factors, both anemia (odds ratio [OR] 1.53; 95% confidence interval [CI]: 1.07-2.99) and increased levels of NT-proBNP (OR 4.09; 95% CI: 2.19-7.64) remained independent predictors for postoperative cardiac events. However, increased levels of NT-proBNP were not predictive for the risk of adverse cardiac events in the subgroup of anemic patients (OR 2.16; 95% CI: 0.90-5.21). CONCLUSIONS: Both anemia and NT-proBNP are independently associated with an increased risk for postoperative cardiac events in patients undergoing vascular surgery. NT-proBNP has less predictive value in anemic patients.

Anemia as an independent predictor of perioperative and long-term cardiovascular outcome in patients scheduled for elective vascular surgery.

Anemia is common in patients scheduled for vascular surgery and is a risk factor for adverse cardiac outcome. However, it is unclear whether this is an independent risk factor or an expression of underlying co-morbidities. In total, 1,211 patients (77% men, 68 +/- 11 years of age) were enrolled. Anemia was defined as serum hemoglobin levels <13 g/dl for men and <12 g/dl for women and was divided into tertiles to compare mild (men 12.2 to 13.0, women 11.2 to 12.0), moderate (men 11.0 to 12.1, women 10.2 to 11.1), and severe (men 7.2 to 11.0, women 7.5 to 10.1) anemia with nonanemia. Outcome measurements were 30-day and 5-year major adverse cardiac events (MACEs; cardiac death or myocardial infarction). All risk factors were noted. Multivariable logistic and Cox regression analyses were used, adjusting for all cardiac risk factors, including heart failure and renal disease. Data are presented as hazard ratios with 95% confidence intervals. In total, 74 patients (6%) had 30-day MACEs and 199 (17%) had 5-year MACEs. Anemia was present in 399 patients (33%), 133 of whom had mild anemia, 133 had moderate anemia, and 133 had severe anemia. Presence of anemia was associated with renal dysfunction, diabetes, and heart failure. After adjustment for all clinical risk factors, 30-day hazard ratios for a MACE per anemia group were 1.8 for mild (0.8 to 4.1), 2.3 for moderate (1.1 to 5.4), and 4.7 for severe (2.6 to 10.9) anemia, and 5-year hazard ratios for MACE per anemia group were 2.4 for mild (1.5 to 4.2), 3.6 for moderate (2.4 to 5.6), and 6.1 for severe (4.1 to 9.1) anemia. In conclusion, the presence and severity of preoperative anemia in vascular patients are significant predictors of 30-day and 5-year cardiac events, regardless of underlying heart failure or renal disease.