Increased peak postoperative B-type natriuretic peptide predicts decreased longer-term physical function after primary coronary artery bypass graft surgery

Abstract

Background: Increased peak postoperative B-type natriuretic peptide (BNP) is associated with increased major adverse cardiovascular events and all-cause mortality after coronary artery bypass graft (CABG) surgery. Whether increased postoperative BNP predicts worse postdischarge physical function (PF) is unknown. We hypothesized that peak postoperative BNP associates with PF assessed up to 2 yr after CABG surgery, even after adjusting for clinical risk factors. including preoperative PF.

Methods: This two-institution prospective cohort study included patients undergoing primary CABG surgery with cardiopulmonary bypass. Short Form-36 questionnaires were administered to subjects preoperatively and 6 months, 1 yr, and 2 yr postoperatively. Short Form-36 PF domain scores were calculated using the Short Form-36 norm-based scoring algorithm. Plasma BNP concentrations measured preoperatively and on postoperative days 1-5 were log(10) transformed before analysis. To determine whether peak postoperative BNP independently predicts PF scores 6 months through 2 yr after CABG surgery, multivariable longitudinal regression analysis of the postoperative PF scores was performed, adjusting for important clinical risk factors.

Results: A total of 845 subjects (mean ± SD age, 65 ± 10 yr) were analyzed. Peak postoperative BNP was significantly associated with postoperative PF (effect estimate for log(10) peak BNP, -7.66 PF score points [95% CI, -9.68 to -5.64]; P = <0.0001). After multivariable adjustments, peak postoperative BNP remained independently associated with postoperative PF (effect estimate for log(10) peak BNP, -3.06 PF score points [95% CI, -5.15 to -0.97]; P = 0.004).

Conclusions: Increased peak postoperative BNP independently associates with worse longer-term PF after primary CABG surgery. Future studies are needed to determine whether medical management targeted toward reducing increased postoperative BNP can improve PF after CABG surgery.

Figures

Figure 1

This diagram outlines subject exclusions from the CABG Genomics Program cohort for this study. * A total of 47 of the 1,183 subjects eligible for analysis died during the 2-yr study follow-up period (4%). 17 of these subjects died before 6 month follow-up. †Of the 103 subjects excluded for missing preoperative PF score data, 3 subjects died before 6 month follow-up, and 2 subjects died between 1 and 2 yr follow-up ‡Of the 235 subjects additionally excluded for having no follow-up postoperative PF score follow-up, 14 subjects died before 6 month follow-up, 9 subjects died between 6 months and 1 yr follow-up, and 5 subjects died between 1 and 2 yr follow-up. §Of the 845 analyzed subjects, 2 subjects died between 6 months and 1 yr follow-up, and 12 subjects died between 1 and 2 yr follow-up. BNP = B-type natriuretic peptide; CABG = coronary artery bypass graft; PF = physical function; SF = Short Form

Figure 2

Preoperative and 6 month, 1 yr, and 2 yr postoperative Short Form-36 norm based physical function domain scores for 845 subjects undergoing primary coronary artery bypass graft surgery. The lower and upper borders of the box plots represent the 25th and 75th percentile values, and the ends of the upper and lower whiskers represent the 10th and 90th percentile values. The dashed line connects the median values for preoperative and follow-up time points *signifies significantly higher than preoperative baseline (P < 0.0001). # signifies significantly lower than prior postoperative time point (P = 0.0001). PF = physical function; SF = Short Form