Predictors of improvements in exercise capacity during cardiac rehabilitation in the recovery phase after coronary artery bypass graft surgery versus acute myocardial infarction.

ABSTRACT

This study aimed to elucidate the predictors of improvements in exercise capacity during cardiac rehabilitation (CR) in the recovery phase after coronary artery bypass graft surgery (CABG) versus acute myocardial infarction (AMI). We studied 152 patients (91 after AMI and 61 after CABG) who participated in a 3-month CR program. All patients underwent a cardiopulmonary exercise test, blood tests, maximal quadriceps isometric strength (QIS) measurement, and bioelectrical impedance body composition measurement at the beginning and end of the 3-month CR program. At baseline, the percentage of predicted peak oxygen uptake (%pred-PVO2), maximal QIS, and hemoglobin (Hb) were significantly lower, while C-reactive protein (CRP) was significantly higher, in the CABG than the AMI group. After the 3-month CR, %change in PVO2 (%ΔPVO2) was significantly greater in the CABG than the AMI group (18 ± 15% vs 11 ± 12%, P < 0.01). At univariate analysis, baseline plasma brain natriuretic peptide (BNP), %change in maximal QIS after CR (%Δ maximal QIS), and change in plasma hemoglobin (ΔHb) significantly correlated with %ΔPVO2 in the CABG group, whereas only baseline %pred-PVO2 did so in the AMI group. Multiple regression analysis revealed that the same factors were independent and significant predictors of %ΔPVO2 in the CABG and AMI groups. The predictors of improvements in exercise capacity after CR differed between patients after CABG or AMI. Specifically, in CABG patients both enhancing QIS and correcting anemia may contribute to greater improvements in exercise capacity after CR, while a more effective CR program should be designed for CABG patients with high baseline BNP.