P2493Is exercise training HR above anaerobic threshold level harmful in patients after acute myocardial infarction with high BNP levels?

Abstract

Background: Exercise training heart rate (TrHR) is recommended to be set at the anaerobic threshold (AT) level for high-risk acute myocardial infarction (AMI) patients such as those having heart failure or left ventricular systolic dysfunction. In addition, high intensity exercise training has been reported to aggravate left ventricular (LV) remodeling in the rat model with extensive AMI. However, it remains unknown whether TrHR slightly above AT is actually harmful in AMI patients with elevated B-type natriuretic peptide (BNP) levels. Objective: Accordingly, the objective of this study was to clarify the effects of exercise training at TrHR slightly (0-15%) above AT on exercise capacity and BNP levels in high-risk AMI patients with elevated BNP levels at baseline. Methods: We studied 223 consecutive AMI patients with baseline BNP ≥200pg/ml who participated in our cardiac rehabilitation (CR) program. All patients underwent blood sampling and symptom-limited cardiopulmonary exercise testing (measurements for peak oxygen uptake [PVO2]) at the beginning and the end of the CR. To assess the effects of TrHR below and above AT on PVO2 and BNP, we retrospectively selected consecutive 58 male patients who actively participated in the 3-month supervised outpatient CR program at least once a week and also performed home exercise at least twice a week, according to an individually prescribed TrHR in the range of 90-115% of AT level determined at the initial CPX. They were divided into two groups according to TrHR: Below-AT group (TrHR 97.7±2.6% of AT level, n=13) and Above-AT group (107.0±4.0% of AT level, n=45). Results: At baseline, age (Below-AT: 71y vs Above-AT: 68y, NS), left ventricular ejection fraction (LVEF; 38 vs 38%, NS), BNP (372 vs 415pg/ml, NS), PVO2 (17.9 vs 18.9 ml/kg/min, NS), number of CR attendance in 3 months (26 vs 29 sessions, NS), and exercise training duration (4.4 vs 5.0 hour/week, NS) and frequency (5 vs 6 times/week, NS) were similar in both groups. Notably, after 3-month CR, Above-AT group showed a significantly greater increase in PVO2 than Below- AT group (5.0% vs 13.9%, P=0.03), with equivalent significant BNP decreases (-221pg/ml vs -212pg/ml, NS). No exercise-related cardiac event occurred in both groups. Conclusion: TrHR slightly (0-15%, average 7%) above AT level may result in a greater improvements in PVO2 than that slightly below AT level without aggravating BNP even in high-risk AMI patients with elevated BNP levels at baseline.