Aerobic capacity in patients entering cardiac rehabilitation

Abstract

Background: Symptom-limited treadmill testing is commonly performed on entry to cardiac rehabilitation (CR) for its prognostic value and to design a safe and effective exercise program. Normative values for this evaluation are not available. The primary goals of this study were to establish normative values for peak aerobic capacity (peak V(O2)) for patients entering CR and to create nomograms for conversion of peak V(O2) to a percentage of predicted exercise capacity,stratified by age, gender, and diagnosis.

Methods and results: Peak V(O2) was measured in 2896 patients entering CR from 1996 to 2004. Peak V(O2) was higher in men than in women: 19.3 +/- 6.1 mL.kg(-1).min(-1) (range, 5.2 to 49.7 mL.kg(-1).min(-1)) versus 14.5 +/- 3.9 mL.kg(-1).min(-1) (range, 3.8 to 29.8 mL.kg(-1).min(-1)) (P < 0.0001). Peak V(O2) decreased steadily with age with a greater rate of decline in men than women (0.242 versus 0.116 mL.kg(-1).min(-1) per year) (P < 0.01). Factors associated with lower peak V(O2) include coronary artery bypass grafting (CABG), angina at stress testing, hypertension,and, in women, beta-blocking medications. Nomograms are presented for individual values to be compared with mean values by age, gender, and cardiac diagnosis. These include a nomogram to convert estimated maximal metabolic equivalents to actual peak V(O2) for patients who do not undergo direct measurement of peak V(O2).

Conclusions: Values of peak V(O2) on entry to CR are extremely low, particularly in women, approaching values seen with severe chronic heart failure. This underscores the importance of CR after a major cardiac event to improve physical function and long-term prognosis.