Aerobic capacity in patients entering cardiac rehabilitation

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 VO2) for patients entering CR and to create nomograms for conversion of peak VO2 to a percentage of predicted exercise capacity, stratified by age, gender, and diagnosis. Methods and Results - Peak VO2 was measured in 2896 patients entering CR from 1996 to 2004. Peak VO2 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 VO2 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 VO2 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 VO2 for patients who do not undergo direct measurement of peak VO2. Conclusions - Values of peak VO2 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.