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 V̇ o 2 ) for patients entering CR and to create nomograms for conversion of peak V̇ o 2 to a percentage of predicted exercise capacity, stratified by age, gender, and diagnosis. Methods and Results— Peak V̇ o 2 was measured in 2896 patients entering CR from 1996 to 2004. Peak V̇ o 2 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 V̇ o 2 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 V̇ o 2 include coronary artery bypass grafting (CABG), angina at stress testing, hypertension, and, in women, β-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 V̇ o 2 for patients who do not undergo direct measurement of peak V̇ o 2 . Conclusions— Values of peak V̇ o 2 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.