Rationale:

The measurement of peak aerobic exercise capacity is an important prognostic factor in patients with coronary heart disease and is central to developing an exercise prescription.

Objective:

While normative values for peak VO₂ in healthy individuals are well known, similar measures are not available for patients with coronary heart disease. The objective of this study is to report aerobic exercise capacity in a diverse population entering into cardiac rehabilitation (CR).

Methodology:

Between 1996 and 2004, peak VO₂ was measured in 2896 patients entering into CR in Burlington, VT (1502) and Detroit, MI (1394). Peak VO₂, was assessed continuously during a symptom limited graded treadmill exercise tolerance test. Cardiopulmonary measures were averaged every 20 seconds and the highest value was termed peak VO₂, expressed in relative (mL* kg^-1 * min^-1) and absolute (L*min^-1) terms.

Results:

Overall, age of subjects was similar between centers (61 +/- 11 years, range = 21 to 100 years). The Detroit center had more women (33.3 % vs 23.4 %, P <.0001) and more minorities (59 % vs 1 %, P <.0001) than Vermont. Mean peak VO₂ for the entire cohort was 17.9 +/- 6.0 mL* kg^-1 * min^-1 and mean peak respiratory quotient was 1.09 +/- 0.12. Relative and absolute peak VO₂ were significantly lower in women compared to men (14.4 +/- 3.9 mL* kg^-1 * min^-1 vs 19.3 +/- 6.1 mL* kg^-1 * min^-1 and 1.13 +/- 0.36 and 1.74 +/- 0.61 L*min^-1, respectively) (P <.0001), even when adjusted for age. Women were slightly older than men (62 +/- 11 vs 60 +/- 11 years, respectively, P <.0001). Patients undergoing coronary bypass surgery had a significantly lower peak VO₂ than non-surgical patients (post-myocardial infaction, percutaneous revascularization and chronic angina) for both females (13.6 +/- 3.4 vs 14.8 +/- 4.1 mL*kg^-1 * min^-1, P <.0001) and males (17.9 +/- 4.8 vs 20.3 +/- 6.7 mL* kg^-1 * min^-1, P <.0001).

Conclusions:

These results demonstrate that peak VO₂ at entry into CR is remarkably low, particularly in women and post surgical patients. Given the negative prognostic implications of a low peak VO₂, these results reinforce the importance of CR exercise training.