Sex Differences and Correlates of the Utility of the Cardiopulmonary Exercise Test for Prescribing Exercise at Entry to Cardiac Rehabilitation.

Abstract

Background: Despite the importance of objective measures for prescribing aerobic exercise for mitigating cardiovascular risk in people with coronary artery disease (CAD), no study has examined sex differences in the utility of the cardiopulmonary exercise test (CPET) for developing the exercise prescription.

Methods: CPET results from 1,352 females and 5,875 males with CAD were analyzed to determine if there was a sex difference in achieving maximal oxygen uptake (VO2max) or an identifiable first ventilatory threshold (VT1). Secondary outcomes were to determine correlates of not achieving VO2max or VT1 in all patients and males and females separately.

Results: A greater proportion of males than females achieved VO2max or VT1 (89.7% vs 71.3%; p<0.001), specifically achieving VO2max (40.2% vs 26.7%; p<.001) and VT1 (88.0% vs 69.2%; p<.001). The most influential correlates of not achieving VO2max or VT1 were female sex (OR=3.1:95% CI, 2.6-3.7), age >60 yrs, tested on treadmill vs cycle, depressive symptoms, and a secondary heart failure diagnosis. At entry to cardiac rehabilitation, these correlates were more prevalent in females than males. Correlates differed by sex. The threshold for when age affected achieving VO2max or VT1 on the cycle CPET was earlier for females (>50 yrs) than males (>70 yrs) with no difference on treadmill (>80 yrs, both).

Conclusions: While most patients achieved VO2max or VT1 on the CPET, females were 3 times less likely to achieve VO2max or VT1 than males. Strategies to improve utility of CPETs for females such as alternative exercise test protocols and investigation into underlying mechanisms for effects of depressive symptoms should be conducted.