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 1352 females and 5875 males with CAD were analysed to determine if there was a sex difference in achieving maximal oxygen uptake (V˙O_2max) or an identifiable first ventilatory threshold (VT₁). Secondary outcomes were to determine correlates of not achieving V˙O_2max or VT₁ in all patients and in males and females separately.

Results: A greater proportion of males than females achieved V˙O_2max or VT₁ (89.7% vs 71.3%; P < 0.001) as well as specifically achieving V˙O_2max (40.2% vs 26.7%; P < 0.001) and VT₁ (88.0% vs 69.2%; P < 0.001). The most influential correlates of not achieving V˙O_2max or VT₁ were female sex (odds ratio 3.1, 95% confidence interval 2.6-3.7), age > 60 years, 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 in males. Correlates differed by sex. The threshold for when age affected achieving V˙O_2max or VT₁ on the cycle CPET was earlier for females (> 50 years of age) than for males (> 70 years of age) with no difference on treadmill (> 80 years of age for both).

Conclusions: Although most patients achieved V˙O_2max or VT₁ on the CPET, females were 3 times less likely than males to achieve V˙O_2max or VT₁. 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.