The effects of the menopause on left ventricular mechanics

Abstract

Ageing is associated with sex-specific decreases in cardiac function that may be explained by the menopause. However, the effects of the menopause on regional myocardial function and the practical implications of menopause-related differences in cardiac function are unknown. The aim of this thesis was to investigate the effects of the menopause on left ventricular (LV) function and mechanics at rest, and in response to physiological tests and exercise training. In the first study, resting LV function and mechanics were compared between middle-aged pre- and post-menopausal women, as part of an ageing study comprising young adult and middle-aged men and women. Post-menopausal women had lower LV function and mechanics than pre-menopausal women. Middle-aged men had greater peak systolic apical LV mechanics compared with middle-aged women, but there was no evidence that apical mechanics differed between younger men and women. These findings suggest that the menopause lowers LV mechanics, but may only partly explain sex-specific differences in LV apical mechanics with ageing. In the second study, the effects of 12 weeks of high-intensity aerobic interval training on LV function and mechanics were compared between pre- and post-menopausal women. Post-menopausal women had a smaller increase in peak aerobic capacity after exercise training, compared with pre-menopausal women. Physiological testing with lower body negative pressure and submaximal supine cycling revealed higher LV basal mechanics in pre-menopausal women after exercise training compared with post-menopausal women, in contrast to the age-related sex differences observed at the apex in the first study. These findings suggest that the menopause may reduce aerobic adaptability and influence regional LV mechanics. To investigate whether exercise training mitigates the effects of the menopause on LV function and mechanics, the Bayes factor was used to complement statistical inferences from P-values in the third study. Exercise training in post-menopausal women caused an average 5% increase in likelihood of similar LV mechanics relative to untrained pre-menopausal women. Collectively, this thesis provides new evidence for the effects of the menopause on regional LV mechanics and aerobic adaptability. Future work should investigate the potential effects of exercise training intensity and duration on LV mechanics and aerobic adaptability between pre- and post-menopausal women.