Exercise Tolerance in Ageing and Hypertrophic Cardiomyopathy

In a recent WCMR Science Seminar, we heard from PhD student Amy Fuller about her research that involves investigating exercise tolerance in ageing and hypertrophic cardiomyopathy. Amy’s project covers pathophysiology to lifestyle interventions and you can read more here.

Hypertrophic cardiomyopathy (HCM) is the most common inherited disease of the heart and is the most common cause of sudden cardiac death in adults under 35 years of age. HCM may result in impaired exercise (functional) capacity. Exercise tolerance is defined as the level of physical exertion a person may achieve before reaching a state of exhaustion. In the clinic, the limit of exercise tolerance is assessed using cardiopulmonary exercise stress testing (CPET). During these tests, a measurement known as maximal or peak O2 consumption (VO2max or VO2peak respectively) is made, which is representative of exercise tolerance.

The ability to measure VO2max in HCM patients is important as it is a good tool to assess disease progression. Exercise training has been shown to significantly increase exercise tolerance in HCM patients, however it has limited effect on the heart structure. Dietary supplementation with inorganic nitrate (i.e., concentrated nitrate-rich beetroot juice) has been shown to improve exercise capacity, blood supply to the heart and the ability of the heart to stretch to increase ventricular blood volume during exercise and rest, whilst reducing arterial stiffness, all of which are linked to the ability of the left ventricle to relax.

Lifestyle interventions including exercise training and dietary nitrate supplementation can safely improve exercise tolerance in patients with heart failure, but few studies have reported the effects in patients with HCM. Therefore, the aim of this study was to assess the effect of a novel lifestyle intervention on exercise tolerance, clinical symptoms, and quality of life in HCM. The intervention comprised of an increase in physical activity (increase in step count by 2000 steps on average per day) and consumption of a 70ml beetroot juice shot daily for 16 weeks. 29 participants took part in the study, 20 participants were in the intervention group and 9 were in the control group (no intervention).

Parameters analysed so far demonstrate a trend of increased resting stroke volume and cardiac output, as well as lowered blood pressure parameters in participants following the lifestyle intervention. There was also a trend towards an increase in peak heart rate, stroke volume and cardiac output following exercise, as well as an increase in quality of life. In contrast, in the control group, there was a trend towards a decrease in resting stroke volume and cardiac output, an increase in blood pressure parameters, and a decrease in peak exercise parameters and quality of life score. These data suggest a trend of decreased cardiac stress and increased quality of life after completion of the lifestyle intervention in individuals with HCM.