The effect of a novel lifestyle intervention on autonomic and haemodynamic function in individuals with hypertrophic cardiomyopathy

Abstract

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement no. 777204. Background Autonomic nervous system may play an important role in the pathophysiology of hypertrophic cardiomyopathy (HCM). Lifestyle interventions have been shown to improve signs and symptoms in individuals with heart failure. Purpose To evaluate the effect of a novel lifestyle intervention incorporating physical activity and dietary nitrate supplementation on cardiac autonomic and haemodynamic function in individuals with HCM. Methods Twenty-eight individuals with HCM were recruited into a single-centre pilot study (N=7 females, age 54±15 years) and randomised into the intervention (N=20) or control (N=8) group. Participants completed short-term (5-minute) non-invasive heart rate variability (HRV) measurements under resting (supine) conditions using the TaskForce (CNSystems, Graz, Austria). Frequency-domain HRV measures including spectral analysis of RR interval (i.e. absolute and normalised low frequency power (LF), high frequency power (HF) and LF/HF ratio) were recorded. Non-invasive haemodynamic variables including cardiac output (CO), and stroke volume (SV)were simultaneously recorded using bioimpedance technology integrated within the TaskForce. Intervention participants consumed 6 mmol of nitrate daily (concentrated beetroot juice) and increased and maintained their daily physical activity by ≥2000 steps/day above baseline for 16 weeks. Participants in the control group continued with their usual lifestyle and monitored daily step counts. Physical activity was evaluated objectively using pedometers (Omron Health, Japan). All participants were monitored weekly via telephone calls and average daily activity levels were recorded using diaries. However, participants in the control group were asked not to change their physical activity and dietary habits. Results Participants in the intervention group significantly increased their average physical activity by 3029 steps post intervention (i.e, 6234±2389 vs 9263± 3341 steps/day, p<0.01) compared to control (7559±3257 vs 7604± 2901 steps/day, p=0.96). There was a significant increase in post-intervention HF power (7.54±2.14 vs. 8.78±1.60 ms2, p<0.01) and LF power (6.89±2.33 vs. 8.17±1.55, p<0.01) respectively, but not in the control group (i.e., HF (7.05±3.39 vs. 7.64±2.56 ms2, p=0.33) and LF power (6.78±3.31 vs. 7.06±2.43 ms2 p=0.63)). There was a non-significant change in SV index in the intervention (33±9.83 vs. 29±8.56 ml/beat/m2, p=0.06) and control groups (34±6.27 vs. 33±8.1 ml/beat/m2, p=0.79). Similarly, there was no significant change in cardiac index in the intervention or control groups (intervention: 2.35±0.44 vs. 2.38±0.52 L/min/m2, p=0.77; control: 2.27±0.40 vs. 2.67±0.78, p=0.06). Conclusions Lifestyle intervention incorporating physical activity and dietary nitrate supplementation led to a significant increase in daily physical activity and improved parasympathetic activity in hypertrophic cardiomyopathy.