THE RELATIONSHIP BETWEEN HRV(rMSSD) AND OTHER CARDIOVASCULAR RISKS IN HEALTHY PARTICIPANTS AND PATIENTS WITH CHRONIC HEART FAILURE USING NOVEL INSTRUMENTS

Heart rate variability (HRV) reflects the modulation of cardiac function by autonomic and other physiological regulatory systems. HRV is accepted as a reliable and reproducible technique for assessing autonomic activity. Impaired autonomic function (measured through a reduction in HRV) predicts mortality and is associated with several disease states. Excess adiposity is also associated with higher risk of cardiovascular diseases, type 2 diabetes, cancer and other health disorders. Body composition analysis involves the measurement of adipose tissue and other components such as muscle, bone and minerals in the human body. The relationship between excess adiposity and autonomic dysfunction has also been reported. The present thesis is divided into three parts: (i) validation studies, (ii) control studies and (iii) heart failure studies. The first validation study compares HRV (rMSSD) measured simultaneously with a Polar s810i and Ithlete on an iPod touch, in both healthy and heart failure populations. The second study examines measurement options for body composition by comparing several bioelectrical impedance analysis devices in a healthy population. Four studies were then undertaken with control subjects, assessing differences in gender, ethnicity and lifestyle factors using the devices validated in the previous chapters. Finally, Ithlete software was used with heart failure participants to gauge the feasibility of using the device daily and obtaining user feedback. Ithlete was then used in a cardiac rehabilitation programme to help participants get the most out of the programme, by guiding their exercise to rest ratio. The relationships between HRV, HR and body composition have been explored in this research work and have contributed to the knowledge around how these relationships can be used in healthcare. The benefit of novel devices to measure these relationships in both clinical and healthy populations has also been demonstrated, with an emphasis on low cost devices with good reliability