Validation of a novel, low-cost, portable MRI-compatible exercise device in healthy volunteers and patients with pulmonary hypertension

Introduction The value of exercise cardiovascular magnetic resonance (CMR) has been shown in many clinical scenarios. We have developed a MR-compatible exercise apparatus and aim to validate it against the reference standard MR-conventional ergometer. Methods The novel device consisted of two half-pipes fixed to a wooden base, with participants wearing knee-length socks with a 0.5kg weight in each sock. Increased workload was achieved by increasing the rate of alternating leg flexion and extension in time with a bleep sound of increasing frequency. Twenty subjects (10 healthy volunteers, 10 patients with pulmonary hypertension) performed two CMR-augmented cardiopulmonary exercise tests (CMR-CPET) using the novel exercise apparatus and a conventional ergometer in a randomised order. Results Comparing peak metrics elicited on both exercise devices, there was a moderate correlation in peak oxygen consumption (VO2, r=0.86, P<0.001), cardiac output (CO, r=0.66, P=0.002), stroke volume (SV, r=0.75, P<0.001), peak heart rate (HR, r=0.65, P=0.002) and peak arteriovenous oxygen content gradient (△avO2, r=0.71, P<0.001). However, all metrics (except peak SV) were significantly lower from the novel device. Both devices were able to elicit statistically significant differences in VO2, HR and RVEF between patients and healthy subjects (P≤0.036). Conclusions We have created a simple, easy to use and affordable exercise apparatus for CMR environment. This may encourage greater dissemination of exercise CMR in clinical and research practice. Keywords: exercise CMR device, pulmonary hypertension, systemic sclerosis