Compact MR‐compatible ergometer and its application in cardiac MR under exercise stress: A preliminary study

Abstract

Purpose To develop a compact MR‐compatible ergometer for exercise stress and to initially evaluate the reproducibility of myocardial native T1 and myocardial blood flow (MBF) measurements during exercise stress performed on this ergometer. Methods The compact ergometer consists of exercise, workload, and data processing components. The exercise stress can be achieved by pedaling on a pair of cylinders at a predefined frequency with adjustable resistances. Ten healthy subjects were recruited to perform cardiac MRI scans twice in a 3.0T MR scanner, at different days to assess reproducibility. Myocardial native T1 and MBF were acquired at rest and during a moderate exercise. The reproducibility of the two tests was determined by the intra‐group correlation coefficient (ICC) and coefficient of variation (CoV). Results The mean exercise intensity in this pilot study was 45 Watts (W), with an exercise duration of 5 min. Stress induced a significant increase in systolic blood pressure (from 113 ± 11 mmHg to 141 ± 12, P < 0.05) and maximal increase in heart rate by 74 ± 19%. The rate pressure product increased two‐fold (P < 0.001). Excellent reproducibility was demonstrated in native T1 during the exercise (CoV = 3.0%), whereas the reproducibility of MBF and myocardial perfusion reserve during the exercise was also good (CoV = 10.7% and 8.8%, respectively). Conclusion This pilot study demonstrated that it is possible to acquire reproducible measurements of myocardial native T1 and MBF during the exercise stress in healthy volunteers using our new compact ergometer.

State of the Art and New Advances: Cardiac MRI

“…A novel stress testing technique is supine MRI-compatible exercise ergometer. With a better safety profile than pharmacological stressors, physical stress on the heart visualized via CMR can provide insight into tissue function and characteristics specific to ischemia [60]. For post processing of stress perfusion sequences, currently most centers use visual estimation for stress perfusion.…”

Exercise stress cardiac magnetic resonance imaging in the assessment of induced cardiovascular responses in cardiac patients: a scoping review protocol

“…9 In fact, studies using the supine ergometer test have reported that leg muscle fatigue led to premature test termination 10 and some patients' imaging acquisitions were excluded due to motion artifacts. 22 Another study using the isometric handgrip demonstrated that the hemodynamic changes achieved during exercise did not reach the extent of bicycle or treadmill exercises performed to maximum exertion. 23 Despite progress made to enable exercising in an MRI scanner, researchers warn about the excessive motion that exercise conditions can produce and the lack of Ex-CMR studies that have taken the constraints imposed by the MRI scanner into consideration for the acquisition of images.…”

“…Despite numerous reported advantages of these 2 types of Ex-CMR protocols, previous studies have reported some limitations, including motion artifacts and leg muscle fatigue during supine cycle ergometer use 21 as well as the inability to achieve peak stress when performing an isometric handgrip exercise 9 . In fact, studies using the supine ergometer test have reported that leg muscle fatigue led to premature test termination 10 and some patients’ imaging acquisitions were excluded due to motion artifacts 22 . Another study using the isometric handgrip demonstrated that the hemodynamic changes achieved during exercise did not reach the extent of bicycle or treadmill exercises performed to maximum exertion 23 …”