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

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.

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).

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).

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.