Exercise MRI stress testing of the human heart at 3 Tesla: measurement precision of biventricular function and aortic blood flow during steady-state bicycling exercise

OBJECTIVE: This work aimed to demonstrate the feasibility of quantifying heart function during bicycling exercise with dynamic real-time cine MRI at 3 Tesla, and to assess its measurement precision.

MATERIALS AND METHODS: Twelve volunteers performed steady-state bicycling exercise, while real-time cine MR images were collected using a 72-channel receiver coil array and a parallel imaging acceleration factor of 5. Biventricular end-diastolic and end-systolic (ESV) volumes and function during exercise were compared with resting-state real-time cine MRI and conventional cardiac-gated cine MRI under breath holding, and validated against 2D phase-contrast MRI-based estimates of aortic blood flow. Precision was evaluated as the inter-session measurement repeatability.

RESULTS: Left (LV) and right ventricular (RV) stroke volumes (SV) increased progressively with exercise intensity, which was mediated by a decrease in ESV. Likewise, LV SV estimated with 2D phase-contrast MRI increased from 90 ± 17 mL at rest to 114 ± 29 mL during vigorous-intensity exercise. Repeatability coefficients were 52% and 41% for LV SV at moderate- and vigorous-intensity exercise, while RV SV repeatability coefficients were 58% and 42%, respectively.

DISCUSSION: We established an exercise MRI stress testing protocol for quantifying biventricular volumes and function during moderate- and vigorous-intensity steady-state bicycling exercise.