Feasibility of real-time in-magnet exercise cardiovascular MRI with an individualized exercise protocol: Quantitative assessment at low, intermediate, and high exercise intensities.

Abstract

Background: Exercise cardiovascular MRI (ExCMR) offers unique diagnostic potential, combining quantitative cardiac imaging with physiological provocation. Clinical adoption is limited by difficulty achieving high exercise workloads while maintaining diagnostic image quality.

Purpose: To develop an individualized in-bore supine exercise protocol capable of achieving high levels of exercise with the goal of reaching symptom- or fatigue-limited peak exercise. Age-predicted maximal heart rate (APMHR%) and Borg rating of perceived exertion (RPE) were used for peak effort while acquiring images suitable for quantitative analysis.

Methods: Healthy and patient volunteers with dyspnea on exertion (DOE) underwent in-bore, supine ergometer ExCMR with simultaneous imaging using a highly accelerated real-time (RT) cine pulse sequence (temporal resolution 22.1-23.7 ms and spatial resolution 2mm). After rest imaging, subjects underwent continuously increased ramped resistance to achieve staged targets based on %APMHR (65%, 75%, > 85%) with corresponding RPE (10-13, 14-16, 17-20). During each stage, resistance was held steady while RT cine images were acquired. Two expert reviewers evaluated image quality using a 1-4 Likert scale. Biventricular functions were quantified at rest and all exercise stages.

Results: Twelve healthy subjects (5 males, 7 females) completed peak exercise imaging with an average of 86% APMHR (Range77%-96%). Peak exercise was rated "extremely hard" (Average RPE 19, range 17-20). Cardiac output increased from rest (4.9±1.2L/min) to peak exercise (14.3±2.2L/min; p<.001). Image quality was rated "good" at each stage of exercise. All eight patient subjects completed the exercise protocol, achieving an average 75% APMHR (range 45-97%) and RPE 19 (range 18-20) at peak exercise.

Conclusion: We developed a ramped and staged supine in-bore ExCMR protocol targeting graded APMHR% and RPE enabling individualized testing to achieve a high level of exercise. Highly accelerated, high resolutionRT cine images were successfully acquired for quantification of volumes and cardiac output.