Quantification of exercised-induced myocardial deformation with exercise CMR

Area of Science:

• Cardiology
• Biomedical Engineering
• Medical Imaging

Background:

• Physiological stress can unmask myocardial deformations not apparent at rest.
• Exercise cardiovascular magnetic resonance (Ex-CMR) assesses myocardial deformation during both rest and exercise.
• Myocardial torsional reserve (MTR) is a novel metric for exercise-induced rotational deformation.

Purpose of the Study:

• To develop and evaluate MTR as a marker for abnormal myocardial mechanics in patients with heart failure with preserved ejection fraction (HFpEF).
• To assess the utility of MTR in differentiating HFpEF patients from healthy controls and those with non-cardiac dyspnea.

Main Methods:

• Single-beat myocardial tagging images were acquired at rest and post-exercise using 3T Ex-CMR.
• Apical and basal rotation angles were measured to calculate torsion, with MTR defined as the ratio of stress to rest torsion.
• Retrospective analysis of 67 participants (24 controls, 17 non-cardiac dyspnea, 15 exercise-induced HFpEF, 11 overt HFpEF) with invasive exercise testing.

Main Results:

• MTR measurement demonstrated good to excellent repeatability (inter-observer ICC=0.90, intra-observer ICC=0.95).
• MTR was significantly reduced in both exercise-induced HFpEF (1.1±0.1) and overt HFpEF (1.2±0.2) compared to healthy controls (1.7±0.4) and non-cardiac dyspnea (1.6±0.4) groups.
• No significant difference in MTR was observed between healthy controls and non-cardiac dyspnea patients (p=0.978).

Conclusions:

• Ex-CMR-derived MTR quantifies exercise-induced rotational deformation and mechanical reserve.
• MTR effectively distinguishes patients with exercise-induced or overt HFpEF from healthy individuals and those with non-cardiac dyspnea.
• MTR shows potential as a valuable marker for abnormal myocardial response to exercise.