Quantitative Assessment of Myocardial Velocity and Dyssynchrony in Fontan Circulation Using MR Tissue Phase Mapping

Area of Science:

• Cardiology
• Biomedical Engineering
• Medical Imaging

Background:

• Fontan-associated physiology presents unique challenges in assessing cardiac function.
• Magnetic resonance tissue phase mapping (TPM) is a valuable tool for quantifying myocardial motion velocity.

Purpose of the Study:

• To quantify myocardial motion velocity alterations in the functional ventricle of Fontan patients using TPM.
• To investigate the relationship between myocardial motion and cardiac function (ejection fraction, cardiac output) in Fontan patients.

Main Methods:

• Prospective enrollment of 28 Fontan patients and 42 healthy controls.
• Assessment of myocardial motion velocities (longitudinal, radial, circumferential) using TPM.
• Evaluation of peak velocities, time-to-peak, dyssynchrony index, and circumferential motion parameters.

Main Results:

• Fontan patients showed significantly reduced peak longitudinal (Vz) and radial (Vr) velocities and prolonged time-to-peak (TTP) compared to controls.
• Altered diastolic longitudinal and systolic radial dyssynchrony indices were observed in Fontan patients.
• Ejection fraction correlated positively with peak systolic Vr and negatively with mid circumferential peak-to-peak (PTP) values. Cardiac output correlated positively with peak systolic Vr and diastolic DIz.

Conclusions:

• TPM can identify quantitative magnetic resonance biomarkers for regional myocardial motion abnormalities in Fontan patients.
• Impaired myocardial motion velocities, delayed contraction timing, and altered synchronization suggest global ventricular dysfunction.
• Findings offer insights into mechanisms of reduced ejection fraction and cardiac output in Fontan physiology.