Differential Adaptation of Biventricular Myocardial Kinetic Energy in Patients With Repaired Tetralogy of Fallot Assessed by MR Tissue Phase Mapping

Background: The myocardial kinetic energy (KE) and its association with pulmonary regurgitation (PR) have yet to be investigated in repaired tetralogy of Fallot (rTOF) patients. Purpose: To evaluate the adaptation of myocardial KE in rTOF patients by tissue phase mapping (TPM). Study Type: Prospective. Population: A total of 49 rTOF patients (23 ± 5 years old; male = 32), 47 normal controls (22 ± 1 year old; male = 29). Field Strength/Sequence: 3-T/2D dark-blood three-directional velocity-encoded gradient-echo sequence. Assessment: Left and right ventricle (LV, RV) myocardial KE in radial (KE _r ), circumferential (KE _ø ), longitudinal (KE _z ) directions. The proportions of KE in each direction to the sum of all KE (KE _røz ): %KE _r , %KE _ø , %KE _z . PR fraction. Statistical Test: Student's t test, multivariable regression. Statistical significance: P < 0.05. Results: In rTOF group, LV KE _z remained normal in systole (P = 0.565) and diastole (P = 0.210), whereas diastolic LV %KE _z (62% ± 14% vs. 72% ± 7%) and systolic LV %KE _ø (9% ± 6% vs. 20% ± 7%) were significantly decreased. The KE _r and %KE _r of both ventricles significantly increased in the rTOF group (RV in diastole: 6 ± 3 vs. 3 ± 1 μJ and 54% ± 13% vs. 27% ± 7%). The rTOF group exhibited significantly higher RV/LV ratios of %KE _r (systole: 1.3 ± 0.3 vs. 1.0 ± 0.3) and %KE _ø (systole: 1.6 ± 0.8 vs. 1.0 ± 0.3) and significantly lower ratios of %KE _z in systole (0.7 ± 0.2 vs. 1.0 ± 0.1) and diastole (0.5 ± 0.2 vs. 0.9 ± 0.1). In multivariable regression analysis, the RV peak systolic KE _røz , RV systolic KE _z , and LV diastolic %KE _ø were independently associated with PR fraction in the rTOF group (adjusted R ²  = 0.479). Data Conclusion: In rTOF patients, the adaptation of the KE proportion occurred earlier than that of the KE amplitude, and the biventricular balance of %KE was disrupted. PR may cause differential KE adaptation in RV and LV. TPM-derived KE may be useful in investigation of myocardial adaptation in rTOF patients. Evidence Level: 2. Technical Efficacy: Stage 3.