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 (KEr), circumferential (KEempty set), longitudinal (KEz) directions. The proportions of KE in each direction to the sum of all KE (KErempty setz): %KEr, %KEempty set, %KEz. PR fraction. Statistical Test: Student's t test, multivariable regression. Statistical significance: P < 0.05. Results: In rTOF group, LV KEz remained normal in systole (P = 0.565) and diastole (P = 0.210), whereas diastolic LV %KEz (62% +/- 14% vs. 72% +/- 7%) and systolic LV %KEempty set (9% +/- 6% vs. 20% +/- 7%) were significantly decreased. The KEr and %KEr of both ventricles significantly increased in the rTOF group (RV in diastole: 6 +/- 3 vs. 3 +/- 1 mu J and 54% +/- 13% vs. 27% +/- 7%). The rTOF group exhibited significantly higher RV/LV ratios of %KEr (systole: 1.3 +/- 0.3 vs. 1.0 +/- 0.3) and %KEempty set (systole: 1.6 +/- 0.8 vs. 1.0 +/- 0.3) and significantly lower ratios of %KEz 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 KErempty setz, RV systolic KEz, and LV diastolic %KEempty set 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.