Abstract
The purpose of this study was to evaluate the adaptive remodeling mechanism by assessing cardiac morphology, myocardial function, and flow in patients with repaired tetralogy of Fallot (rTOF) and preserved left ventricle (LV) global function. Interaction of myocardium and flow was also assessed in kinetic energy (KE) aspects so as to realize the impact of overloading pathology on the cardiac compliance. We recruited 47 rTOF patients and 38 age-matched normal volunteers. Tissue phase mapping (TPM) was performed for evaluating the LV and RV regional myocardial motion and twist function. Flow pattern and hemodynamic parameter in the pulmonary and intraventricular flow were visualized and quantified based on 4D flow MRI. Most rTOF patient revealed flatter interventricular septum and thus larger radius ratio (P < 0.001). They also showed significantly decreased systolic and diastolic longitudinal velocity (Vz) on most of the RV segments and several LV segments. As for radial velocity (Vr), patients showed significantly decreased Vr in systole but substantially increased Vr in diastole on RV free wall. Flow pattern of intraventricular flow revealed differences between rTOF patients and normal subjects in late diastolic period for absent vortex with a high velocity. The observation of increased late diastolic RV intraventricular flow KE was also correlated with KE of regurgitation as well as pulmonary flow, suggesting the impaired RV-PA coupling. Retarded intraventricular flow at the downstream was detected in using KE gradient and the retarded flow propagation were closely correlated with elevated RVPA pressure gradient. The establishments of those indices in this study can help to comprehend the adaptive remodeling mechanism of rTOF patients before LV global dysfunction and might be helpful for patient managements regarding the timing of undergoing pulmonary valve replacement (PVR) surgery.