Abstract
Modifications of the myocardial architecture can cause abnormal electrical activity of the heart. Fibro-fatty infiltrations have been implicated in various cardiac pathologies associated with arrhythmias and sudden cardiac death, such as arrhythmogenic right ventricular cardiomyopathy (ARVC). Here, we report the development of an MRI protocol to observe these modifications at 9.4 T. Two fixed ex vivo human hearts, one healthy and one ARVC, were imaged with an Iterative decomposition with echo asymmetry and least-square estimations (IDEAL) and a magnetization transfer (MT) 3D sequences. The resulting fat fraction and MT ratio (MTR) were analyzed and compared to histological analysis of the three regions (“ARVC triangle”) primarily involved in ARVC structural remodeling. In the ARVC heart, high fat content was observed in the “ARVC triangle” and the superimposition of the MTR and fat fraction allowed the identification of fibrotic regions in areas without the presence of fat. The healthy heart exhibited twice less fat than the ARVC heart (31.9%, 28.7% and 1.3% of fat in the same regions, respectively). Localization of fat and fibrosis were confirmed by means of histology. This non-destructive approach allows the investigation of structural remodeling in human pathologies where fibrosis and/or fatty tissue infiltrations are expected to occur.
Highlights
Modifications of the myocardial architecture can cause abnormal electrical activity of the heart
Structural modifications mainly appear in the right ventricle (RV) inflow tract, the outflow tract (RVOT) and apex of the RV; these are regarded as the “arrhythmogenic right ventricular cardiomyopathy (ARVC) triangle” or “triangle of dysplasia”[7,8]
The amount of epicardial fat is larger in the ARVC heart than in the healthy heart
Summary
Modifications of the myocardial architecture can cause abnormal electrical activity of the heart. Abbreviations ARVC Arrhythmogenic right ventricular cardiomyopathy FoV Field of view GRAPPA Generalized autocalibrating partial parallel acquisition IDEAL Iterative decomposition of water and fat with echo asymmetry and least-squares estimation LV Left ventricle MGE Multiple gradient echo MT Magnetization transfer MTR Magnetization transfer ratio NA Number of averages PDFF Proton density fat fraction RARE Rapid acquisition with relaxation enhancement ROI Region of interest RV Right ventricle RVOT Right ventricle outflow tract TE Echo time TR Repetition time Various cardiac arrhythmias, such as atrial fibrillation, ventricular tachycardia and ventricular fibrillation can be caused and maintained by alterations in the tissue architecture and intercellular coupling, through for example fibro-fatty infiltrations[1]. For precise visualization of fat and fibrosis in the RV, current spatial resolution of clinical MR images remains limited[15]
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