969-97 Regional Strain and Wall Motion of the Transplanted Left Ventricle in Pediatric Patients Using Magnetic Resonance Tagging

Abstract

The biomechanical properties of the transplanted left ventricle (LV) may not be the same as the normal LV which is innervated, has not undergone ischemic arrest, and is not at risk for cellular rejection. Abnormal LV systolic torsion has been noted during histologic rejection in adult transplant patients. This has not been assessed in pediatric patients. We studied 8 transplant patients (ages 5.1 ± 3.7 years, 2.6 ± 1.2 years post-transplant) who underwent 9 magnetic resonance imaging studies using spatial modulation of magnetization, a tissue tagging technique, to quantify regional wall motion and deformation. Imaging was done within 6 days of endomyocardial biopsy in 7 of 9 studies. Seven normal adults were imaged as controls. Magnetic tagging was performed at 2 LV short axis levels, atrioventricular valve (AW) and apex, through 12 phases in systole. Intersection points were tracked, and regional wall motion and strain (using the 2-dimensional strain tensor) was determined. The myocardium was divided into 4 anatomic regions (ventricular septum. IW = inferior wall, PW = posterior wall. and SW = superior wall) and subdivived further into endocardial and epicardial regions. Review of 7 biopsy specimens revealed 2 with rejection (grade 1A and grade 2). Cardiac catheterization demonslrated normal hemodynamics in all except the patient with grade 2 rejection. Seven of 8 patients had clockwise twist of the SW, IW, and/or PW. and all had regions of no twist. Four patients had akinetic regions and 2 demonstrated paradoxical motion of the ventricular septum. Controls had counterclockwise twist in all regions. In transplant patients, strain and strain heterogeneity were similar between the 4 regions at the AW and the apex. The ralio of endocardial to epicardial strain was similar between all regions at the AW, but not at the apex. Strain was not different between transplant patients and controls for each region. Strain heterogeneity was different between the 2 groups at the SW of the AW, and at the ventricular septum of the AW and apex. When comparing AW to apex, there was no difference in strain, or the endocardial-to-epicardial strain ratio. between transplant patients and controls for each region. Pediatric transplant patients demonstrale regional wall motion abnormalities in the absence of rejection. Compared to controls, the transplanted LV maintains normal strain in the presence of abnormal twist. This may be a compensatory mechanism and may have clinical implications.