Cardiac Structure-Function MRI in Patients After Heart Transplantation

BackgroundFollowing heart transplantation (Tx), recipients are closely monitored using endomyocardial biopsy, which is limited by cost and invasiveness, and echocardiography, which is limited regarding detailed structural and functional evaluation. PurposeTo test the feasibility of comprehensive structure-function cardiac MRI as a noninvasive modality to assess changes in myocardial structure and function. Study TypeProspective. SubjectsMR was performed in 61 heart transplant recipients (age 47.916.3 years, 39% female) and 14 age-matched healthy controls (age 47.716.7 years, 36% female). Field Strength/Sequence1.5T; 2D CINE steady state free precession (SSF)P imaging, T-2-mapping, pre- and postgadolinium contrast T-1-mapping, and tissue-phase mapping (TPM). AssessmentQuantification of myocardial T-2 (as a measure of edema), pre- and post-Gd T-1 (allowing calculation of extracellular volume (ECV) to estimate interstitial expansion), and TPM-based assessment of peak regional left ventricular (LV) velocities, dyssynchrony, and twist. Statistical TestsComparisons between transplant recipients and controls were performed using independent samples t-tests. Relationships between structural (T-2, T-1, ECV) and functional measures (myocardial velocities, dyssynchrony, twist) were assessed using Pearson correlation analysis. ResultsT(2) and T-1 were significantly elevated in transplant recipients compared to controls (global T-2: 50.53.4 msec vs. 45.22.3 msec, P < 0.01; global T-1: 1037.8 +/- 48.0 msec vs. 993.8 +/- 34.1 msec, P < 0.01). Systolic longitudinal function was impaired in transplant recipients compared to controls (reduced peak systolic longitudinal velocities, 2.9 +/- 1.1cm/s vs. 5.1 +/- 1.2cm/s, P < 0.01; elevated systolic longitudinal dyssynchrony, 60.2 +/- 30.2msec vs. 32.1 +/- 25.1msec, P < 0.01). Correlation analysis revealed a significant positive relationship between T-2 and ECV (r=0.45,P < 0.01). In addition, peak systolic longitudinal velocities demonstrated a significant inverse relationship with T-2 (global r=-0.29, P=0.02), and systolic radial dyssynchrony was positively associated with peak T-2 and peak T-1 (r=0.26,P=0.04; r=0.27,P=0.03). Data ConclusionMR techniques are sensitive to structural and functional differences in transplant recipients compared to controls. Structural (T-2, T-1) and functional (peak myocardial velocities, dyssynchrony) measures were significantly associated, suggesting a structure-function relationship of cardiac abnormalities following heart transplant. Level of Evidence: 2 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;49:678-687.