Cardiac Structure-Function MRI in Patients After Heart Transplantation

Abstract

Background: Following 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.

Purpose: To test the feasibility of comprehensive structure-function cardiac MRI as a noninvasive modality to assess changes in myocardial structure and function.

Study type: Prospective.

Subjects: MR was performed in 61 heart transplant recipients (age 47.9 ± 16.3 years, 39% female) and 14 age-matched healthy controls (age 47.7 ± 16.7 years, 36% female).

Field strength/sequence: 1.5T; 2D CINE steady state free precession (SSF)P imaging, T₂ -mapping, pre- and postgadolinium contrast T₁ -mapping, and tissue-phase mapping (TPM).

Assessment: Quantification of myocardial T₂ (as a measure of edema), pre- and post-Gd T₁ (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 tests: Comparisons between transplant recipients and controls were performed using independent samples t-tests. Relationships between structural (T₂ , T₁ , ECV) and functional measures (myocardial velocities, dyssynchrony, twist) were assessed using Pearson correlation analysis.

Results: T₂ and T₁ were significantly elevated in transplant recipients compared to controls (global T₂ : 50.5 ± 3.4 msec vs. 45.2 ± 2.3 msec, P < 0.01; global T₁ : 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 ± 1.1 cm/s vs. 5.1 ± 1.2 cm/s, P < 0.01; elevated systolic longitudinal dyssynchrony, 60.2 ± 30.2 msec vs. 32.1 ± 25.1 msec, P < 0.01). Correlation analysis revealed a significant positive relationship between T₂ and ECV (r = 0.45,P < 0.01). In addition, peak systolic longitudinal velocities demonstrated a significant inverse relationship with T₂ (global r = -0.29, P = 0.02), and systolic radial dyssynchrony was positively associated with peak T₂ and peak T₁ (r = 0.26,P = 0.04; r = 0.27,P = 0.03).

Data conclusion: MR techniques are sensitive to structural and functional differences in transplant recipients compared to controls. Structural (T₂ , T₁ ) 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.

Keywords: T1-mapping; T2-mapping; cardiac; heart transplantation; tissue phase mapping.