Myocardial velocity, intra‐, and interventricular dyssynchrony evaluated by tissue phase mapping in pediatric heart transplant recipients

Abstract

Background Endomyocardial biopsy (EMB) is the standard method for detecting allograft rejection in pediatric heart transplants (Htx). As EMB is invasive and carries a risk of complications, there is a need for a noninvasive alternative for allograft monitoring. Purpose To quantify left and right ventricular (LV & RV) peak velocities, velocity twist, and intra‐/interventricular dyssynchrony using tissue phase mapping (TPM) in pediatric Htx compared with controls, and to explore the relationship between global cardiac function parameters and the number of rejection episodes to these velocities and intra‐/interventricular dyssynchrony. Study Type Prospective. Subjects Twenty Htx patients (age: 16.0 ± 3.1 years, 11 males) and 18 age‐ and sex‐matched controls (age: 15.5 ± 4.3 years, nine males). Field Strength/Sequence 5T; 2D balanced cine steady‐state free‐precession (bSSFP), TPM (2D cine phase contrast with three‐directional velocity encoding). Assessment LV and RV circumferential, radial, and long‐axis velocity–time curves, global and segmental peak velocities were measured using TPM. Short‐axis bSSFP images were used to measure global LV and RV function parameters. Statistical Tests A normality test (Lilliefors test) was performed on all data. For comparisons, a t‐test was used for normally distributed data or a Wilcoxon rank‐sum test otherwise. Correlations were determined by a Pearson correlation. Results Htx patients had significantly reduced LV (P < 0.05–0.001) and RV (P < 0.05–0.001) systolic and diastolic global and segmental long‐axis velocities, reduced RV diastolic peak twist (P < 0.01), and presented with higher interventricular dyssynchrony for long‐axis and circumferential motions (P < 0.05–0.001). LV diastolic long‐axis dyssynchrony (r = 0.48, P = 0.03) and RV diastolic peak twist (r = –0.64, P = 0.004) significantly correlated with the total number of rejection episodes. Data Conclusion TPM detected differences in biventricular myocardial velocities in pediatric Htx patients compared with controls and indicated a relationship between Htx myocardial velocities and rejection history. Level of Evidence: 2 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;51:1212–1222.

Multi-parametric cardiovascular magnetic resonance with regadenoson stress perfusion is safe following pediatric heart transplantation and identifies history of rejection and cardiac allograft vasculopathy

“…In recent years, CMR has shown substantial promise for detection of graft dysfunction in adult heart transplant recipients [ 21 , 23 , 24 , 28 , 37 , 49 – 53 ], however, data are quite limited in PHT [ 37 , 38 , 40 , 43 , 54 , 55 ]. Our study demonstrates the safety and feasibility of comprehensive CMR with regadenoson stress perfusion for graft surveillance in PHT.…”

“…Echocardiography-derived strain and CMR derived myocardial velocities are often abnormal during an acute rejection episode or with cumulative history of repetitive rejections [ 11 – 13 , 28 , 37 , 37 , 40 , 41 , 62 , 63 ]. Miller et al [ 30 ] have reported an association of reduced GCS by CMR tagging with clinically significant ACR (grade 2 R or higher) in adult heart transplant recipients.…”

“…There is emerging data reporting on the use of CMR in diagnosing graft dysfunction in the heart transplant population. These techniques have shown utility in diagnosis of acute rejection, CAV and clinical outcomes in adult patients [ 20 – 36 ] but data in the pediatric population are limited [ 37 – 43 ].…”

Automated segmentation of biventricular contours in tissue phase mapping using deep learning

“…CMR has the ability to non-invasively characterize intramyocardial function using techniques such as myocardial tagging, 4,5 strain-encoded (SENC) imaging, 6 cine displacement-encoded imaging with stimulated echoes (DENSE), 7,8 and tissue phase mapping (TPM). 9,10 These techniques have proven useful in diagnosing and monitoring abnormal myocardial function in a wide range of cardiovascular conditions including congenital heart diseases, 11,12 cardiotoxicities, 13,14 cardiac transplantation, [15][16][17] left ventricular dyssynchrony, 18,19 and various cardiomyopathies. [20][21][22] In this study, we will focus on TPM, which is a black-blood 2D cine phase contrast MRI pulse sequence with three-directional tissue velocity encoding for quantification of regional biventricular myocardial velocities.…”

“…23 Recently, several studies have demonstrated significant differences in biventricular global and regional velocities in heart transplant (HTx) patients (adult and pediatric) with and without transplant rejection. 15,16 Despite these studies demonstrating feasibility, the clinical translation of TPM is hampered by the requisite labor-intensive manual segmentation of the myocardial contours for all cardiac frames. In general, manual segmentation of TPM images is more challenging for the RV than the LV, because the former has a thinner wall, highly trabeculated myocardium, and epicardial fat partially superimposed on the myocardial wall.…”