Evaluating Biventricular Myocardial Velocity and Interventricular Dyssynchrony in Adult Patients During the First Year After Heart Transplantation

Abstract

BackgroundMagnetic resonance tissue phase mapping (TPM) measures three‐directional myocardial velocities of the left and right ventricle (LV, RV). This noninvasive technique may supplement endomyocardial biopsy (EMB) in monitoring grafts post‐heart transplantation (HTx).PurposeTo assess biventricular myocardial velocity alterations in grafts and investigate the relationship between velocities and acute cellular rejection (ACR) episodes.Study TypeProspective.SubjectsTwenty‐seven patients within 1 year post‐HTx (49 ± 13 years, 19 M) and 18 age‐matched controls (49 ± 15 years, 12 M).Field Strength/Sequence1.5T, 2D balanced steady‐state free precession, and TPM.AssessmentVentricular function: end‐diastolic and end‐systolic volumes, stroke volumes, ejection fraction (EF), and myocardial mass. TPM velocities: peak‐systolic and peak‐diastolic velocities, cardiac twist, and interventricular dyssynchrony. ACR rejection episodes: International Society for Heart and Lung Transplantation grading of EMB specimens.Statistical TestsThe Lilliefors test for normality, unpaired t‐tests, and Wilcoxon rank‐sum tests for normally and nonnormally distributed data, respectively, were used, as well as multivariate regression for confounding variables and Pearson's correlation for associations between TPM velocities and global function.ResultsCompared to controls, HTx patients demonstrated reduced biventricular systolic longitudinal velocities (LV: 5.2 ± 2.1 vs. 4.0 ± 1.5 cm/s, P < 0.05; RV: 4.2 ± 1.3 vs. 3.1 ± 1.2 cm/s, P < 0.01). Correlation analysis revealed significant positive relationships for biventricular EF with radial peak velocities of the same ventricle in both systole and diastole (LV systole: r = 0.48, P < 0.01; LV diastole: r = 0.28, P < 0.05; RV systole: r = 0.35, P < 0.01; RV diastole: r = 0.36, P < 0.01). Segmentally, longitudinal velocities were impaired in 7/16 LV segments and 5/10 RV segments in systole and 7/10 RV segments in diastole. TPM analysis in studies with >4 preceding ACR episodes showed globally reduced RV and LV systolic radial velocity, and segmentally reduced radial and longitudinal systolic velocities.Data ConclusionBiventricular global and segmental velocities were reduced in HTx patients. Patients with >4 rejection episodes showed reduced myocardial velocities. The TPM sequence may add functional information for monitoring graft dysfunction.Level of Evidence2Technical Efficacy Stage2 J. Magn. Reson. Imaging 2020;52:920–929.

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

“…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.…”

“…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.…”

“…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.…”