Insight Into Myocardial Microstructure of Athletes and Hypertrophic Cardiomyopathy Patients Using Diffusion Tensor Imaging

Abstract

Background: Hypertrophic cardiomyopathy (HCM) remains the commonest cause of sudden cardiac death among young athletes. Differentiating between physiologically adaptive left ventricular (LV) hypertrophy observed in athletes' hearts and pathological HCM remains challenging. By quantifying the diffusion of water molecules, diffusion tensor imaging (DTI) MRI allows voxelwise characterization of myocardial microstructure. Purpose: To explore microstructural differences between healthy volunteers, athletes, and HCM patients using DTI. Study Type: Prospective cohort. Population: Twenty healthy volunteers, 20 athletes, and 20 HCM patients. Field Strength/Sequence: 3T/DTI spin echo. Assessment: In-house MatLab software was used to derive mean diffusivity (MD) and fractional anisotropy (FA) as markers of amplitude and anisotropy of the diffusion of water molecules, and secondary eigenvector angles (E2A)-reflecting the orientations of laminar sheetlets. Statistical Tests: Independent samples t-tests were used to detect statistical significance between any two cohorts. Analysis of variance was utilized for detecting the statistical difference between the three cohorts. Statistical tests were twotailed. A result was considered statistically significant at P ≤ 0.05. Results: DTI markers were significantly different between HCM, athletes, and volunteers. HCM patients had significantly higher global MD and E2A, and significantly lower FA than athletes and volunteers. (MD HCM = 1.52 ± 0.06 × 10 −3 mm 2 /s, MD Athletes = 1.49 ± 0.03 × 10 −3 mm 2 /s, MD volunteers = 1.47 ± 0.02 × 10 −3 mm 2 /s, P < 0.05; E2A HCM = 58.8 ± 4 , E2A athletes = 47 ± 5 , E2A volunteers = 38.5 ± 7 , P < 0.05; FA HCM = 0.30 ± 0.02, FA Athletes = 0.35 ± 0.02, FA volunteers = 0.36 ± 0.03, P < 0.05). HCM patients had significantly higher E2A in their thickest segments compared to the remote (E2A thickest = 66.8 ± 7, E2A remote = 51.2 ± 9, P < 0.05). Data Conclusion: DTI depicts an increase in amplitude and isotropy of diffusion in the myocardium of HCM compared to athletes and volunteers as reflected by increased MD and decreased FA values. While significantly higher E2A values in HCM and athletes reflect steeper configurations of the myocardial sheetlets than in volunteers, HCM patients

Phenotyping hypertrophic cardiomyopathy using cardiac diffusion magnetic resonance imaging: the relationship between microvascular dysfunction and microstructural changes

“…Previous studies have observed absolute E2A to be globally increased in HCM patients compared to controls suggesting that the myocardial sheetlets adopt hypercontracted configurations during systole 13 , 14 , 26 ; however, in this study, we demonstrate this to be the case even in segments with normal thickness and normal perfusion. Previous authors have speculated whether the compressive deformation of intramyocardial blood vessels during systole can explain the increased coronary flow resistance in these patients 27 ; however, results from our study are unable to corroborate this, as absolute E2A did not vary significantly between segments with normal and abnormal perfusion reserve.…”

“…The study sample is relatively small, but in keeping with similar studies. 14 cDTI volunteers were not age-matched to the HCM subjects; however, it is yet to be established whether DTI parameters change with age. The ECV, MPR, and LGE of healthy volunteers were not obtained, as it was not felt ethically justifiable to administer contrast in this cohort.…”

“… 13 At peak systole, HCM patients have higher global absolute E2A than controls, indicating their sheetlets adopt significantly steeper configurations. 13 , 14 Furthermore, their sheetlet mobility is impaired, so their sheetlets remain in a relatively steeper configuration in diastole than controls. 13 While cDTI studies to date have provided insights into general microstructural abnormalities, their findings are predominantly based on global difference in parameters between HCM patients and controls.…”

Quantification of Tissue Microstructure Using Tensor-Valued Diffusion Encoding: Brain and Body

“…Motion-compensated diffusion encoding overcomes this limitation [160][161][162][163]. Most of the cardiac dMRI studies are based on single diffusion encoding, which has already led to interesting insights in the healthy [28,90,96,161,162] and diseased heart, including myocardial infarction [29], hypertrophic and dilated cardiomyopathy [164], amyloidosis [165] and athlete's heart [166]. Isotropic diffusion encoding can be used to estimate mean diffusivity (MD) in a shorter time compared to conventional single diffusion encoding [71,75].…”

Editorial for “Insight Into Myocardial Microstructure of Athletes and Hypertrophic Cardiomyopathy Patients Using Diffusion Tensor Imaging”

“…In this issue of JMRI, Das et al reported a cardiac DTI study that compares athletes who developed physiological ventricular hypertrophy with HCM patients and healthy volunteers. 10 DTI data were acquired at mid-systole using a 2 nd -order motion-compensated spin-echo planar imaging sequence. By showing E2A volunteers < E2A athletes < E2A HCM , the study demonstrated that LV hypertrophy may contribute to elevated systolic E2A.…”