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 two-tailed. 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 mm² /s, MD_Athletes = 1.49 ± 0.03 × 10^-3 mm² /s, MD_volunteers = 1.47 ± 0.02 × 10^-3 mm² /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 demonstrated an eccentric rise in E2A in their thickest segments, while athletes demonstrated a concentric rise. Further studies are required to determine the diagnostic capabilities of DTI.

Evidence level: 1 TECHNICAL EFFICACY STAGE: 2.

Keywords: athlete's heart; diffusion tensor imaging; hypertrophic cardiomyopathy; magnetic resonance imaging.