Evaluation of post-contrast myocardial t1 in duchenne muscular dystrophy using cardiac magnetic resonance imaging

Abstract

The objective of the study was to perform a retrospective pilot study to evaluate the potential of myocardial T1 in assessment of Duchenne muscular dystrophy (DMD) cardiomyopathy. Early identification of DMD cardiac disease, particularly myocardial fibrosis, would allow earlier therapy, potentially improving outcomes. Shortened myocardial T1 measured by cardiac MRI (CMR) is a measure of cardiac fibrosis that may be detected before late gadolinium enhancement (LGE). We hypothesized that the post-contrast T1 obtained from the Look-Locker sequences (T1LL), an easily obtainable surrogate of myocardial T1, would be abnormally shortened in DMD compared with controls. T1LL measurement was performed on 21 DMD subjects and 11 controls; to account for individual variations in gadolinium distribution, myocardial T1LL was divided by blood pool T1LL, deriving T1LL ratios. DMD subjects had shorter mean T1LL ratio than controls (1.42 vs 1.72, p < 0.001). Subset analyses in DMD subjects with normal LVEF and without LGE also demonstrated significantly shorter T1LL ratio (-0.28, p < 0.001 and -0.25, p = 0.028). Post-contrast T1LL ratio is abnormally shortened in DMD compared with controls, even in DMD patients with otherwise normal CMRs. The application of more aggressive therapy for those with shorter T1LL may favorably alter morbidity and improve mortality associated with DMD cardiomyopathy. These data suggest that further prospective evaluation of myocardial T1 will be of benefit to patients with DMD.

Figure 1. Myocardial segmentation

Myocardial segmentation in short axis (A). Representative T1LL map (B).

Figure 2. Boxplot of post-contrast myocardial T1LL

DMD subjects have shorter myocardial T1LL when compared with controls, especially in the inferior, inferolateral, and anterolateral segments of DMD; control subjects have relatively constant myocardial T1LL across segments.

Figure 3. Representative T1LL maps

Representative maps of post-contrast myocardial T1LL in control (A) and DMD (B). Note significant difference in T1LL of blood pool and of myocardium, despite identical color maps. Map of T1LL ratio (myocardial T1LL/blood pool T1LL) in control (C) and DMD (D) demonstrates more comparable T1LL ratio of “normal” myocardium and blood pool, allowing for better comparison between patients. Post-contrast myocardial T1LL in DMD is visibly shorter in the inferior, inferolateral, and anterolateral segments as compared with control myocardium.