Longitudinal Cardiac Magnetic Resonance Imaging by Strain Encoding in Duchenne Muscular Dystrophy Detects Abnormal Strain and MyoHealth Score Detecting Progressive Cardiomyopathy

Background: Duchenne muscular dystrophy (DMD) is characterized by early and progressive cardiomyopathy with abnormal strain and myocardial fibrosis by late gadolinium enhancement (LGE) followed by global cardiac dysfunction by left ventricular ejection fraction (LVEF) later in the disease process by cardiac magnetic resonance imaging (CMR). We previously showed that DMD patients have abnormal myocardial strain and MyoHealth score by strain encoding (SENC) in a cross-sectional cohort of DMD patients with various disease stages. We sought to determine the ability of SENC by SCMR to detect changes in both global longitudinal (GLS) and circumferential strain (GCS) and MyoHealth score over time, and which component is impacted earlier.

Methods: This is retrospective longitudinal IRB approved study. Clinical CMR studies with SENC sequence were assessed. All studies were performed using 3.0T Siemens Skyra scanner (Siemens Healthineers, Germany) including SENC assessment. We utilized SENC imaging to assess both longitudinal (GLS) and circumferential strain (GCS) using MyoStrain (Myocardial Solutions, Morrisville, NC) generating 37 total segments from 3 short axis and 3 long axis images. GCS, GLS and MyoHealth scores were followed overtime.

Results: 76 DMD patients had serial follow-up over 12–16-month period. Compared to published normal MyoHealth score of 80, DMD had abnormal MyoHealth score of 44.2±21 at baseline and 46.2 ± 18.7at follow-up (Figure 1) despite preserved global ventricular function by ejection fraction > 55%. Though both global longitudinal and circumferential strain were abnormal at baseline and follow-up at - 15.2 ± 3.07% and -16.3 ± 2.4% at baseline and remained stable at -17.1 ± 1.9 and -15.1 ± 2.6 at follow-up (Figure 2). The predominant impact on MyoHealth decline occurs more impacted by the longitudinal component and to a lesser extent by the circumferential direction. Additionally, MyoHealth Score was able to detect those with improvement from baseline to follow-up study with LVEF remains unchanged (Figure 3).

Conclusion: Our study showed that MyoHealth is abnormal at baseline and follow-up despite preserved global function by left ventricular ejection fraction. In our patients, it appears that the predominant cause of MyoHealth decline is GLS and to a lesser extent GCS. The use of MyoHealth in combination with both GLS and GCS can help improved understanding of DMD-associated cardiomyopathy use SENC which has been shown to be feasible and performed over 1-2 heart beats which allows assessment in patients who may not be able to breath-hold. Future, studies is needed to assess the impact of MyoHealth and myocardial strain combined with LGE which could improve diagnostic yield for earlier disease assessment.

Figure 1: Serial MyoHealth Score by Strain Encoding showing abnormal and persistent decline in MyoHealth
Figure 2: Serial Global longitudinal and circumferential strain by Strain Encoding showing abnormal GLS and GCS with relatively lower GLS
Figure 3: Scatter Plot of MyoHealth Values at Baseline and Follow-up Study showing improvement in a subset of patients despite not changes in LVEF.