Prevalence and distribution of regional scar in dysfunctional myocardial segments in Duchenne muscular dystrophy.

BACKGROUND: The segmental relationship between cardiovascular magnetic resonance (CMR) peak circumferential strain (Ecc) and myocardial scar has not been well characterized in Duchenne muscular dystrophy (DMD), and it is unknown whether echocardiography accurately measures Ecc in DMD. We assessed segmental Ecc and scar using CMR with myocardial tissue tagging and late gadolinium enhancement (LGE) in patients with DMD, then compared CMR with echocardiographic velocity vector imaging (VVI) for regional Ecc based on independent observer assessments.

RESULTS: Participants enrolled (n = 16; age 8-23) had median left ventricular (LV) ejection fraction of 0.52 (range 0.28-0.69), and 156 basal and mid-cavity myocardial segments from the 13 patients completing the LGE protocol were analyzed for strain and scar. Segmental CMR Ecc in the most negative quartile (quartile 4) ruled out scar in that segment, but scar was present in 46% of segments in the least negative (most dysfunctional) Ecc quartile 1, 33% of Ecc quartile 2 segments, and 15% of Ecc quartile 3 segments. Overall scar prevalence in inferior, inferolateral, and anterolateral segments was eight times higher than in inferoseptal, anteroseptal, and anterior segments (p < 0.001). This increased proportion of scar in lateral versus septal segments was consistent across CMR Ecc quartiles (quartile 1: 76% versus 11%, p = 0.001; quartile 2: 65% versus 9%, p < 0.001; quartile 3: 38% versus 0%, p < 0.001). Echocardiographic analysis could be performed in 12 of 14 patients with CMR exams and had to be limited to mid-cavity slices. Echo segmental Ecc in the most negative quartile made scar by CMR in that segment highly unlikely, but the correlation in segmental Ecc between CMR and echo was limited (r = 0.27; p = 0.02).

CONCLUSIONS: The relationship between scar and Ecc in DMD is complex. Among myocardial segments with depressed Ecc, scar prevalence was much higher in inferior, inferolateral, and anterolateral segments, indicating a regionally dependent association between abnormal Ecc and scar, with free wall segments commonly developing dysfunction with scar and septal segments developing dysfunction without scar. Although normal echocardiographic Ecc predicted absence of scar, regional echocardiographic Ecc by VVI has only a limited association with CMR Ecc in DMD.