Ultrasound tissue characterization detects preclinical myocardial structural changes in children affected by Duchenne muscular dystrophy

OBJECTIVES: Our goal was to identify early changes in myocardial physical properties in children with Duchenne muscular dystrophy (DMDch). BACKGROUND: Duchenne muscular dystrophy (DMD) is caused by the absence of dystrophin, which triggers complex molecular and biological events in skeletal and cardiac muscle tissues. Although about 30% of patients display overt signs of cardiomyopathy in the late stage of the disease, it is unknown whether changes in myocardial physical properties can be detected in the early (preclinical) stages of the disease. METHODS: We performed an ultrasonic tissue characterization (UTC) analysis of myocardium in DMDch with normal systolic myocardial function and no signs of cardiomyopathy. Both the cyclic variation of integrated backscatter (cvIBS) and the calibrated integrated backscatter (cIBS) were assessed in 8 myocardial regions of 20 DMDch, age 7 ± 2 years (range 4 to 10 years), and in 20 age-matched healthy controls. RESULTS: We found large differences in the UTC data between DMDch and controls; the mean value of cvIBS was 4.4 ± 1.5 dB versus 8.8 ± 0.8 dB, whereas the mean value of cIBS was 36.4 ± 7.1 dB versus 26.9 ± 2.0 dB (p <10^-6 for both). In DMDch, all eight sampled segments showed cIBS mean values to be significantly higher and cvIBS mean values to be significantly lower than those in the controls. Finally, interindividual differences were greater in DMDch than in controls for both parameters. CONCLUSIONS: The myocardium in DMDch displays UTC features different from those in healthy controls. These results show that lack of dystrophin is commonly associated with changes in myocardial features well. before the onset of changes of systolic function and overt cardiomyopathy.