Cardiomyopathy is the leading cause of death in Duchenne muscular dystrophy (DMD), however, in the mdx mouse model of DMD, the cardiac phenotype differs from that seen in DMD-associated cardiomyopathy. Although some have used pharmacologic stress to enhance the cardiac phenotype in the mdx model, many methods lead to high mortality, variable cardiac outcomes, and do not recapitulate the structural and functional cardiac changes seen in human disease. Here, we describe a simple and effective method to enhance the cardiac phenotype model in mdx mice using advanced 2D and 4D high-frequency ultrasound to monitor cardiac dysfunction progression in vivo. For our study, mdx and wild-type (WT) mice received daily low-dose (2 mg/kg/day) isoproterenol injections for 10 days. Histopathologic assessment showed that isoproterenol treatment increased myocyte injury, elevated serum cardiac troponin I levels, and enhanced fibrosis in mdx mice. Ultrasound revealed reduced ventricular function, decreased wall thickness, increased volumes, and diminished cardiac reserve in mdx mice compared to wild-type. Our findings highlight the utility of low-dose isoproterenol in mdx mice as a valuable model for exploring therapies targeting DMD-associated cardiac complications.

OBJECTIVE: Complex fetal behavior involving multiple parts of the body, called general movement (GM), has been considered an essential predictor of neurological functional development because it directly reflects the integrity of the brain and central and peripheral nervous systems. We have developed a novel method for quantitative analysis of fetal behavior using four-dimensional ultrasound (4DUS) and conducted a pilot study for quantitative assessment of fetal GM in the early second trimester.
METHODS: All subjects underwent 4DUS to depict the whole fetal body, and maximum velocity (MAXV), median velocity (MV), average velocity (AV), and mode velocity (MOV) were calculated by utilizing optical flow analysis. Receiver operating characteristic (ROC) curve analysis was performed to analyze the optimal speed parameters for detecting GM in the fetus. The Mann-Whitney U test was used to validate MAXV, AV, and MV ability to detect fetal GM.
RESULTS: The presence of fetal GMs and the absence of fetal GMs were 226 and 107, respectively, based on optical flow analysis. Mann-Whitney U test revealed a significant difference in the presence or absence of fetal GM in MAXV, MV, AV, and MOV. ROC analysis showed that the area under the curve (AUC) of MAXV was 0.959; the threshold was 0.421, the sensitivity was 86%, and the specificity was 93%. In contrast, the AUC/threshold for AV and MV was 0.700/0.110 (sensitivity 71% and specificity 76%) and 0.521/0.119 (sensitivity 21% and specificity 90%), respectively. Spearman\'s rank correlation analysis also showed a weak negative correlation between GM and MAXV (r = - 0.235, P < 0.01) and AV (r = - 0.28, P < 0.01).
CONCLUSIONS: In this study, we conducted a quantitative analysis of fetal behavior based on optical flow using 4DUS and demonstrated that it was highly accurate for detecting GMs and for evaluating developmental changes in GMs. The implementation of quantitative analysis of fetal GMs in the early second trimester has been very preliminary, and there is much debate on how it will be clinically applied to perinatal assessment.