Left ventricular dysfunction in Duchenne muscular dystrophy

Contiguous Xp21 deletion involving Duchenne muscular dystrophy and McLeod neuroacanthocytosis syndrome results in rapidly progressive and fatal cardiomyopathy

Dilated cardiomyopathy is an expected manifestation and common cause of death in patients with Duchenne muscular dystrophy. We present an unusually rapid progression of cardiomyopathy in a boy with Duchenne muscular dystrophy. Expanded genetic testing revealed a contiguous Xp21 deletion involving dystrophin and XK genes, responsible for Duchenne muscular dystrophy and McLeod neuroacanthocytosis syndrome, respectively, resulting in a more severe cardiac phenotype.

Genetic Panel Reveals Coexisting Neuromuscular Disorders in Patients With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy is a genetically based neuromuscular disorder characterized by progressive physical impairment and cardiomyopathy in children, leading to fatal cardiac or respiratory failure. Duchenne muscular dystrophy shares some overlapping clinical features with other disorders, complicating clinical differentiation. We hypothesized that some Duchenne muscular dystrophy patients may have a secondary neuromuscular disorders that could negatively skew data during pharmaceutical clinical trials and lead to incomplete treatment plans. Consecutive genetic panels on 353 patients were reviewed. Thirty-two (32; 9.1%) patients with Duchenne muscular dystrophy were identified. Three (3; 9.4%) were found to have at least 1 genetically confirmed secondary neuromuscular disorder. Overlooking these coexisting disorders could lead to unexpected treatment failures, potentially affecting medication efficacy in trials or commercial use. Secondary neuromuscular disorders should be considered in Duchenne muscular dystrophy patients before clinical trial enrollment or treatment planning, with expanded genetic testing, such as whole exome sequencing or whole genome sequencing, likely to reveal even more secondary disorders.

Similar disease progression in nonsense Duchenne muscular dystrophy boys as general natural history: Single Brazilian center 15 years registry view

Duchenne muscular dystrophy is a progressive and fatal X-linked neuromuscular disease. Emergent disease-modifying therapy (DMT) in nonsense Duchenne muscular dystrophy (nmDMD) has brought new perspectives to slow down functional decline in this fatal disease. To investigate if there are differences in natural history between nmDMD and other genotypes, we described a retrospective cohort analysis of 25 nonsense mutation DMD (nmDMD) boys without disease-modifying therapy, aged between 1 and 22 years, over the last 15 years (2007-2022) in a single neuromuscular center in Rio de Janeiro and use published data on DMD natural history for comparison. Regarding prognostic factors, there were remarkable and statistically significant early loss of ambulation (at 9.1y ±2.1) and shortening of life expectancy (17.6y ±2.1) in our nmDMD group. Late acquisition of neurodevelopmental milestones and annual rates of decline in respiratory, cardiac, and timed motor function tests are the same between nmDMD patients with standard care and other DMD genotypes as described in the literature. Our data indicates the similarity of natural history and disease progression among DMD boys with nmDMD mutations compared to different mutations.

Functional cardiac consequences of β-adrenergic stress-induced injury in a model of Duchenne muscular dystrophy

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 stimulate injury and enhance cardiac pathology in the mdx model, many methods lead to high mortality with 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. mdx and wild-type mice received daily low-dose (2 mg/kg/day) isoproterenol injections for 10 days. Histopathological 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 compared to wild-type mice. Our findings highlight the utility of challenging mdx mice with low-dose isoproterenol as a valuable model for exploring therapies targeting DMD-associated cardiac pathologies.

Hypertrophic cardiomyopathy in Duchenne muscular dystrophy: a case series

Duchenne muscular dystrophy is characterised by fibrofatty replacement of muscle, resulting in dilated cardiomyopathy. Hypertrophic cardiomyopathy affects 1:200-1:500 people and is characterised by asymmetric ventricular septal hypertrophy. To date, there have been two separately reported cases describing the combined pathology of these disorders. Herein, we expand upon these reports with a case series describing longitudinal findings in three patients with Duchenne muscular dystrophy who developed hypertrophic cardiomyopathy.

Novel Cardiac Imaging Risk Score for Mortality Prediction in Duchenne Muscular Dystrophy

Cardiovascular disease is the leading cause of death in patients with Duchenne Muscular Dystrophy (DMD), but there is significant cardiomyopathy phenotypic variability. Some patients demonstrate rapidly progressive disease and die at a young age while others survive into the fourth decade. Criteria to identify DMD subjects at greatest risk for early mortality could allow for increased monitoring and more intensive therapy. A risk score was created describing the onset and progression of left ventricular dysfunction and late gadolinium enhancement in subjects with DMD. DMD subjects prospectively enrolled in ongoing observational studies (which included cardiac magnetic resonance [CMR]) were used to validate the risk score. A total of 69 subjects had calculable scores. During the study period, 12 (17%) died from complications of DMD. The median risk score was 3 (IQR [2,5]; range [0,9]). The overall risk score applied at the most recent imaging age was associated with mortality at a median age of 17 years (IQR [16,20]) (HR 2.028, p < 0.001). There were no deaths in subjects with a score of less than two. Scores were stable over time. An imaging-based risk score allows risk stratification of subjects with DMD. This can be quickly calculated during a clinic visit to identify subjects at greatest risk of early death.

Positive Airway Pressure and Metabolic Markers in Children With Obstructive Sleep Apnea

BACKGROUND

Increasing evidence suggests an association between childhood obstructive sleep apnea (OSA) and metabolic syndrome, with more research available on the potential impacts of positive airway pressure (PAP) on metabolic markers in children. The purpose of this systematic review is to provide a systematic synthesis of the evidence on the effect of PAP use on metabolic markers in children with OSA.

METHODS

A search strategy with terms for "OSA" and metabolic markers in pediatrics was run to systematically assess 5 databases until August 26, 2022. Two reviewers independently screened eligible articles, extracted data, and conducted quality appraisal. Meta-analysis was done using random-effects models. Body mass index (BMI), glycemic, lipid, cardiovascular, and other metabolic and inflammatory markers were reported.

RESULTS

Sixteen studies (N = 1,213) were included, 15 observational studies and 1 randomized controlled trial (RCT); most reported outcomes in children with obesity. Meta-analysis of 4 studies found no changes in BMI at median average follow-up of 12 months after PAP initiation. A reduction in heart rate and blood pressure parameters was demonstrated in several studies in children with OSA with and without obesity at a median average follow-up of 4.9 months after PAP initiation. Research in echocardiographic outcomes is limited, including one RCT in children with Down syndrome and OSA showing no changes in heart rate variability parameters. Evidence of improvements in glycemic and/or lipid control, liver enzymes, and inflammatory markers with PAP therapy is even more limited and of limited clinical importance. Risk of bias was moderate to critical and outcome evidence very low.

CONCLUSIONS

Although evidence on effects of PAP on metabolic markers in children with OSA is encouraging, available literature is limited. Longitudinal studies are still required to further assess the long-term influence of PAP on metabolic and inflammatory markers, particularly in children with obesity.

Functional cardiac consequences of β-adrenergic stress-induced injury in the mdx mouse model of Duchenne muscular dystrophy

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.

Prophylactic use of cardiac medications for delay of left ventricular dysfunction in Duchenne muscular dystrophy

BACKGROUND

Epidemiological support for prophylactic treatment of left ventricular dysfunction (LVD) in Duchenne muscular dystrophy is limited. We used retrospective, population-based surveillance data from the Muscular Dystrophy Surveillance, Tracking and Research Network to evaluate whether prophylaxis delays LVD onset.

METHODS

We analyzed 455 males born during 1982-2009. Age at first abnormal echocardiogram (ejection fraction <55% or shortening fraction <28%) determined LVD onset. Prophylaxis was defined as cardiac medication use at least 1 year prior to LVD. Corticosteroid use was also coded. Kaplan-Meier curve estimation and Cox Proportional Hazard modeling with time-varying covariates describe associations.

RESULTS

LVD was identified among 40.7%; average onset age was 14.2 years. Prophylaxis was identified for 20.2% and corticosteroids for 57.4%. Prophylaxis showed delayed LVD onset (p < .001) and lower hazard of dysfunction (adjusted hazard ratio [aHR] = 0.39, 95%CL = 0.22, 0.65) compared to untreated. Compared to no treatment, continuous corticosteroids only (aHR = 1.01, 95%CL = 0.66, 1.53) and prophylaxis only (aHR = 0.67, 95%CL = 0.25, 1.50) were not cardioprotective, but prophylaxis plus continuous corticosteroids were associated with lower hazard of dysfunction (aHR = 0.37, 95%CL = 0.15, 0.80).

CONCLUSIONS

Proactive cardiac treatment and monitoring are critical aspects of managing Duchenne muscular dystrophy. Consistent with clinical care guidelines, this study supports clinical benefit from cardiac medications initiated prior to documented LVD and suggests further benefit when combined with corticosteroids.

Duchenne muscular dystrophy involves the myocardium and causes arrhythmia: Case report

Background

Patients with muscular dystrophy have mutations in the gene that can lead to severe muscle wasting, respiratory issues or heart failure between ages 30 and 40. Currently, there is no effective treatment for DMD-induced heart failure.

Case presentation

We report a patient with recurrent unexplained fever and muscle soreness was definitely diagnosed with DMD. An analysis of the patient's genetics revealed a nonsense mutation (C.1207G > T). His DMD was treated with hormones. Also, the patient's fever is under control because of hormone therapy. However, as the disease progresses, the heart structure and function gradually change, and eventually malignant arrhythmias occur.

Conclusion

We report a rare case of DMD involving the heart causing heart failure and malignant arrhythmia. Currently, no complete treatment is available for these patients, but our treatment regimen may benefit our patient and improve his outcomes.

The role of the dystrophin glycoprotein complex in muscle cell mechanotransduction

Dystrophin is the central protein of the dystrophin-glycoprotein complex (DGC) in skeletal and heart muscle cells. Dystrophin connects the actin cytoskeleton to the extracellular matrix (ECM). Severing the link between the ECM and the intracellular cytoskeleton has a devastating impact on the homeostasis of skeletal muscle cells, leading to a range of muscular dystrophies. In addition, the loss of a functional DGC leads to progressive dilated cardiomyopathy and premature death. Dystrophin functions as a molecular spring and the DGC plays a critical role in maintaining the integrity of the sarcolemma. Additionally, evidence is accumulating, linking the DGC to mechanosignalling, albeit this role is still less understood. This review article aims at providing an up-to-date perspective on the DGC and its role in mechanotransduction. We first discuss the intricate relationship between muscle cell mechanics and function, before examining the recent research for a role of the dystrophin glycoprotein complex in mechanotransduction and maintaining the biomechanical integrity of muscle cells. Finally, we review the current literature to map out how DGC signalling intersects with mechanical signalling pathways to highlight potential future points of intervention, especially with a focus on cardiomyopathies.

A review of the function of the Dystrophic Glycoprotein Complex (DGC) in mechanosignaling provides an overview of the various components of DGC and potential mechanopathogenic mechanisms, particularly as they relate to muscular dystrophy.

Direct costs of adhering to selected Duchenne muscular dystrophy Care Considerations: Estimates from a midwestern state

INTRODUCTION/AIMS

The multidisciplinary Duchenne muscular dystrophy (DMD) Care Considerations were developed to standardize care and improve outcomes. We provide cumulative cost estimates for selected key preventive (ie, excluding new molecular therapies and acute care) elements of the care considerations in eight domains (neuromuscular, rehabilitation, respiratory, cardiac, orthopedic, gastrointestinal, endocrine, psychosocial management) independent of completeness of uptake or provision of nonpreventive care.

METHODS

We used de-identified insurance claims data from a large midwestern commercial health insurer during 2018. We used Current Procedural Terminology and national drug codes to extract unit costs for clinical encounters representing key preventive elements of the DMD Care Considerations. We projected per-patient cumulative costs from ages 5 to 25 years for these elements by multiplying a schedule of recommended frequencies of preventive services by unit costs in 2018 US dollars.

RESULTS

Assuming a diagnosis at age 5 years, independent ambulation until age 11, and survival until age 25, we estimated 670 billable clinical events. The 20-year per-patient cumulative cost was $174 701 with prednisone ($2.3 million with deflazacort) and an expected total of $12 643 ($29 194) for out-of-pocket expenses associated with those events and medications.

DISCUSSION

Standardized monitoring of disease progression and treatments may reduce overall costs of illness. Costs associated with these services would be needed to quantify potential savings. Our approach demonstrates a method to estimate costs associated with implementation of preventive care schedules.

Cardiovascular phenotype of the Dmdmdx rat - a suitable animal model for Duchenne muscular dystrophy

Besides skeletal muscle abnormalities, Duchenne muscular dystrophy (DMD) patients present with dilated cardiomyopathy development, which considerably contributes to morbidity and mortality. Because the mechanisms responsible for the cardiac complications in the context of DMD are largely unknown, evidence-based therapy approaches are still lacking. This has increased the need for basic research efforts into animal models for DMD. Here, we characterized in detail the cardiovascular abnormalities of Dmd^mdx rats, with the aim of determining the suitability of this recently established dystrophin-deficient small animal as a model for DMD.

Various methods were applied to compare cardiovascular properties between wild-type and Dmd^mdx rats, and to characterize the Dmd^mdx cardiomyopathy. These methods comprised echocardiography, invasive assessment of left ventricular hemodynamics, examination of adverse remodeling and endothelial cell inflammation, and evaluation of vascular function, employing wire myography. Finally, intracellular Ca²⁺ transient measurements, and recordings of currents through L-type Ca²⁺ channels were performed in isolated single ventricular cardiomyocytes. We found that, similar to respective observations in DMD patients, the hearts of Dmd^mdx rats show significantly impaired cardiac function, fibrosis and inflammation, consistent with the development of a dilated cardiomyopathy. Moreover, in Dmd^mdx rats, vascular endothelial function is impaired, which may relate to inflammation and oxidative stress, and Ca²⁺ handling in Dmd^mdx cardiomyocytes is abnormal.

These findings indicate that Dmd^mdx rats represent a promising small-animal model to elucidate mechanisms of cardiomyopathy development in the dystrophic heart, and to test mechanism-based therapies aiming to combat cardiovascular complications in DMD.

Summary: We characterized the cardiovascular abnormalities of Dmd^mdx rats, demonstrating that Dmd^mdx rats show similar cardiac and vascular endothelial function impairments to Duchenne muscular dystrophy patients, representing a model of the dystrophic heart.