Cardiac Involvement Classification and Therapeutic Management in Patients with Duchenne Muscular Dystrophy

Disturbed Atrial Conduction in Patients with Duchenne Muscular Dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD)-related cardiomyopathy is associated with hemodynamic and conduction abnormalities and begins at an early age with subtle symptoms.

METHODS

The study population included 55 patients with DMD and 54 healthy controls. We compared electrocardiogram (ECG), conventional echocardiography, and tissue Doppler imaging (TDI) assessments between patients with DMD and healthy controls. Also, we investigated atrial electromechanical delay, which has not been previously studied in DMD patients. Mitral, septal, and tricuspid segments were analyzed by TDI.

RESULTS

The mean age was 13.6 ± 2.5 years (range, 9.3-17.9 years) in the patient group and 12.8 ± 2.6 years (range, 8-17.5 years) in the control group (P = .1). Patients had higher heart rates, longer QTc intervals, and P-wave dispersion (PWD) than controls (P < .001, P = .004, P < .001, respectively). The patient group had larger left ventricular end-systolic dimension (P < .001), lower left ventricular ejection fraction (EF) (P < .001), MAPSE (P < .001), TAPSE (P < .001), and mitral-E/A (P = .029) values than control subjects. Myocardial performance index (P < .001) was higher, and the E'/A' ratio (P < .001) was lower at all 3 segments in the patient group. Also, atrial electromechanical delay was longer in the patient group at these segments (P < .001). Patients had significantly longer interatrial (P = .033) electromechanical conduction delays. EF was negatively correlated with atrial conduction time variables.

CONCLUSION

We have shown deterioration in systolic and diastolic function in both ventricles, PWD, and atrial conduction in children with DMD. Patients with DMD may be at risk of atrial arrhythmias due to disturbed atrial conduction.

Comprehensive review of adverse reactions and toxicology in ASO-based therapies for Duchenne Muscular Dystrophy: From FDA-approved drugs to peptide-conjugated ASO

Duchenne Muscular Dystrophy (DMD) is a devastating X-linked genetic disorder characterized by progressive muscle degeneration due to mutations in the dystrophin gene. This results in the absence or dysfunction of the dystrophin protein, leading to muscle weakness, loss of ambulation, respiratory issues, and cardiac complications, often leading to premature death. Recently, antisense oligonucleotide (ASO)-mediated exon skipping has emerged as a promising therapeutic strategy for DMD. Notably, the FDA has conditionally approved four ASO therapies for DMD, with numerous others in various stages of clinical development, indicating the growing interest and potential in this field. To enhance ASO-based therapies, researchers have explored the novel concept of conjugating peptides to the phosphorodiamidate morpholino backbone (PMO) of ASOs, leading to the development of peptide-conjugated PMOs (PPMOs). These PPMOs have demonstrated significantly improved pharmacokinetic profiles, potentially augmenting their therapeutic effectiveness. Despite the optimism surrounding ASOs and PPMOs, concerns persist regarding their efficacy and safety. To comprehensively evaluate these therapies, it is imperative to expand patient populations in clinical trials and conduct thorough investigations into the associated risks. This article provides a comprehensive review and discussion of the available data pertaining to adverse reactions and toxicology associated with FDA-approved ASO drugs for DMD. Furthermore, it offers insights into the emerging category of peptide-conjugated ASO drugs those are clinical and preclinical trials, shedding light on their potential benefits and challenges.

Asymmetric Myocardial Involvement as an Early Indicator of Cardiac Dysfunction in Pediatric Dystrophinopathies: A Study on Cardiac Magnetic Resonance (CMR) Parametric Mappings

Dystrophinopathies, such as Duchenne and Becker muscular dystrophy, frequently lead to cardiomyopathy, being its primary cause of mortality. Detecting cardiac dysfunction early is crucial, but current imaging methods lack insight into microstructural remodeling. This study aims to assess the potential of cardiac magnetic resonance (CMR) parametric mappings for early detection of myocardial involvement in dystrophinopathies and explores whether distinct involvement patterns may indicate impending dysfunction. In this prospective study, 23 dystrophinopathy patients underwent CMR with tissue mappings. To establish a basis for comparison, a control group of 173 subjects was analyzed. CMR protocols included SSFP, T2-weighted and T1-weighted sequences pre and post gadolinium, and tissue mappings for native T1 (nT1), extracellular volume (ECV), and T2 relaxation times. The difference between the left ventricular posterior wall and the interventricular septum was calculated to reveal asymmetric myocardial involvement. Significant differences in LV ejection fraction (LVEF), myocardial mass, and late gadolinium enhancement confirmed abnormalities in patients. Tissue mappings: nT1 (p < 0.001) and ECV (p = 0.002), but not T2, displayed substantial variations, suggesting sensitivity to myocardial involvement. Asymmetric myocardial involvement in nT1 (p = 0.01) and ECV (p = 0.012) between septal and LV posterior wall regions was significant. While higher mapping values didn't correlate with dysfunction, asymmetric involvement in nT1 (ρ=-0.472, p = 0.023) and ECV (ρ=-0.460, p = 0.049) exhibited a significant negative correlation with LVEF. CMR mappings show promise in early myocardial damage detection in dystrophinopathies. Although mapping values may not directly correspond to dysfunction, the negative correlation between asymmetric involvement in nT1 and ECV with LVEF suggests their potential as early biomarkers. Larger, longitudinal studies are needed for a comprehensive understanding and improved risk stratification in dystrophinopathies.

Development of respiratory care guidelines for Duchenne muscular dystrophy in the UK: key recommendations for clinical practice

Significant inconsistencies in respiratory care provision for Duchenne muscular dystrophy (DMD) are reported across different specialist neuromuscular centres in the UK. The absence of robust clinical evidence and expert consensus is a barrier to the implementation of care recommendations in public healthcare systems as is the need to increase awareness of key aspects of care for those living with DMD. Here, we provide evidenced-based and/or consensus-based best practice for the respiratory care of children and adults living with DMD in the UK, both as part of routine care and in an emergency.

METHODOLOGY

Initiated by an expert working group of UK-based respiratory physicians (including British Thoracic Society (BTS) representatives), neuromuscular clinicians, physiotherapist and patient representatives, draft guidelines were created based on published evidence, current practice and expert opinion. After wider consultation with UK respiratory teams and neuromuscular services, consensus was achieved on these best practice recommendations for respiratory care in DMD.

RESULT

The resulting recommendations are presented in the form of a flow chart for assessment and monitoring, with additional guidance and a separate chart setting out key considerations for emergency management. The recommendations have been endorsed by the BTS.

CONCLUSIONS

These guidelines provide practical, reasoned recommendations for all those managing day-to-day and acute respiratory care in children and adults with DMD. The hope is that this will support patients and healthcare professionals in accessing high standards of care across the UK.

Receptor interacting protein kinase-3 mediates both myopathy and cardiomyopathy in preclinical animal models of Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a progressive muscle degenerative disorder, culminating in a complete loss of ambulation, hypertrophic cardiomyopathy and a fatal cardiorespiratory failure. Necroptosis is the form of necrosis that is dependent upon the receptor-interacting protein kinase (RIPK) 3; it is involved in several inflammatory and neurodegenerative conditions. We previously identified RIPK3 as a key player in the acute myonecrosis affecting the hindlimb muscles of the mdx dystrophic mouse model. Whether necroptosis also mediates respiratory and heart disorders in DMD is currently unknown.

METHODS

Evidence of activation of the necroptotic axis was examined in dystrophic tissues from Golden retriever muscular dystrophy (GRMD) dogs and R-DMDdel52 rats. A functional assessment of the involvement of necroptosis in dystrophic animals was performed on mdx mice that were genetically depleted for RIPK3. Dystrophic mice aged from 12 to 18 months were analysed by histology and molecular biology to compare the phenotype of muscles from mdxRipk3+/+ and mdxRipk3-/- mice. Heart function was also examined by echocardiography in 40-week-old mice.

RESULTS

RIPK3 expression in sartorius and biceps femoris muscles from GRMD dogs positively correlated to myonecrosis levels (r = 0.81; P = 0.0076). RIPK3 was also found elevated in the diaphragm (P ≤ 0.05). In the slow-progressing heart phenotype of GRMD dogs, the phosphorylated form of RIPK1 at the Serine 161 site was dramatically increased in cardiomyocytes. A similar p-RIPK1 upregulation characterized the cardiomyocytes of the severe DMDdel52 rat model, associated with a marked overexpression of Ripk1 (P = 0.007) and Ripk3 (P = 0.008), indicating primed activation of the necroptotic pathway in the dystrophic heart. MdxRipk3-/- mice displayed decreased compensatory hypertrophy of the heart (P = 0.014), and echocardiography showed a 19% increase in the relative wall thickness (P < 0.05) and 29% reduction in the left ventricle mass (P = 0.0144). Besides, mdxRipk3-/- mice presented no evidence of a regenerative default or sarcopenia in skeletal muscles, moreover around 50% less affected by fibrosis (P < 0.05).

CONCLUSIONS

Our data highlight molecular and histological evidence that the necroptotic pathway is activated in degenerative tissues from dystrophic animal models, including the diaphragm and the heart. We also provide the genetic proof of concept that selective inhibition of necroptosis in dystrophic condition improves both histological features of muscles and cardiac function, suggesting that prevention of necroptosis is susceptible to providing multiorgan beneficial effects for DMD.

Systemic deletion of DMD exon 51 rescues clinically severe Duchenne muscular dystrophy in a pig model lacking DMD exon 52

Duchenne muscular dystrophy (DMD) is a fatal X-linked disease caused by mutations in the DMD gene, leading to complete absence of dystrophin and progressive degeneration of skeletal musculature and myocardium. In DMD patients and in a corresponding pig model with a deletion of DMD exon 52 (DMDΔ52), expression of an internally shortened dystrophin can be achieved by skipping of DMD exon 51 to reframe the transcript. To predict the best possible outcome of this strategy, we generated DMDΔ51-52 pigs, additionally representing a model for Becker muscular dystrophy (BMD). DMDΔ51-52 skeletal muscle and myocardium samples stained positive for dystrophin and did not show the characteristic dystrophic alterations observed in DMDΔ52 pigs. Western blot analysis confirmed the presence of dystrophin in the skeletal muscle and myocardium of DMDΔ51-52 pigs and its absence in DMDΔ52 pigs. The proteome profile of skeletal muscle, which showed a large number of abundance alterations in DMDΔ52 vs. wild-type (WT) samples, was normalized in DMDΔ51-52 samples. Cardiac function at age 3.5 mo was significantly reduced in DMDΔ52 pigs (mean left ventricular ejection fraction 58.8% vs. 70.3% in WT) but completely rescued in DMDΔ51-52 pigs (72.3%), in line with normalization of the myocardial proteome profile. Our findings indicate that ubiquitous deletion of DMD exon 51 in DMDΔ52 pigs largely rescues the rapidly progressing, severe muscular dystrophy and the reduced cardiac function of this model. Long-term follow-up studies of DMDΔ51-52 pigs will show if they develop symptoms of the milder BMD.

Functional and Clinical Outcomes Associated with Steroid Treatment among Non-ambulatory Patients with Duchenne Muscular Dystrophy1

BACKGROUND

Evidence on the long-term efficacy of steroids in Duchenne muscular dystrophy (DMD) after loss of ambulation is limited.

OBJECTIVE

Characterize and compare disease progression by steroid treatment (prednisone, deflazacort, or no steroids) among non-ambulatory boys with DMD.

METHODS

Disease progression was measured by functional status (Performance of Upper Limb Module for DMD 1.2 [PUL] and Egen Klassifikation Scale Version 2 [EK] scale) and by cardiac and pulmonary function (left ventricular ejection fraction [LVEF], forced vital capacity [FVC] % -predicted, cough peak flow [CPF]). Longitudinal changes in outcomes, progression to key disease milestones, and dosing and body composition metrics were analyzed descriptively and in multivariate models.

RESULTS

This longitudinal cohort study included 86 non-ambulatory patients with DMD (mean age 13.4 years; n = 40 [deflazacort], n = 29 [prednisone], n = 17 [no steroids]). Deflazacort use resulted in slower average declines in FVC % -predicted vs. no steroids (+3.73 percentage points/year, p < 0.05). Both steroids were associated with significantly slower average declines in LVEF, improvement in CPF, and slower declines in total PUL score and EK total score vs. no steroids; deflazacort was associated with slower declines in total PUL score vs. prednisone (all p < 0.05). Both steroids also preserved functional abilities considered especially important to quality of life, including the abilities to perform hand-to-mouth function and to turn in bed at night unaided (all p < 0.05 vs. no steroids).

CONCLUSIONS

Steroid use after loss of ambulation in DMD was associated with delayed progression of important pulmonary, cardiac, and upper extremity functional deficits, suggesting some benefits of deflazacort over prednisone.

Calcium handling maturation and adaptation to increased substrate stiffness in human iPSC-derived cardiomyocytes: The impact of full-length dystrophin deficiency

Cardiomyocytes differentiated from human induced Pluripotent Stem Cells (hiPSC- CMs) are a unique source for modelling inherited cardiomyopathies. In particular, the possibility of observing maturation processes in a simple culture dish opens novel perspectives in the study of early-disease defects caused by genetic mutations before the onset of clinical manifestations. For instance, calcium handling abnormalities are considered as a leading cause of cardiomyocyte dysfunction in several genetic-based dilated cardiomyopathies, including rare types such as Duchenne Muscular Dystrophy (DMD)-associated cardiomyopathy. To better define the maturation of calcium handling we simultaneously measured action potential and calcium transients (Ca-Ts) using fluorescent indicators at specific time points. We combined micropatterned substrates with long-term cultures to improve maturation of hiPSC-CMs (60, 75 or 90 days post-differentiation). Control-(hiPSC)-CMs displayed increased maturation over time (90 vs 60 days), with longer action potential duration (APD), increased Ca-T amplitude, faster Ca-T rise (time to peak) and Ca-T decay (RT50). The progressively increased contribution of the SR to Ca release (estimated by post-rest potentiation or Caffeine-induced Ca-Ts) appeared as the main determinant of the progressive rise of Ca-T amplitude during maturation. As an example of severe cardiomyopathy with early onset, we compared hiPSC-CMs generated from a DMD patient (DMD-ΔExon50) and a CRISPR-Cas9 genome edited cell line isogenic to the healthy control with deletion of a G base at position 263 of the DMD gene (c.263delG-CMs). In DMD-hiPSC-CMs, changes of Ca-Ts during maturation were less pronounced: indeed, DMD cells at 90 days showed reduced Ca-T amplitude and faster Ca-T rise and RT50, as compared with control hiPSC-CMs. Caffeine-Ca-T was reduced in amplitude and had a slower time course, suggesting lower SR calcium content and NCX function in DMD vs control cells. Nonetheless, the inotropic and lusitropic responses to forskolin were preserved. CRISPR-induced c.263delG-CM line recapitulated the same developmental calcium handling alterations observed in DMD-CMs. We then tested the effects of micropatterned substrates with higher stiffness. In control hiPSC-CMs, higher stiffness leads to higher amplitude of Ca-T with faster decay kinetics. In hiPSC-CMs lacking full-length dystrophin, however, stiffer substrates did not modify Ca-Ts but only led to higher SR Ca content. These findings highlighted the inability of dystrophin-deficient cardiomyocytes to adjust their calcium homeostasis in response to increases of extracellular matrix stiffness, which suggests a mechanism occurring during the physiological and pathological development (i.e. fibrosis).

Chest Pain and Electrocardiographic Changes in a Child With Duchenne Muscular Dystrophy

A 12-year-old boy known to have Duchenne muscular dystrophy presented to our Emergency Department with acute onset central chest pain.

A 12-lead electrocardiogram (ECG) was performed showing ST-segment elevation with reciprocal changes. An echocardiogram showed reduced left ventricular systolic function with an ejection fraction of 45%. Initial cardiac biomarkers were significantly elevated, with troponin-T result recorded at 7,065 ng/L (reference range: 0-14 ng/L). The patient was admitted to the pediatric intensive care unit with a differential diagnosis of acute myocardial infarction or acute myocardial injury related to cardiomyopathy and commenced on an ACE (angiotensin-converting enzyme) inhibitor. Computed tomography (CT) of the coronary arteries was performed, which showed normal coronary arteries and cardiac anatomy.

The patient was discharged on day 5 and continues to follow up in the pediatric cardiology clinic. He was commenced on a beta blocker at one-month follow-up when he was asymptomatic.

CD38-NADase is a new major contributor to Duchenne muscular dystrophic phenotype

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle degeneration. Two important deleterious features are a Ca²⁺ dysregulation linked to Ca²⁺ influxes associated with ryanodine receptor hyperactivation, and a muscular nicotinamide adenine dinucleotide (NAD⁺) deficit. Here, we identified that deletion in mdx mice of CD38, a NAD⁺ glycohydrolase‐producing modulators of Ca²⁺ signaling, led to a fully restored heart function and structure, with skeletal muscle performance improvements, associated with a reduction in inflammation and senescence markers. Muscle NAD⁺ levels were also fully restored, while the levels of the two main products of CD38, nicotinamide and ADP‐ribose, were reduced, in heart, diaphragm, and limb. In cardiomyocytes from mdx/CD38^−/− mice, the pathological spontaneous Ca²⁺ activity was reduced, as well as in myotubes from DMD patients treated with isatuximab (SARCLISA^®) a monoclonal anti‐CD38 antibody. Finally, treatment of mdx and utrophin–dystrophin‐deficient (mdx/utr^−/−) mice with CD38 inhibitors resulted in improved skeletal muscle performances. Thus, we demonstrate that CD38 actively contributes to DMD physiopathology. We propose that a selective anti‐CD38 therapeutic intervention could be highly relevant to develop for DMD patients.

Transiently expressed CRISPR/Cas9 induces wild-type dystrophin in vitro in DMD patient myoblasts carrying duplications

Among the mutations arising in the DMD gene and causing Duchenne Muscular Dystrophy (DMD), 10–15% are multi-exon duplications. There are no current therapeutic approaches with the ability to excise large multi-exon duplications, leaving this patient cohort without mutation-specific treatment. Using CRISPR/Cas9 could provide a valid alternative to achieve targeted excision of genomic duplications of any size. Here we show that the expression of a single CRISPR/Cas9 nuclease targeting a genomic region within a DMD duplication can restore the production of wild-type dystrophin in vitro. We assessed the extent of dystrophin repair following both constitutive and transient nuclease expression by either transducing DMD patient-derived myoblasts with integrating lentiviral vectors or electroporating them with CRISPR/Cas9 expressing plasmids. Comparing genomic, transcript and protein data, we observed that both continuous and transient nuclease expression resulted in approximately 50% dystrophin protein restoration in treated myoblasts. Our data demonstrate that a high transient expression profile of Cas9 circumvents its requirement of continuous expression within the cell for targeting DMD duplications. This proof-of-concept study therefore helps progress towards a clinically relevant gene editing strategy for in vivo dystrophin restoration, by highlighting important considerations for optimizing future therapeutic approaches.

Cardiac MRI and Echocardiography for Early Diagnosis of Cardiomyopathy Among Boys With Duchenne Muscular Dystrophy: A Cross-Sectional Study

BACKGROUND

Cardiomyopathy is an important cause of morbidity and mortality in boys with Duchenne muscular dystrophy (DMD). Early diagnosis is a prerequisite for timely institution of cardioprotective therapies.

OBJECTIVE

We compared cardiac MRI (CMRI) with transthoracic echocardiography (TTE) including tissue Doppler imaging (TDI) and speckle tracking echocardiography (STE) for diagnosis of cardiomyopathy in early ambulatory boys with DMD.

METHODOLOGY

This cross-sectional study was conducted between June 2018 and December 2020. Consecutive boys between 7 and 15 years of age with DMD were enrolled. Percentage ejection fraction (EF), fractional shortening, wall motion abnormalities, early diastolic mitral annulus velocity (Ea), medial mitral annulus ratio (E/Ea), and global strain were measured with STE. CMRI-derived EF, segmental hypokinesia, and late gadolinium enhancement (LGE) were studied and compared.

RESULTS

A total of 38 ambulatory boys with DMD were enrolled. The mean age was 8.8 ± 1.6 years, and none had clinical features suggestive of cardiac dysfunction. In the TTE, EF was ≤55% in 5 (15%), FS was ≤28% in 3 (9%), and one each had left ventricular wall thinning and wall hypokinesia. In TDI, none had diastolic dysfunction, and STE showed reduced global strain of < 18% in 3 (9%) boys. CMRI-derived EF was ≤55% in 20 (53%) boys and CMRI showed the presence of left ventricular wall hypokinesia in 9 (24%) and LGE in 4 (11%) boys.

CONCLUSION

Cardiomyopathy remains clinically asymptomatic among early ambulatory boys with DMD. A significantly higher percentage of boys revealed early features of DMD-related cardiomyopathy in CMRI in comparison with echocardiography.

Right Ventricular Function and T1-Mapping in Boys With Duchenne Muscular Dystrophy

BACKGROUND

Clinical management of boys with Duchenne muscular dystrophy (DMD) relies on in-depth understanding of cardiac involvement, but right ventricular (RV) structural and functional remodeling remains understudied.

PURPOSE

To evaluate several analysis methods and identify the most reliable one to measure RV pre- and postcontrast T1 (RV-T1) and to characterize myocardial remodeling in the RV of boys with DMD.

STUDY TYPE

Prospective.

POPULATION

Boys with DMD (N = 27) and age-/sex-matched healthy controls (N = 17) from two sites.

FIELD STRENGTH/SEQUENCE

3.0 T using balanced steady state free precession, motion-corrected phase sensitive inversion recovery and modified Look-Locker inversion recovery sequences.

ASSESSMENT

Biventricular mass (Mi), end-diastolic volume (EDVi) and ejection fraction (EF) assessment, tricuspid annular excursion (TAE), late gadolinium enhancement (LGE), pre- and postcontrast myocardial T1 maps. The RV-T1 reliability was assessed by three observers in four different RV regions of interest (ROI) using intraclass correlation (ICC).

STATISTICAL TESTS

The Wilcoxon rank sum test was used to compare RV-T1 differences between DMD boys with negative LGE(-) or positive LGE(+) and healthy controls. Additionally, correlation of precontrast RV-T1 with functional measures was performed. A P-value <0.05 was considered statistically significant.

RESULTS

A 1-pixel thick RV circumferential ROI proved most reliable (ICC > 0.91) for assessing RV-T1. Precontrast RV-T1 was significantly higher in boys with DMD compared to controls. Both LGE(-) and LGE(+) boys had significantly elevated precontrast RV-T1 compared to controls (1543 [1489-1597] msec and 1550 [1402-1699] msec vs. 1436 [1399-1473] msec, respectively). Compared to healthy controls, boys with DMD had preserved RVEF (51.8 [9.9]% vs. 54.2 [7.2]%, P = 0.31) and significantly reduced RVMi (29.8 [9.7] g vs. 48.0 [15.7] g), RVEDVi (69.8 [29.7] mL/m² vs. 89.1 [21.9] mL/m² ), and TAE (22.0 [3.2] cm vs. 26.0 [4.7] cm). Significant correlations were found between precontrast RV-T1 and RVEF (β = -0.48%/msec) and between LV-T1 and LVEF (β = -0.51%/msec).

DATA CONCLUSION

Precontrast RV-T1 is elevated in boys with DMD compared to healthy controls and is negatively correlated with RVEF.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 2.

Cardioprotective Effect of Whole Body Periodic Acceleration in Dystrophic Phenotype mdx Rodent

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle wasting and the development of a dilated cardiomyopathy (DCM), which is the leading cause of death in DMD patients. Despite knowing the cause of DMD, there are currently no therapies which can prevent or reverse its inevitable progression. We have used whole body periodic acceleration (WBPA) as a novel tool to enhance intracellular constitutive nitric oxide (NO) production. WBPA adds small pulses to the circulation to increase pulsatile shear stress, thereby upregulating endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) and subsequently elevating the production of NO. Myocardial cells from dystrophin-deficient 15-month old mdx mice have contractile deficiency, which is associated with elevated concentrations of diastolic Ca²⁺ ([Ca²⁺]_d), Na⁺ ([Na⁺]_d), and reactive oxygen species (ROS), increased cell injury, and decreased cell viability. Treating 12-month old mdx mice with WBPA for 3 months reduced cardiomyocyte [Ca²⁺]_d and [Na⁺]_d overload, decreased ROS production, and upregulated expression of the protein utrophin resulting in increased cell viability, reduced cardiomyocyte damage, and improved contractile function compared to untreated mdx mice.

Alpha-dystroglycan binding peptide A2G80-modified stealth liposomes as a muscle-targeting carrier for Duchenne muscular dystrophy

Safe and efficient gene therapy for the treatment of Duchenne muscular dystrophy (DMD), a genetic disorder, is required. For this, the muscle-targeting delivery system of genes and nucleic acids is ideal. In this study, we focused on the A2G80 peptide, which has an affinity for α-dystroglycan expressed on muscle cell membranes, as a muscle targeted nanocarrier for DMD and developed A2G80-modified liposomes. We also prepared A2G80-modified liposomes coated with long- and short-chain PEG, called A2G80-LSP-Lip, to improve the blood circulation of liposomes using microfluidics. The liposomes had a particle size of approximately 80 nm. A2G80-LSP-Lip showed an affinity for the muscle tissue section of mice by overlay assay. When the liposomes were administered to DMD model mice (mdx mice) via the tail vein, A2G80-LSP-Lip accumulated efficiently in muscle tissue compared to control liposomes. These results suggest that A2G80-LSP-Lip can function as a muscle-targeting liposome for DMD via systemic administration, and may be a useful tool for DMD treatment.

T1-Mapping and extracellular volume estimates in pediatric subjects with Duchenne muscular dystrophy and healthy controls at 3T

BACKGROUND

Cardiovascular disease is the leading cause of death in patients with Duchenne muscular dystrophy (DMD)-a fatal X-linked genetic disorder. Late gadolinium enhancement (LGE) imaging is the current gold standard for detecting myocardial tissue remodeling, but it is often a late finding. Current research aims to investigate cardiovascular magnetic resonance (CMR) biomarkers, including native (pre-contrast) T1 and extracellular volume (ECV) to evaluate the early on-set of microstructural remodeling and to grade disease severity. To date, native T1 measurements in DMD have been reported predominantly at 1.5T. This study uses 3T CMR: (1) to characterize global and regional myocardial pre-contrast T1 differences between healthy controls and LGE + and LGE- boys with DMD; and (2) to report global and regional myocardial post-contrast T1 values and myocardial ECV estimates in boys with DMD, and (3) to identify left ventricular (LV) T1-mapping biomarkers capable of distinguishing between healthy controls and boys with DMD and detecting LGE status in DMD.

METHODS

Boys with DMD (N = 28, 13.2 ± 3.1 years) and healthy age-matched boys (N = 20, 13.4 ± 3.1 years) were prospectively enrolled and underwent a 3T CMR exam including standard functional imaging and T1 mapping using a modified Look-Locker inversion recovery (MOLLI) sequence. Pre-contrast T1 mapping was performed on all boys, but contrast was administered only to boys with DMD for post-contrast T1 and ECV mapping. Global and segmental myocardial regions of interest were contoured on mid LV T1 and ECV maps. ROI measurements were compared for pre-contrast myocardial T1 between boys with DMD and healthy controls, and for post-contrast myocardial T1 and ECV between LGE + and LGE- boys with DMD using a Wilcoxon rank-sum test. Results are reported as median and interquartile range (IQR). p-Values < 0.05 were considered significant. Receiver Operating Characteristic analysis was used to evaluate a binomial logistic classifier incorporating T1 mapping and LV function parameters in the tasks of distinguishing between healthy controls and boys with DMD, and detecting LGE status in DMD. The area under the curve is reported.

RESULTS

Boys with DMD had significantly increased global native T1 [1332 (60) ms vs. 1289 (56) ms; p = 0.004] and increased within-slice standard deviation (SD) [100 (57) ms vs. 74 (27) ms; p = 0.001] compared to healthy controls. LGE- boys with DMD also demonstrated significantly increased lateral wall native T1 [1322 (68) ms vs. 1277 (58) ms; p = 0.001] compared to healthy controls. LGE + boys with DMD had decreased global myocardial post-contrast T1 [565 (113) ms vs 635 (126) ms; p = 0.04] and increased global myocardial ECV [32 (8) % vs. 28 (4) %; p = 0.02] compared to LGE- boys. In all classification tasks, T1-mapping biomarkers outperformed a conventional biomarker, LV ejection fraction. ECV was the best performing biomarker in the task of predicting LGE status (AUC = 0.95).

CONCLUSIONS

Boys with DMD exhibit elevated native T1 compared to healthy, sex- and age-matched controls, even in the absence of LGE. Post-contrast T1 and ECV estimates from 3T CMR are also reported here for pediatric patients with DMD for the first time and can distinguish between LGE + from LGE- boys. In all classification tasks, T1-mapping biomarkers outperform a conventional biomarker, LVEF.

Duchenne muscular dystrophy: an overview to the cardiologist

INTRODUCTION

Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy in children, affecting approximately one in 3,500-5,000 liveborn boys. The main signs and symptoms include gait disturbances beginning in early childhood, with later onset of respiratory and cardiac function disorders, both directly affecting the prognosis.

AREAS COVERED

The recent improvement of mechanical ventilation increased the mean DMD survival age; however, there has been little progress in the treatment and prevention of cardiac complications, which currently predominantly impact survival. Cardiological evaluation with imaging methods, such as echocardiography and magnetic resonance imaging, can improve the understanding and detect changes in cardiac function early.

EXPERT OPINION

Close monitoring by the cardiologists and early treatment, with adequate heart disease stratification, may be the key to prolong the lives of these patients until more promising therapies are available and can predict DMD prognosis and progression more accurately. The objective of this brief review is to update the cardiologists by highlighting the most relevant aspects of treatment and follow-up, in a practical and concise way.

Duchenne Dilated Cardiomyopathy: Cardiac Management from Prevention to Advanced Cardiovascular Therapies

Duchenne muscular dystrophy (DMD) cardiomyopathy (DCM) is characterized by a hypokinetic, dilated phenotype progressively increasing with age. Regular cardiac care is crucial in DMD care. Early recognition and prophylactic use of angiotensin converting enzyme inhibitors (ACEi) are the main stay therapeutic strategy to delay incidence of DMD-DCM. Pharmacological treatment to improve symptoms and left ventricle (LV) systolic function, have been widely implemented in the past years. Because of lack of DMD specific drugs, actual indications for established DCM include current treatment for heart failure (HF). This review focuses on current HF strategies to identify, characterize, and treat DMD-DCM.

Obstructive sleep apnea syndrome and autonomic dysfunction in Duchenne muscular dystrophy

PURPOSE

Cardiac and respiratory involvement constitutes serious complications of Duchenne muscular dystrophy (DMD). We hypothesized that obstructive sleep apnea syndrome (OSAS) may play a role in cardiac autonomic dysfunction in DMD. We sought to assess the presence of cardiac autonomic function in patients with DMD by analyzing heart rate variability (HRV) during polysomnography (PSG).

METHODS

In a prospective study, all participants had whole-night PSG recorded and scored according to American Academy of Sleep Medicine guidelines. HRV analysis was performed on electrocardiography recordings from PSG recordings.

RESULTS

Twelve consecutive males with DMD (mean age 9.0 ± 3.1 years, mean BMI 20.6 ± 4.8 kg/m2) and eight age-matched healthy males were enrolled. On clinical evaluation, 58% of patients with DMD had at least one symptom related to OSAS, such as snoring, witnessed apnea, or restless sleep. None of the controls had OSAS-related complaints. By PSG none of the controls had OSAS, while 42% of patients with DMD had OSAS (p = 0.004). Average R-R duration and mean percentage of successive R-R intervals > 50 ms values were significantly lower in patients with DMD than those in controls (p < 0.006). In patients with DMD and OSAS, LF/HF (low/high-frequency) ratio was significantly increased in NREM sleep compared with those in controls (p = 0.005). Higher apnea-hypopnea index and lower oxygen saturation showed significant correlations with higher LF power and LF/HF ratio (p < 0.001).

CONCLUSION

Cardiac autonomic dysfunction is present in DMD, being more pronounced in the presence of OSAS.

Advances in Stem Cell Modeling of Dystrophin-Associated Disease: Implications for the Wider World of Dilated Cardiomyopathy

Familial dilated cardiomyopathy (DCM) is mostly caused by mutations in genes encoding cytoskeletal and sarcomeric proteins. In the pediatric population, DCM is the predominant type of primitive myocardial disease. A severe form of DCM is associated with mutations in the DMD gene encoding dystrophin, which are the cause of Duchenne Muscular Dystrophy (DMD). DMD-associated cardiomyopathy is still poorly understood and orphan of a specific therapy. In the last 5 years, a rise of interest in disease models using human induced pluripotent stem cells (hiPSCs) has led to more than 50 original studies on DCM models. In this review paper, we provide a comprehensive overview on the advances in DMD cardiomyopathy disease modeling and highlight the most remarkable findings obtained from cardiomyocytes differentiated from hiPSCs of DMD patients. We will also describe how hiPSCs based studies have contributed to the identification of specific myocardial disease mechanisms that may be relevant in the pathogenesis of DCM, representing novel potential therapeutic targets.

Mental health and coping strategies in families of children and young adults with muscular dystrophies

BACKGROUND

Living with a progressive disease as muscular dystrophy (MD) can be challenging for the patient and the entire family from both emotional and practical point of view. We aimed to extend our previously published data about mental health in patients with MDs, also investigating coping profiles of both themselves and their parents. Furthermore, we wanted to verify whether psychological adaptation of patients can be predicted by coping strategies, taking also into account physical impairment, cognitive level and socioeconomic status.

METHODS

112 patients with MDs, aged 2-32 were included. Their emotional and behavioural features were assessed through parent- and self-report Achenbach System for Empirically Based Assessment questionnaires and Strength and Difficulties Questionnaires. Development and Well-Being Assessment or Autism Diagnostic Observation Schedule were administered to confirm suspected diagnoses. Coping profile of both parents and patients was assessed through the self-administered New Italian Version of the Coping Orientation to the Problems Experienced questionnaire and its relationship with emotional/behavioural outcome was examined in linear regression analyses.

RESULTS

High prevalence of intellectual disability and autism spectrum disorders was confirmed in Duchenne MD. Despite the high rate of internalizing symptomatology, we did not report higher rate of psychopathological disorders compared to general population. Parents tend to rely more on positive reinterpretation and less on disengagement coping. Avoidance coping, whether used by parents or patients, and ID, predicted increased emotional/behavioural problems.

CONCLUSIONS

Psychosocial interventions should address problems of anxiety and depression that people with MDs frequently experience, even through fostering parents' and childrens' engagement coping over disengagement coping.

Recurrent hypotension induced by sacubitril/valsartan in cardiomyopathy secondary to Duchenne muscular dystrophy: A case report

BACKGROUND

Duchenne muscular dystrophy (DMD), which is caused by a mutation/deletion in the dystrophin gene on the X-chromosome, is the most common type of neuromuscular disorder in pediatrics. Skeletal muscle weakness progressively develops in DMD patients and usually leads to respiratory failure in the early adolescent years. Cardiac muscle is frequently affected in DMD patients, which leads to a high burden of cardiomyopathy and heart failure. In the era of improved respiratory care, cardiac deaths are becoming the major cause of mortality in DMD patients.

CASE SUMMARY

We report the case of a 15-year-old boy who presented to the hospital due to recurrent orthopnea for 6 mo and palpitations for 4 mo. He was diagnosed with progressive muscular dystrophy at the age of 3 years and was confined to a wheelchair at 12 years. He was prescribed diuretics and digoxin at the outpatient clinic; however, his symptoms did not resolve. Sacubitril/valsartan was added 1 mo prior to presentation, but he experienced recurrent episodes of palpitations. The electrocardiogram showed atrial tachycardia with a heart rate of 201 bpm, and he was then hospitalized. Hypotension was found following the administration of sacubitril/valsartan tablets; he could not tolerate even a small dose, always developing tachyarrhythmia. His symptoms were relieved after discontinuing sacubitril/valsartan, and his heart rate was controlled by a small dose of metoprolol tartrate and digoxin. Atrial tachycardia spontaneously converted in this patient, and his symptoms attenuated in the following 6 mo, without palpitation episodes.

CONCLUSION

Blood pressure should be closely monitored in DMD patients with advanced heart failure when taking sacubitril/valsartan.

Autophagy in the heart is enhanced and independent of disease progression in mus musculus dystrophinopathy models

Background

Duchenne muscular dystrophy is a muscle wasting disease caused by dystrophin gene mutations resulting in dysfunctional dystrophin protein. Autophagy, a proteolytic process, is impaired in dystrophic skeletal muscle though little is known about the effect of dystrophin deficiency on autophagy in cardiac muscle. We hypothesized that with disease progression autophagy would become increasingly dysfunctional based upon indirect autophagic markers.

Methods

Markers of autophagy were measured by western blot in 7-week-old and 17-month-old control (C57) and dystrophic (mdx) hearts.

Results

Counter to our hypothesis, markers of autophagy were similar between groups. Given these surprising results, two independent experiments were conducted using 14-month-old mdx mice or 10-month-old mdx/Utrn^± mice, a more severe model of Duchenne muscular dystrophy. Data from these animals suggest increased autophagosome degradation.

Conclusion

Together these data suggest that autophagy is not impaired in the dystrophic myocardium as it is in dystrophic skeletal muscle and that disease progression and related injury is independent of autophagic dysfunction.

Preliminary Evidences of Safety and Efficacy of Flavonoids- and Omega 3-Based Compound for Muscular Dystrophies Treatment: A Randomized Double-Blind Placebo Controlled Pilot Clinical Trial

Background: Nutritional compounds can exert both anti-inflammatory and anti-oxidant effects. Since these events exacerbate the pathophysiology of muscular dystrophies, we investigated nutraceutical supplementation as an adjuvant therapy in dystrophic patients, to low costs and easy route of administration. Moreover, this treatment could represent an alternative therapeutic strategy for dystrophic patients who do not respond to corticosteroid treatment.

Objective: A 24 weeks randomized double-blind placebo-controlled clinical study was aimed at evaluating the safety and efficacy of daily oral administration of flavonoids- and omega3-based natural supplement (FLAVOMEGA) in patients affected by muscular dystrophy with recognized muscle inflammation.

Design: We screened 60 patients diagnosed for Duchenne (DMD), Facioscapulohumeral (FSHD), and Limb Girdle Muscular Dystrophy (LGMD). Using a computer-generated random allocation sequence, we stratified patients in a 2:1:1 ratio (DMD:FSHD:LGMD) to one of two treatment groups: continuous FLAVOMEGA, continuous placebo. Of 29 patients included, only 24 completed the study: 15 were given FLAVOMEGA, 14 placebo.

Results: FLAVOMEGA was well tolerated with no reported adverse events. Significant treatment differences in the change from baseline in 6 min walk distance (6MWD; secondary efficacy endpoint) (P = 0.033) and in isokinetic knee extension (P = 0.039) (primary efficacy endpoint) were observed in LGMD and FSHD subjects. Serum CK levels (secondary efficacy endpoint) decreased in all FLAVOMEGA treated groups with significant difference in DMD subjects (P = 0.039).

Conclusions: Although the small number of patients and the wide range of disease severity among patients reduced statistical significance, we obtained an optimal profile of safety and tolerability for the compound, showing valuable data of efficacy in primary and secondary endpoints.

Trial registration number: NCT03317171

Retrospectively registered 25/10/2017

Peptide-conjugate antisense based splice-correction for Duchenne muscular dystrophy and other neuromuscular diseases

Duchenne muscular dystrophy (DMD) is an X-linked disorder characterized by progressive muscle degeneration, caused by the absence of dystrophin. Exon skipping by antisense oligonucleotides (ASOs) has recently gained recognition as therapeutic approach in DMD. Conjugation of a peptide to the phosphorodiamidate morpholino backbone (PMO) of ASOs generated the peptide-conjugated PMOs (PPMOs) that exhibit a dramatically improved pharmacokinetic profile. When tested in animal models, PPMOs demonstrate effective exon skipping in target muscles and prolonged duration of dystrophin restoration after a treatment regime. Herein we summarize the main pathophysiological features of DMD and the emergence of PPMOs as promising exon skipping agents aiming to rescue defective gene expression in DMD and other neuromuscular diseases. The listed PPMO laboratory findings correspond to latest trends in the field and highlight the obstacles that must be overcome prior to translating the animal-based research into clinical trials tailored to the needs of patients suffering from neuromuscular diseases.

Targeting angiogenesis in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) represents one of the most devastating types of muscular dystrophies which affect boys already at early childhood. Despite the fact that the primary cause of the disease, namely the lack of functional dystrophin is known already for more than 30 years, DMD still remains an incurable disease. Thus, an enormous effort has been made during recent years to reveal novel mechanisms that could provide therapeutic targets for DMD, especially because glucocorticoids treatment acts mostly symptomatic and exerts many side effects, whereas the effectiveness of genetic approaches aiming at the restoration of functional dystrophin is under the constant debate. Taking into account that dystrophin expression is not restricted to muscle cells, but is present also in, e.g., endothelial cells, alterations in angiogenesis process have been proposed to have a significant impact on DMD progression. Indeed, already before the discovery of dystrophin, several abnormalities in blood vessels structure and function have been revealed, suggesting that targeting angiogenesis could be beneficial in DMD. In this review, we will summarize current knowledge about the angiogenesis status both in animal models of DMD as well as in DMD patients, focusing on different organs as well as age- and sex-dependent effects. Moreover, we will critically discuss some approaches such as modulation of vascular endothelial growth factor or nitric oxide related pathways, to enhance angiogenesis and attenuate the dystrophic phenotype. Additionally, we will suggest the potential role of other mediators, such as heme oxygenase-1 or statins in those processes.

Evaluation of Left-Sided Heart Chambers With Novel Echocardiographic Techniques in Men With Duchenne or Becker Muscular Dystrophy

Left ventricular systolic dysfunction (LVSD) is a common finding in patients with Duchenne (DMD) and Becker (BMD) muscular dystrophies. Novel echocardiographic techniques have been used for the detection of LVSD in several heart diseases. We aim to compare cardiac anatomic and functional data studied by three-dimensional (3DE) and two-dimensional (2DE) echocardiography and to analyze the myocardial strain for the detection of early LVSD in DMD and BMD patients. We performed a cross-sectional study of 46 DMD and 14 BMD patients. We measured left atrium volume and left ventricle volumes and ejection fraction using 3DE and 2DE techniques. Myocardial strain analysis was derived from global longitudinal strain (GLS) measurements. GLS was measured by 2DE with the speckle tracking technique. The correlation between 3DE and 2DE for the measurement of left atrium volume as well as left ventricle diastolic and systolic volumes was strong. 2DE presented larger left atrium and left ventricle volumes. Left ventricle ejection fraction was similar between the two techniques. Myocardial strain analysis was able to detect early LVSD in 50.0% of DMD patients and in 9.1% of BMD patients. In conclusion, two-dimensional echocardiography appears to be a good alternative for the anatomical and functional evaluation of the left heart chambers in DMD and BMD patients. Myocardial strain analysis detects early LVSD in a sizable portion of patients with dystrophinopathies.

Are there real benefits to implanting cardiac devices in patients with end-stage dilated dystrophinopathic cardiomyopathy? Review of literature and personal results

Cardiomyopathy associated with dystrophinopathies - Duchenne muscular Dystrophy (DMD), Becker muscular dystrophy (BMD), X-linked dilated cardiomyopathy (XL-CM) and cardiomyopathy of Duchenne/Becker (DMD/BMD carriers - is an almost constant manifestation of these neuromuscular disorders and contribute significantly to their morbidity and mortality. Dystrophinopathic cardiomyopathy is the result of the dystrophin protein deficiency at the myocardium level, parallel to that occurring at the skeletal muscle level. Typically, cardiomyopathy begins as a "presymptomatic" stage in the first decade of life and evolves in a stepwise manner toward an end-stage dilated cardiomyopathy. Nearly complete replacement of the myocardium by fibrous and fatty connective tissue results in an irreversible cardiac failure, characterized by a further reduction of ejection fraction (EF < 30%) and frequent episodes of acute heart failure (HF). The picture of a severe dilated cardiomyopathy with intractable heart failure is typical of dystrophinopathies. Despite an appropriate pharmacological treatment, this condition is irreversible because of the extensive loss of myocites. Heart transplantation is the only curative therapy for patients with end-stage heart failure, who remain symptomatic despite an optimal medical therapy. However there is a reluctance to perform heart transplantation (HT) in these patients due to the scarcity of donors and the concerns that the accompanying myopathy will limit the benefits obtained through this therapeutic option. Therefore the only possibility to ameliorate clinical symptoms, prevent fatal arrhythmias and cardiac death in dystrophinopathic patients could be the implantation of intracardiac device (ICD) or resynchronizing devices with defibrillator (CRT-D). This overview reports the personal series of patients affected by DMD and BMD and DMD carriers who received ICD or CRT-D system, describe the clinical outcomes so far published and discuss pro and cons in the use of such devices.

Accuracy of B-natriuretic peptide for the diagnosis of decompensated heart failure in muscular dystrophies patients with chronic respiratory failure

Heart failure and restrictive respiratory insufficiency are complications in muscular dystrophies. We aimed to assess the accuracy of the B-natriuretic peptide (BNP) for the diagnosis of decompensated heart failure in muscular dystrophy. We included patients with muscular dystrophy and chronic respiratory insufficiency admitted in the Intensive Care Unit of the Raymond Poincare hospital (Garches, France) for suspected decompensated heart failure. Thirtyseven patients were included, among them, 23 Duchenne muscular dystrophy (DMD) (62%), 10 myotonic dystrophy type 1(DM1) (27%). Median age was 35 years [27.5; 48.5]. 86.5% of patients were on home mechanical ventilation (HMV). Median left ventricular ejection fraction (LVEF) was 47% [35.0; 59.5]. Median BNP blood level was 104 pg/mL [50; 399]. The BNP level was significantly inversely associated with LVEF (r= –0.37, p 0.03) and positively associated with the LVEDD (left ventricular end diastolic diameter) (r=0.59, P<0.001). The discriminative value of the BNP level for the diagnosis of decompensated heart failure was high with an AUROC=0.94 (P<0.001). The best discriminating BNP threshold was 307 pg/mL (Youden index 0.85).

The BNP level measurement may add a supplemental key for the final diagnosis of decompensated heart failure.

Clinical management of Duchenne muscular dystrophy: the state of the art

INTRODUCTION

Duchenne muscular dystrophy (DMD) is a devastating, progressive neuromuscular disorder for which there is no cure. As the dystrophin gene is located on the X chromosome, DMD occurs predominately in males. DMD is caused by a lack of functional dystrophin protein resulting from mutations in the 2.2-Mb DMD gene, whichdisrupts the reading frame. Care considerations for DMD advocate a coordinated, multidisciplinary approach to the management of DMD in order to optimize management of the primary manifestations of DMD as well as any secondary complications that may arise.

METHODS

This review provides an overview of the multidisciplinary clinical management of DMD with regard to the respiratory, cardiology, orthopedic, and nutritional needs of patients with DMD. Recent advances in novel disease-modifying treatments for DMD are also discussed with specific reference to exon skipping and suppression of premature stop codons as promising genetic therapies.

RESULTS

The combination of multidisciplinary clinical management alongside novel gene therapiesoffers physicians a powerful armamentarium for the treatment of DMD.

Natural history of cardiac function in Duchenne and Becker muscular dystrophies on home mechanical ventilation

Heart impairment is classical in dystrophinopathies and its management relies on medical drugs. Mechanical ventilation is used to treat respiratory failure, but can affect cardiac function. We aimed to investigate the natural history of cardiac function in patients with Duchenne (DMD) and Becker (BMD) muscular dystrophies on home mechanical ventilation (HMV).We reviewed the chart of DMD and BMD patients, followed in our institution, to obtain ventilation setting at HMV initiation and echocardiographic data at baseline and end follow up, as well as onset cardiac events and thoracic mechanical complication. We analyzed cumulative incidence of cardiac events as well as echocardiographic parameters evolution and its association with ventilation settings.We included 111 patients (101 DMD and 10 BMD). Median age was 21 years [18-26], median pulmonary vital capacity (VC) 15% of predicted [10-24]. All patients were on HMV and 46% ventilated using tracheostomy. After a median follow up of 6.3 years, we found a slight decrease of the left ventricular ejection fraction (LVEF) (45% at end follow up vs 50% at baseline P = .019) and a stabilization of the LV end diastolic diameter indexed (LVEDD indexed 29.4 mm/m vs 30.7 mm/m at end follow up, P = .17). Tidal volume (VT) level was inversely associated with the annual rate of the LVEF decline (r = -0.29, P = .025). Left atrium (LA) diameter decreased with mechanical ventilation (24 mm vs 20 mm, P = .039) and we found a reduction of systolic pulmonary pressure (35 mm Hg vs 25 mm Hg, P = .011). The cumulative incidence of cardiac events was 12.6%. Pneumothorax occurred in 4% of patients. Hypoxic arrest secondary to the presence of tracheal plugin occurred in 4% of patients with invasive ventilation.HMV is not harmful, decreases pulmonary pressure and may protect heart in dystrophinopathies, in addition with cardioprotective drugs. In patients with DMD and BMD on HMV, cumulative incidence of cardiac events remains moderate and incidence of pneumothorax is rare.

Predictors of early left ventricular systolic dysfunction in duchenne muscular dystrophy patients

INTRODUCTION

Early detection of left ventricular systolic dysfunction (LVSD) is important for therapeutic strategies for Duchenne muscular dystrophy (DMD) patients. We analyzed myocardial strain using echocardiography for early detection of LVSD and determined the predictors of early LVSD.

METHODS

This investigation was a cross-sectional study of 40 DMD patients with normal left ventricular ejection fraction. Global longitudinal strain (GLS) was used to analyze subtle disturbances in longitudinal contraction of the myocardium. Patients were determined to have early LVSD (GLS > -18) or normal left ventricular systolic function (GLS ≤ -18).

RESULTS

Patients who had early LVSD were older and had a higher frequency of corticosteroid therapy and of mutations in exons 45, 46, 47, 48, 49, 50, and 52.

DISCUSSION

Myocardial strain measurements are useful for the early diagnosis of LVSD in DMD patients. Older age, use of corticosteroids, and mutations within the "hot-spot" region of the DMD gene are associated with early LVSD. Muscle Nerve, 2018.

Photobiomodulation therapy protects skeletal muscle and improves muscular function of mdx mice in a dose-dependent manner through modulation of dystrophin

This study aimed to analyze the protective effects of photobiomodulation therapy (PBMT) with combination of low-level laser therapy (LLLT) and light emitting diode therapy (LEDT) on skeletal muscle tissue to delay dystrophy progression in mdx mice (DMD ^mdx ). To this aim, mice were randomly divided into five different experimental groups: wild type (WT), placebo-control (DMD ^mdx ), PBMT with doses of 1 J (DMD ^mdx ), 3 J (DMD ^mdx ), and 10 J (DMD ^mdx ). PBMT was performed employing a cluster probe with 9 diodes (1 x 905nm super-pulsed laser diode; 4 x 875nm infrared LEDs; and 4 x 640nm red LEDs, manufactured by Multi Radiance Medical®, Solon - OH, USA), 3 times a week for 14 weeks. PBMT was applied on a single point (tibialis anterior muscle-bilaterally). We analyzed functional performance, muscle morphology, and gene and protein expression of dystrophin. PBMT with a 10 J dose significantly improved (p < 0.001) functional performance compared to all other experimental groups. Muscle morphology was improved by all PBMT doses, with better outcomes with the 3 and 10 J doses. Gene expression of dystrophin was significantly increased with 3 J (p < 0.01) and 10 J (p < 0.01) doses when compared to placebo-control group. Regarding protein expression of dystrophin, 3 J (p < 0.001) and 10 J (p < 0.05) doses also significantly showed increase compared to placebo-control group. We conclude that PBMT can mainly preserve muscle morphology and improve muscular function of mdx mice through modulation of gene and protein expression of dystrophin. Furthermore, since PBMT is a non-pharmacological treatment which does not present side effects and is easy to handle, it can be seen as a promising tool for treating Duchenne's muscular dystrophy.