Cardiac involvement in Becker muscular dystrophy

Is Cardiac Transplantation Still a Contraindication in Patients with Muscular Dystrophy-Related End-Stage Dilated Cardiomyopathy? A Systematic Review

Inherited muscular diseases (MDs) are genetic degenerative disorders typically caused by mutations in a single gene that affect striated muscle and result in progressive weakness and wasting in affected individuals. Cardiac muscle can also be involved with some variability that depends on the genetic basis of the MD (Muscular Dystrophy) phenotype. Heart involvement can manifest with two main clinical pictures: left ventricular systolic dysfunction with evolution towards dilated cardiomyopathy and refractory heart failure, or the presence of conduction system defects and serious life-threatening ventricular arrhythmias. The two pictures can coexist. In these cases, heart transplantation (HTx) is considered the most appropriate option in patients who are not responders to the optimized standard therapeutic protocols. However, cardiac transplant is still considered a relative contraindication in patients with inherited muscle disorders and end-stage cardiomyopathies. High operative risk related to muscle impairment and potential graft involvement secondary to the underlying myopathy have been the two main reasons implicated in the generalized reluctance to consider cardiac transplant as a viable option. We report an overview of cardiac involvement in MDs and its possible association with the underlying molecular defect, as well as a systematic review of HTx outcomes in patients with MD-related end-stage dilated cardiomyopathy, published so far in the literature.

Advances in Dystrophinopathy Diagnosis and Therapy

Dystrophinopathies are x-linked muscular disorders which emerge from mutations in the Dystrophin gene, including Duchenne and Becker muscular dystrophy, and dilated cardiomyopathy. However, Duchenne muscular dystrophy interconnects with bone loss and osteoporosis, which are exacerbated by glucocorticoids therapy. Procedures for diagnosing dystrophinopathies include creatine kinase assay, haplotype analysis, Southern blot analysis, immunological analysis, multiplex PCR, multiplex ligation-dependent probe amplification, Sanger DNA sequencing, and next generation DNA sequencing. Pharmacological therapy for dystrophinopathies comprises glucocorticoids (prednisone, prednisolone, and deflazacort), vamorolone, and ataluren. However, angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and β-blockers are the first-line to prevent dilated cardiomyopathy in dystrophinopathy patients. Duchenne muscular dystrophy gene therapy strategies involve gene transfer, exon skipping, exon reframing, and CRISPR gene editing. Eteplirsen, an antisense-oligonucleotide drug for skipping exon 51 from the Dystrophin gene, is available on the market, which may help up to 14% of Duchenne muscular dystrophy patients. There are various FDA-approved exon skipping drugs including ExonDys-51 for exon 51, VyonDys-53 and Viltolarsen for exon 53 and AmonDys-45 for exon 45 skipping. Other antisense oligonucleotide drugs in the pipeline include casimersen for exon 45, suvodirsen for exon 51, and golodirsen for exon 53 skipping. Advances in the diagnosis and therapy of dystrophinopathies offer new perspectives for their early discovery and care.

Prognosis of Right Ventricular Systolic Dysfunction in Patients With Duchenne Muscular Dystrophy

Background Chronic respiratory failure and heart involvement may occur in Duchenne muscular dystrophy. We aimed to assess the prognostic value of the right ventricular (RV) systolic dysfunction in patients with Duchenne muscular dystrophy. Methods and Results We studied 90 genetically proven patients with Duchenne muscular dystrophy from 2010 to 2019, to obtain respiratory function and Doppler echocardiographic RV systolic function. Prognostic value was assessed in terms of death and cardiac events. The median age was 27.5 years, and median forced vital capacity was at 10% of the predicted value: 83 patients (92%) were on home mechanical ventilation. An RV systolic dysfunction was found in 46 patients (51%). In patients without RV dysfunction at inclusion, a left ventricular systolic dysfunction at inclusion was associated with a higher risk of developing RV dysfunction during follow-up with an odds ratio of 4.5 (P=0.03). RV systolic dysfunction was significantly associated with cardiac events, mainly acute heart failure (62%) and cardiogenic shock (23%). In a multivariable Cox model, the adjusted hazard ratio was 4.96 (95% CI [1.09-22.6]; P=0.04). In terms of death, we found a significant difference between patients with RV dysfunction versus patients without RV dysfunction in the Kaplan-Meier curves (log-rank P=0.045). Conclusions RV systolic dysfunction is frequently present in patients with Duchenne muscular dystrophy and is associated with increased risk of cardiac events, irrespective of left ventricular dysfunction and mechanical ventilation. Registration URL: https://www.clinicaltrials.org; unique identifier: NCT02501083.

Cardiac magnetic resonance in patients with muscular dystrophies

Muscular dystrophies are inherited disorders sharing similar clinical features and dystrophic changes on muscle biopsy. Duchenne muscular dystrophy is the most common inherited muscle disease of childhood, and Becker muscular dystrophy is a milder allelic variant with a slightly lower prevalence. Myotonic dystrophy is the most frequent form in adults. Cardiac magnetic resonance is the gold standard technique for the quantification of cardiac chamber volumes and function, and also enables a characterisation of myocardial tissue. Most cardiac magnetic resonance studies in the setting of muscular dystrophy were carried out at single centres, evaluated small numbers of patients and used widely heterogeneous protocols. Even more importantly, those studies analysed more or less extensively the patterns of cardiac involvement, but usually did not try to establish the added value of cardiac magnetic resonance to standard echocardiography, the evolution of cardiac disease over time and the prognostic significance of cardiac magnetic resonance findings. As a result, the large and heterogeneous amount of information on cardiac involvement in muscular dystrophies cannot easily be translated into recommendations on the optimal use of cardiac magnetic resonance. In this review, whose targets are cardiologists and neurologists who manage patients with muscular dystrophy, we try to summarise cardiac magnetic resonance findings in patients with muscular dystrophy, and the results of studies evaluating the role of cardiac magnetic resonance as a tool for diagnosis, risk stratification and follow-up. Finally, we provide some practical recommendations about the need and timing of cardiac magnetic resonance examination for the management of patients with muscular dystrophy.

Prevalence and potential genetic determinants of young sudden unexplained death victims with suspected arrhythmogenic mitral valve prolapse syndrome

Background

Mitral valve prolapse (MVP) is largely considered a benign condition. However, MVP is over-represented consistently in sudden unexplained death in the young (SUDY) cohorts.

Objective

To determine the prevalence and potential genetic underpinnings of suspected arrhythmogenic MVP in a referral cohort of SUDY cases.

Methods

In this retrospective study, medical records/autopsy reports and whole exome molecular autopsy (WEMA) results for 77 SUDY victims (27 female; average age at death 20.6 ± 8.9 years) were reviewed for evidence of myxomatous MVP and left ventricle (LV) fibrosis. Variants detected in the prespecified 147 WEMA gene panel with a minor allele frequency ≤ 0.001 in public exomes/genomes were classified using the 2015 American College of Medical Genetics (ACMG) guidelines.

Results

Overall, 6 of 77 (7.8%; 2 female; average age at death 20.7 ± 6.9 years) SUDY cases had MVP as the lone abnormal postmortem finding. The majority had bileaflet involvement (5/6; 83%) and microscopic LV fibrosis (5/6; 83%). In 2 SUDY cases (33%), subjects were diagnosed with MVP by echocardiography prior to death. Unexpectedly, an ACMG pathogenic/likely pathogenic (P/LP) was more likely to be detected in SUDY cases with MVP than those without (3/6 [50%] vs 9/71 [13%]; P < .05). Interestingly, the 3 variants identified in MVP-positive SUDY cases localized to genes associated previously with a cardiomyopathy/channelopathy predisposition (p.E1518fsX25-DMD, p.S285N-RYR2, and p.R109X-TTN).

Conclusion

This WEMA series provides additional evidence that the combination of MVP and LV fibrosis underlies an unexpected number of SUDY cases. Whether P/LP variants in cardiomyopathy/channelopathy-susceptibility genes contribute to the pathogenesis of arrhythmogenic MVP requires further investigation.

Improved Cardiac Outcomes by Early Treatment with Angiotensin-Converting Enzyme Inhibitors in Becker Muscular Dystrophy

Background:

The latest practice guidelines from the American College of Cardiology/American Heart Association recommend the prescription of an ACE-i for patients presenting with non-ischemic cardiomyopathy when left ventricular ejection fraction (LVEF) falls below 40%.

Objective:

To determine if the initiation of treatment with an angiotensin-converting enzyme inhibitor (ACE-i) earlier than recommended by practice guidelines issued by professional societies improves the long-term cardiac outcomes of patients presenting with Becker muscular dystrophy (MD) cardiomyopathy.

Methods:

From a multicenter registry of Becker MD, we selected retrospectively patients presenting between January 1990 and April 2019 with a LVEF ≥40 and ≤49%. We used a propensity score analysis to compare the risk of a) hospitalization for management of heart failure (HF), and b) a decrease in LVEF to <35% in patients who received an ACE-i when LVEF fell below 40% (conventional treatment), versus below 50% (early treatment).

Results:

From the 183 patients entered in our registry, we identified 85 whose LVEF was between 40 and 49%, 51 of whom received early and 34 received conventional ACE-i treatment. Among patients with early versus conventional treatments, 2 (3.9%) versus 4 (11.8%) were hospitalized for management of HF [hazard ratio (HR) 0.151; 95% confidence interval (CI) 0.028 to 0.822; p = 0.029], and 9 (17.6%) versus 10 (29.4%) had a decrease in LVEF below 35% (HR 0.290; 95% CI 0.121 to 0.694; p = 0.005).

Conclusions:

The long-term cardiac outcome of patients presenting with Becker MD was significantly better when treatment with ACE-i was introduced after a decrease in LVEF below 50%, instead of below 40% as recommended in the current practice guidelines issued by professional societies.

Respiratory decline in adult patients with Becker muscular dystrophy: A longitudinal study

Becker muscular dystrophy (BMD) is a rare hereditary neuromuscular disease, caused by a genetic defect in the Duchenne Muscular Dystrophy (DMD) gene. We studied the natural history of respiratory function and its affecting factors in 23 adult BMD patients. These important data are needed for (future) clinical trials in BMD but are largely lacking. Patients had a median age of 51 years (28-78y) and median follow-up duration of 14 years (2-25y). We analysed 190 pulmonary function measurements with a median interval of one year (1-17y) and measured a 1.00% decline of Forced Vital Capacity percent predicted (FVC%pred) per year (p = 0.004). Loss of ambulation significantly increased the annual rate of FVC decline and was dependent of patient's body mass index (BMI; p = 0.015), with increases in BMI correlating with an even more rapid deterioration of FVC. A decline in Medical Research Council (MRC) sum score was significantly correlated with a decline in FVC (p = 0.003). We conclude that adult BMD patients experience a significant but mild respiratory decline. However, this decline is significantly more rapid and clinically relevant after loss of ambulation, which warrants a more vigilant follow-up of respiratory function in this subgroup.

Differential diagnosis of arrhythmogenic cardiomyopathy: phenocopies versus disease variants

Arrhythmogenic cardiomyopathy (ACM) is a genetic heart muscle disease caused by mutations of desmosomal genes in about 50% of patients. Affected patients may have defective non-desmosomal genes. The ACM phenotype may occur in other genetic cardiomyopathies, cardio-cutaneous syndromes or neuromuscular disorders. A sizeable proportion of patients have non-genetic diseases with clinical features resembling ACM (phenocopies). The identification of biventricular and left-dominant phenotypic variants has made differential diagnosis more difficult because of the broader spectrum of phenocopies which requires a detailed clinical study with appropriate evaluation of most prominent and discriminatory disease features. Conditions that enter into differential diagnosis of ACM include heart muscle diseases affecting the right ventricle, the left ventricle, or both. To confirm a conclusive diagnosis of ACM, these differential possibilities need to be reasonably excluded by an accurate and targeted clinical evaluation. This article reviews the clinical and imaging features of major phenocopies of ACM and provides indications for differential diagnosis. The recent etiologic classification of Arrhythmogenic Cardiomyopathies, whose common denominator is the distinctive phenotype characterized by a hypokinetic and non-dilated ventricle with a large amount of myocardial fibrosis underlying its propensity to generate ventricular arrhythmias is also addressed.

Progressive left ventricular dysfunction and myocardial fibrosis in Duchenne and Becker muscular dystrophy: a longitudinal cardiovascular magnetic resonance study

This study examined the progression of left ventricular dysfunction and myocardial fibrosis in patients with Duchenne muscular dystrophy (DMD) or Becker muscular dystrophy (BMD) to evaluate the effects of angiotensin-converting enzyme inhibitor (ACEI). Ninety-eight cardiovascular magnetic resonance (CMR) studies in 34 consecutive patients with DMD (n = 21) or BMD (n = 13) were retrospectively reviewed. Left ventricular ejection fraction (LVEF) and the extent of myocardial late gadolinium enhancement (LGE) were semiautomatically quantified. During the study period, five patients had already been treated with ACEI at the first CMR; five were started on ACEI at LVEF ≥ 55% and 10 at LVEF < 55%. All patients had hyperenhanced myocardium on LGE images at the first CMR (median extent, 3.3%; interquartile range 0.1-14.3%). A mixed-effects model for longitudinal data of each patient, adjusted for age, type of muscular dystrophy, steroid use, and ACEI use showed that higher age (β = - 1.1%/year; 95% confidence interval [CI], - 1.8% to - 0.4%; p = 0.005) and no use of ACEI (β = - 3.1%; 95% CI, - 5.4% to - 0.8%; p = 0.009) were significantly associated with a lower LVEF. When ACEI use was stratified by time of initiation (LVEF ≥ 55% vs. < 55%), only ACEI initiation at LVEF < 55% had a beneficial effect on LVEF at each imaging examination (β = 3.7%; 95% CI, 0.9-6.4%; p = 0.010). ACEI use or the time of initiation of ACEI did not significantly affect age-related increase in LGE. ACEI attenuated the age-related decline in LVEF only in patients with DMD or BMD and reduced LVEF, suggesting that further investigation on prophylactic use of cardioprotective therapy in these patients is warranted.

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.

Cardiac-Specific Expression of ΔH2-R15 Mini-Dystrophin Normalized All Electrocardiogram Abnormalities and the End-Diastolic Volume in a 23-Month-Old Mouse Model of Duchenne Dilated Cardiomyopathy

Heart disease is a major health threat for Duchenne/Becker muscular dystrophy patients and carriers. Expression of a 6-8 kb mini-dystrophin gene in the heart holds promise to change the disease course dramatically. However, the mini-dystrophin gene cannot be easily studied with adeno-associated virus (AAV) gene delivery because the size of the minigene exceeds AAV packaging capacity. Cardiac protection of the ΔH2-R19 minigene was previously studied using the cardiac-specific transgenic approach. Although this minigene fully normalized skeletal muscle force, it only partially corrected electrocardiogram and heart hemodynamics in dystrophin-null mdx mice that had moderate cardiomyopathy. This study evaluated the ΔH2-R15 minigene using the same transgenic approach in mdx mice that had more severe cardiomyopathy. In contrast to the ΔH2-R19 minigene, the ΔH2-R15 minigene carries dystrophin spectrin-like repeats 16 to 19 (R16-19), a region that has been suggested to protect the heart in clinical studies. Cardiac expression of the ΔH2-R15 minigene normalized all aberrant electrocardiogram changes and improved hemodynamics. Importantly, it corrected the end-diastolic volume, an important diastolic parameter not rescued by ΔH2-R19 mini-dystrophin. It is concluded that that ΔH2-R15 mini-dystrophin is a superior candidate gene for heart protection. This finding has important implications in the design of the mini/micro-dystrophin gene for Duchenne cardiomyopathy therapy.

Clinical Manifestations and Overall Management Strategies for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder that causes progressive weakness and wasting of skeletal muscular and myocardium in boys due to mutation of dystrophin. The structural integrity of each individual skeletal and cardiac myocyte is significantly compromised upon physical stress due to the absence of dystrophin. The progressive destruction of systemic musculature and myocardium causes affected patients to develop multiple organ disabilities, including loss of ambulation, physical immobility, neuromuscular scoliosis, joint contracture, restrictive lung disease, obstructive sleep apnea, and cardiomyopathy. There are some central nervous system-related medical problems, as dystrophin is also expressed in the neuronal tissues. Although principal management is to mainly delay the pathological process, an enhanced understanding of underlying pathological processes has significantly improved quality of life and longevity for DMD patients. Future research in novel molecular approach is warranted to answer unanswered questions.

Neuromuscular Disorders and the Role of the Clinical Electrophysiologist

Cardiac involvement is common and may be the presenting or predominant manifestation in a variety of neuromuscular disorders, most notably the inherited muscle disorders, or muscular dystrophies. Cardiac manifestations of the neuromuscular disorders result from pathological involvement of the myocardium and the cardiac conduction system, with resulting cardiomyopathy or rhythm disturbances including supraventricular arrhythmias, life-threatening ventricular arrhythmias, and sudden cardiac death. Many of these neuromuscular disorders are rare and may be unrecognized by even experienced specialists in internal and cardiovascular medicine. Furthermore, the initial cardiac manifestations in these patients are often asymptomatic. The goal of this investigation is to review the scope of cardiac conduction defects and rhythm disturbances in these disorders and to propose some practical recommendations for arrhythmia monitoring and management of these patients.

Dystrophic Cardiomyopathy: Complex Pathobiological Processes to Generate Clinical Phenotype

Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and X-linked dilated cardiomyopathy (XL-DCM) consist of a unique clinical entity, the dystrophinopathies, which are due to variable mutations in the dystrophin gene. Dilated cardiomyopathy (DCM) is a common complication of dystrophinopathies, but the onset, progression, and severity of heart disease differ among these subgroups. Extensive molecular genetic studies have been conducted to assess genotype-phenotype correlation in DMD, BMD, and XL-DCM to understand the underlying mechanisms of these diseases, but the results are not always conclusive, suggesting the involvement of complex multi-layers of pathological processes that generate the final clinical phenotype. Dystrophin protein is a part of dystrophin-glycoprotein complex (DGC) that is localized in skeletal muscles, myocardium, smooth muscles, and neuronal tissues. Diversity of cardiac phenotype in dystrophinopathies suggests multiple layers of pathogenetic mechanisms in forming dystrophic cardiomyopathy. In this review article, we review the complex molecular interactions involving the pathogenesis of dystrophic cardiomyopathy, including primary gene mutations and loss of structural integrity, secondary cellular responses, and certain epigenetic and other factors that modulate gene expressions. Involvement of epigenetic gene regulation appears to lead to specific cardiac phenotypes in dystrophic hearts.

Cardiomyopathy in becker muscular dystrophy: Overview

Becker muscular dystrophy (BMD) is an X-linked recessive disorder involving mutations of the dystrophin gene. Cardiac involvement in BMD has been described and cardiomyopathy represents the number one cause of death in these patients. In this paper, the pathophysiology, clinical evaluations and management of cardiomyopathy in patients with BMD will be discussed.

X-Linked Dilated Cardiomyopathy: A Cardiospecific Phenotype of Dystrophinopathy

X-linked dilated cardiomyopathy (XLDCM) is a distinct phenotype of dystrophinopathy characterized by preferential cardiac involvement without any overt skeletal myopathy. XLDCM is caused by mutations of the Duchenne muscular dystrophy (DMD) gene and results in lethal heart failure in individuals between 10 and 20 years. Patients with Becker muscular dystrophy, an allelic disorder, have a milder phenotype of skeletal muscle involvement compared to Duchenne muscular dystrophy (DMD) and sometimes present with dilated cardiomyopathy. The precise relationship between mutations in the DMD gene and cardiomyopathy remain unclear. However, some hypothetical mechanisms are being considered to be associated with the presence of some several dystrophin isoforms, certain reported mutations, and an unknown dystrophin-related pathophysiological mechanism. Recent therapy for Duchenne muscular dystrophy, the severe dystrophinopathy phenotype, appears promising, but the presence of XLDCM highlights the importance of focusing on cardiomyopathy while elucidating the pathomechanism and developing treatment.

Early-progressive dilated cardiomyopathy in a family with Becker muscular dystrophy related to a novel frameshift mutation in the dystrophin gene exon 27

We report a family in which two male siblings with Becker muscular dystrophy (BMD) developed severe dilated cardiomyopathy (DCM) and progressive heart failure (HF) at age 11; one died at age 14 years while awaiting heart transplant and the other underwent left ventricular assist device (LVAD) implantation at the same age. Genetic analysis of one sibling showed a novel frameshift mutation in exon 27 of Duchenne muscular dystrophy (DMD) gene (c.3779_3785delCTTTGGAins GG), in which 7 base pairs are deleted and two are inserted. While this predicts an amino acid substitution and premature termination (p.Thr1260Argfs*8), muscle biopsy dystrophin immunostaining instead indicates that the mutation is more likely to alter splicing. Despite relatively preserved skeletal muscular performance, both siblings developed progressive heart failure secondary to early onset DCM. In addition, their 7 year old nephew with delayed gross motor development, mild proximal muscle weakness, and markedly elevated serum creatine kinase (CK) level (> 13,000 IU/L) at 16 months was recently demonstrated to have the familial DMD mutation. Here we report a novel genotype of BMD with early onset DCM and progressive lethal heart failure during early adolescence.

Ultrasound tissue characterization does not differentiate genotype, but indexes ejection fraction deterioration in becker muscular dystrophy

The aims of the study were, first, to assess whether myocardial ultrasound tissue characterization (UTC) in Becker muscular dystrophy (BMD) can be used to differentiate between patients with deletions and those without deletions; and second, to determine whether UTC is helpful in diagnosing the evolution of left ventricular dysfunction, a precursor of dilated cardiomyopathy. Both cyclic variation of integrated backscatter and calibrated integrated backscatter (cIBS) were assessed in 87 patients with BMD and 70 controls. The average follow-up in BMD patients was 48 ± 12 mo. UTC analysis was repeated only in a subgroup of 40 BMD patients randomly selected from the larger overall group (15 with and 25 without left ventricular dysfunction). Discrimination between BMD patients with and without dystrophin gene deletion was not possible on the basis of UTC data: average cvIBS was 5.2 ± 1.2 and 5.5 ± 1.4 dB, and average cIBS was 29.9 ± 4.7 and 29.6 ± 5.8, respectively, significantly different (p < 0.001) only from controls (8.6 ± 0.5 and 24.6 ± 1.2 dB). In patients developing left ventricular dysfunction during follow-up, cIBS increased to 31.3 ± 5.4 dB, but not significantly (p = 0.08). The highest cIBS values (34.6 ± 5.3 dB, p < 0.09 vs. baseline, p < 0.01 vs BMD patients without left ventricular dysfunction) were seen in the presence of severe left ventricular dysfunction. Multivariate statistics indicated that an absolute change of 6 dB in cIBS is associated with a high probability of left ventricular dysfunction. UTC analysis does not differentiate BMD patients with or without dystrophin gene deletion, but may be useful in indexing left ventricular dysfunction during follow-up.

Left ventricular systolic function and the pattern of late-gadolinium-enhancement independently and additively predict adverse cardiac events in muscular dystrophy patients

BACKGROUND

Cardiac involvement is a frequent finding in patients with Duchenne (DMD) and Becker (BMD) muscular dystrophies. With this study, we aimed at elucidating the relationship between the phenotypic expression of cardiac involvement and the occurrence of adverse cardiac events in DMD/BMD patients.

METHODS

Eighty-eight male DMD/BMD patients (age 29 ± 14 yrs) were prospectively enrolled. All patients underwent cardiovascular magnetic resonance (CMR) comprising cine- and late-gadolinium-enhancement (LGE)-CMR at study entry and were subsequently followed-up for adverse cardiac events. The primary endpoint was defined as all-cause/cardiac death or cardiac transplantation. Secondary endpoints were (1) hospitalization for heart failure and/or (2) occurrence of non-/sustained ventricular tachycardia (VT).

RESULTS

During a mean follow-up time of 47 ± 18 months, the primary endpoint was observed in three (3%) and the secondary endpoint in 21 (24%) patients. On multivariable analysis, LV-EF (HR, 95% CI: 0.94, 0.89-0.97, p = 0.001) and the presence of "transmural" LGE (HR, 95% CI: 2.89, 1.09-7.68, p = 0.033) were the only independent predictors for secondary endpoints. A cut-off for LV-EF of 45% was associated with the highest hazard ratio (HR, 95% CI: 11.50, 4.49-29.43, p < 0.0001) in a Cox regression survival analysis. In the group of patients with a LV-EF (>45%), those patients already showing "transmural" LGE had a significantly lower event-free-survival (HR, 95% CI: 13.48, 1.89-96.12, p = 0.009) compared to those without.

CONCLUSIONS

An impaired LV systolic function (LV-EF ≤45%) and a "transmural" pattern of myocardial fibrosis independently predict the occurrence of adverse cardiac events in DMD/BMD patients. Even in DMD/BMD patients with relatively preserved LV-EF (>45%), the simple and visually assessable parameter "transmural LGE" is of additive prognostic value.

Development of multiexon skipping antisense oligonucleotide therapy for Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an incurable, X-linked progressive muscle degenerative disorder that results from the absence of dystrophin protein and leads to premature death in affected individuals due to respiratory and/or cardiac failure typically by age of 30. Very recently the exciting prospect of an effective oligonucleotide therapy has emerged which restores dystrophin protein expression to affected tissues in DMD patients with highly promising data from a series of clinical trials. This therapeutic approach is highly mutation specific and thus is personalised. Therefore DMD has emerged as a model genetic disorder for understanding and overcoming of the challenges of developing personalised genetic medicines. One of the greatest weaknesses of the current oligonucleotide approach is that it is a mutation-specific therapy. To address this limitation, we have recently demonstrated that exons 45–55 skipping therapy has the potential to treat clusters of mutations that cause DMD, which could significantly reduce the number of compounds that would need to be developed in order to successfully treat all DMD patients. Here we discuss and review the latest preclinical work in this area as well as a variety of accompanying issues, including efficacy and potential toxicity of antisense oligonucleotides, prior to human clinical trials.

Beta-blockers, left and right ventricular function, and in-vivo calcium influx in muscular dystrophy cardiomyopathy

Beta-blockers are used to treat acquired heart failure in adults, though their role in early muscular dystrophy cardiomyopathy is unclear. We treated 2 different dystrophic mouse models which have an associated cardiomyopathy (mdx: model for Duchenne Muscular Dystrophy, and Sgcd-/-: model for limb girdle muscular dystrophy type 2F) and wild type controls (C57 Bl10) with the beta blocker metoprolol or placebo for 8 weeks at an early stage in the development of the cardiomyopathy. Left and right ventricular function was assessed with cardiac magnetic resonance imaging (MRI) and in-vivo myocardial calcium influx with manganese enhanced MRI. In the mdx mice at baseline there was reduced stroke volume, cardiac index, and end-diastolic volume with preserved left ventricular ejection fraction. These abnormalities were no longer evident after treatment with beta-blockers. Right ventricular ejection fraction was reduced and right ventricular end-systolic volume increased in the mdx mice. With metoprolol there was an increase in right ventricular end-diastolic and end-systolic volumes. Left and right ventricular function was normal in the Sgcd-/- mice. Metroprolol had no significant effects on left and right ventricular function in these mice, though heart/body weight ratios increased after treatment. In-vivo myocardial calcium influx with MEMRI was significantly elevated in both models, though metoprolol had no significant effects on either. In conclusion, metoprolol treatment at an early stage in the development of cardiomyopathy has deleterious effects on right ventricular function in mdx mice and in both models no effect on increased in-vivo calcium influx. This suggests that clinical trials need to carefully monitor not just left ventricular function but also right ventricular function and other aspects of myocardial metabolism.

A case of Becker muscular dystrophy with early manifestation of cardiomyopathy

An 18-year-old boy was admitted with chest discomfort, nausea, and dyspnea at rest. At the age of 3 years, he underwent muscle biopsy and dystrophin gene analysis owing to an enlarged calf muscle and elevated serum kinase level (6,378 U/L) without overt weakness; based on the results, Becker muscular dystrophy (BMD) was diagnosed. The dystrophin gene showed deletion of exons 45 to 49. He remained ambulant and could step upstairs without significant difficulties. A chest roentgenogram showed cardiomegaly (cardiothoracic ratio, 54%), and his electrocardiogram (ECG) showed abnormal ST-T wave, biatrial enlargement, and left ventricular hypertrophy. The 2-dimensional and M-mode ECGs showed a severely dilated left ventricular cavity with diffuse hypokinesis. The systolic indices were reduced, including fractional shortening (9%) and ejection fraction (19%). Despite receiving intensive medical treatment, he died from congestive heart failure 5 months after the initial cardiac symptoms. We report a case of BMD with early-onset dilated cardiomyopathy associated with deletion of exons 45 to 49. Early cardiomyopathy can occur in BMD patients with certain genotypes; therefore, careful follow-up is required even in patients with mild phenotypes of BMD.

Occult left ventricular dysfunction diagnosed by myocardial performance index in patients with limb girdle muscle dystrophy: A case control study

The myocardial performance index (MPI) was assessed in 30 patients with limb girdle muscle dystrophy (LGMD) with a normal left ventricular ejection fraction (greater than 50%), as well as in 30 age- and sex-matched healthy adults with a left ventricular ejection fraction greater than 50%. MPIs derived by pulsed-wave Doppler and tissue Doppler were also compared. The MPI was 0.37±0.09 in the LGMD patients and 0.29±0.09 in the control group (P=0.003). These data show that patients with LGMD have occult cardiac dysfunction as evidenced by a higher MPI than the controls. There was good agreement between the MPIs measured by pulsed-wave Doppler and tissue Doppler methods in these patients.

Dystrophin quantification and clinical correlations in Becker muscular dystrophy: implications for clinical trials

Duchenne muscular dystrophy is caused by mutations in the DMD gene that disrupt the open reading frame and prevent the full translation of its protein product, dystrophin. Restoration of the open reading frame and dystrophin production can be achieved by exon skipping using antisense oligonucleotides targeted to splicing elements. This approach aims to transform the Duchenne muscular dystrophy phenotype to that of the milder disorder, Becker muscular dystrophy, typically caused by in-frame dystrophin deletions that allow the production of an internally deleted but partially functional dystrophin. There is ongoing debate regarding the functional properties of the different internally deleted dystrophins produced by exon skipping for different mutations; more insight would be valuable to improve and better predict the outcome of exon skipping clinical trials. To this end, we have characterized the clinical phenotype of 17 patients with Becker muscular dystrophy harbouring in-frame deletions relevant to on-going or planned exon skipping clinical trials for Duchenne muscular dystrophy and correlated it to the levels of dystrophin, and dystrophin-associated protein expression. The cohort of 17 patients, selected exclusively on the basis of their genotype, included 4 asymptomatic, 12 mild and 1 severe patient. All patients had dystrophin levels of >40% of control and significantly higher dystrophin (P = 0.013), β-dystroglycan (P = 0.025) and neuronal nitric oxide synthase (P = 0.034) expression was observed in asymptomatic individuals versus symptomatic patients with Becker muscular dystrophy. Furthermore, grouping the patients by deletion, patients with Becker muscular dystrophy with deletions with an end-point of exon 51 (the skipping of which could rescue the largest group of Duchenne muscular dystrophy deletions) showed significantly higher dystrophin levels (P = 0.034) than those with deletions ending with exon 53. This is the first quantitative study on both dystrophin and dystrophin-associated protein expression in patients with Becker muscular dystrophy with deletions relevant for on-going exon skipping trials in Duchenne muscular dystrophy. Taken together, our results indicate that all varieties of internally deleted dystrophin assessed in this study have the functional capability to provide a substantial clinical benefit to patients with Duchenne muscular dystrophy.

AAV-microdystrophin therapy improves cardiac performance in aged female mdx mice

Dystrophin deficiency leads to lethal dilated Duchenne cardiomyopathy. A promising therapy is to deliver a highly abbreviated microdystrophin gene to the heart using adeno-associated virus (AAV). Microdystrophin has been shown to mitigate dystrophin-deficient skeletal muscle disease. However, it is not clear whether microdystrophin is equally effective in treating Duchenne cardiomyopathy. To evaluate microdystrophin therapy in the heart, we injected 5 × 10(12) viral genome particles/mouse of AAV-9 ΔR4-23/ΔC microdystrophin vector via tail vein to ~16-20-month-old (average 18.7-month-old) female mdx mice, a manifesting model of Duchenne cardiomyopathy. Cardiac transduction and heart function were examined at 2-8 months after gene transfer. We observed robust myocardial microdystrophin expression. Electrocardiography (ECG) and left ventricular catheter hemodynamic assays also revealed significant improvement. Furthermore, AAV-microdystrophin therapy prevented dobutamine-stress induced acute cardiac death. We demonstrate for the first time that AAV microdystrophin therapy significantly ameliorates functional deficiency in a phenotypic model of Duchenne cardiomyopathy. Our results support further exploration of microdystrophin therapy to treat Duchenne cardiomyopathy.

Long-term improvement in mdx cardiomyopathy after therapy with peptide-conjugated morpholino oligomers

AIMS

The cardiomyopathy found in Duchenne muscular dystrophy (DMD) is responsible for death due to heart failure in approximately 30% of patients and additionally contributes to many DMD morbidities. Strategies to bypass DMD-causing mutations to allow an increase in body-wide dystrophin have proved promising, but increasing cardiac dystrophin continues to be challenging. The purpose of this study was to determine if therapeutic restoration of cardiac dystrophin improved the significant cardiac hypertrophy and diastolic dysfunction identified in X-linked muscular dystrophy (mdx) dystrophin-null mouse due to a truncation mutation over time after treatment.

METHODS AND RESULTS

Mice lacking dystrophin due to a truncation mutation (mdx) were given an arginine-rich, cell-penetrating, peptide-conjugated phosphorodiamidate morpholino oligomer (PPMO) that delivered a splice-switching oligonucleotide-mediated exon skipping therapy to restore dystrophin in mdx mice before the development of detectable cardiomyopathy. PPMO successfully restored cardiac dystrophin expression, preserved cardiac sarcolemma integrity, and prevented the development of cardiac pathology that develops in mdx-null mice over time. By echocardiography and Doppler analysis of the mitral valve, we identified that PPMO treatment of mdx mice prevented the cardiac hypertrophy and diastolic dysfunction identified in sham-treated, age-matched mdx mice, characteristic of DMD patients early in the disease process, in as little as 5-6 weeks after the initiation of treatment. Surprisingly, despite the short-term replacement of cardiac dystrophin (<1% present after 12 weeks by immunodetection), PPMO therapy also provided a durable cardiac improvement in cardiac hypertrophy and diastolic dysfunction for up to 7 months after the initiation of treatment.

CONCLUSION

These results demonstrate for the first time that PPMO-mediated exon skipping therapy early in the course of DMD may effectively prevent or slow down associated cardiac hypertrophy and diastolic dysfunction with significant long-term impact.

Analysis of dystrophin deletion mutations predicts age of cardiomyopathy onset in becker muscular dystrophy

BACKGROUND

Becker muscular dystrophy (BMD) and X-linked dilated cardiomyopathy often result from deletion mutations in the dystrophin gene that may lead to expression of an altered dystrophin protein in cardiac muscle. Cardiac involvement is present in approximately 70% of BMD and all X-linked dilated cardiomyopathy cases. To date, the timing of cardiomyopathy development remains unpredictable. We analyzed 78 BMD and X-linked dilated cardiomyopathy patients with common deletion mutations predicted to alter the dystrophin protein and correlated their mutations to cardiomyopathy age of onset. This approach was chosen to connect dystrophin structure with function in the heart.

METHODS AND RESULTS

Detailed cardiac information was collected for BMD and X-linked dilated cardiomyopathy patients with defined dystrophin gene deletion mutations. Patients were grouped based on the dystrophin protein domain affected by the deletion. Deletions affecting the amino-terminal domain are associated with early-onset dilated cardiomyopathy (DCM; mid-20s), whereas deletions removing part of the rod domain and hinge 3 have a later-onset DCM (mid-40s). Further, we modeled the effects of the most common mutations occurring in the rod domain on the overall structure of the dystrophin protein. By combining genetic and protein information, this analysis revealed a strong correlation between specific protein structural modifications and DCM age of onset.

CONCLUSIONS

We identified specific regions of the dystrophin gene that when mutated predispose BMD patients to early-onset DCM. In addition, we propose that some mutations lead to early-onset DCM by specific alterations in protein folding. These findings have potential implications for early intervention in the cardiac care of BMD patients and for therapeutic approaches that target the heart in dystrophinopathies.

Cardiac expression of a mini-dystrophin that normalizes skeletal muscle force only partially restores heart function in aged Mdx mice

Duchenne muscular dystrophy (DMD) affects both skeletal and cardiac muscle. It is currently unclear whether the strategies developed for skeletal muscle can ameliorate cardiomyopathy. Synthetic mini-/micro-dystrophin genes have yielded impressive skeletal muscle protection in animal models. The 6-kb DeltaH2-R19 minigene is particularly promising because it completely restores skeletal muscle force to wild-type levels. Here, we examined whether expressing this minigene in the heart, but not skeletal muscle, could normalize cardiac function in the mdx model of DMD cardiomyopathy. Transgenic mdx mice were generated to express the DeltaH2-R19 minigene under the control of the alpha-myosin heavy-chain promoter. Heart structure and function were examined in adult and very old mice. The DeltaH2-R19 minigene enhanced cardiomyocyte sarcolemmal strength and prevented myocardial fibrosis. It also restored the dobutamine response and enhanced treadmill performance. Surprisingly, heart-restricted DeltaH2-R19 minigene expression did not completely normalize electrocardiogram and hemodynamic abnormalities. Overall, systolic function and ejection fraction were restored to normal levels but stroke volume and cardiac output remained suboptimal. Our results demonstrate that the skeletal muscle-proven DeltaH2-R19 minigene can correct cardiac histopathology but cannot fully normalize heart function. Novel strategies must be developed to completely restore heart function in DMD.

Cardiac involvement in Becker muscular dystrophy

The present review gives an overview of the clinical and subclinical manifestations of cardiac involvement (CI) in Becker muscular dystrophy (BMD), its pathophysiological background, diagnostic possibilities and therapeutic options for CI in BMD patients and carriers. CI may be subclinical or symptomatic. Up to 100% of patients develop subclinical CI. The onset of symptomatic CI is usually in the third decade of life, rarely in the first decade. One-third of patients develop dilative cardiomyopathy with concomitant heart failure. In BMD patients, CI manifests as electrocardiographic abnormalities, hypertrophic cardiomyopathy, dilation of the cardiac cavities with preserved systolic function, dilative cardiomyopathy or cardiac arrest. There is no correlation between CI and the severity of myopathy. CI is more prominent in patients than carriers. As soon as the diagnosis of BMD is established, a comprehensive cardiac examination should be performed. Because CI in BMD is progressive and adequate therapy is available, cardiac investigations need to be regularly repeated. If CI in BMD is recognized early, appropriate therapy may be applied early, resulting in a more favourable outcome.

Dystrophin-deficient cardiomyopathy in mouse: expression of Nox4 and Lox are associated with fibrosis and altered functional parameters in the heart

Duchenne muscular dystrophy (DMD; dystrophin-deficiency) causes dilated cardiomyopathy in the second decade of life in affected males. We studied the dystrophin-deficient mouse heart (mdx) using high-frequency echocardiography, histomorphometry, and gene expression profiling. Heart dysfunction was prominent at 9-10months of age and showed significantly increased LV internal diameter (end systole) and decreased posterior wall thickness. This cardiomyopathy was associated with a 30% decrease in shortening fraction. Histologically, there was a 10-fold increase in connective tissue volume (fibrosis). mRNA profiling with RT-PCR validation showed activation of key pro-fibrotic genes, including Nox4 and Lox. The Nox gene family expression differed in mdx heart and skeletal muscle, where Nox2 was specifically induced in skeletal muscle while Nox4 was specifically induced in heart. This is the first report of an altered profibrotic gene expression profile in cardiac tissue of dystrophic mice showing echocardiographic evidence of cardiomyopathy.

Cardiomyopathy with a unique finding of bicuspid aortic valve in Becker's muscular dystrophy

We describe a patient with Becker's muscular dystrophy and cardiac failure caused by a combination of dilated cardiomyopathy and congenital bicuspid aortic valve with aortic stenosis. There is no documented association between congenital valve disease and human dystrophinopathies, and to our knowledge, this is the first reported case.

Cardiac involvement in Fukuyama-type congenital muscular dystrophy

BACKGROUND

Fukuyama-type congenital muscular dystrophy is an autosomal recessive disorder characterized by generalized skeletal muscle weakness and hypotonia from early infancy and by mental retardation. Little is known about cardiac involvement in patients with Fukuyama-type congenital muscular dystrophy. This study evaluated whether cardiac involvement exists in patients with Fukuyama-type congenital muscular dystrophy.

METHODS AND RESULTS

We evaluated left ventricular function using M-mode and Doppler echocardiography in 34 patients with Fukuyama-type congenital muscular dystrophy. The age ranged from 6 months to 30 years (median: 6 years). A total of 64 recordings were analyzed. Left ventricular dimensions and parameters of systolic function measured included left ventricular end-diastolic dimension, left ventricular fractional shortening, left ventricular wall thickness, and the mean velocity of circumferential fiber shortening and end-systolic wall stress relationship. Left ventricular end-diastolic dimension z score >2 was observed in 2 patients (6%). Left ventricular fractional shortening <0.28 and/or reduced mean velocity of circumferential fiber shortening in the mean velocity of circumferential fiber shortening-end-systolic wall stress relationship were observed in 16 patients (47%). A significant correlation between age and left ventricular fractional shortening was observed, and left ventricular fractional shortening decreased with age. Of 12 patients >15 years of age, 10 (83%) showed decreased left ventricular systolic function. Left ventricular fractional shortening was normal in most patients <10 years of age, and it was reduced in most patients >15 years of age. Five patients died of heart failure or respiratory problems, and a histologic examination confirmed the presence of myocardial fibrosis. No patients showed increased left ventricular wall thickness or a conduction abnormality on electrocardiograms.

CONCLUSION

Cardiac involvement exists in patients with Fukuyama-type congenital muscular dystrophy and becomes evident in older children in the second decade. A cardiac evaluation, including echocardiograms and subsequent follow-up, is important, especially in patients >10 years of age.

Severe dilated cardiomyopathy and quadriceps myopathy due to lamin A/C gene mutation: A phenotypic study

This study reports a family affected by a new phenotype associated with dilated cardiomyopathy and quadriceps myopathy.

METHODS

29 family members underwent a physical and neurological examination, including an electromyogram and biopsy of muscle abnormalities. A cardiac examination was performed in all subjects.

RESULTS

The family pedigree (n=72) demonstrated that transmission was autosomal dominant. Eleven subjects had cardiac involvement, only four had quadriceps muscle involvement. Cardiac impairment preceded neurological involvement. The mean age for neurological involvement was 44+/-0.8 years (range 43-45) and cardiac involvement was 37+/-7.9 years (range: 24-45). Cardiac involvement consisted of: hypokinetic dilated cardiomyopathy (64%); atrial fibrillation (100%); ventricular arrhythmias (64%); impaired conduction with bundle branch or complete atrio ventricular block (73%). Four patients required pacemakers and anti arrhythmic therapies. Four patients died: two of refractory heart failure and two of sudden death; two patients were resuscitated following cardiac arrest. Three patients required a prophylactic implantable cardiac defibrillator (ICD). Muscle morphological abnormalities were characterized by a variable number of fibers with rimmed vacuoles. The quadriceps deteriorated progressively without impairment of other muscles. Genotypic study showed a lamin A/C gene mutation.

CONCLUSIONS

This family was affected by a new phenotype composed of an autosomal dominant severe dilated cardiomyopathy with conduction defects or arrhythmias and quadriceps myopathy. Cardiac abnormalities preceded neuromuscular disorders and defined the prognosis of this disease.

Cardiomyopathie dilatée et toxicité musculaire des hypolipémiants : une maladie de Becker de révélation tardive

INTRODUCTION

The Becker's muscular dystrophy is a genetic myopathy due to mutations of the dystrophin gene, located in the Xp21 region, with a clinical expression usually occurring in young adults.

EXEGESIS

We report an atypical case of late onset Becker's muscular dystrophy diagnosed at the age of 57. The patient suffered from mild skeletal muscle involvement revealed by the use of statins and fibrates, associated with severe dilating cardiomyopathy. The DNA analysis showed a deletion of the exons 11-13 in the Xp21 gene.

CONCLUSION

The diagnostic of Becker's muscular dystrophy must be considered in all patients with persistently elevated CPK and/or primitive dilated cardiomyopathy, whatever the age of the patient.

Gene mutations in adult Japanese patients with dilated cardiomyopathy

BACKGROUND

Some patients with dilated cardiomyopathy (DCM) have mutations of the genes that encode sarcomeric or cytoskeletal proteins of cardiomyocytes, but the prevalence of these mutations in Japan remains unclear.

METHODS AND RESULTS

A group of 99 unrelated adult patients with DCM (familial n=27, sporadic n=72) were screened for the following genes: cardiac beta-myosin heavy chain, cardiac myosin-binding protein C (MYBPC3), regulatory and essential myosin light chains, alpha cardiac actin, alpha tropomyosin, cardiac troponin T, cardiac troponin I, cardiac troponin C, dystrophin, and lamin A/C. A mutation (R820Q) in MYBPC3 was found in an aged patient. In addition, dystrophin mutations were identified in 3 male patients (2 with exon 45-48 deletion and 1 with exon 48-52 deletion). The prevalence of dystrophin mutations in male patients with DCM was 4.4% (3 of 68). No mutations involving amino acid changes were identified in the other genes.

CONCLUSIONS

Although cases of adult patients with DCM caused by mutations of the genes encoding sarcomeric or cytoskeletal proteins of cardiomyocytes are infrequent in Japan, it may be advisable to screen older DCM patients for MYBPC3 mutations, and male patients with familial DCM for dystrophin mutations.

Multiple pathogenetic mechanisms in X linked dilated cardiomyopathy

X linked dilated cardiomyopathy is a familial disease that is allelic to Duchenne and Becker muscular dystrophies and caused by mutations in the dystrophin gene. In several families with X linked dilated cardiomyopathy, the pattern of expression of dystrophin mutations in cardiac muscle differs from that in skeletal muscle. A number of these mutations affect transcription and splicing of the dystrophin gene in a tissue specific manner; others may affect regions of dystrophin that are presumed to have a more important role in cardiac than in skeletal muscle. These mutations are important because they highlight the fundamental differences in processing of the dystrophin gene between skeletal and cardiac tissues, as well as differences in the functional domains more relevant for one tissue or the other. This review focuses on the major mechanisms that have been proposed to explain this disorder.

Different expressions of X-linked cardiomyopathy in monozygotic triplets with Becker's dystrophy

Cardiac involvement is common in skeletal muscles disorders associated with dystrophin defect. It has been suggested however, that X-linked dilated cardiomyopathies with minimal or absent skeletal disease are distinct entities, resulting from mutations in cardiac-specific regions of dystrophin gene. This study presents a unique observation of phenotypic variability in monozygotic triplets with Becker's muscular dystrophy. The expressions of the disease range from severe peripheral myopathy to severe congestive heart failure. No deletion in dystrophin gene was observed and the mechanisms responsible for selective impairment of morphologically and functionally different muscles in three monozygotic siblings remain unclear.

Evidence of early impairments in both right and left ventricular inotropic reserves in children with Duchenne's muscular dystrophy

In Duchenne's muscular dystrophy (DMD), cardiac function deteriorates with time and heart failure is one of the major causes of death. The aim of the study was to determine if a decrease in the ventricular inotropic reserves could be an early sign of cardiac dysfunction in these children. Nineteen children with DMD (aged 9 to 18 years, mean age 13.6 +/- 2.4) underwent equilibrium radionuclide angiography at rest and during an inotropic stimulation with low-dose dobutamine perfusion (7.5 to 15 microg. kg(-1). min(-1)). In all patients, this investigation was short (<30 minutes), successful, and uncomplicated. At rest, left ventricular (LV) ejection fraction (EF) was normal (>0.50) in 79% of patients, and right ventricular (RV) EF was normal (>0.45) in 95%. There was a trend toward a decrease with age for rest LVEF (p = 0.051) but not for rest RVEF (p = 0.8). By contrast, marked declines with age could be documented for the increases (Delta) in LVEF and RVEF during dobutamine perfusion (p = 0.002 for DeltaLVEF and p = 0.015 for DeltaRVEF). Thus, by multivariate analysis, the sole best indicator of decline in cardiac function with age was LVEF determined with dobutamine. In children with DMD, low-dose dobutamine radionuclide angiography gives evidence of an early decline with age of the inotropic reserves of both ventricles.

Cardiac complications of childhood myopathies

The management of individuals with a neuromuscular disorder is usually focused on the skeletal muscle weakness and resulting complications, such as respiratory failure. Long-term prognosis of a number of neuromuscular conditions is, however, also determined by the type and severity of cardiac involvement. Early recognition and treatment of the cardiovascular complications are part of the task of the multidisciplinary team involved in the care of these patients. Although for several of the common conditions, there is general consensus on the cardiac investigations and treatments, in the rarer disorders, evidence-based recommendations are not available, and suggestions from experts provide an acceptable solution. This review summarizes the recent advances in our understanding of the pathogenesis and phenotypic diversity of cardiac complications associated with pediatric myopathies and provides a rational framework for planning the monitoring and therapeutic intervention in individual conditions.