Cardioprotection for Duchenne's muscular dystrophy

Utilities and Limitations of Cardiac Magnetic Resonance Imaging in Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the most common types of non-ischemic cardiomyopathy. DCM is characterized by left ventricle (LV) dilatation and systolic dysfunction without coronary artery disease or abnormal loading conditions. DCM is not a single disease entity and has a complex historical background of revisions and updates to its definition because of its diverse etiology and clinical manifestations. In cases of LV dilatation and dysfunction, conditions with phenotypic overlap should be excluded before establishing a DCM diagnosis. The differential diagnoses of DCM include ischemic cardiomyopathy, valvular heart disease, burned-out hypertrophic cardiomyopathy, arrhythmogenic cardiomyopathy, and non-compaction. Cardiac magnetic resonance (CMR) imaging is helpful for evaluating DCM because it provides precise measurements of cardiac size, function, mass, and tissue characterization. Comprehensive analyses using various sequences, including cine imaging, late gadolinium enhancement imaging, and T1 and T2 mapping, may help establish differential diagnoses, etiological work-up, disease stratification, prognostic determination, and follow-up procedures in patients with DCM phenotypes. This article aimed to review the utilities and limitations of CMR in the diagnosis and assessment of DCM.

Cardiomyopathy as cause of death in Duchenne muscular dystrophy: a longitudinal observational study

Background

Cardiomyopathy has become an important life-limiting factor since survival in Duchenne muscular dystrophy (DMD) has greatly increased with long-term ventilation and cough assistance. The aim of this study was to investigate the association between impaired left ventricular ejection fraction (LVEF) and survival.

Methods

In a >20-year observational study in patients with DMD (age ≥16 years) with at least three echocardiograms, the association between LVEF and survival and time to cardiac or non-cardiac death was investigated using Kaplan-Meier survival analysis and Cox regression (for LVEF).

Results

In 67 DMD patients (430 echocardiograms), the decrease in LVEF over a mean±sd follow-up period of 9.1±5.1 years was -10.0±13.9% absolute, but LVEF progression varied widely. 84% were receiving an angiotensin-converting enzyme inhibitor and 54% a β-blocker at last follow-up with an LVEF of 37.5±12.4% at that time-point. Median (interquartile range) survival was 33 (25-40) years. 28 out of 67 (42%) of the cohort had died and LVEF was a significant negative predictor of survival (hazard ratio 0.95 (95% CI 0.91-0.99); p<0.007). Those who died of cardiac death (53% of known causes of death) had significantly lower LVEF at the time of death (LVEF -11.0% (95% CI -21.1- -0.9%); p=0.035) compared with non-cardiac death and tended to die at a younger age.

Conclusions

Cardiomyopathy with systolic heart failure is the leading cause of death and lower LVEF is an independent predictor of mortality at younger ages in patients with DMD. Patients with DMD appear to be undertreated with respect to heart failure drug therapy.

Prognostic indicators of disease progression in Duchenne muscular dystrophy: A literature review and evidence synthesis

BACKGROUND

Duchenne muscular dystrophy (DMD) is a rare, severely debilitating, and fatal neuromuscular disease characterized by progressive muscle degeneration. Like in many orphan diseases, randomized controlled trials are uncommon in DMD, resulting in the need to indirectly compare treatment effects, for example by pooling individual patient-level data from multiple sources. However, to derive reliable estimates, it is necessary to ensure that the samples considered are comparable with respect to factors significantly affecting the clinical progression of the disease. To help inform such analyses, the objective of this study was to review and synthesise published evidence of prognostic indicators of disease progression in DMD. We searched MEDLINE (via Ovid), Embase (via Ovid) and the Cochrane Library (via Wiley) for records published from inception up until April 23 2021, reporting evidence of prognostic indicators of disease progression in DMD. Risk of bias was established with the grading system of the Centre for Evidence-Based Medicine (CEBM).

RESULTS

Our search included 135 studies involving 25,610 patients from 18 countries across six continents (Africa, Asia, Australia, Europe, North America and South America). We identified a total of 23 prognostic indicators of disease progression in DMD, namely age at diagnosis, age at onset of symptoms, ataluren treatment, ATL1102, BMI, cardiac medication, DMD genetic modifiers, DMD mutation type, drisapersen, edasalonexent, eteplirsen, glucocorticoid exposure, height, idebenone, lower limb surgery, orthoses, oxandrolone, spinal surgery, TAS-205, vamorolone, vitlolarsen, ventilation support, and weight. Of these, cardiac medication, DMD genetic modifiers, DMD mutation type, and glucocorticoid exposure were designated core prognostic indicators, each supported by a high level of evidence and significantly affecting a wide range of clinical outcomes.

CONCLUSION

This study provides a current summary of prognostic indicators of disease progression in DMD, which will help inform the design of comparative analyses and future data collection initiatives in this patient population.

Kidney Function in Patients With Neuromuscular Disease: Creatinine Versus Cystatin C

Background: Accurate measurement of kidney function in patients with neuromuscular disorders is challenging. Cystatin C, a marker not influenced by skeletal muscle degradation, might be of clinical value in these patients.

Methods: We consecutively enrolled 39 patients with neuromuscular disorders. We investigated the association of the eGFR, based on plasma creatinine and Cystatin C, with clinical and biochemical variables associated with kidney function, namely age and galectin-3.

Results: Creatinine-based eGFR was 242 (±80) and Cystatin C-based eGFR was 110 (±23) mL/min/1.73 m². Cystatin C-based eGFR was associated with age (β −0.63 p < 0.0001) and galectin-3 levels (β −0.43 p < 0.01), while creatinine-based eGFR was not (β −0.22 p = 0.20; β −0.28 p = 0.10). Sensitivity analyses in Duchenne and Becker patients revealed the same results: Cystatin C-based eGFR was associated with age (β −0.61 p < 0.01) and galectin-3 levels (β −0.43 p = 0.05), while creatinine-based eGFR was not (β −0.32 p = 0.13; β −0.34 p = 0.14).

Conclusions: These data indicate that estimation of renal function in patients with neuromuscular disorders cannot reliably be achieved with creatinine, while Cystatin C appears a reasonable alternative. Since a large proportion of patients with neuromuscular disorders develops heart failure, and requires heart failure medication, adequate monitoring of renal function is warranted.

Study Protocol for a Multicenter, Open-Label, Single-Arm Study of Tranilast for Cardiomyopathy of Muscular Dystrophy

Duchenne (DMD) and other forms of muscular dystrophy (MD) are collectively rare and affect approx imately 20 per 100,000 people. The on-going development of exon skipping and other novel therapies for DMD is expected to lead to improvements in motor function prognosis. However, improvements in motor dysfunction with these novel therapies are associated with the risk of increase in cardiac burden. Development of therapies to improve cardiac function, therefore, is an urgent issue. This single-arm, open-label, multicenter study will include 20 patients with MD aged 13 years or older. Tranilast, a transient receptor potential cation channel subfamily V member 2 (TRPV2) inhibitor, will be administered orally for a period of 28 weeks at a dose of 300 mg/day divided into three daily doses. If consent to continue administration is obtained at 28 weeks, the drug will be administered for an additional 116 weeks. The primary outcome will be the change in brain natriuretic peptide (BNP) at 6 months after the start of administration compared to baseline. Tranilast is an anti-allergy agent that was developed in Japan. It has been used in a large number of clinical cases, including pediatric cases, and has been shown to be safe. We expect this study to provide basic data for developing new treatment method in cardiomyopathy/skeletal myopathy using TRPV2 inhibitors. Moreover, such therapies may also be effective in treating general heart failure without MD. Therefore, if the effectiveness of TRPV2 inhibitors could be confirmed in this study, great social and economic benefits could be achieved.

A systematic review of pharmacologic therapies for the cardiomyopathy of Duchenne muscular dystrophy

OBJECTIVE

To perform a systematic review of studies evaluating pharmacologic therapies for the cardiomyopathy of Duchenne muscular dystrophy (DMD).

METHODS

PubMed, Google Scholar, and Embase were searched through October 8, 2020. Articles were selected using pre-determined criteria; 26 underwent detailed review by two co-authors. Study quality was assessed with the Newcastle-Ottawa scoring system (NOS); GRADE assessment evaluated their overall clinical importance.

RESULTS

There were few randomized controlled trials. Two of four trials of angiotensin converting enzyme inhibitors (ACEI) or ACEI plus beta-blockers (BB) found improved LV function. Two of two randomized trials of aldosterone antagonists (AA), when added to ACEI and BB therapy, demonstrated less decline of LV circumferential strain over 1 year of treatment. Observational studies of ACEI and BB had differing patient ages, symptomatology, cohort size, study duration and baseline heart function. LV function, assessed via unblinded imaging, was the most frequent outcome measure. LV dysfunction improved in some trials but was unconfirmed in others. Class IV heart failure patients had transient improvement of symptoms and LVEF. Most NOS scores reflected a low level of study quality. The Grade certainty rating, used for the summation of studies, was between "low" and "moderate."

CONCLUSION

Randomized trial evidence was inconsistent that either ACEI or BB or their combination improve LV function and/or alter progressive LV dysfunction. When ACEI and BB therapy are initiated for symptomatic Class IV heart failure, symptoms and LVEF improve transiently. AAs retard the rate of decline of LV function when initiated in younger DMD patients.

Influence of microRNAs and exosomes in muscle health and diseases

microRNAs are short, (18-22 nt) non-coding RNAs involved in important cellular processes due to their ability to regulate gene expression at the post-transcriptional level. Exosomes are small (50-200 nm) extracellular vesicles, naturally secreted from a variety of living cells and are believed to mediate cell-cell communication through multiple mechanisms, including uptake in destination cells. Circulating microRNAs and exosome-derived microRNAs can have key roles in regulating muscle cell development and differentiation. Several microRNAs are highly expressed in muscle and their regulation is important for myocyte homeostasis. Changes in muscle associated microRNA expression are associated with muscular diseases including muscular dystrophies, inflammatory myopathies, and congenital myopathies. In this review, we aim to highlight the biology of microRNAs and exosomes as well as their roles in muscle health and diseases. We also discuss the potential crosstalk between skeletal and cardiac muscle through exosomes and their contents.

Left Ventricular End-Diastolic Diameter and Cardiac Mortality in Duchenne Muscular Dystrophy

PURPOSE

This study aimed to examine weather left ventricular end-diastolic diameter (LVDd) could predict mortality from heart failure in patients with Duchenne muscular dystrophy (DMD) receiving standard cardio-protective therapies.

PATIENTS AND METHODS

One hundred thirty-three patients with DMD aged ≥10 years who underwent echocardiography from 2011 to 2015 were included in this study and retrospectively followed until August 2018. Patients were divided into two groups according to LVDd at initial echocardiography: ≤ 54 mm (Group 1: n=119) and ≥ 55 mm (Group 2: n=14). To identify factors other than LVDd that may affect heart failure-related mortality, Group 2 patients who developed no left atrial (LA) enlargement, moderate mitral regurgitation (MR), or pulmonary hypertension (PH) during the observation period (Group 2A: n=5) were compared with those who newly developed one or more of those complications (Group 2B: n=7). Clinical outcomes were all-cause mortality and mortality from heart failure.

RESULTS

Mean observation period was 5.5±1.5 years in Group 1 and 4.4±1.9 years in Group 2. A total of 14 patients (10.5%) died, including 6 of 119 (5.0%) patients in Group 1 and 8 of 14 (57.1%) patients in Group 2 (p<0.001). Among these, 1 (0.8%) patient in Group 1 and 8 (57.1%) patients in Group 2 died from heart failure (p<0.001). Group 2B patients had shorter survival compared to Group 2A patients (p=0.006).

CONCLUSION

LVDd ≥ 55 mm is a predictive factor for mortality from heart failure in patients with DMD. Complications including LA enlargement, moderate MR, and PH were found to be predictive factors for mortality from heart failure in a short period.

A case report: X-linked dystrophin gene mutation causing severe isolated dilated cardiomyopathy

Background 

X-linked dilated cardiomyopathy (XLDCM) is a rare but rapidly progressive cardiomyopathy caused by dystrophin gene mutation. Mutations are more often associated with Duchenne and Becker Muscular Dystrophy, which are characterized by skeletal muscle weakness or limb girdle dystrophy. However, patients with isolated XLDCM have normal skeletal muscle but complete dystrophin loss in cardiac muscle resulting in isolated myocardial involvement without overt signs of skeletal myopathy.

Case summary 

A previously well 16-year-old boy developed sudden onset dense left-sided weakness and facial droop. Computed tomography (CT) angiography and CT brain showed an occluded right internal carotid artery extending to the right middle cerebral artery. He underwent successful endovascular clot retrieval but developed frank pulmonary oedema and cardiogenic shock requiring inotropic support and intubation. Transthoracic echocardiography demonstrated severe left ventricular (LV) cardiomyopathy and an apical thrombus. Subsequent cardiac magnetic resonance (CMR) imaging confirmed the LV parameters and diffuse late gadolinium enhancement. Despite absence of skeletal manifestations, subsequent genetic testing revealed an X-linked dystrophin gene mutation [c.31+G>T (IVS1G>T)]. He was commenced on empirical heart failure therapy and underwent successful cardiac transplantation.

Discussion 

X-linked dilated cardiomyopathy is a rare, rapidly progressing cardiomyopathy. Patients show normal skeletal muscle dystrophin but absent expression in cardiac muscle, resulting fibrosis, and atrophy. About 20% of affected young males have significantly reduced survival and thus the diagnosis must be considered in cases of idiopathic cardiomyopathy with CMR and genetic testing key to the diagnosis. Whilst evidence exists for empirical heart failure medications, cardiac transplantation remains the definitive treatment.

Imaging the heart to detect cardiomyopathy in Duchenne muscular dystrophy: A review

Duchenne Muscular Dystrophy is the most common paediatric neuromuscular disorder. Mutations in the DMD gene on the X-chromosome result in progressive skeletal muscle weakness as the main clinical manifestation. However, cardiac muscle is also affected, with cardiomyopathy becoming an increasingly recognised cause of morbidity, and now the leading cause of mortality in this group. The diagnosis of cardiomyopathy has often been made late due to technical limitations in transthoracic echocardiograms and delayed symptomatology in less mobile patients. Increasingly, evidence supports earlier pharmacological intervention in cardiomyopathy to improve outcomes. However, the optimal timing of initiation remains uncertain, and the benefits of prophylactic therapy are unproven. Current treatment guidelines suggest initiation of therapy once cardiac dysfunction is detected. This review focuses on new and evolving techniques for earlier detection of Duchenne muscular dystrophy-associated cardiomyopathy. Transthoracic echocardiography or cardiac magnetic resonance imaging performed under physiological stress (dobutamine or exercise), can unmask early cardiac dysfunction. Cardiac magnetic resonance imaging can define cardiac function with greater accuracy and reliability than an echocardiogram, and is not limited by body habitus. Improved imaging techniques, used in a timely fashion, offer the potential for early detection of cardiomyopathy and improved long-term outcomes.

Increased constitutive nitric oxide production by whole body periodic acceleration ameliorates alterations in cardiomyocytes associated with utrophin/dystrophin deficiency

Duchenne Muscular Dystrophy (DMD) cardiomyopathy is a progressive lethal disease caused by the lack of the dystrophin protein in the heart. The most widely used animal model of DMD is the dystrophin-deficient mdx mouse; however, these mice exhibit a mild dystrophic phenotype with heart failure only late in life. In contrast, mice deficient for both dystrophin and utrophin (mdx/utrn^-/-, or dKO) can be used to model severe DMD cardiomyopathy where pathophysiological indicators of heart failure are detectable by 8-10weeks of age. Nitric oxide (NO) is an important signaling molecule involved in vital functions of regulating rhythm, contractility, and microcirculation of the heart, and constitutive NO production affects the function of proteins involved in excitation-contraction coupling. In this study, we explored the efficacy of enhancing NO production as a therapeutic strategy for treating DMD cardiomyopathy using the dKO mouse model of DMD. Specifically, NO production was induced via whole body periodic acceleration (pGz), a novel non-pharmacologic intervention which enhances NO synthase (NOS) activity through sinusoidal motion of the body in a headward-footward direction, introducing pulsatile shear stress to the vascular endothelium and cardiomyocyte plasma membrane. Male dKO mice were randomized at 8weeks of age to receive daily pGz (480cpm, Gz±3.0m/s², 1h/d) for 4weeks or no treatment, and a separate age-matched group of WT animals (pGz-treated and untreated) served as non-diseased controls. At the conclusion of the protocol, cardiomyocytes from untreated dKO animals had, respectively, 4.3-fold and 3.5-fold higher diastolic resting concentration of Ca²⁺ ([Ca²⁺]_d) and Na⁺ ([Na⁺]_d) compared to WT, while pGz treatment significantly reduced these levels. For dKO cardiomyocytes, pGz treatment also improved the depressed contractile function, decreased oxidative stress, blunted the elevation in calpain activity, and mitigated the abnormal increase in [Ca²⁺]_d upon mechanical stress. These improvements culminated in a significant reduction in circulating cardiac troponin T (cTnT) and an extension of the median lifespan of dKO mice from 16 to 31weeks. Treatment with L-NAME (NOS inhibitor) significantly decreased overall lifespan and abolished the cardioprotective properties elicited by pGz. Our results provide evidence that enhancement of NO synthesis by pGz can ameliorate cellular dysfunction in dKO cardiomyocytes and may represent a novel therapeutic intervention in DMD cardiomyopathy patients.

Pharmacological therapy for the prevention and management of cardiomyopathy in Duchenne muscular dystrophy: A systematic review

Cardiomyopathy is a major source of morbidity and mortality in Duchenne muscular dystrophy (DMD) patients now that respiratory care has improved. There is currently no definitive evidence guiding the management of DMD-associated cardiomyopathy (DMD-CM). The objective of this systematic review was to evaluate the effectiveness of pharmacotherapies for the prevention and/or management of DMD-CM and to determine the optimal timing to commence these interventions. A systematic search was conducted in January 2016 using MEDLINE, EMBASE and CINAHL databases and grey literature sources for studies evaluating the use of angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers, beta-blockers or aldosterone antagonists. Study quality assessment was conducted using the Downs and Black quality assessment checklist. PRISMA reporting guidelines were used. Of the 15 studies included in this review, most were of low methodological quality. Meta-analysis was not possible due to heterogeneity of studies. ACE inhibitors, angiotensin receptor blockers, beta-blockers and/or aldosterone antagonists tended to improve or preserve left ventricular systolic function and delay the progression of DMD-CM. While there is evidence supporting the use of heart failure medication in patients with DMD, data regarding these interventions for delaying the onset of DMD-CM and when to initiate therapy are lacking. PROSPERO registration: CRD42015029555.

A Case of Refractory Heart Failure in Becker Muscular Dystrophy Improved With Corticosteroid Therapy

The patient was a 26 year-old man who was referred to our hospital in June 2011 because of severe heart failure. At age 24 years, he was found to have Becker muscular dystrophy. He received enalapril for cardiac dysfunction; however, he had worsening heart failure and was thus referred to our hospital. Echocardiography showed enlargement of the left ventricle, with a diastolic dimension of 77 mm and ejection fraction of 19%. His condition improved temporarily after an infusion of dobutamine and milrinone. He was then administered amiodarone for ventricular tachycardia; however, he subsequently developed hemoptysis. Amiodarone was discontinued and corticosteroid pulse therapy was administered followed by oral prednisolone (PSL). His creatinine phosphokinase (CPK) level and cardiomegaly improved after the corticosteroid therapy. The PSL dose was reduced gradually, bisoprolol was introduced, and the catecholamine infusion was tapered. A cardiac resynchronization device was implanted; however, the patient's condition gradually worsened, which necessitated dobutamine infusion for heart failure. We readministered 30 mg PSL, which decreased the CPK level and improved the cardiomegaly. The dobutamine infusion was discontinued, and the patient was discharged. He was given 7.5 mg PSL as an outpatient, and he returned to normal life without exacerbation of the heart failure. There are similar reports showing that corticosteroids are effective for skeletal muscle improvement in Duchenne muscular dystrophy; however, their effectiveness for heart failure has been rarely reported. We experienced a case of Becker muscular dystrophy in which corticosteroid therapy was effective for refractory heart failure.

Corticosteroids for the treatment of Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy of childhood. Untreated, this incurable disease, which has an X-linked recessive inheritance, is characterised by muscle wasting and loss of walking ability, leading to complete wheelchair dependence by 13 years of age. Prolongation of walking is a major aim of treatment. Evidence from randomised controlled trials (RCTs) indicates that corticosteroids significantly improve muscle strength and function in boys with DMD in the short term (six months), and strength at two years (two-year data on function are very limited). Corticosteroids, now part of care recommendations for DMD, are largely in routine use, although questions remain over their ability to prolong walking, when to start treatment, longer-term balance of benefits versus harms, and choice of corticosteroid or regimen.We have extended the scope of this updated review to include comparisons of different corticosteroids and dosing regimens.

OBJECTIVES

To assess the effects of corticosteroids on prolongation of walking ability, muscle strength, functional ability, and quality of life in DMD; to address the question of whether benefit is maintained over the longer term (more than two years); to assess adverse events; and to compare efficacy and adverse effects of different corticosteroid preparations and regimens.

SEARCH METHODS

On 16 February 2016 we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, EMBASE, CINAHL Plus, and LILACS. We wrote to authors of published studies and other experts. We checked references in identified trials, handsearched journal abstracts, and searched trials registries.

SELECTION CRITERIA

We considered RCTs or quasi-RCTs of corticosteroids (e.g. prednisone, prednisolone, and deflazacort) given for a minimum of three months to patients with a definite DMD diagnosis. We considered comparisons of different corticosteroids, regimens, and corticosteroids versus placebo.

DATA COLLECTION AND ANALYSIS

The review authors followed standard Cochrane methodology.

MAIN RESULTS

We identified 12 studies (667 participants) and two new ongoing studies for inclusion. Six RCTs were newly included at this update and important non-randomised cohort studies have also been published. Some important studies remain unpublished and not all published studies provide complete outcome data.

PRIMARY OUTCOME MEASURE

one two-year deflazacort RCT (n = 28) used prolongation of ambulation as an outcome measure but data were not adequate for drawing conclusions.

SECONDARY OUTCOME MEASURES

meta-analyses showed that corticosteroids (0.75 mg/kg/day prednisone or prednisolone) improved muscle strength and function versus placebo over six months (moderate quality evidence from up to four RCTs). Evidence from single trials showed 0.75 mg/kg/day superior to 0.3 mg/kg/day on most strength and function measures, with little evidence of further benefit at 1.5 mg/kg/day. Improvements were seen in time taken to rise from the floor (Gowers' time), timed walk, four-stair climbing time, ability to lift weights, leg function grade, and forced vital capacity. One new RCT (n = 66), reported better strength, function and quality of life with daily 0.75 mg/kg/day prednisone at 12 months. One RCT (n = 28) showed that deflazacort stabilised muscle strength versus placebo at two years, but timed function test results were too imprecise for conclusions to be drawn.One double-blind RCT (n = 64), largely at low risk of bias, compared daily prednisone (0.75 mg/kg/day) with weekend-only prednisone (5 mg/kg/weekend day), finding no overall difference in muscle strength and function over 12 months (moderate to low quality evidence). Two small RCTs (n = 52) compared daily prednisone 0.75 mg/kg/day with daily deflazacort 0.9 mg/kg/day, but study methods limited our ability to compare muscle strength or function.

ADVERSE EFFECTS

excessive weight gain, behavioural abnormalities, cushingoid appearance, and excessive hair growth were all previously shown to be more common with corticosteroids than placebo; we assessed the quality of evidence (for behavioural changes and weight gain) as moderate. Hair growth and cushingoid features were more frequent at 0.75 mg/kg/day than 0.3 mg/kg/day prednisone. Comparing daily versus weekend-only prednisone, both groups gained weight with no clear difference in body mass index (BMI) or in behavioural changes (low quality evidence for both outcomes, one study); the weekend-only group had a greater linear increase in height. Very low quality evidence suggested less weight gain with deflazacort than with prednisone at 12 months, and no difference in behavioural abnormalities. Data are insufficient to assess the risk of fractures or cataracts for any comparison.Non-randomised studies support RCT evidence in showing improved functional benefit from corticosteroids. These studies suggest sustained benefit for up to 66 months. Adverse effects were common, although generally manageable. According to a large comparative longitudinal study of daily or intermittent (10 days on, 10 days off) corticosteroid for a mean period of four years, a daily regimen prolongs ambulation and improves functional scores over the age of seven, but with a greater frequency of side effects than an intermittent regimen.

AUTHORS' CONCLUSIONS

Moderate quality evidence from RCTs indicates that corticosteroid therapy in DMD improves muscle strength and function in the short term (twelve months), and strength up to two years. On the basis of the evidence available for strength and function outcomes, our confidence in the effect estimate for the efficacy of a 0.75 mg/kg/day dose of prednisone or above is fairly secure. There is no evidence other than from non-randomised trials to establish the effect of corticosteroids on prolongation of walking. In the short term, adverse effects were significantly more common with corticosteroids than placebo, but not clinically severe. A weekend-only prednisone regimen is as effective as daily prednisone in the short term (12 months), according to low to moderate quality evidence from a single trial, with no clear difference in BMI (low quality evidence). Very low quality evidence indicates that deflazacort causes less weight gain than prednisone after a year's treatment. We cannot evaluate long-term benefits and hazards of corticosteroid treatment or intermittent regimens from published RCTs. Non-randomised studies support the conclusions of functional benefits, but also identify clinically significant adverse effects of long-term treatment, and a possible divergence of efficacy in daily and weekend-only regimens in the longer term. These benefits and adverse effects have implications for future research and clinical practice.

Myocardial Fibrosis and Left Ventricular Dysfunction in Duchenne Muscular Dystrophy Carriers Using Cardiac Magnetic Resonance Imaging

The goal of our study was to characterize the degree of myocardial fibrosis and left ventricular dysfunction in our cohort of Duchenne muscular dystrophy (DMD) carriers using cardiac magnetic resonance imaging (CMR). Seventy percent of males with DMD have mothers who are carriers of the Xp21 mutation. Carrier phenotypic characteristics range from asymptomatic to left ventricular (LV) dysfunction and cardiomyopathy. The true prevalence of cardiac involvement in DMD carriers is unknown. We performed a retrospective observational study. All female DMD carriers who underwent clinical CMR studies at Cincinnati Children's Hospital Medical Center from December 6, 2006, to August 28, 2013, were evaluated. Patients underwent standard CMR assessment with LV function assessment and late gadolinium enhancement (LGE). In addition, offline feature tracking strain analysis was performed on the basal, mid, and apical short axis. Twenty-two patients were studied, of which 20 underwent adequate testing for myocardial LGE. Four of 22 patients (18 %) were found to have LV dysfunction (ejection fraction <55 %). Seven of 20 DMD carriers (35 %) were found to have LGE. The patients with evidence of LGE had an overall trend to lower absolute deformation parameters; however, this did not meet statistical significance when correcting for multiple comparisons. Our study demonstrates a high rate of LGE as well as LV dysfunction in DMD carriers. Cardiovascular and musculoskeletal symptoms were not statistically different between those with and without cardiac involvement. This study demonstrates the importance of surveillance CMR evaluation of DMD carriers.

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.

Drug Discovery Approaches for Rare Neuromuscular Diseases

Rare neuromuscular diseases encompass many diverse and debilitating musculoskeletal disorders, ranging from ultra-orphan conditions that affect only a few families, to the so-called ‘common’ orphan diseases like Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA), which affect several thousand individuals worldwide. Increasingly, pharmaceutical and biotechnology companies, in an effort to improve productivity and rebuild dwindling pipelines, are shifting their business models away from the formerly popular ‘blockbuster’ strategy, with rare diseases being an area of increased focus in recent years. As a consequence of this paradigm shift, coupled with high-profile campaigns by not-for-profit organisations and patient advocacy groups, rare neuromuscular diseases are attracting considerable attention as new therapeutic areas for improved drug therapy. Much pioneering work has taken place to elucidate the underlying pathological mechanisms of many rare neuromuscular diseases. This, in conjunction with the availability of new screening technologies, has inspired the development of several truly innovative therapeutic strategies aimed at correcting the underlying pathology. A survey of medicinal chemistry approaches and the resulting clinical progress for new therapeutic agents targeting this devastating class of degenerative diseases is presented, using DMD and SMA as examples. Complementary strategies using small-molecule drugs and biological agents are included.

Cooperative International Neuromuscular Research Group Duchenne Natural History Study demonstrates insufficient diagnosis and treatment of cardiomyopathy in Duchenne muscular dystrophy

INTRODUCTION

Cardiomyopathy is a common cause of morbidity and death in patients with Duchenne muscular dystrophy (DMD).

METHODS

This investigation was a cross-sectional cross-sectional analysis of clinical data from the multi-institutional Cooperative International Neuromuscular Research Group (CINRG) DMD Natural History Study of 340 DMD patients aged 2-28 years. Cardiomyopathy was defined as shortening fraction (SF) <28% or ejection fraction (EF) <55%.

RESULTS

Two hundred thirty-one participants reported a prior clinical echocardiogram study, and 174 had data for SF or EF. The prevalence of cardiomyopathy was 27% (47 of 174), and it was associated significantly with age and clinical stage. The association of cardiomyopathy with age and clinical stage was not changed by glucocorticoid use as a covariate (P > 0.68). In patients with cardiomyopathy, 57% (27 of 47) reported not taking any cardiac medications. Cardiac medications were used in 12% (15 of 127) of patients without cardiomyopathy.

CONCLUSIONS

We found that echocardiograms were underutilized, and cardiomyopathy was undertreated in this DMD natural history cohort.

Cardiomyopathy of Duchenne muscular dystrophy: pathogenesis and prospect of membrane sealants as a new therapeutic approach

Duchenne muscular dystrophy (DMD) is a devastating progressive disease of striated muscle deterioration. This fatal X-linked disorder results from the loss of the protein dystrophin, which in turn causes striated muscle membrane instability. Cardiac dysfunction is a growing problem in patients with DMD, but relatively little is known about the pathophysiology of the dystrophic heart. At present, there is no effective treatment for DMD and the current clinical approaches are primarily supportive in nature. This review will discuss the pathogenesis of DMD in the heart and discuss how these pathogenic processes have led to a new class of agents directed specifically at restoring membrane integrity to dystrophic myocardium. The tri-block poloxamers, specifically poloxamer 188 (P188), are able to stabilize the membranes of dystrophic myocardium in animal models and may offer a new therapeutic approach for cardiac disease in DMD.

[Changes in clinical condition and causes of death of inpatients with Duchenne muscular dystrophy in Japan from 1999 to 2012]

To elucidate changes in medical treatment for Duchenne muscular dystrophy (DMD) in Japan, we analyzed the clinical courses and causes of death of inpatients with DMD registered in the muscular dystrophy ward database of 27 hospitals in Japan specializing in muscular dystrophy treatment since 1999. The total number of hospitalized cases in 1999 was 873, which gradually reduced to 733 in 2012. The mean age of DMD patients in 1999 was 23.6 years old, while that was 30.1 years old in 2012, with patients 40 years and older accounting for 94 cases in the latest year. The respirator dependent rate gradually increased from 58.6% in 1999 to 86.1% in 2012. Artificial respiration therapy was introduced earlier in more recent years and the mean age in recent years was shown to be 17.2 years old. The oral nutritional supply rate in 1999 was 95.1%, which fell to 66.8% in 2012, while gastrostomy feeding gradually increased to 129 cases in 2012. The rate of clinical diagnosis of DMD was 52.3% in 1999 and decreased to 43.7% in 2012, which showed progress towards more accurate diagnosis of DMD. From 2000 to 2012, 521 deaths were reported, with approximately half of the causes heart related, followed by respiratory related. The mean age of death gradually increased to 32.4 years old in 2012 from 26.7 years old in 2000. The mean age of survival of all DMD patients was 37.5 years old. Progress in multidisciplinary medical care for respiratory failure, cardiomyopathy, nutritional problems, and other related factors has extended the lifespan of DMD patients.

Nestin expression in end-stage disease in dystrophin-deficient heart: implications for regeneration from endogenous cardiac stem cells

Nestin(+) cardiac stem cells differentiate into striated cells following myocardial infarct. Transplantation of exogenous stem cells into myocardium of a murine model for Duchenne muscular dystrophy (DMD) increased proliferation of endogenous nestin(+) stem cells and resulted in the appearance of nestin(+) striated cells. This correlated with, and may be responsible for, prevention of dilated cardiomyopathy. We examined nestin(+) stem cells in the myocardium of dystrophin/utrophin-deficient (mdx/utrn(-/-)) mice, a model for DMD. We found that 92% of nestin(+) interstitial cells expressed Flk-1, a marker present on cardiac progenitor cells that differentiate into the cardiac lineage, and that a subset expressed Sca-1, present on adult cardiac cells that become cardiomyocytes. Nestin(+) interstitial cells maintained expression of Flk-1 but lost Sca-1 expression with age and were present in lower numbers in dystrophin-deficient heart than in wild-type heart. Unexpectedly, large clusters of nestin(+) striated cells ranging in size from 20 to 250 cells and extending up to 500 μm were present in mdx/utrn(-/-) heart near the end stage of disease. These cells were also present in dystrophin-deficient mdx/utrn(+/-) and mdx heart but not wild-type heart. Nestin(+) striated cells expressed cardiac troponin I, desmin, and Connexin 43 and correlated with proinflammatory CD68(+) macrophages. Elongated nestin(+) interstitial cells with striations were observed that did not express Flk-1 or the late cardiac marker cardiac troponin I but strongly expressed the early cardiac marker desmin. Nestin was also detected in endothelial and smooth muscle cells. These data indicate that new cardiomyocytes form in dystrophic heart, and nestin(+) interstitial cells may generate them in addition to other cells of the cardiac lineage.

Cardiac and respiratory dysfunction in Duchenne muscular dystrophy and the role of second messengers

Duchenne muscular dystrophy (DMD) affects young boys and is characterized by the absence of dystrophin, a large cytoskeletal protein present in skeletal and cardiac muscle cells and neurons. The heart and diaphragm become necrotic in DMD patients and animal models of DMD, resulting in cardiorespiratory failure as the leading cause of death. The major consequences of the absence of dystrophin are high levels of intracellular Ca(2+) and the unbalanced production of NO that can finally trigger protein degradation and cell death. Cytoplasmic increase in Ca(2+) concentration directly and indirectly triggers different processes such as necrosis, fibrosis, and activation of macrophages. The absence of the neuronal isoform of nitric oxide synthase (nNOS) and the overproduction of NO by the inducible isoform (iNOS) further increase the intracellular Ca(2+) via a hypernitrosylation of the ryanodine receptor. NO overproduction, which further induces the expression of iNOS but decreases the expression of the endothelial isoform (eNOS), deregulates the muscle tissue blood flow creating an ischemic situation. The high levels of Ca(2+) in dystrophic muscles and the ischemic state of the muscle tissue would culminate in a positive feedback loop. While efforts continue toward optimizing cardiac and respiratory care of DMD patients, both Ca(2+) and NO in cardiac and respiratory muscle pathways have been shown to be important to the etiology of the disease. Understanding the mechanisms behind the fine regulation of Ca(2+) -NO may be important for a noninterventional and noninvasive supportive approach to treat DMD patients, improving the quality of life and natural history of DMD patients.

Utility of transmural myocardial strain profile for prediction of early left ventricular dysfunction in patients with Duchenne muscular dystrophy

Myocardial damage in Duchenne muscular dystrophy (DMD) has lethal outcomes, making early detection of myocardial changes in patients with DMD vital, because early treatment can help prevent the development of myocardial fibrosis. The aim of the present study was, therefore, to test the hypothesis that transmural strain profile (TMSP) analysis can predict future left ventricular (LV) dysfunction in patients with DMD with preserved ejection fraction. We studied 82 consecutive patients with DMD without LV wall motion abnormality, with an ejection fraction of 60 ± 5% (all ≥55%) and age 11 ± 3 years. Echocardiography was performed at baseline and 1 year of follow-up. TMSP in the posterior wall was evaluated from the mid-LV short-axis view. A normal TMSP pattern (1 peak in the endocardium, group 1) was seen in 44 patients, and TMSP with a notch (2 peaks in the endocardium, group 2) in the remaining 38 (46%). Wall motion abnormality in the posterior wall was observed in 16 patients (42%) in group 2 at 1 year of follow-up but in none of the patients in group 1 (42% vs 0%; p <0.001). Importantly, multivariate analysis showed that only TMSP with a notch (odds ratios 1.524, p <0.001) was an independent determinant of the presence of LV posterior wall motion abnormality at 1 year of follow-up. In conclusion, subclinical LV dysfunction can be detected by evaluation of TMSP in patients with DMD who do not have wall motion abnormalities by conventional echocardiography. TMSP with a notch proved effective for evaluating subtle early changes in patients with DMD and might be useful for predicting LV dysfunction.

Injection of vessel-derived stem cells prevents dilated cardiomyopathy and promotes angiogenesis and endogenous cardiac stem cell proliferation in mdx/utrn-/- but not aged mdx mouse models for duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy. DMD patients lack dystrophin protein and develop skeletal muscle pathology and dilated cardiomyopathy (DCM). Approximately 20% succumb to cardiac involvement. We hypothesized that mesoangioblast stem cells (aorta-derived mesoangioblasts [ADMs]) would restore dystrophin and alleviate or prevent DCM in animal models of DMD. ADMs can be induced to express cardiac markers, including Nkx2.5, cardiac tropomyosin, cardiac troponin I, and α-actinin, and adopt cardiomyocyte morphology. Transplantation of ADMs into the heart of mdx/utrn(-/-) mice prior to development of DCM prevented onset of cardiomyopathy, as measured by echocardiography, and resulted in significantly higher CD31 expression, consistent with new vessel formation. Dystrophin-positive cardiomyocytes and increased proliferation of endogenous Nestin(+) cardiac stem cells were detected in ADM-injected heart. Nestin(+) striated cells were also detected in four of five mdx/utrn(-/-) hearts injected with ADMs. In contrast, when ADMs were injected into the heart of aged mdx mice with advanced fibrosis, no functional improvement was detected by echocardiography. Instead, ADMs exacerbated some features of DCM. No dystrophin protein, increase in CD31 expression, or increase in Nestin(+) cell proliferation was detected following ADM injection in aged mdx heart. Dystrophin was observed following transplantation of ADMs into the hearts of young mdx mice, however, suggesting that pathology in aged mdx heart may alter the fate of donor stem cells. In summary, ADMs delay or prevent development of DCM in dystrophin-deficient heart, but timing of stem cell transplantation may be critical for achieving benefit with cell therapy in DMD cardiac muscle.

Focal but reversible diastolic sheet dysfunction reflects regional calcium mishandling in dystrophic mdx mouse hearts

Cardiac dysfunction is a primary cause of patient mortality in Duchenne muscular dystrophy, potentially related to elevated cytosolic calcium. However, the regional versus global functional consequences of cellular calcium mishandling have not been defined in the whole heart. Here we sought for the first time to elucidate potential regional dependencies between calcium mishandling and myocardial fiber/sheet function as a manifestation of dystrophin-deficient (mdx) cardiomyopathy. Isolated-perfused hearts from 16-mo-old mdx (N = 10) and wild-type (WT; N = 10) were arrested sequentially in diastole and systole for diffusion tensor MRI quantification of myocardial sheet architecture and function. When compared with WT hearts, mdx hearts exhibited normal systolic sheet architecture but a lower diastolic sheet angle magnitude (|β|) in the basal region. The regional diastolic sheet dysfunction was normalized by reducing perfusate calcium concentrations. Optical mapping of calcium transients in isolated hearts (3 mdx and 4 WT) revealed a stretch-inducible regional defect of intracellular calcium reuptake, reflected by a 25% increase of decay times (T(50)) and decay constants, at the base of mdx hearts. The basal region of mdx hearts also exhibited greater fibrosis than did the apex, which matched the regional sheet dysfunction. We conclude that myocardial diastolic sheet dysfunction is observed initially in basal segments along with calcium mishandling, ultimately culminating in increased fibrosis. The preservation of relatively normal calcium reuptake and diastolic/systolic sheet mechanics throughout the rest of the heart, together with the rapid reversibility of functional defects by reducing cytosolic calcium, points to the significance of regional mechanical factors in the progression of the disease.

Effects of angiotensin-converting enzyme inhibitors and/or beta blockers on the cardiomyopathy in Duchenne muscular dystrophy

Cardiomyopathy is a consequence of Duchenne muscular dystrophy (DMD). Suggested treatments include angiotensin-converting enzyme (ACE) inhibitors and/or β blockers (BBs), but few large series have been reported. We present 42 patients with DMD and cardiomyopathy treated with an ACE inhibitor or an ACE inhibitor plus a BB. Serial echocardiograms were recorded. Adequate ejection fractions (EFs) were obtained at initiation of therapy (EF <55%). ACE inhibitor dosage adjustments were made if a continued decrease in EF was noted. BB therapy was initiated when average heart rate on Holter monitoring exceeded 100 beats/min. Data were analyzed using paired t test and linear regression. Before ACE inhibition, patients (n = 22) demonstrated decreased EF over time (r(2) = 0.23). At ACE inhibitor therapy initiation, mean age was 14.1 ± 4.6 years and mean EF was 44.2 ± 6.8%. BB therapy was used in 24 of 42 patients. Mean age for the ACE inhibitor + BB group was 15.7 ± 3.9 years. The 2 groups showed significant improvement (p <0.0001 for ACE inhibitor and ACE inhibitor plus BB) compared to the pretherapy group. No significant differences were noted between treatment groups. Patients with DMD demonstrated a gradual decrease in myocardial function. Treatment with ACE inhibitor or ACE inhibitor plus BB resulted in significant improvement compared to pretherapy. No significant difference occurred in EF improvement between treatment groups. In conclusion, treatment with ACE inhibitor or ACE inhibitor plus BB can delay progression of cardiomyopathy.

Predicting scores for left ventricular dysfunction in Duchenne muscular dystrophy

BACKGROUND

The aim of this study was to predict left ventricular (LV) dysfunction and the timing to perform echocardiography in patients with Duchenne muscular dystrophy (DMD). We developed a scoring system using clinical parameters and examined its efficacy. It is indispensable to utilize echocardiogram for evaluating myocardial damage of DMD patients, but there is no established guideline for determining the clinical conditions which require echocardiographic examination.

METHODS

We retrospectively analyzed 86 patients with DMD who were treated in Kobe University Hospital from 2007 to 2009. The multiple logistic regression analysis on routine clinical data was performed to identify parameters that can find abnormal LV contraction, and to develop a weighted scoring system. Echocardiogram was performed as the gold standard for detecting LV dysfunction.

RESULTS

Four parameters were associated with abnormal LV contraction: (i) brain natriuretic peptide (BNP); (ii) creatine kinase; (iii) scoliosis; and (iv) body surface area. When BNP was used as the only predictor to evaluate LV systolic dysfunction, sensitivity and specificity were 36.4% and 92.1%, respectively. In contrast, abnormal LV contraction was detected in high accuracy (sensitivity: 95.5%; specificity: 68.3%) when we used a two-step scoring system in which BNP was combined with the other three factors, raising the sensitivity compared to using BNP levels as the single parameter (P= 0.008).

CONCLUSION

Our scoring system detects the early heart dysfunction of DMD patients, especially when BNP level is not elevated. This system is useful to determine the timing for echocardiographic examination and consulting cardiologists.

The effect of enalapril and carvedilol on left ventricular dysfunction in middle childhood and adolescent patients with muscular dystrophy

BACKGROUND AND OBJECTIVES

In Duchenne and Becker muscular dystrophies, cardiac function deteriorates with time resulting in heart failure which is often fatal. We prospectively evaluated the effect of enalapril and carvedilol on left ventricular (LV) dysfunction in middle childhood and adolescent patients with muscular dystrophy.

SUBJECTS AND METHODS

Twenty-three patients with LV dysfunction (22 with Duchenne muscular dystrophy, 1 with Becker muscular dystrophy) were enrolled. We prescribed enalapril (13 patients) or carvedilol (10 patients) randomly from July 2008 to August 2010 and followed up the patients until September 2011. The changes in LV function parameters before and after the treatment were evaluated by echocardiography.

RESULTS

The mean age at the start of treatment with enalapril or carvedilol was 12.6±3.7 years (median 13 years), and mean follow-up duration was 20.1±8.9 months. In the enalapril group, LV fractional shortening (FS) increased from 25.8±2.1 to 26.6±3.0 (p=0.241). In the carvedilol group, LV FS increased from 26.4±1.1 to 28.6±4.2 (p=0.110). In all 23 patients, LV FS significantly increased from 26.1±1.7 (before) to 27.6±3.7 (after treatment) (p<0.046). Indexed LV dimension at end diastole and LV end-diastolic volume decreased slightly, but without statistical significance by tri-plane volumetry. LV diastolic functional parameters were maintained during follow-up period.

CONCLUSION

Enalapril or carvedilol could improve LV systolic function in middle childhood and adolescent patients with muscular dystrophy without significant adverse effects.

Long-term systemic administration of unconjugated morpholino oligomers for therapeutic expression of dystrophin by exon skipping in skeletal muscle: implications for cardiac muscle integrity

Duchenne muscular dystrophy (DMD) is a lethal X-linked inherited disease caused by mutations in the dystrophin gene and consequent lack of dystrophin in the skeletal, cardiac, and smooth musculature and in the nervous system. Patients die during their mid-twenties because of severe muscle loss and life-threatening respiratory and cardiac complications. The splicing modulation approach mediated by antisense oligonucleotides can restore the production of a partially functional quasi-dystrophin in skeletal muscles. We recently showed that a chronic, 12-month treatment with phosphorodiamidate morpholino oligomers efficiently restored dystrophin in widespread skeletal muscles and led to normal locomotor activity indistinguishable from that of dystrophin-expressing C57 mice. However, no detectable dystrophin expression was observed in the hearts of treated mice. In the present study, histological analyses show a more severe cardiac pathology compared with untreated animals in the face of enhanced locomotor behavior. This observation implies that the increase in locomotor activity of treated mdx mice may have a paradoxical detrimental effect on the dystrophic heart. In the context of skeletal muscle-centric therapies for DMD, our data suggest that particular vigilance should be instigated to monitor emergence of accelerated cardiac dysfunction.

[A longitudinal cause-of-death analysis of patients with Duchenne muscular dystrophy]

Mechanical ventilation (MV) and cardiac protective therapy have improved the prognosis and quality of life of patients with Duchenne muscular dystrophy (DMD). To understand how these therapies have changed prognosis, we performed a cause-of-death analysis in DMD patients. Mean age at death before initiation of MV (January 1977-July 1984) was 18.9±4.1 years. After the introduction of MV, from August 1984 to December 1993 (1(st) term), it was 20.0±4.5 years, from January 1994 to December 2003 (2(nd) term), it was 25.2±4.6 years, and from January 2004 to December 2010 (3(rd) term), it was 31.1±5.4 years. Almost half of all deaths before MV were due to respiratory failure (RF). Because MV was performed by a tracheostomy in the initial stage, some patients were reluctant to use it, and as a result, RF accounted for 43% of deaths in the 1(st) term. Over time, patients started to accept non-invasive ventilation and home mechanical ventilation, which became available in the 1990s. Consequently, no DMD patients have died from RF since 2000. Respiratory physiotherapy and risk management became important tools, because many patients undergo decades of respiratory managements at home. Cardiac treatments for patients with DMD consisted mainly of diuretics and digitalis in the 1(st) term, angiotensin-converting enzyme inhibitors (ACEI) in the 2(nd) term, and a combination of ACEIs and beta blockers in the 3(rd) term. Compared to the 2(nd) term, the ratios of severe cardiac dysfunction (fractional shortening <10%, left ventricle diastolic dimension >75mm, plasma brain natriuretic peptide >1,000pg/ml) were reduced in the 3(rd) term. In the 3(rd) term, 14% of patients died from renal failure nevertheless their cardiac indices remained mildly abnormal or normal. We should pay enough attention for cardio-renal association.

Cardiac assessment of patients with late stage Duchenne muscular dystrophy

Background. Duchenne muscular dystrophy (DMD) patients used to die mainly from pulmonary problems. However, as advances in respiratory care increase life expectancy, mortality due to cardiomyopathy rises. Echocardiography remains the standard diagnostic modality for cardiomyopathy in DMD patients, but is hampered by scoliosis and poor echocardiographic acoustic windows in adult DMD patients. Multigated cardiac radionuclide ventriculography (MUGA) does not suffer from these limitations. N-terminal proBNP (NTproBNP) has shown to be a diagnostic factor for heart failure. We present our initial experience with plasma NT-proBNP measurement in the routine screening and diagnosis of cardiomyopathy in adult mechanically ventilated DMD patients.Methods. Retrospective study, 13 patients. Echocardiography classified left ventricular (LV) function as preserved or depressed. NT-proBNP was determined using immunoassay. LV ejection fraction (LVEF) was determined using MUGA.Results. Median (range) NT-proBNP was 73 (25 to 463) ng/l. Six patients had an NT-proBNP >125 ng/l. Seven patients showed an LVEF <45% on MUGA. DMD patients with depressed LV function (n=4) as assessed by echocardiography had significantly higher median NT-proBNP than those (n=9) with preserved LV function: 346 (266 to 463) ng/l versus 69 (25 to 257) ng/l (p=0.003). NT-proBNP significantly correlated with depressed LV function on echocardiogram and with LVEF determined by MUGA.Conclusion. Although image quality of MUGA is superior to echocardiography, the combination of echocardiography and NT-proBNP achieves similar results in the evaluation of left ventricular function and is less time consuming and burdensome for our patients. We advise to add NT-proBNP to echocardiography in the routine cardiac assessment of DMD patients. (Neth Heart J 2009;17:232-7.).

Cardiac assessment in duchenne and becker muscular dystrophies

Mutations in the dystrophin gene cause Duchenne and Becker muscular dystrophies. In addition to muscle disease, there nearly always is an associated cardiomyopathy in Duchenne or Becker muscular dystrophy. In these muscular dystrophies, the severity of cardiomyopathy and congestive heart failure may not parallel the severity of skeletal muscle disease. Loss of normal dystrophin function in the heart produces four-chamber dilation and reduction in left ventricular function that develop after the onset of muscle weakness. Arrhythmias affecting both atrial and ventricular rhythms occur and may be life threatening. The degree to which hypoventilation and pulmonary dysfunction are present also directly affect cardiac function in muscular dystrophy. Care guidelines recently were issued to outline surveillance and treatment strategies for the younger patient with Duchenne muscular dystrophy. Herein, we review those guidelines, and additionally, provide recommendations for monitoring and treating cardiac disease in the populations of advanced Duchenne and Becker muscular dystrophies.

Evaluation of the therapeutic utility of phosphodiesterase 5A inhibition in the mdx mouse model of duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a devastating and ultimately fatal disease characterized by progressive muscle wasting and weakness. DMD is caused by the absence of a functional dystrophin protein, which in turn leads to reduced expression and mislocalization of dystrophin-associated proteins including neuronal nitric oxide (NO) synthase mu (nNOSμ). Disruption of nNOSμ signaling results in muscle fatigue and unopposed sympathetic vasoconstriction during exercise, thereby increasing contraction-induced damage in dystrophin-deficient muscles. The loss of normal nNOSμ signaling during exercise is central to the vascular dysfunction proposed over 40 years ago to be an important pathogenic mechanism in DMD. Recent preclinical studies focused on circumventing defective nNOSμ signaling in dystrophic skeletal and cardiac muscle by inhibiting phosphodiesterase 5A (PDE5A) have shown promising results. This review addresses nNOS signaling in normal and dystrophin-deficient muscles and the potential of PDE5A inhibition as a therapeutic approach for the treatment of cardiovascular deficits in DMD.

Duchenne muscular dystrophy: survival by cardio-respiratory interventions

We describe survival in Duchenne dystrophy by invasive and noninvasive ventilation vs. untreated. Patients were untreated prior to 1984 (Group 1), underwent tracheotomy from 1984 until 1991 (Group 2), and were managed by noninvasive mechanical ventilation and cardioprotective medications subsequently (Group 3). Symptoms, vital capacity, and blood gases were monitored for all and spirometry, cough peak flows, carbon dioxide tension, and oximetry for Group 3. Sleep nasal ventilation was initiated for symptomatic hypoventilation. An oximeter and mechanical cough assistance were prescribed for maximum assisted cough peak flow <300 L/m. Patients used continuous noninvasive ventilation and mechanically assisted coughing as needed to maintain pulse oxyhemoglobin saturation ≥95%. Survival was compared by Kaplan-Meier analysis. The 56 of Group 1 died at 18.6±2.9, the 21 Group 2 at 28.1±8.3 years of age with three still alive, and the 88 using noninvasive ventilation had 50% survival to 39.6 years, p<0.001, respectively. We conclude that noninvasive mechanical ventilation and assisted coughing provided by specifically trained physicians and therapists, and cardioprotective medication can result in more favorable outcomes and better survival by comparison with invasive treatment.

Chronic systemic therapy with low-dose morpholino oligomers ameliorates the pathology and normalizes locomotor behavior in mdx mice

The administration of antisense oligonucleotides (AOs) to skip one or more exons in mutated forms of the DMD gene and so restore the reading frame of the transcript is one of the most promising approaches to treat Duchenne muscular dystrophy (DMD). At present, preclinical studies demonstrating the efficacy and safety of long-term AO administration have not been conducted. Furthermore, it is essential to determine the minimal effective dose and frequency of administration. In this study, two different low doses (LDs) of phosphorodiamidate morpholino oligomer (PMO) designed to skip the mutated exon 23 in the mdx dystrophic mouse were administered for up to 12 months. Mice treated for 50 weeks showed a substantial dose-related amelioration of the pathology, particularly in the diaphragm. Moreover, the generalized physical activity was profoundly enhanced compared to untreated mdx mice showing that widespread, albeit partial, dystrophin expression restores the normal activity in mdx mice. Our results show for the first time that a chronic long-term administration of LDs of unmodified PMO, equivalent to doses in use in DMD boys, is safe, significantly ameliorates the muscular dystrophic phenotype and improves the activity of dystrophin-deficient mice, thus encouraging the further clinical translation of this approach in humans.