Cardiomyopathy in neuromuscular disorders

Developing multidisciplinary clinics for neuromuscular care and research

Multidisciplinary care is considered the standard of care for both adult and pediatric neuromuscular disorders and has been associated with improved quality of life, resource utilization, and health outcomes. Multidisciplinary care is delivered in multidisciplinary clinics that coordinate care across multiple specialties by reducing travel burden and streamlining care. In addition, the multidisciplinary care setting facilitates the integration of clinical research, patient advocacy, and care innovation (e.g., telehealth). Yet, multidisciplinary care requires substantial commitment of staff time and resources. We calculated personnel costs in our ALS clinic in 2015 and found an average cost per patient visit of $580, of which only 45% was covered by insurance reimbursement. In this review, we will describe classic and emerging concepts in multidisciplinary care models for adult and pediatric neuromuscular disease. We will then explore the financial impact of multidisciplinary care with emphasis on sustainability and metrics to demonstrate quality and value. Muscle Nerve 56: 848-858, 2017.

Prospect of gene therapy for cardiomyopathy in hereditary muscular dystrophy

INTRODUCTION

Cardiac involvement is a common feature in muscular dystrophies. It presents as heart failure and/or arrhythmia. Traditionally, dystrophic cardiomyopathy is treated with symptom-relieving medications. Identification of disease-causing genes and investigation on pathogenic mechanisms have opened new opportunities to treat dystrophic cardiomyopathy with gene therapy. Replacing/repairing the mutated gene and/or targeting the pathogenic process/mechanisms using alternative genes may attenuate heart disease in muscular dystrophies.

AREAS COVERED

Duchenne muscular dystrophy is the most common muscular dystrophy. Duchenne cardiomyopathy has been the primary focus of ongoing dystrophic cardiomyopathy gene therapy studies. Here, we use Duchenne cardiomyopathy gene therapy to showcase recent developments and to outline the path forward. We also discuss gene therapy status for cardiomyopathy associated with limb-girdle and congenital muscular dystrophies, and myotonic dystrophy.

EXPERT OPINION

Gene therapy for dystrophic cardiomyopathy has taken a slow but steady path forward. Preclinical studies over the last decades have addressed many fundamental questions. Adeno-associated virus-mediated gene therapy has significantly improved the outcomes in rodent models of Duchenne and limb girdle muscular dystrophies. Validation of these encouraging results in large animal models will pave the way to future human trials.

Lessons learned from the Pediatric Cardiomyopathy Registry (PCMR) Study Group

Cardiomyopathy is a rare disorder of the heart muscle, affecting 1.13 cases per 100,000 children, from birth to 18 years of age. Cardiomyopathy is the leading cause of heart transplantation in children over the age of 1. The Pediatric Cardiomyopathy Registry funded in 1994 by the National Heart, Lung, and Blood Institute was established to examine the epidemiology of the disease in children below 18 years of age. More than 3500 children across the United States and Canada have been enrolled in the Pediatric Cardiomyopathy Registry, which has followed-up these patients until death, heart transplantation, or loss to follow-up. The Pediatric Cardiomyopathy Registry has provided the most in-depth illustration of this disease regarding its aetiology, clinical course, associated risk factors, and patient outcomes. Data from the registry have helped in guiding the clinical management of cardiomyopathy in children under 18 years of age; however, questions still remain regarding the most clinically effective diagnostic and treatment approaches for these patients. Future directions of the registry include the use of next-generation whole-exome sequencing and cardiac biomarkers to identify aetiology-specific treatments and improve diagnostic strategies. This article provides a brief synopsis of the work carried out by the Pediatric Cardiomyopathy Registry since its inception, including the current knowledge on the aetiologies, outcomes, and treatments of cardiomyopathy in children.

The pediatric cardiomyopathy registry and heart failure: key results from the first 15 years

Cardiomyopathy is a serious disorder of the heart muscle and, although rare, is a common cause of heart failure in children and the most common cause for heart transplantation in children older than 1 year of age. Funded by the National Heart Lung and Blood Institute since 1994, the Pediatric Cardiomyopathy Registry (PCMR) has followed more than 3500 North American children with cardiomyopathy. Early analyses determined estimates for the incidence of pediatric cardiomyopathy (1.13 cases per 100,000 children per year), risk factors for cardiomyopathy (age <1 year, male sex, black race, and living in New England as opposed to the central southwestern states), the prevalence of heart failure at diagnosis (6%-84% depending on cause), and 10-year survival (29%-94% depending on cause). More recent analyses explored cause-specific functional status, survival and transplant outcomes, and risk factors in greater detail. For many topics these analyses are based on the largest and best-documented samples of children with disease such as the muscular dystrophies, mitochondrial disorders, and Noonan syndrome. Data from the PCMR continue to provide valuable information that guides clinical management and the use of life-saving therapies, such as cardiac transplantation and approaches to treating heart failure, and prepares children, their families, and their caregivers to deal with this serious condition.

Cardiac manifestations of neuromuscular disorders in children

Cardiac abnormalities occur in association with many of the neuromuscular disorders that present in childhood. Genetic defects involving the cytoskeleton, nuclear membrane, and mitochondrial function have all been described in patients with skeletal myopathy and cardiac involvement. The most common classes of neuromuscular disorders with cardiac manifestations are the muscular dystrophies- Duchenne, Becker, limb-girdle and Emery Dreifuss. Friedreich Ataxia and myotonic dystrophy also have important cardiac involvement. The type and extent of cardiac manifestations are specific to the type of neuromuscular disorder. The most common cardiac findings include dilated or hypertrophic cardiomyopathy, atrioventricular conduction defects, atrial fibrillation and ventricular arrhythmias. Screening for cardiac involvement should be performed in all children with neuromuscular disorders that have the potential for cardiac involvement. This review discusses the cardiac findings associated with specific neuromuscular disorders and outlines the indications for evaluation and treatment.

Characteristics and outcomes of cardiomyopathy in children with Duchenne or Becker muscular dystrophy: a comparative study from the Pediatric Cardiomyopathy Registry

OBJECTIVE

The aim of this study was to determine in pediatric Duchenne (DMD) and Becker muscular dystrophy (BMD) or other dilated cardiomyopathies (ODCM) whether outcomes differ by diagnosis.

BACKGROUND

Children with dilated cardiomyopathy are treated as a single undifferentiated group.

METHODS

This cohort study of 128 children with DMD, 15 with BMD, and 312 with ODCM uses outcome measures of left ventricular (LV) size and function, death, heart transplant, and death or transplant.

RESULTS

At cardiomyopathy diagnosis, the DMD and BMD groups had similar mean ages (14.4 and 14.6 years), prevalence of congestive heart failure (CHF) (30% and 33%), and LV fractional shortening (FS) Z-scores (median, -5.2 for DMD and -6.7 for BMD). The BMD group had more severe mitral regurgitation (P = .05) and a higher mean LV end-diastolic dimension Z-score than the DMD group (2.9 +/- 1.5 vs 1.2 +/- 1.9, P = .002). Duchenne muscular dystrophy group survival was lower than in BMD or ODCM groups (P = .06) at 5 years (57%, 100%, and 71%, respectively). In BMD, 25% received cardiac transplants within 0.4 years of cardiomyopathy diagnosis. The combined DMD and BMD group had less LV dilation and a closer-to-normal LV FS at cardiomyopathy diagnosis than the ODCM group. After 2 years, LV dilation increased, and LV FS did not change in the combined DMD and BMD group; for ODCM patients, LV dilation did not progress, and LV FS improved.

CONCLUSIONS

Children with DMD and cardiomyopathy have a higher mortality. Becker muscular dystrophy has a high heart transplantation rate in the 5 years after diagnosis of cardiomyopathy. Serial echocardiography demonstrates a different disease course for DMD and BMD patients compared with ODCM patients.