Elsevier

Heart Rhythm

Volume 9, Issue 11, November 2012, Pages 1890-1895
Heart Rhythm

Contemporary review
Arrhythmias in the muscular dystrophies

https://doi.org/10.1016/j.hrthm.2012.06.038Get rights and content

The muscular dystrophies are a group of inherited diseases affecting skeletal muscle that also affect cardiac muscle. Cardiac involvement occurs as a degenerative process with fibrosis and fatty replacement of the myocardium. Electrophysiologists are asked to participate in the care of muscular dystrophy patients because of the risk of atrial arrhythmias, conduction disease, bradycardia, ventricular arrhythmias, and sudden death. Duchenne, Becker, and limb-girdle types 2C−2F and 2I are muscular dystrophies in which the development of a dilated cardiomyopathy is common. Arrhythmias and conduction disease occur after the development of the dilated cardiomyopathy. Patients are considered for pacemakers or implantable cardioverter-defibrillators on the basis of guidelines used for nonischemic cardiomyopathies. Myotonic types 1 and 2, Emery-Dreifuss, limb-girdle type 1B, and facioscapulohumeral muscular dystrophies present with conduction disease and associated arrhythmias and variably with a dilated cardiomyopathy. In myotonic type 1, Emery-Dreifuss, and limb-girdle type 1B muscular dystrophies, conduction abnormalities are frequent and often require pacing. Recent studies support the use of prophylactic implantable cardioverter-defibrillators rather than pacemakers. In all the muscular dystrophies, respiratory muscle involvement can impact quality and quantity of life and needs to be factored in when considering a prophylactic device.

Introduction

The muscular dystrophies are a group of inherited skeletal muscle diseases. Most also have direct effects on cardiac muscle, with manifestations including heart failure, conduction disease, atrial and ventricular arrhythmias, and sudden death. With multidisciplinary care, patients are surviving to older ages, paradoxically leading to a higher risk of symptomatic cardiac involvement. Electrophysiologists are asked to be part of the team evaluating and treating patients because of the risk of arrhythmias and sudden death. An issue that arises is whether the patient's condition necessitates prophylactic pacemaker or implantable cardioverter-defibrillator (ICD) placement. In this review, the muscular dystrophies that more commonly manifest cardiac and arrhythmia involvement are evaluated and the literature assessing device use is examined. Table 1 summarizes relevant information useful in evaluating the muscular dystrophy patient.

Section snippets

Nomenclature, genetic basis, and cardiac pathology

A comprehensive review of the molecular pathophysiology of muscular dystrophies is beyond the scope of the article. However, knowledge of the relationship between the genetic basis of these diseases and the skeletal and cardiac muscle pathology can assist the clinician in understanding cardiac phenotypes.

Duchenne and Becker muscular dystrophies are X-linked recessive disorders in which a mutation is present in the dystrophin gene.1, 2 Duchenne is the most common muscular dystrophy. The

Noncardiac clinical considerations relevant to the electrophysiologist

Progressive skeletal muscle involvement can lead to loss of ambulation and later to respiratory failure. In Duchenne muscular dystrophy, the use of steroids, spinal surgery to treat scoliosis, and respiratory support has improved survival. Patients are often choosing invasive ventilation, and median survival is now 35 years.15 In myotonic dystrophy type 1, about one-half of the deaths are caused by respiratory failure at a median age of 55 years.16 The electrophysiologist evaluating the

Nonarrhythmia cardiac clinical considerations

Electrocardiograms (ECGs) are a common screening test and have prognostic significance in some of the muscular dystrophies. Echocardiograms are indicated in the majority of referred patients. Cardiac magnetic resonance imaging may allow earlier diagnosis. Cardiac magnetic resonance circumferential strain detects early involvement in Duchenne muscular dystrophy.19 The cardiac magnetic resonance signal-to-noise ratio variance, a measure of myocardial fibrosis heterogeneity, correlates with

Bradycardias, conduction disease, and the use of pacemakers

In muscular dystrophies in which the primary cardiac manifestation is a dilated cardiomyopathy including Duchenne, Becker, and limb-girdle types 2C−2F and 2I, the likelihood of conduction disease is proportional to the severity of ventricular dysfunction. The need for pacemakers in these muscular dystrophies is limited and described in single patient case reports.

In muscular dystrophies in which the primary cardiac manifestation is conduction disease including myotonic, Emery-Dreifuss, and

Atrial arrhythmias

Atrial arrhythmias including tachycardia, flutter, and fibrillation are observed in muscular dystrophies. In Duchenne, Becker, and limb-girdle types 2C−2F and 2I, atrial arrhythmias occur after the development of a dilated cardiomyopathy or as a consequence of respiratory failure and cor pulmonale.

In muscular dystrophies associated with conduction involvement, atrial arrhythmias are common. Up to 15% of a myotonic dystrophy type 1 cohort with a median age of 41 years developed atrial

Ventricular arrhythmias, sudden death, and the use of ICDs

Ventricular arrhythmias and sudden death occur in the muscular dystrophies. In Duchenne and Becker muscular dystrophy, ventricular premature beats and nonsustained ventricular tachycardia are observed primarily in patients who have a dilated cardiomyopathy. Similar findings are anticipated but less well studied in the limb-girdle muscular dystrophies types 2C−2F and 2I. Sustained ventricular arrhythmias are described. In Duchenne muscular dystrophy, sudden death occurs primarily in patients

Future directions and conclusions

In all the muscular dystrophies, a better understanding of the genetic causes and molecular pathogenesis opens a potential for future gene-based therapies. In the interim, there remains a need for studies to determine risk factors for arrhythmias and sudden death and to assess the efficacy of therapies. In these diseases, it is unlikely that randomized controlled trials will be done. Rather, clinical decisions will need to be based on nonrandomized registries and observational treatment trials

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      Ablate and pace (with biventricular or dual chamber pacemakers) may be an important option among patients with atypical AFl and poorly controlled ventricular rate.38 Muscular dystrophies encompass a wide spectrum of inherited disorders characterized by progressive involvement of the skeletal muscles, and most of the muscular dystrophies also affect the myocardium.43,44 Disorders associated with mutations of dystrophin and dystrophin-associated glycoproteins (eg, Duchenne and Becker muscular dystrophies), which connect the myocyte’s contractile proteins to the sarcolemma, are associated with progressive loss of myocardiocytes and fibrofatty replacement, leading to dilated cardiomyopathy; arrhythmias (both ventricular and supraventricular) occur late in the disease course.43

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    The research was supported by grants from the Muscular Dystrophy Association (Tucson, AZ).

    This manuscript was processed by a guest editor.

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