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Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 September 25, 2018 e323 CLINICAL STATEMENTS AND GUIDELINES

er or ICD implantation. There should be a high level of concern for those patients with muscular dystrophy who present with arrhythmia symptoms.S7.8-15 The current guideline focuses on VA and indications for implantation of an ICD. The indications for permanent pacemaker are discussed in another ACC/AHA/HRS guideline.S7.8-16

Recommendation-Specific Supportive Text

1.	 In general, the indications for an ICD in patients with muscular dystrophy should follow standard ICD recommendations for patients with NICM (see Section 7.2.1 on Secondary Prevention and Section 7.2.2 on Primary Prevention of SCD with NICM). A high index of suspicion for bundlebranch reentrant tachycardia is warranted in patients with myotonic dystrophy who exhibit wide QRS complex tachycardia or tachycardiarelated symptoms.S7.8-2 2.	 In patients with Emery-Dreifuss and limb-girdle type 1B muscular dystrophies associated with Lamin A/C mutations, SCD accounts for about one third of all deaths.S7.8-4 Observational studies show a significant rate of appropriate ICD therapy in patients with cardiac conduction disorders who are gene positive for Lamin A/C mutation even if LV function is preserved.S7.8-3,S7.8-5,S7.8-17 In an observational study in which 38% had isolated skeletal muscular involvement but included patients with conduction defects and other risk factors (including PR interval >240 ms, left bundle-branch block, NSVT, or bradycardia requiring a permanent pacemaker) life-threatening VAs were relatively common; with 52% of patients receiving appropriate ICD therapy including approximately 40% of those patients with an LVEF ≥45%.S7.8-3 A study of patients who had Lamin A/C mutation, in which approximately 21% had a skeletal muscular dystrophy phenotype, SCD and appropriate ICD therapy were associated with NSVT, LVEF <45%, male sex, and Lamin A/C nonmissense mutations.S7.8-4 These observational studies support the use of an ICD when a pacing indication is present and likely also when evidence of progressive cardiac involvement such as cardiac conduction defects, NSVT or reduced LVEF is present.S7.8-8

There is a paucity of data regarding the rare form of x-linked recessive Emery-Dreifuss muscular dystrophy (related to the Emerin gene mutation), but arrhythmias may be less frequent than for the Lamin A/C mutations.S7.8-15 3.	 Cardiac involvement can occur in a number of neuromuscular dystrophies (Table 9). To determine cardiac involvement, a 12-lead ECG and echocardiogram are important for the initial clinical assessment, independent of symptom status. In general, the more extensive the cardiac involvement, including evidence of distal conduction disease, ventricular dysfunction, and atrial arrhythmias, the more likely a VA will occur. The initial evaluation for myotonic dystrophy patients includes ambulatory monitoring. In asymptomatic patients, some experts advocate for annual follow-up during the concealed phase of the disease with an annual

Table 9.  Neuromuscular Disorders Associated With Heart Disease

Muscular Dystrophy Inheritance Gene/Protein

Affected Primary Cardiac

Pathology Frequency of Cardiac Involvement Causes of Death Associated With

Sudden Death?

Duchenne X-linked recessive Dystrophin NICM >90% Respiratory, HF Yes, uncertain etiology Becker X-linked recessive Dystrophin NICM 60%–75% HF, respiratory Yes, uncertain etiology Limb-girdle type 1B Autosomal dominant Lamin A/C Conduction system

disease and NICM >90% Sudden, HF Yes

Limb-girdle type 2C-2F Autosomal recessive Sarcoglycan NICM <25% Respiratory, HF Uncertain Limb-girdle type 2I Autosomal recessive Fukutin-related

protein NICM 20%–80% Respiratory, HF Uncertain

Myotonic type 1 Autosomal dominant CTG repeat

expansion Conduction system

disease and NICM 60%–80% Respiratory, sudden, HF 30% of deaths, uncertain bradycardia

versus tachycardia

Myotonic type 2 Autosomal dominant CCTG repeat

expansion Conduction system

disease 10%–25% Normal causes Reported

Emery-Dreifuss X-linked and autosomal dominant

or recessive Emerin, Lamin A/C Conduction system

disease and NICM >90% Sudden, HF Yes

Facioscapulohumeral Autosomal dominant D4Z4 repeat

contraction Possibly conduction

disease 5%–15% Normal causes, respiratory rarely Not reported

HF indicates heart failure; and NICM, nonischemic cardiomyopathy. Adapted with permission from Groh, et al.S7.8–15

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