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Neuromuscular Diseases: Cardiac Awareness

Learning Objectives

By the end of this rotation, you should be able to:

  1. Know which neuromuscular diseases have cardiac involvement
  2. Recognize cardiac symptoms in patients with known NMD
  3. Understand the importance of cardiac screening in these patients
  4. Know when to refer to cardiology

Key Concept

Many neuromuscular diseases (NMD) have associated cardiomyopathy and/or arrhythmias. Cardiac disease may be the main cause of morbidity/mortality in these patients.

Conditions with Significant Cardiac Involvement

Condition Cardiac Issues When to Screen
Duchenne muscular dystrophy (DMD) DCM (nearly universal by late teens), arrhythmias At diagnosis, then annually by age 10
Becker muscular dystrophy DCM (variable onset) At diagnosis, periodically
Myotonic dystrophy Conduction disease, arrhythmias, sudden death At diagnosis, annually
Friedreich ataxia HCM, arrhythmias At diagnosis, annually
Emery-Dreifuss MD Heart block, atrial arrhythmias Early and ongoing

Duchenne Muscular Dystrophy: Most Common

What Residents Should Know

  • Nearly all develop cardiomyopathy by late teens/early 20s
  • Cardiac symptoms may be masked by limited mobility
  • Standard heart failure symptoms may not be present - look for:
  • New fatigue
  • Decreased appetite
  • Orthopnea
  • Sleep disturbances
  • ACE inhibitors are often started prophylactically at age 10 or when early dysfunction appears

Screening Protocol (Simplified)

  • ECG and echo at diagnosis
  • Annual screening starting by age 10
  • More frequent if abnormalities detected

Myotonic Dystrophy: Arrhythmia Risk

What Residents Should Know

  • Conduction disease is common - may need pacemaker
  • At risk for sudden death from arrhythmias
  • Symptoms may include:
  • Palpitations
  • Syncope (concerning!)
  • Dizziness

Key Point

Any syncope in a patient with myotonic dystrophy needs urgent cardiology evaluation.

Friedreich Ataxia: HCM Pattern

  • Develops hypertrophic cardiomyopathy (unlike other NMDs which get DCM)
  • May also have arrhythmias
  • Screen with echo at diagnosis and regularly thereafter

When to Refer/Consult Cardiology

Immediate

  • Syncope or near-syncope
  • New heart failure symptoms
  • Significant arrhythmia on ECG

Soon

  • New diagnosis of at-risk neuromuscular disease
  • Declining function on echo
  • ECG abnormalities
  • For routine surveillance (should have established cardiology care)

Key Teaching Points for Residents

  1. DMD = expect cardiomyopathy - nearly universal
  2. Myotonic dystrophy = arrhythmia risk - syncope is concerning
  3. Symptoms may be masked by limited mobility - fatigue may be the only sign
  4. These patients need cardiac surveillance - should have cardiology involved
  5. Ask about cardiac symptoms when seeing NMD patients for other issues

Key Guidelines

2018 AHA Scientific Statement: Cardiovascular Health Supervision for Individuals Affected by Duchenne Muscular Dystrophy Circulation. 2018;137(12):e265-e270 PMID: 29269519

Board Pearls

Pearl: DMD = cardiomyopathy is nearly universal by late teens

Start cardiac screening at diagnosis, annual echo by age 10. ACE inhibitors are often started prophylactically.

Pearl: Myotonic dystrophy + syncope = urgent cardiology evaluation

Conduction disease is common and can cause sudden death. These patients may need pacemaker or ICD.

Pearl: Symptoms of heart failure may be masked by limited mobility

Look for subtle signs: increased fatigue, decreased appetite, orthopnea, sleep disturbances.