Is Lambert-Eaton myasthenic syndrome (LEMS) associated with non-ischemic cardiomyopathy?

Lambert-Eaton Myasthenic Syndrome and Non-Ischemic Cardiomyopathy

Based on current medical evidence, Lambert-Eaton myasthenic syndrome (LEMS) is not associated with non-ischemic cardiomyopathy. There is no documented relationship between these two conditions in the available medical literature.

Understanding LEMS

Lambert-Eaton myasthenic syndrome is an autoimmune disorder characterized by:

• Antibodies targeting presynaptic voltage-gated calcium channels (VGCC), particularly P/Q-type 1
• Decreased acetylcholine release at the neuromuscular junction
• Clinical presentation including:
  • Proximal muscle weakness that progresses craniocaudally (legs first)
  • Autonomic symptoms (dry mouth, constipation)
  • Hyporeflexia or areflexia
  • Weakness that improves with repeated effort or exercise 1, 2

LEMS occurs in two forms:

1. Paraneoplastic (P-LEMS): Associated with malignancy, most commonly small cell lung cancer (SCLC) in up to 60% of cases 2, 3
2. Non-paraneoplastic/autoimmune (NT-LEMS): Associated with other autoimmune disorders 2, 4

Cardiac Involvement in LEMS

The available evidence does not indicate any direct relationship between LEMS and non-ischemic cardiomyopathy:

• None of the major studies or guidelines on LEMS mention cardiac involvement or cardiomyopathy as a manifestation or complication 2, 3, 5, 6
• The pathophysiology of LEMS involves antibodies against P/Q-type VGCCs at the neuromuscular junction, not cardiac tissue 1
• Comprehensive reviews of non-ischemic cardiomyopathy etiologies do not list LEMS as a cause 7

Non-Ischemic Cardiomyopathy Etiologies

Non-ischemic cardiomyopathy has numerous established causes including:

• Toxins (alcohol, chemotherapeutic agents)
• Familial/genetic inheritance
• Infections
• Infiltrative disorders
• Autoimmune conditions
• Metabolic derangements
• Arrhythmias 7

While some autoimmune conditions can cause non-ischemic cardiomyopathy, LEMS is not documented among them. Conditions with established cardiac involvement include:

• Systemic lupus erythematosus
• Systemic sclerosis
• Rheumatoid arthritis
• Sarcoidosis 7

Clinical Implications

For patients with LEMS:

• Cardiac evaluation is not routinely indicated based solely on the LEMS diagnosis
• Focus should remain on:
  • Screening for underlying malignancy (especially SCLC)
  • Managing neuromuscular symptoms with 3,4-diaminopyridine
  • Appropriate immunosuppression for non-paraneoplastic cases 1, 3

Conclusion

The current medical literature does not support an association between Lambert-Eaton myasthenic syndrome and non-ischemic cardiomyopathy. Patients with LEMS should be monitored for their primary condition and any associated malignancies, but specific cardiac monitoring for non-ischemic cardiomyopathy is not indicated based on the LEMS diagnosis alone.