Novel SCN5A mutation in amiodarone-responsive multifocal ventricular ectopy-associated cardiomyopathy

Area of Science:

• Cardiovascular Genetics
• Molecular Cardiology
• Ion Channel Physiology

Background:

• Mutations in SCN5A, encoding the cardiac sodium channel NaV1.5, are linked to arrhythmias and conduction defects.
• Recent studies associate SCN5A mutations with heart failure and diverse arrhythmias.

Observation:

• A novel de novo SCN5A mutation (NaV1.5-R225P) was identified in a boy with prenatal arrhythmia, impaired cardiac contractility, and multifocal ventricular ectopy.
• The ectopy was suppressed by amiodarone, indicating a potential therapeutic response.

Findings:

• The NaV1.5-R225P mutation caused significant abnormalities in channel activation and inactivation, leading to aberrant sodium influx.
• Increased persistent sodium current and altered voltage dependence of activation were observed, similar to other SCN5A voltage sensor mutations.
• Amiodarone treatment stabilized channel inactivation and suppressed persistent sodium current.

Implications:

• This study elucidates the functional consequences and pharmacologic response of a novel SCN5A mutation linked to arrhythmia-associated cardiomyopathy.
• Abnormal voltage dependence of activation appears to be a common biophysical mechanism underlying SCN5A voltage sensor mutation-related syndromes.
• Understanding these mechanisms may guide therapeutic strategies for related cardiac conditions.