Hereditary progressive cardiac conduction defect

Hereditary progressive cardiac conduction defect, also known as Lenègre-Lev disease or progressive cardiac conduction defect (PCCD), is a rare genetic disorder affecting the heart's electrical conduction system. The disease is characterized by progressive alteration of cardiac conduction through the His-Purkinje system, leading to widening of the QRS complex on electrocardiogram (ECG) with right or left bundle branch block and widening of the PR interval. Over time, the conduction defects worsen and may lead to complete atrioventricular (AV) block, which can cause syncope (fainting), bradycardia (abnormally slow heart rate), and in severe cases, sudden cardiac death due to ventricular standstill or ventricular fibrillation. The condition primarily affects the cardiac conduction system, with progressive fibrosis and sclerosis of the conduction tissue being the hallmark pathological finding. Patients may initially be asymptomatic, with conduction abnormalities detected incidentally on routine ECG. As the disease progresses, symptoms such as dizziness, fatigue, exercise intolerance, presyncope, and syncope may develop. The most well-characterized genetic form is caused by mutations in the SCN5A gene, which encodes the cardiac sodium channel Nav1.5. Other genes implicated include TRPM4, SCN1B, and LMNA. Some forms may also be associated with congenital heart defects or dilated cardiomyopathy. There is currently no curative treatment for hereditary progressive cardiac conduction defect. Management focuses on surveillance with regular ECG monitoring and clinical assessment to detect progression of conduction abnormalities. The primary therapeutic intervention is implantation of a permanent cardiac pacemaker when significant conduction block develops, particularly complete AV block or symptomatic bradycardia. Genetic counseling is recommended for affected families. First-degree relatives should undergo cardiac screening, including ECG evaluation, to identify presymptomatic individuals who may be at risk for sudden cardiac events.

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