What are the abnormal cardiac conduction (heart conduction) syndromes that can cause sudden cardiac death?

From the Guidelines

Abnormal conduction syndromes that can cause sudden cardiac death include Wolff-Parkinson-White syndrome, Brugada syndrome, Long QT syndrome, Short QT syndrome, Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT), Progressive Cardiac Conduction Disease (PCCD), and hypertrophic cardiomyopathy (HCM) with abnormal conduction properties. These conditions disrupt the heart's normal electrical pathways, potentially triggering fatal arrhythmias.

Key Conditions

• Wolff-Parkinson-White syndrome involves an accessory pathway that bypasses the AV node, with a risk of sudden cardiac death (SCD) ranging from 0.15 to 0.39% over 3- to 22-year follow-up 1.
• Brugada syndrome affects sodium channels in ventricular cells, increasing the risk of SCD.
• Long and Short QT syndromes involve abnormal ventricular repolarization due to ion channel dysfunction, which can lead to SCD.
• CPVT causes exercise-induced ventricular arrhythmias due to calcium handling abnormalities.
• PCCD features progressive conduction system degeneration, increasing the risk of SCD.
• HCM with abnormal conduction properties, such as those seen in patients with myotonic dystrophy Type 1 or LMNA gene mutations, can also lead to SCD 1.

Management and Prevention

Management typically includes risk stratification, medication (beta-blockers, sodium channel blockers, or potassium channel blockers depending on the syndrome), lifestyle modifications, and implantable cardioverter-defibrillators for high-risk patients. Early identification through ECG screening and genetic testing is crucial, as many of these conditions have genetic components and may remain asymptomatic until a catastrophic event occurs. For patients with HCM, risk stratification is essential to identify those at high risk of SCD, and management may include medication, lifestyle modifications, and implantable cardioverter-defibrillators 1. In patients with NICM and AV conduction abnormalities, initial implantation of an ICD with appropriate pacing capabilities is recommended, particularly in the presence of accompanying AV block 1.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Abnormal Conduction Syndromes

The following abnormal conduction syndromes can cause sudden cardiac death:

• Long QT syndrome 2
• Brugada syndrome 2, 3, 4, 5
• Hypertrophic cardiomyopathy 2
• Arrhythmogenic right ventricular cardiomyopathy 2
• Wolff-Parkinson-White syndrome 6, 3, 4, 5

Characteristics of Each Syndrome

Each of these syndromes has distinct characteristics, including:

• Long QT syndrome: often the first manifestation is sudden death, and patients with an episode of syncope while on beta-blockade should be offered an implantable cardioverter-defibrillator (ICD) 2
• Brugada syndrome: ICDs are often the most effective treatment of primary and secondary prevention of cardiac arrest, and risk stratification is crucial in identifying those at greatest risk 2
• Wolff-Parkinson-White syndrome: can result in cardiac arrhythmias, and sudden cardiac death can occur in patients with mild or unrecognized structural abnormality 6

Coexistence of Syndromes

In some cases, these syndromes can coexist, posing management challenges, such as:

• Coexistent Brugada syndrome and Wolff-Parkinson-White syndrome: requires careful consideration of treatment approach and timing of ventricular stimulation after accessory pathway ablation 3, 4, 5