Wolff Parkinson white pattern in Danon disease: When preexcitation is not what it seems

Area of Science:

• Cardiology
• Genetics
• Electrophysiology

Background:

• Danon disease is a rare X-linked dominant disorder affecting cardiac and skeletal muscle.
• It typically presents with severe hypertrophic cardiomyopathy (HCM) and Wolff-Parkinson-White (WPW) pre-excitation.
• The nature of the accessory pathway causing pre-excitation in Danon disease remains debated.

Observation:

• A teenager with Danon disease and preexcitation developed a first-degree AV block.
• This occurred without changes in QRS morphology, which is atypical for standard accessory pathways.

Findings:

• The observed clinical presentation favors the presence of fasciculoventricular pathways (FVP) over atrioventricular (AV) accessory pathways.
• This case challenges the conventional understanding of preexcitation in Danon disease.

Implications:

• Identifying FVP in Danon disease patients has significant clinical implications for management and prognosis.
• Absence of AV accessory pathways may reduce risks of sudden cardiac death (SCD) during atrial arrhythmias and reentrant AV tachycardia.