Fasciculoventricular and Atrioventricular Accessory Pathways in Patients with Danon Disease and Preexcitation: A Multicenter Experience

Abstract Background Studies have suggested that a fasciculoventricular pathway (FVP) may be the cause of preexcitation in patients with Danon disease, a rare X-linked dominant genetic disorder of hypertrophic cardiomyopathy. Objectives To describe the prevalence of ventricular preexcitation on resting 12-lead ECG in patients with Danon disease and the electrophysiology study (EPS) results of those with preexcitation. Methods Patients with confirmed Danon disease diagnosed with preexcitation (PR ≤ 120 ms, delta wave and QRS > 110 ms) on ECG were included from a multicenter registry. The incidence of arrhythmias, implantable cardiac defibrillator (ICD) procedures, ICD shocks and EPS results were collected. Results Thirteen of 40 (32.5%) patients with Danon disease were found to have preexcitation (mean age 17.3 years, 38% women). An EPS was performed in 9/13 (69%) patients demonstrating FVP only in 2/9 (22.2%), extranodal pathway without exclusion of FVP in 2/9 (22.2%), and both FVP and extranodal pathway in 5/9 (55.6%). Two patients had malignant AP properties. Over a median follow-up of 842 (IQR: 138 – 1678) days, 11 patients (85%) had ICD placement and 6 (46.1%) underwent heart transplantation. No patients required therapy for ventricular tachycardia and two (15%) patients had paroxysmal atrial fibrillation. Conclusion In a large multicenter cohort of patients with Danon disease, there was a high prevalence of FVP and extranodal pathways diagnosed on EPS in those with preexcitation. These findings suggest patients with preexcitation and Danon disease should undergo an EPS to assess for a FVP and a potentially malignant extranodal AP.