Eligibility for subcutaneous implantable cardioverter defibrillators in the adult congenital heart disease population

BACKGROUND: Patients with adult congenital heart disease (ACHD) have an increased risk of arrhythmic and sudden cardiac death. The subcutaneous implantable cardioverter defibrillator (S-ICD) provides a potentially safer alternative to transvenous ICDs in ACHD. Suitability for S-ICD depends on the surface electrocardiogram (ECG), which is often abnormal in ACHD patients. This study investigates the proportion of ACHD patients who meet the screening criteria for S-ICD implantation. METHODS: A standard screening ECG was performed in 102 patients with complex ACHD (Tetralogy of Fallot, Fontan circulation, and transposition of the great arteries). This process was repeated postexercise for patients who also had an exercise test. RESULTS: Three quarters (75.4%) of ACHD patients meet screening criteria for an S-ICD with at least one suitable vector. The most common number of acceptable vectors in the eligible group was two (35% of total population). In only 12% of total population, all three vectors were suitable while only one vector was suitable in 28% of total population. The primary vector (equivalent of ECG lead III) was the most common suitable vector, found in 62% of participants who had appropriate sensing vectors. Twenty-five (24.5%) patients failed to meet the S-ICD screening criteria. Of these, 14 had repaired tetralogy of Fallot. A total of 92% of patients with a Fontan circulation met ECG screening criteria. Of those who had the protocol repeated following their cardiopulmonary exercise test (n = 14), only one additional patient failed to meet the eligibility criteria. CONCLUSIONS: A quarter of ACHD patients do not meet the eligibility criteria for the S-ICD. However, more than 90% of patients with a Fontan circulation are suitable for an S-ICD.