Appropriate and Inappropriate ICD Shocks in Children, Adolescents, and Adults with Congenital Heart Disease

Objectives: ICDs are implanted for primary and secondary prevention of sudden cardiac death (SCD) in pediatric patients and adults with congenital heart disease (CHD). However, besides life-saving appropriate ICD-shocks, inappropriate discharges are a common problem in pediatric patients and patients with CHD. Aim of the present study was to describe the prevalence of and to identify contributing factors for inappropriate ICD discharges in those patients.

Methods and patients: A single center retrospective chart-review of patients with an ICD was performed. All pediatric patients or adult patients with CHD in whom an ICD had been implanted at our center since 1995 were included.

Results: Data from 195 patients were analyzed. At implantation, mean age was 23 ± 14 (range: 0–58) years and mean body weight was 59 ± 26 (range: 5–136) kg. Indication was primary prophylaxis of SCD in 129 (66%) and secondary prophylaxis of SCD in 66 (34%) patients. Underlying disease was CHD in 94 (48%) individuals, cardiomyopathies in 61 (31%) patients and primary electrical disease in the remaining 40 (21%) patients. An extracardiac (EC) ICD-system was implanted in 42 (22%) individuals whereas an endocardial system was implanted in 153 (78%). Follow-up data from 194 patients were available; mean follow-up was 4.2 (0–21) years. Adequate ICD shocks occurred in 32 (16%) individuals, inadequate discharges were documented in 19 (10%) patients. Patients with EC-ICD experienced more adequate shocks than individuals with endocardial systems (29%, n = 42 vs. 13%, n = 152; p = 0.03). There was no difference in the prevalence of inadequate shocks between EC- and endocardial systems (11%, n = 42 vs. 9%, n = 152, n.s.). Rapidly conducted SVT/IART was the most common reason for inadequate shocks (82%), followed by lead dysfunction (17%) and external DC current (1%). Patients with CHD had significantly more inadequate ICD discharges than patients with cardiomyopathies (14 vs. 3%, n = 0.05).

Conclusion: As rapidly conducted SVT/IART was the most common reason for inadequate ICD shocks, rigorous treatment of these arrhythmias and proper ICD-programming are mandatory to protect patients from inadequate ICD discharges. As a subset of patients after CHD repair is prone to develop SVT/IART in the long-term course after cardiac surgery, those patients deserve special attention in with respect to ICD-programming and treatment of SVT/IART. EC-ICD systems were not inferior compared with endocardial systems.