Indications For Implantable Cardioverter-Defibrillator Placement In Pediatric Patients With Hypertrophic Cardiomyopathy

Background: Sudden cardiac death (SCD) is the most common cause of death in children and adolescents with hypertrophic cardiomyopathy (HCM). Implantable cardio-defibrillators (ICD) are highly effective in preventing SCD, however, indications for ICD placement in the young is mainly guided from the adult experience. Methods: We conducted a retrospective single institution study of all children with HCM who had an ICD implanted from July 1999 through February 2016. Results: Thirty-three patients were identified. The mean age at ICD placement was 12.3±3 years with a mean follow up of 3.6±2.5 years. The mean maximal septal wall thickness Z score was 9.3± 2.9 and mean peak LV outflow tract gradient 17±12 mmHg. The median number of indications for ICD placement per patient was 3 (21%, 52%, 15% and 12% of the patients had 2, 3, 4 and 5 indications respectively). The most common indications were: severe HCM (Z-score ≥ + 6) (84%), abnormal blood pressure response to exercise (51%) and late gadolinium enhancement (LGE) (27%). Using the European Society of Cardiology HCM SCD risk calculator, the 5-year SCD risk was highest when the indication was ventricular tachycardia (VT). However, no patient with VT received ICD therapy (shock or anti tachycardia pacing (ATP)) during the study period. Fifteen patients received ICD therapy; 73% appropriately (73% a shock, 9% ATP and 18% both). Inappropriate shocks were delivered to 67% of the patients. One patient had slow rate VT (below the therapy zone) and one patient had ventricular fibrillation that did not elicit ICD therapy and required external defibrillation. The incidence rate ratios for appropriate ICD therapy were higher when the indication for the ICD placement was LGE (3.69), severe HCM (2.3) or compound heterozygosity (1.2) p <0.05. The majority of patients (>95%) were alive and free of transplant at 1 and 5 years after ICD placement. Conclusions: The risk stratification and selection of patients for ICD placement in the pediatric population is challenging. LGE, severe HCM and compound heterozygosity are associated with higher rate of appropriate ICD therapy. Optimal functioning of the ICD device in children and adolescents is difficult. The overall immediate survival and freedom from transplant is excellent.