Subcutaneous implantable defibrillators in young patients: arrhythmias, complications, and physical activity

Background: The safety of subcutaneous implantable cardioverter defibrillator (S-ICD) recipients who lead active lifestyles and engage in recreational sports is unknown. We aimed to evaluate the association between lifestyle and recreational sports and the occurrence of arrhythmia- and device-related complications, appropriate and inappropriate shocks in S-ICD recipients. Methods: We assessed a cohort of young-adult (15-65 years) S-ICD patients, evaluated their physical activity with IPAQ (International Physical Activity Questionnaire), and assessed the association between lifestyle and recreational sports on S-ICD safety and shocks. Results: We enrolled 602 S-ICD recipients (77% males; age, 46±14 years). According to the IPAQ, patients were categorized as inactive subjects (26.4%), moderately active subjects (45.2%), or highly active subjects (28.4%). Among moderately/highly active subjects, 163 (27.1%) were recreational athletes. During follow-up (47.3 [interquartile range, 27.0-67.6] months), 23 patients (3.8%) reached the safety end point of arrhythmia- or device-related complications, with moderately and highly active subjects showing in multivariate analysis similar incidence compared with inactive subjects (P=0.59 and P=0.83, respectively). Forty-four patients had 87 appropriate shocks. In multivariate analysis, moderately and highly active subjects showed a nonsignificantly lower incidence of appropriate shocks compared with inactive subjects (P=0.12 and P=0.11, respectively). Consistently, there was a nonsignificant lower incidence of appropriate shocks in athletes versus nonathletes (P=0.06). Thirty-nine patients had 46 inappropriate shocks. Moderately and highly active subjects had similar incidence of inappropriate shocks compared with inactive subjects (P=0.92 and P=0.88, respectively). Conclusions: Young S-ICD patients often lead active lifestyles and participate in sports. Higher activity levels were not associated with increased implantable cardioverter defibrillator-related complications or increased risk of implantable cardioverter defibrillator shocks.