Cardiovascular Implantable Electronic Devices -> Tachycardia Devices: -> Device Technology D-PO06 - Poster Session VI (ID 26) Poster


Background: Current subcutaneous ICD (S-ICD) devices deliver a maximum of 80J. Functional defibrillation testing is recommended at S-ICD implantation, and it is usually conducted by delivering a shock energy of 65J to ensure a safety defibrillation margin of at least 15J. Although high rates of successful conversion were reported at 65J, limited data exist on the defibrillation margin extent.
Objective: To evaluate the efficacy of conversion test performed at 40J (defibrillation margin ≥40J), and to identify factors potentially associated with test failure.
Methods: Ventricular fibrillation was induced and conversion test was performed by delivering a 40J shock. Success was defined as termination of VF by the first shock delivered in standard polarity. S-ICD system positioning was evaluated with the PRAETORIAN score using bidirectional chest X-rays.
Results: 361 consecutive patients underwent S-ICD implantation in 29 centers. Conversion test was not performed in 17 patients for clinical instability, ventricular fibrillation not inducible in 15 patients, 21 patients were excluded from the analysis for protocol deviation. The remaining 308 patients (81% male, 49±14 years, BMI 26±4kg/m2, ejection fraction 45±16%, inherited arrhythmic disorders 49%) underwent conversion test at 40J. The generator was positioned in an intermuscular pocket in 301 patients (98%). The PRAETORIAN score was <90 (low risk of conversion failure) in 293 (95%) patients. Overall, VF termination occurred in 259 (84%) patients with 40J. The BMI and the shock impedance were similar in patients with successful and unsuccessful termination (26±4kg/m2 versus 27±6kg/m2, p=0.126) and (64±16Ohm versus 68±18Ohm, p=0.192), respectively. The efficacy was comparable in patients with inherited arrhythmic disorders versus other conditions (82% versus 87%, p=0.182). PRAETORIAN score was not associated with shock efficacy at 40J (83% with score <90 versus 86% with score ≥90, p=0.801).
Conclusion: The safety margin was higher than 40J (conversion was effective at 40J) in 84% of patients who received optimally positioned S-ICD devices. Body habitus and shock impedance seemed not associated with test failure. Current 80J S-ICD devices seem to ensure consistently high defibrillation safety margin.