Defibrillation Testing in Patients Undergoing Replacement of the S-ICD Generator: Is There Still a Need?

Area of Science:

• Cardiology
• Biomedical Engineering
• Medical Device Technology

Background:

• Intraoperative defibrillation threshold (DFT) testing can be omitted for transvenous implantable cardioverter defibrillators (ICDs).
• Data regarding the necessity of DFT testing for subcutaneous-ICDs (S-ICDs), particularly during generator replacement, is lacking.

Purpose of the Study:

• To evaluate the outcome of intraoperative DFT during S-ICD generator replacement.
• To identify predictors of conversion failure during S-ICD generator replacement procedures.

Main Methods:

• Retrospective analysis of 112 consecutive patients undergoing S-ICD generator replacement and routine testing.
• Assessment of intraoperative DFT outcomes and correlation with patient characteristics, PRAETORIAN score, and high-voltage (HV) impedance.

Main Results:

• Successful DFT testing was achieved in 87.3% of patients during generator replacement without major adverse events.
• The PRAETORIAN score was generally lower, and HV impedance increased compared to initial implantation.
• Conversion failure risk increased with higher PRAETORIAN risk class; PRAETORIAN score and HV impedance were the most accurate predictors of failure.

Conclusions:

• Routine omission of DFT testing during S-ICD generator replacement is not advisable.
• New algorithms utilizing low impedance DFT measurements and the PRAETORIAN score can predict conversion failure.
• Patients with HV impedance <70 Ohms and PRAETORIAN score <90 have a very low risk of conversion failure. DFT testing is recommended for patients with PRAETORIAN score >150 during generator replacement.