Failure in executing the defibrillation threshold test after subcutaneous implantable cardioverter defibrillator implantation as a predictor of adverse clinical outcomes
M Abrantes De Figueiredo, D Marques, F Ferreira, A S Jacinto, H Santos, G Portugal, P Silva Cunha, A Lousinha, B Valente, M OliveiraAbstract
Introduction
Defibrillation threshold test (DFT) for a subcutaneous implantable cardioverter defibrillator (S-ICD) is a procedure performed after implantation to ensure the device can effectively treat a life-threatening ventricular arrhythmia and it’s highly recommended.
Purpose
To analyze the completion of the DFT after S-ICD implantation and its relation with clinically significant outcomes.
Methods
A retrospective analysis of all patients who underwent S-ICD implantation until November 2025 was conducted. Data on procedural aspects related to the DFT execution and patient follow-up regarding mortality and other electrophysiological significant events (ventricular arrhythmias, inappropriate therapy, loss of sensing vectors, oversensing or undersensing) was retrieved. Correlations between baseline population characteristics, clinical outcomes and absence of DFT execution were evaluated with chi-square analysis and independent samples t-test. Furthermore, time-to-event analysis was also performed.
Results
Between its inception and December 2025, 76 S-ICD implantations were performed with an absence of the DFT in 9.2% of the cases. In the patients where the DFT wasn’t conducted, it was mainly because of pre-procedural contraindications (low ejection fraction, apical thrombus and previous cardioembolic stroke), with only 1 case being because of non-sustained ventricular fibrillation. Comparative baseline population characteristics analysis showed no differences between mean age, underlying etiology or prevention strategy between DFT and non-DFT groups. Regarding clinical outcomes, the non-DFT showed a greater proportion of clinically significant events (p= 0.040), particularly global mortality (p = 0.015) and cardiovascular mortality (p = 0.004). Time-to-event analysis (Figure 1) showed an increase in overall mortality (log-rank test, p = 0.048) and cardiovascular mortality (log-rank test, p = 0.035) in the non-DFT group.
Conclusion
DFT is highly recommended after S-ICD and its absence because of pre-procedural contraindications may serve as a marker of adverse clinical outcomes, mainly greater mortality.FIgure 1