Relation Between Instability of Ventricular Fibrillation Detection During Defibrillation Testing and Sudden Death in Future.

Background: Sudden death (SD) due to ventricular tachycardia or fibrillation (VT/VF) detection failure in patients with implantable cardioverter-defibrillators (ICDs) has been reported, despite its rarity. However, the relationship between VF detection instability during defibrillation testing (DT) and SD risk is unknown.

Objective: To investigate whether VF sensing status during DT predicts SD and VT/VF detection failure in patients with ICD/cardiac resynchronization therapy with defibrillator (CRT-D).

Methods: Consecutive 97 patients with ICD/CRT-D (Medtronic) who underwent DT were identified retrospectively. "Induced VF with detection failure" was defined as an episode with at least four ventricular sensed beats out of the VF detection interval in the most recent 18 sensed beats during DT. Patients were divided into two groups (detection-failure or appropriate-detection group) according to the presence of "induced VF with detection failure". We investigated whether "induced VF with detection failure" predicts SD and inappropriate treatment interruption for clinically occurring VT/VF.

Results: Induced VF with detection failure was found in 8 of the 97 (8%) patients. During a median follow-up of 9.9 years (interquartile range: 7.2-11.8 years), 9 SD occurred. Univariate analysis showed induced VF with detection failure was the only predictor for SD (hazard ratio, 7.94, 95% confidence interval, 1.96 - 32.1, p = 0.004). During the follow-up, clinical VT/VF occurred in 41 patients. SD with inappropriate treatment interruption for a clinical VT/VF was observed in only three patients, two of them were in the detection-failure group [detection-failure: 2/5 (40%), appropriate-detection: 1/36 (3%)].

Conclusion: The instability of VF detection in DT may predict the uncertainty of detection during clinically occurring VT/VF that causes SD.