Synthesized V7 QRS Amplitude and Oversensing Episodes in Patients With Subcutaneous Implantable Cardioverter-Defibrillators.

Background: Patients with subcutaneous implantable cardioverter-defibrillators (S-ICDs) experience an oversensing episode (OS) more frequently than those with transvenous ICDs. However, no established electrocardiography (ECG) parameters can accurately detect an OS. This study aimed to evaluate the incidence of an OS in real-world clinical practice and the association of synthesized 18-lead ECG (syn18-ECG) parameters with an OS.

Methods: We retrospectively included 21 consecutive patients who underwent S-ICD implantation and collected syn18-ECG parameters. We placed the generator in a deep posterior position and defined an OS as an inappropriate charging episode caused by cardiac or noncardiac signals. A SMART pass filter and two tachyarrhythmia zones were programed.

Results: The most frequent underlying heart disease was Brugada/J wave syndrome (n = 7). During a median follow-up period of 1188 days, an OS was observed in six patients (28.6%). The QRS amplitude in synthesized V7 lead (synV7) was significantly lower in the OS group than in the non-OS group (0.59 ± 0.17 vs. 0.91 ± 0.35 mV, p = 0.019). The optimal cutoff value of synV7 QRS amplitude was 0.61 mV, with a sensitivity of 80.0% and a specificity of 83.7% for predicting an OS. Univariate logistic analysis showed that a synV7 QRS amplitude of <0.61 mV was only associated with an OS (odd ratio, 20.0; 95% confidence interval, 1.66-241.72; p = 0.018).

Conclusions: In patients with S-ICDs, an OS was not a rare complication during long-term follow-up. A low synV7 QRS amplitude was associated with a high OS incidence.