S‐ICD screening revisited: do passing vectors sometimes fail?

Abstract

Introduction Pre‐implant ECG screening is performed to ensure that S‐ICD recipients have at least one suitable sensing vector, yet cardiac over‐sensing remains the commonest cause of inappropriate shock therapy in the S‐ICD population. One explanation would be the presence of dynamic variations in ECG morphology that result in variations in vector eligibility. Methods Adult ICD patients had a 24‐h ambulatory ECG performed using a digital Holter positioned to record all three S‐ICD vectors. Using an S‐ICD simulator, automated screening was then performed at one‐minute intervals. In vectors with a mean vector score > 100 (the accepted value for a passing vector when screened on a single occasion), the percentage of all screening assessments that passed, eligible vector time (EVT), was calculated. EVT was compared statistically to QRS duration, corrected time to peak T (pTc) and mean vector score. Results Ambulatory monitoring was performed in 14 patients (mean age 63.7 ± 5.2 years, 71.4% male) with 42 vectors analysed. In 19 vectors the mean vector score was > 100. Within this “passing” cohort EVT varied between 42.7% and 100%. In 7/19 (37%) the EVT was <75%. A negative correlation was found between QRS duration and EVT (Pearson correlation ‐.60, p = .007). No correlation was found between EVT and mean vector score or pTc. Conclusion Vector eligibility is dynamic. When “passing” vectors are subjected to repeated screening, 37% are found to be ineligible, more than a quarter of the time. Further investigation is required to determine the clinical significance of these findings.

Role of deep learning methods in screening for subcutaneous implantable cardioverter defibrillator in heart failure

“…The concept of the potential varying of S‐ICD vectors eligibility over time was previously presented in a study by (Wiles et al, 2021). The study demonstrated that the vector score which determines S‐ICD eligibility is in fact dynamic in real‐life ICD population.…”

“…The concept of the potential varying of S-ICD vectors eligibility over time was previously presented in a study by (Wiles et al, 2021).…”

The subcutaneous implantable cardioverter-defibrillator should be reserved for niche indications

“…Up to 10% of patients can fail this screening process in all 3 vectors, and up to 37% of passing vectors may fail upon rescreening. 9 , 10 This severely restricts the eligible patient population. Furthermore, the proportion shrinks dramatically when looking at patients who benefit the most from an extravascular device.…”

Deep learning-based insights on T:R ratio behaviour during prolonged screening for S-ICD eligibility

“…The authors of this paper have previously introduced the concept of the potential varying of S-ICD vectors eligibility over time in a recently published study by Wiles et al which has demonstrated that the vector score which determines S-ICD eligibility is in fact dynamic in real-life ICD population. For that study, an S-ICD simulator provided by the device manufacturer was utilised for vector assessment [32]. The clinical significance for this dynamicity is not clear, but it sheds the light on the possibility that acquiring screening data over a much longer period than for conventional screening across the three S-ICD vectors can enable more reliable and descriptive screening of the vectors and can aid patient and vector selection in S-ICD candidates.…”