SMART pass will prevent inappropriate operation of S-ICD

Abstract

Background: Compared to screening ECG before implantation of a subcutaneous implantable cardioverter-defibrillator (S-ICD), selectable vectors without T-wave oversensing increase after S-ICD implantation. Newer algorithms have recently become available to reduce T-wave oversensing, such as SMART pass (SP). With this function, more selectable vectors are identified after S-ICD implantation. However, this improvement in eligibility utilizing SP has not yet been well validated. We aimed to clarify S-ICD eligibility before and after S-ICD implantation with and without SP.

Methods: Participants comprised 34 patients implanted with an S-ICD at Okayama University Hospital and its affiliated hospitals between February 2016 and August 2017. A total of 102 S-ICD vectors were assessed for eligibility before and after S-ICD implantation, at rest and during exercise testing. Vector availability was evaluated in the presence and absence of SP after S-ICD implantation.

Results: Subcutaneous implantable cardioverter-defibrillator eligibility was significantly better after implantation even without SP than S-ICD screening before S-ICD implantation, both at rest (before 65.7% vs after 95.1%, P < 0.01) and during exercise (before 59.3% vs after 90.6%, P < 0.01). SP improved S-ICD eligibility during exercise (SP on 97.9% vs off 90.6%, P = 0.03). Multivariate analysis showed the prevalence of S-ICD eligibility increased significantly after S-ICD implantation compared to screening before implantation. SP further increased selectable vectors in multivariate analysis.

Conclusion: Available vectors increased significantly after S-ICD implantation compared to preoperative vectors as assessed by S-ICD screening ECG. T-wave oversensing during exercise has been an unresolved issue for S-ICD, but SP will help prevent inappropriate operation with S-ICD.

Keywords: SMART Pass; T‐wave oversensing; implantable cardioverter‐defibrillator; inappropriate shock; subcutaneous implantable cardioverter‐defibrillator.

Figure 1

Prevalence of selectable vectors before and after S‐ICD implantation. Selectable vectors are significantly increased after S‐ICD implantation both at rest (upper row) and during exercise testing (bottom row). SP improves the selectivity of vectors during exercise testing (right column)