Evaluating the magnet response in deep subcutaneous implanted cardioverter defibrillator implants. Issue 2 (26th November 2022)

• Record Type: Journal Article
• Authors: Richman, Tuppence; Stanton, Tony; Fryer, Michael; Dayananda, Naresh; Tung, Matthew
• Is Part Of: Pacing and clinical electrophysiology. Volume 46:Issue 2(2023)
• Page Start: 93
• Page End: 99
• Publication Date: 2022-11-26
• Subjects: implantable cardiac devices -- magnet response -- subcutaneous implantable cardioverter defibrillators; Cardiac pacing -- Periodicals; Electrophysiology -- Periodicals; 617.4120645
• DOI: 10.1111/pace.14609
• Languages: English
• ISSNs: 0147-8389

Abstract

Abstract: Introduction: The manufacturer of subcutaneous implantable cardioverter defibrillators (S‐ICDs) acknowledges that 'deep implants' may fail to elicit a magnet response, however, does not define 'deep implant' or recommend a maximum implant depth. This study aims to systematically evaluate the effect of subcutaneous tissue depth and magnet types on evoked magnet response. Methods: Sunshine Coast University Hospital's S‐ICD cohort underwent magnet response evaluation; where bar and donut magnets were compared and the evoked magnet response was recorded in three separate zones, guided by a template. Ordinal regression (OR) models assessed the relationship between the evoked magnet response and tissue depth (TD), measured via post‐implant X‐Ray. The patient's ability to hear the magnet response audible tone was recorded. Results: Patients ( n = 39) with measurable TD ( n = 30) were analyzed. The bar magnet evoked a magnet response in all zones in 53% of patients, compared with 73% of patients with the donut magnet ( p = 0.18). The relationship between bar magnet response and TD showed the odds of an evoked magnet response decreased by 11% every 1 mm increase in TD (OR of 0.89, p < 0.01), whereas the donut magnet decreased by 16% per 1 mm (OR of 0.84, p < 0.01). Directly over the S‐ICD was the most effective in evoking magnet response with the bar (85% of patients), and off‐centre was most effective for the donut magnet (100%). BMI and Praetorian score were not significantly associated with magnet response. We found 23% of patients were unable to detect the audible tone. Conclusion: We observed a statistically significant association between TD and ability to evoke magnet response. The bar magnet was less reliable than the donut magnet for therapy inhibition in deep implants.