P2880Incidence and clinical relevance of oversensing due to extracardiac signals in subcutaneous implantable cardiac defibrillator (S-ICD)

Abstract

Abstract Background S-ICD is an ICD system completely extrathoracic, composed of a generator in a left infra-axillary position and a parasternal lead. Arrhythmia detection is done by analyzing extracardiac signals registered in a dipole that is several centimeters in length, larger than in a transvenous ICD. Hence, it could potentially be more susceptible to external interference (eg. myopotentials or electromagnetic noise). Purpose To assess real-world incidence and clinical relevance of oversensing due to extracardiac signals (OES) in S-ICD. Methods Retrospective review of medical reports and remote monitoring system in two Spanish hospitals. Events were assessed by EHRA-certified specialists in cardiac devices. Differences in patients with OES were sought by univariate analysis using parametric or non-parametric methods according to sample characteristics. Results 117 patients since October 2014 were analyzed. 88 (75,2%) men, age at implant 49,1±13,8 years. Implants were indicated mainly in primary prevention (72; 61,5%), due to ischemic cardiomyopathy (52; 44,4%), NYHA functional class I-II (107; 91,5%). 24 (20,5%) had intraventricular conduction disorders (9 right bundle branch, 2 left, 13 delayed intraventricular conduction). Electrodes implanted mostly left parasternal (107; 91,5%). On implant, gain ×1 in 90 (96,7% cases with data registered; 24 cases not registered), SmartPass activated in every device with such tool available. Patients were followed-up for 1,9±1,2 years (maximum 4,2). 4 (3,4%) received appropriate shocks, 10 (8,5%) inappropriate: 3 OES, 3 T-wave oversensing, 3 voltage decrease (leading to SmartPass deactivation), 1 lead dysfunction. In 8 cases OES was identified (incidence 3,7 /100 patients/year): in 3 (37,5%) cases inappropriate shocks were delivered. OES occurred 1,9 (interquartile range, IQR, 0,9–2,9) years after implant. No differences in OES were found depending on sex, indication, S-ICD or lead model, lead position, intraventricular conduction disorders, detection vector at implant, number of suitable vectors at screening, tachycardia detection rate or SmartPass automatic deactivation during follow-up In 5 cases, a cause for OES was identified: 4 myopotentials, 1 interference from electric engine. Cases were managed by changing sensing vector (3), increasing tachycardia detection rate (2), watchful waiting (2, OES source unidentified) or providing instructions to the patient (1). No OES recurrence after 0,8 years (IQR 0,6–1,1). Example of OES Conclusions S-ICD has an incidence of OES of 3,7 cases /100 patients/year. OES can be successfully managed with a conservative approach.