Air entrapment as a cause of S-ICD inappropriate shocks.

Abstract

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is noninferior to the transvenous ICD concerning device-related complications or inappropriate shocks (IASs) in patients with an indication for defibrillator therapy and not in need of pacing. 1 Knops R.E. Olde Nordkamp L.R.A. Delnoy P.P.H.M. et al. Subcutaneous or transvenous defibrillator therapy. N Engl J Med. 2020; 383: 526-536 Crossref PubMed Scopus (149) Google Scholar The main causes of IAS in S-ICD recipients are T-wave oversensing, oversensing of ventricular tachycardia/ventricular fibrillation below the therapy zone, myopotentials, and low-amplitude signals. 2 Burke M.C. Aasbo J.D. El-Chami M.F. et al. 1-Year prospective evaluation of clinical outcomes and shocks. JACC Clin Electrophysiol. 2020; 6: 1537-1550 Crossref PubMed Scopus (15) Google Scholar ,3 Gold M.R. Lambiase P.D. El-Chami M.F. et al. Primary results from the Understanding Outcomes With the S-ICD in Primary Prevention Patients With Low Ejection Fraction (UNTOUCHED) trial. Circulation. 2021; 143: 7-17 Crossref PubMed Scopus (45) Google Scholar Subcutaneous air entrapment has recently been considered an underdiagnosed cause of early postimplant IAS, accounting for a part of oversensing of low-amplitude signals. 4 Chinitz J.S. Nadraus P. Darge A. Cacciabaudo J. Altman E.J. Inappropriate shocks within 24 hours after implantation of a subcutaneous defibrillator with a two-incision technique. J Innovations Card Rhythm Manag. 2016; 7: 2295-2298 Crossref Google Scholar ,5 Nishinarita R. Kishihara J. Matsuura G. et al. Early inappropriate shock in a subcutaneous cardiac defibrillator due to subcutaneous air. J Arrhythm. 2019; 35: 682-684 Crossref PubMed Scopus (2) Google Scholar Few data are available about the incidence, prevention, and management of postprocedural IAS due to subcutaneous air entrapment. We searched for case reports on IAS due to subcutaneous air entrapment published in PubMed, Google Scholar, Scopus, and EMBASE from 2012 to December 2021. For each of them, we analyzed the patients’ clinical characteristics, the S-ICD implantation technique, the timing and mode of IAS diagnosis, and the management of complications. A total 15 patients with S-ICD (66% male) with a median age of 55 years (interquartile range 17–75 years) were included. The indication for S-ICD implantation was primary prevention in 6 patients (40%) and secondary prevention in 9 patients (60%). A 3-incision technique was used in 7 patients (46.6%) and a 2-incision technique in 6 patients (40%). IAS was experienced on the same day of the procedure in 66.6% of cases and after discharging in 33.3%, always within 4 days of S-ICD implantation. Intraprocedural chest radiography was performed for checking the correct S-ICD system positioning in 40% of cases; in none of them, the presence of air entrapment has been reported. Subcutaneous air entrapment was diagnosed by postoperative chest radiography in 11 cases (73.3%), whereas the diagnosis was based on device interrogation and reproduction of the electrogram alterations by manipulation in 2 cases (13.3%). The most common localization of air entrapment was around the proximal electrode (46.6%, n = 7), followed by the distal electrode (26.6%, n = 4) and ICD generator (20.0%, n = 3); in 1 case, the precise localization was not investigated. Reprogramming the sensing vector and waiting the time necessary for oversensing resolution and air reabsorption were the most common strategies used to manage this complication (80.0%, n = 12). After 2 weeks, in 73.3% of patients, no further shocks occurred and chest radiography did not show residual air. Table 1 summarizes patients’ clinical characteristics, timing and management of IAS from 14 case reports/case series. On the basis of these data, the air entrapment should be considered an early complication (<24 hours) and an uncommon cause of IAS in S-ICD recipients, even if its epidemiology may be biased by misdiagnosing and underreporting. The relationship between air entrapment and S-ICD implantation technique is still controversial; however, a slightly increased incidence with the 3-incision technique was shown. The diagnosis should be made by performing a systematic approach including device interrogation, provocative maneuvers, and chest radiography. Reprogramming a different sensing vector or temporally switching off the S-ICD system, until air reabsorption, are part of the management of acute complications. Reassessing patients at 2 weeks with further device interrogation during provocative maneuvers may be useful. Value are presented as mean ± SD or n (%). DCM = dilatative cardiomyopathy; HCM = hypertrophic cardiomyopathy; IAS = inappropriate shock; ICD = implantable cardioverter-defibrillator; IHD = ischemic heart disease; PMs = physical maneuvers.