Transient Pneumopericardium During Implantation of an Extravascular Implantable Cardioverter-Defibrillator.

BACKGROUND: Extravascular implantable cardioverter-defibrillators (EV-ICDs) use a substernal route to avoid intravascular lead placement, but substernal tunneling carries a risk of pericardial injury not encountered with transvenous systems. CASE SUMMARY: A 48-year-old man with ischemic cardiomyopathy (ejection fraction 14%) survived an out-of-hospital cardiac arrest due to monomorphic ventricular tachycardia at 240 beats/min. Cardiac magnetic resonance confirmed an extensive nonviable inferior scar. An EV-ICD was implanted for secondary prevention. Substernal tunneling was complicated by pericardial puncture and pneumopericardium. After lead repositioning, intraoperative defibrillation testing (DFT) failed twice, with subsequent sensing deterioration. Therapies were deactivated. Serial chest radiographs confirmed complete pneumopericardium resorption by day 30 with stable lead position. Repeat DFT at 5 weeks succeeded without reintervention. Device parameters remained normal at 1-year follow-up. DISCUSSION: Pneumopericardium is an under-recognized complication of substernal EV-ICD implantation that can transiently impair sensing and DFT. Conservative management with deferred re-testing illustrated a safe pathway, avoiding unnecessary system revisions.