First-in-Human Chronic Implant Experience of the Substernal Extravascular Implantable Cardioverter-Defibrillator

Ian Crozier, Haris Haqqani, Emily Kotschet, David Shaw, Anil Prabhu, Nicholas Roubos, Jeffrey Alison, Iain Melton, Russell Denman, Tina Lin, Aubrey Almeida, Bridget Portway, Robert Sawchuk, Amy Thompson, Lou Sherfesee, Samuel Liang, Linnea Lentz, Paul DeGroot, Alan Cheng, David O'Donnell

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Objectives: The aim of this study was to evaluate the safety and performance of an extravascular (EV) implantable cardioverter-defibrillator (ICD). Background: Limitations of existing transvenous and subcutaneous ICD systems include lead reliability and morbidity issues associated with ICD lead implantation in the vasculature or lack of pacing therapies (e.g., antitachycardia pacing) in subcutaneous systems. The EV defibrillator uses a novel substernal lead placement to address these limitations. Methods: This was a prospective, nonrandomized, chronic pilot study conducted at 4 centers in Australia and New Zealand. Participants were 21 patients referred for ICD implantation. Patients received EV ICD systems. Data collection included major systemic and procedural adverse events, defibrillation testing at implantation, and sensing and pacing thresholds. Results: Among 20 patients who underwent successful implantation, the median defibrillation threshold was 15 J, and 90% passed defibrillation testing with a ≥10-J safety margin. Mean R-wave amplitude was 3.4 ± 2.0 mV, mean ventricular fibrillation amplitude was 2.8 ± 1.7 mV, and pacing was successful in 95% at ≤10 V. There were no intraprocedural complications. Two patients have undergone elective chronic system removal since hospital discharge. In the 15 patients presently implanted, the systems are stable in long-term follow-up. Conclusions: This first-in-human evaluation of an EV ICD demonstrated the feasibility of substernal lead placement, defibrillation, and pacing with a chronically implanted system. There were no acute major complications, and pacing, defibrillation, and sensing performance at implantation were successful in most patients. (Extravascular ICD Pilot Study [EV ICD]; NCT03608670)

Original languageEnglish (US)
Pages (from-to)1525-1536
Number of pages12
JournalJACC: Clinical Electrophysiology
Issue number12
StatePublished - Nov 2020
Externally publishedYes


  • ICD
  • anterior mediastinum
  • defibrillation
  • extravascular
  • substernal

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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