Therapy From a Novel Substernal Lead: The ASD2 Study

Lucas V.A. Boersma, Béla Merkely, Petr Neuzil, Ian G. Crozier, Devender N. Akula, Liesbeth Timmers, Zbigniew Kalarus, Lou Sherfesee, Paul J. DeGroot, Amy E. Thompson, Daniel R. Lexcen, Bradley P. Knight

Research output: Contribution to journalArticle

5 Citations (Scopus)


Objectives: The ASD2 (Acute Extravascular Defibrillation, Pacing, and Electrogram) study evaluated the ability to adequately sense, pace, and defibrillate patients with a novel implantable cardioverter-defibrillator (ICD) lead implanted in the substernal space. Background: Subcutaneous ICDs are an alternative to a transvenous defibrillator system when transvenous implantation is not possible or desired. An alternative extravascular system placing a lead under the sternum has the potential to reduce defibrillation energy and the ability to deliver pacing therapies. Methods: An investigational lead was inserted into the substernal space via a minimally invasive subxiphoid access, and a cutaneous defibrillation patch or subcutaneous active can emulator was placed on the left mid-axillary line. Pacing thresholds and extracardiac stimulation were evaluated. Up to 2 episodes of ventricular fibrillation were induced to test defibrillation efficacy. Results: The substernal lead was implanted in 79 patients, with a median implantation time of 12.0 ± 9.0 min. Ventricular pacing was successful in at least 1 vector in 76 of 78 patients (97.4%), and 72 of 78 (92.3%) patients had capture in ≥1 vector with no extracardiac stimulation. A 30-J shock successfully terminated 104 of 128 episodes (81.3%) of ventricular fibrillation in 69 patients. There were 7 adverse events in 6 patients causally (n = 5) or possibly (n = 2) related to the ASD2 procedure. Conclusions: The ASD2 study demonstrated the ability to pace, sense, and defibrillate using a lead designed specifically for the substernal space.

Original languageEnglish
Pages (from-to)186-196
Number of pages11
JournalJACC: Clinical Electrophysiology
Issue number2
Publication statusPublished - Feb 2019



  • anterior mediastinum
  • defibrillation lead
  • extravascular
  • implantable cardioverter-defibrillator
  • substernal
  • tachyarrhythmia

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

Cite this

Boersma, L. V. A., Merkely, B., Neuzil, P., Crozier, I. G., Akula, D. N., Timmers, L., Kalarus, Z., Sherfesee, L., DeGroot, P. J., Thompson, A. E., Lexcen, D. R., & Knight, B. P. (2019). Therapy From a Novel Substernal Lead: The ASD2 Study. JACC: Clinical Electrophysiology, 5(2), 186-196.