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Published on: February 28, 2012
Efficacy and Safety of an Extravascular Implantable Cardioverter-Defibrillator
Paul Friedman1, Francis Murgatroyd1, Lucas V A Boersma1
1From Mayo Clinic, Rochester (P.F.), and Medtronic, Mounds View (A.E.T., C.W., S.W.) - both in Minnesota; King's College Hospital, London (F.M.); the Cardiology Department, St. Antonius Hospital, Nieuwegein (L.V.A.B.), and Amsterdam University Medical Centers, Amsterdam (L.V.A.B., R.E.K.) - both in the Netherlands; London Health Sciences Centre, London, ON, Canada (J.M.); Austin Hospital, Heidelberg, VIC, Australia (D.O.); Northwestern University, Evanston, IL (B.P.K.); Centre Hospitalier Régional Universitaire de Tours-Hôpital Trousseau, Tours (N.C.), and Centre Hospitalier Universitaire de Rennes-Hôpital Pontchaillou, Rennes (C.L.) - both in France; Riverside Methodist Hospital, Columbus, OH (A.A.); Heart and Vascular Center, Semmelweis University, Budapest, Hungary (B.P.M.); the University of California, San Diego, La Jolla (U.M.B.-G.), and Sequoia Hospital, Redwood City (G.E.) - both in California; Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong, China (J.Y.S.C.); the Cardiology Unit, Cardiac Thoracic and Vascular Department, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy (M.B.); Hospital Universitario Reina Sofía, Cordoba, Spain (I.M.C.); Northwell Health, Manhasset, NY (L.M.E.); Baptist Health, Jacksonville, FL (V.S.); Odense Universitetshospital, Odense, Denmark (J.B.J.); Klinika Zaburzeń Rytmu Serca/Narodowy Instytut Kardiologii-Stefana Kardynała Wyszyńskiego, Warsaw, Poland (M.S.); Kepler University Hospital, Linz, Austria (C.S.); the Iowa Heart Center, West Des Moines (T.H.); the Cardiovascular Institute of the South, Houma, LA (R.A.); and Christchurch Hospital, Christchurch, New Zealand (I.C.).
Background:
The extravascular implantable cardioverter-defibrillator (ICD) has a single lead implanted substernally to enable pause-prevention pacing, antitachycardia pacing, and defibrillation energy similar to that of transvenous ICDs. The safety and efficacy of extravascular ICDs are not yet known.
Methods:
We conducted a prospective, single-group, nonrandomized, premarket global clinical study involving patients with a class I or IIa indication for an ICD, all of whom received an extravascular ICD system. The primary efficacy end point was successful defibrillation at implantation. The efficacy objective would be met if the lower boundary of the one-sided 97.5% confidence interval for the percentage of patients with successful defibrillation was greater than 88%. The primary safety end point was freedom from major system- or procedure-related complications at 6 months. The safety objective would be met if the lower boundary of the one-sided 97.5% confidence interval for the percentage of patients free from such complications was greater than 79%.
Results:
A total of 356 patients were enrolled, 316 of whom had an implantation attempt. Among the 302 patients in whom ventricular arrhythmia could be induced and who completed the defibrillation testing protocol, the percentage of patients with successful defibrillation was 98.7% (lower boundary of the one-sided 97.5% confidence interval [CI], 96.6%; P<0.001 for the comparison with the performance goal of 88%); 299 of 316 patients (94.6%) were discharged with a working ICD system. The Kaplan-Meier estimate of the percentage of patients free from major system- or procedure-related complications at 6 months was 92.6% (lower boundary of the one-sided 97.5% CI, 89.0%; P<0.001 for the comparison with the performance goal of 79%). No major intraprocedural complications were reported. At 6 months, 25 major complications were observed, in 23 of 316 patients (7.3%). The success rate of antitachycardia pacing, as assessed with generalized estimating equations, was 50.8% (95% CI, 23.3 to 77.8). A total of 29 patients received 118 inappropriate shocks for 81 arrhythmic episodes. Eight systems were explanted without extravascular ICD replacement over the 10.6-month mean follow-up period.
Conclusions:
In this prospective global study, we found that extravascular ICDs were implanted safely and were able to detect and terminate induced ventricular arrhythmias at the time of implantation. (Funded by Medtronic; ClinicalTrials.gov number, NCT04060680.).
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