Acute defibrillation performance of a novel, non-transvenous shock pathway in adult ICD indicated patients.
OBJECTIVE
The purpose of this study was to evaluate the efficacy of a totally subcutaneous, anteroposterior defibrillation shock pathway using a long time-constant shock waveform that emulates a proposed device having approximately twice the capacitance and thus twice the available energy of traditional transvenous devices.


BACKGROUND
A non-transvenous defibrillation system potentially offers advantages over a transvenous system including simplification of the implant procedure and reduction of the impact of device complications by eliminating the need to place a lead within the heart. Previous non-transvenous defibrillation efficacy studies have been reported using anterolateral and anterior-anterior shock vectors. An external anteroposterior shock vector has demonstrated superior efficacy compared to anterolateral shock vectors but a prospective study on an anteroposterior shock vector with implanted electrodes has not been previously reported.


METHODS
The non-transvenous shock vector consisted of an anterior low pectorally-placed active can emulator electrode and a posterior subcutaneous coil electrode. The shock waveform was a biphasic with 50% tilt per phase and a time constant of decay of 12 ms. Defibrillation efficacy was characterized using a step-down defibrillation threshold protocol (35 J, 25 J, 15 J).


RESULTS
A total of 33 patients with standard ICD indications were enrolled in the study with 32 fully completing the protocol. The patient population was 69% male, with a mean age of 59 +/- 12 years. Mean ejection fraction was 27 +/- 12%. Of the 32 patients tested, 26 patients (81%) were successfully defibrillated at 35 J or less, 18 patients were defibrillated at 25 J or less and 9 patients were successfully defibrillated at 15 J.


CONCLUSIONS
Defibrillation using a long time-constant waveform delivered through an anteroposterior non-transvenous pathway including a pectoral active can emulator electrode and a posterior subcutaneous coil electrode is feasible with over 80% of patients defibrillated successfully using 35 J or less.
Harper Hospital, Detroit, Michigan, USA. rlieberm@dmc.org
Randy
R
Lieberman
William J
WJ
Havel
Eric
E
Rashba
Paul J
PJ
DeGroot
Kurt
K
Stromberg
Stephen R
SR
Shorofsky
D000208:Acute Disease; D000367:Age Factors; D016757:Death, Sudden, Cardiac; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods; D004566:Electrodes; D005260:Female; D006352:Heart Ventricles / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013318:Stroke Volume; D014693:Ventricular Fibrillation / Q000401:mortality / Q000628:therapy*