Multistage electrotherapy delivered through chronically-implanted leads terminates atrial fibrillation with lower energy than a single biphasic shock.
OBJECTIVE
The goal of this study was to develop a low-energy, implantable device-based multistage electrotherapy (MSE) to terminate atrial fibrillation (AF).


BACKGROUND
Previous attempts to perform cardioversion of AF by using an implantable device were limited by the pain caused by use of a high-energy single biphasic shock (BPS).


METHODS
Transvenous leads were implanted into the right atrium (RA), coronary sinus, and left pulmonary artery of 14 dogs. Self-sustaining AF was induced by 6 ± 2 weeks of high-rate RA pacing. Atrial defibrillation thresholds of standard versus experimental electrotherapies were measured in vivo and studied by using optical imaging in vitro.


RESULTS
The mean AF cycle length (CL) in vivo was 112 ± 21 ms (534 beats/min). The impedances of the RA-left pulmonary artery and RA-coronary sinus shock vectors were similar (121 ± 11 Ω vs. 126 ± 9 Ω; p = 0.27). BPS required 1.48 ± 0.91 J (165 ± 34 V) to terminate AF. In contrast, MSE terminated AF with significantly less energy (0.16 ± 0.16 J; p < 0.001) and significantly lower peak voltage (31.1 ± 19.3 V; p < 0.001). In vitro optical imaging studies found that AF was maintained by localized foci originating from pulmonary vein-left atrium interfaces. MSE Stage 1 shocks temporarily disrupted localized foci; MSE Stage 2 entrainment shocks continued to silence the localized foci driving AF; and MSE Stage 3 pacing stimuli enabled consistent RA-left atrium activation until sinus rhythm was restored.


CONCLUSIONS
Low-energy MSE significantly reduced the atrial defibrillation thresholds compared with BPS in a canine model of AF. MSE may enable painless, device-based AF therapy.
Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, Missouri.
Ajit H
AH
Janardhan
Department of Biomedical Engineering, Washington University, St. Louis, Missouri.
Sarah R
SR
Gutbrod
Department of Biomedical Engineering, Washington University, St. Louis, Missouri.
Wenwen
W
Li
Department of Biomedical Engineering, Washington University, St. Louis, Missouri.
Di
D
Lang
Department of Biomedical Engineering, Washington University, St. Louis, Missouri; Department of Surgery, Cardiothoracic Division, Washington University School of Medicine, St. Louis, Missouri.
Richard B
RB
Schuessler
Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, Missouri; Department of Biomedical Engineering, Washington University, St. Louis, Missouri. Electronic address: igor@wustl.edu.
Igor R
IR
Efimov
D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000628:therapy*; D006328:Cardiac Catheterization; D004195:Disease Models, Animal; D004285:Dogs; D004554:Electric Countershock / Q000379:methods*; D004599:Electric Stimulation Therapy / Q000295:instrumentation*; D004562:Electrocardiography; D004567:Electrodes, Implanted; D006325:Heart Atria / Q000503:physiopathology*
ASET; BPS; CS; DFT; HRP; LA; LPA; MSE; OAP; PV; RA; RAA; VSET; atrial fibrillation; atrial shock excitation threshold; cardioversion; coronary sinus; defibrillation; defibrillation threshold; high-rate pacing; left atrium; left pulmonary artery; low energy; multistage electrotherapy; optical action potential; pulmonary vein; right atrial appendage; right atrium; single biphasic shock; ventricular shock excitation threshold