Effects of procainamide on electrical activity in thoracic veins and atria in canine model of sustained atrial fibrillation.
Focal discharges (FDs) are present in thoracic veins during atrial fibrillation (AF). We hypothesize that procainamide exerts its anti-AF action by suppressing FDs in the thoracic veins. We studied six mongrel dogs (22-27 kg) with sustained (>6 h) AF induced by 47 +/- 20 days of chronic rapid LA appendage (LAA) or pulmonary vein (PV) pacing. Procainamide was infused intravenously until AF was terminated or a cumulative dose of 20 mg/kg was reached. High-resolution mapping during AF showed FDs in the vein of Marshall, PVs, and the LAA. Procainamide significantly (P < 0.05) reduced the frequency of these FDs and suppressed the interactions of wave fronts between PVs and LA. The cumulative dose of PA needed to terminate AF correlated negatively (r =-0.9, P < 0.05) with the baseline effective refractory period (ERP) of PV and positively (r = 0.8, P < 0.05) with the baseline maximum dominant frequency (DF) of AF. In four of five dogs, AF converted to atrial tachycardia originating from the PVs before termination. Attempts to reinduce sustained AF were unsuccessful in these five dogs. AF was resistant to procainamide in the sixth dog. In conclusion, procainamide reduced the rate of FDs in the thoracic veins and the LA and suppressed the interaction between PVs and LA. Second, FDs in the PV are more resistant to procainamide's action than FDs in the atria. Third, inherent PV ERP is important in determining the antifibrillatory efficacy of procainamide.
Chou
Chung-Chuan
CC
Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
Zhou
Shengmei
S
Miyauchi
Yasushi
Y
Pak
Hui-Nam
HN
Okuyama
Yuji
Y
Fishbein
Michael C
MC
Karagueuzian
Hrayr S
HS
Chen
Peng-Sheng
PS
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001281:Atrial Fibrillation / Q000503:physiopathology*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D006321:Heart / Q000187:drug effects / Q000503:physiopathology*; D006325:Heart Atria; D006339:Heart Rate; D007275:Injections, Intravenous; D011342:Procainamide / Q000008:administration & dosage / Q000494:pharmacology*; D012032:Refractory Period, Electrophysiological; D013610:Tachycardia / Q000503:physiopathology; D013909:Thorax / Q000098:blood supply*; D014680:Veins / Q000187:drug effects / Q000503:physiopathology
D000889:Anti-Arrhythmia Agents; D011342:Procainamide