[The study of inhibiting heart rate and rapidly terminating atrial flutter of ibutilide on canine].
OBJECTIVE
To observe the electrophysiological effects of ibutilide on canine and to explore the potential mechanisms of ibutilide on terminating atrial flutter.


METHODS
Eighteen mongrel dogs were anesthetized and intubated. The heart was exposed through thoracotomy for electrodes implantation. The electrophysiologic variables (heart rate, the conduction of intraatrium and interatrium, the conduction ratio of isthmus, the effective refractory period) were measured in the absence or presence of ibutilide (10 minute infusion with 0.10 mg/kg ibutilide, 30 minutes later with a maintaining dose of 0.01 mg/min).


RESULTS
Ibutilide significant suppressed sinus atrial node function, the peak effect was observed at 20 - 30 min post drug infusion and heart rate returned to normal at 2 hours post infusion. Post ibutilide infusion, 1 canine developed sinus pause for 5 seconds and 2:1 atrioventricular conduction block was evidenced in another canine. The atrial, ventricular and pulmonary vein effective refractory periods were all significant prolonged (all P < 0.05) post ibutilide infusion. However, conduction of intraatrium, interatrium and isthmus remained unchanged post ibutilide infusion (all P > 0.05).


CONCLUSIONS
Ibutilide could suppress sinus atrial node and the atrioventricular node function. The mechanism of ibutilide on rapidly terminating atrial flutter might be related to the prolongation of the refractory periods which might then result in the reduction of the whole excitable gap of the reentrant circuit and induce proceed inability of reentrant wavefront.
Department of Geriatric Cardiology, Chinese PLA General Hospital, Beijing 100853, China. sunjianling2000@yahoo.com.cn
Jian-ling
JL
Sun
Xiao-ying
XY
Li
Ji-hong
JH
Guo
Peng
P
Liu
Ping
P
Zhang
Zhong
Z
Yi
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001282:Atrial Flutter / Q000188:drug therapy* / Q000503:physiopathology; D004285:Dogs; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D013449:Sulfonamides / Q000494:pharmacology*
D000889:Anti-Arrhythmia Agents; D013449:Sulfonamides; C067192:ibutilide