Flunarizine significantly increased cycle length and terminated ventricular tachycardia induced by ouabain (P<=0.001), but had no significant effect on ischemia-induced ventricular tachycardia.
Does flunarizine alter the cycle length and terminate ventricular tachycardia differently based on the underlying arrhythmia mechanism in a canine model?
Flunarizine effectively terminates ventricular tachycardia caused by triggered activity (ouabain intoxication) but not abnormal automaticity (ischemia), suggesting utility in differentiating arrhythmia mechanisms in vivo.
p-value: p=<=0.001
The calcium antagonist flunarizine suppresses pathologic accumulation of calcium intracellularly without affecting the fast sodium or the slow calcium channel. To establish its value in differentiating between mechanisms of arrhythmias in the canine heart, the effect of flunarizine was investigated on ventricular tachycardia (VT) induced by ouabain intoxication or occurring 16-24 hours after occlusion of the left anterior descending coronary artery. Four groups of dogs were studied. Group 1 consisted of 13 animals with VT induced by ouabain intoxication (triggered-activity group). Group 2 included nine dogs in whom VT developed 16-24 hours after occlusion of the left anterior descending coronary artery (abnormal automaticity group). Group 3 included six dogs with normally conducted sinus beats, whereas group 4 consisted of six animals having a ventricular escape rhythm. With the exception of group 3, all dogs had surgically induced complete atrioventricular block. All animals were studied while conscious and without premedication. In groups 1 and 2, 2-3 mg/kg flunarizine was given intravenously after VT had persisted for at least 20 minutes. In groups 3 and 4, 2 mg/kg flunarizine was given after the rhythm was registered for 20 minutes. The cycle lengths of the different rhythms were compared before and after flunarizine. In group 1, flunarizine increased the cycle length of the VT from 300 +/- 30 to 410 +/- 50 msec (p less than or equal to 0.001). Termination of VT was seen in 11 out of 13 animals. In group 2, flunarizine resulted in a nonsignificant shortening of the RR interval from 450 +/- 60 to 440 +/- 60 msec. Persistent termination was observed in only one of nine dogs.(ABSTRACT TRUNCATED AT 250 WORDS)
Vos et al. (Mon,) conducted a other in Ventricular tachycardia (n=34). Flunarizine vs. Baseline (before flunarizine) was evaluated on Cycle length of the different rhythms before and after flunarizine (p=<=0.001). Flunarizine significantly increased cycle length and terminated ventricular tachycardia induced by ouabain (P<=0.001), but had no significant effect on ischemia-induced ventricular tachycardia.