Effects of dantrolene sodium on occlusion and reperfusion arrhythmias in the canine heart

The effects of dantrolene sodium on occlusion and reperfusion ventricular arrhythmias (VA) were studied in a canine model. Transient ischemia was induced by a 10 min occlusion period of the left anterior descending coronary artery in 27 conrol dogs and 32 dogs pretreated with dantrolene sodium (2.5 mg/kg). In the control group, 14 (52%) dogs experienced VA during occlusion. Five of these had ventricular fibrillation, 3 of which were fatal. Eight of 24 control dogs which reached reperfusion experienced ventricular fibrillation during the first 30 sec of reperfusion. Dantrolene sodium did not lower the frequency of VA during occlusion 22/32 (69%). Moreover, the incidence of fatal ventricular fibillation during occlusion was significantly (p<0.025) higher in the drug treated-group (12/32; 37.5%) than in the control group (3/27; 11%). Dantrolene sodium also significantly reduced the time that lasted from the commencement of occlusion to the appearance of ventricular fibrillation (240 ± 1 sec versus 166 ± 9 seconds, control and drug group, respectively p<0.05) without significantly altering either heart rate of blood pressure (169 ± 4 b.p.m., and 170 ± b.p.m.; 101 ± 10 mmHg and 104 ± 9 mmHg, before and after dantrolene sodium, respectively). These results indicate that dantrolene sodium might have an arrhythmogenic effect in the ischemic canine heart.