ウアバインの洞房, 房室伝導に及ぼす影響

実験的検討

抄録

The effect of ouabain on sinoatrial and atrioventricular conduction, and the time required to intoxication was studied in 10 dogs with intact autonomic state, 8 dogs with vagotomy, 4 dogs with sympathectomy and 5 dogs with autonomic blockade state (vagotomy+ sympathectomy). The sinoatrial conduction time was determinded by using the premature atrial stimulation method and was represented as antegrade plus retrograde conduction time (SACT_A+R). Ouabain (10μg/kg) was administrated intravenously at 10 minute intervals until toxic arrhythmias developed. At each time interval, SACT_A+R and His bundle EKG was recorded. In intact autonomic group, as the dose of ouabain was increased, SACT_A+R was prolonged and reached to the peak at 40-80% subtoxic dose. However, when the dose was further increased, the prolongation of SACT_A+R was decreased and the SACT_A+R shortened in some cases. In vagotomized group (P < 0.05) and autonomic blockade group (P < 0.025), the prolongation of SACT_A+R was less marked than in intact group. On the other hand, in sympathectomized group, the SACT_A+R was markedly prolonged (P < 0.005) and the prolongation remained unchanged until toxic dose was reached. We concluded that the prolongation of SACT_A+R following ouabain adminstration was mainly dependent on vagal nerve activity, while the later decrease of prolongation was dependent on sympathetic nerve activity.
The A-H time was prolonged as to the ouabain dose was increased. The prolongation of A-H time was most marked in sympathectomized group, while less marked in vagotomized group and autonomic blockade group than in intact group. The time required to ouabain intoxication tended to be longer in sympathectomized and autonomic blockade group.
These results indicate that the effect of ouabain on SACT_A+R, A-V conduction and ouabain intoxication was mainly dependent on autonomic influences. The consideration on autonomic state is necessary to evaluate the SACT and A-V conduction time in digitalized patients.