Fumihiro Kiya

Effect of verapamil directly administered into A-V node artery on A-V junctional automaticity and A-V conduction in dogs.

Summary: We investigated the direct effects of verapamil, which was infused into the A-V node artery at two doses of 0.01 and 0.1 μg/kg/min on the A-V conduction and the A-V junctional automaticity in the dog with experimentally induced A-V junctional rhythm. Verapamil significantly prolonged the A-H interval, but not the H-V interval, in the His bundle electrogram during atrial pacing at a rate of 100 beats/min. Effective and functional refractory periods of the A-V node also were prolonged significantly by verapamil. On the other hand, verapamil showed less propensity to decrease the spontaneous A-V junctional rate and to prolong the A-V junctional recovery time after atrial overdrive at a rate of 100 beats/min for 60 s. These results indicate that suppressive effects of verapamil on the A-V junctional automaticity are much weaker when compared with that on the A-V conduction.

DEMONSTRATION OF DUAL AV NODAL PATHWAYS IN 8 PATIENTS

発作性上室性頻拍の機序の一つとして二重房室伝導経路(dual AV nodal Pathways)によるリエントリーが臨床的にも確認されている.われわれは発作性上室性頻拍の7例を含む計56例において,二重房室伝導経路の存在を検認した.方法はヒス束心電図および高位右房心電図記録下に心房期外刺激法を行ない房室結節部の有効および機能的不応期の測定,心房期外刺激の連結期(A1A2)の変化(5～10msec)に伴う房室伝導時間(A2H2およびH1H2)の変動などについて検討した.その結果, 56例中8例にA1A2に対するA2H2およびH1H2曲線にjumpが認められ,房室結節部に速伝導経路および遅伝導経路からなる機能的分離,すなわち二重房室伝導経路の存在が証明された.このjumpの大きさは基礎心周期によつても異なるが, 8例におけるjumpの最大値はA2H2が56～270msec, H1H2が44～260msecであつた.またアトロピン1mg静注後は速および遅伝導経路の有効ならびに機能的不応期はともに短縮した.心房期外刺激法で,発作性上室性頻拍の誘発されたのは発作性上室性頻拍の既往が明らかな2例のみであつた.心房連続ぺーシングでは8例全例に非典型的Wenckebach周期が認められた.また,通常の心電図で間歇性PR延長の所見が2例に認められた.