His-Purkinje伝導能のoverdrive suppressionに関する臨床的研究

Overdrive Suppression of Conduction in the His-Purkinje System in Human

　高度ないし完全房室ブロック（AVB,HVブロック）の既往があり，検査時には1：1伝導（9例）あるいは第2度AVB（3例）であった症例を対象に，His-Purkinje（H-P）伝導能のoverdrive suppression of conduction（OSC）につき検討した．1：1房室伝導であった9症例中3例に，また第2度AVBであった3例中2例で心室ペーシング後にOSCが生じ，その程度はペーシング頻度が高いほど，また，長いほど著しかった．一方，心房ペーシング後にはOSCは生じなかった．リドカイン（L）投与前にOSCを生じた5症例中4例でL投与後にOSCの程度が増強し，L投与前にはOSCを生じなかった1例でL投与後にOSCを生じた．LではOSCを受けず，ベラパミルによりOSCを生じた稀な1例がみられた．心室ペーシングあるいはL負荷＋心室ペーシングによりH-P系の潜在性伝導障害を顕性化させる負荷試験は1：1房室伝導の症例では33％と低く，他の薬剤負荷による検討が望まれる．

The purpose of this study was to determine whether overdrive suppression of conduction (OSC). i.e., tran-sient worsening of conduction or development of atrioventricular block after cessation of rapid pacing. could be produced in patients with diseased His Purkin-je system. Atrial and ventricular pacing at a rate of 70 -160 beats/min and duration of 30-18Osec were conduct-ed in patients with 1:1 atrioventricular (AV) conduc-tion (n=9), 2:1 AV conduction (n=2) and 3:1 AV conduction (n=1) who had a history of 2° or 3° infra-Hisian block which required implantation of a perma-nent pacemaker. We found that OSC occured after rapid ventricular pacing but not after atrial pacing. OSC was related to the duration and cycle length of pacing. Lidocaine increased the degree and duration of OSC in Opts. In one patient. OSC was induced only following administration of lidocaine. On the other hand, verapamil increased the degree and duration of OSC in one patient in whom lidocaine did not affect the degree and duration of OSC. Our data suggest that 1) In some patients. rapid ventricular pacing could be used as a stress test for the diseased His-Purkinje system, 2) It is to be added that although a positive response is of diagnostic value, a negative response does not exclude disease in the His-Purkinje system.