心房内刺戟伝導に関する実験的研究(第1報) : 蟇心房の刺戟伝導様式に就て(1)

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So far two different theories one opposing the other have been forwarded concerning stimulus conduction in atrium, one that of a conduction through the definite passage namely the specific heart muscle and the other diffusible conduction through the normal heart muscle.The purpose of the study here is to make a minute investigation into the formation of the stimulus conduction in the atrium.First the author has made a foundamental experiment of the study using toad's heart. The E.C.G. were taken simultaneously by means of the unipolar lead with the different electrodes placed on the atrial surface and the sinus venosus and the indifferent electrode on the left hind limb, and calculated the activation time at different points on the atrial surface. In obedience to these results of calculation, author concluded the formation of the stimulus conduction in the atrium.Authorities differ as to which one of those points on the intrinsic deflection in the E.C.G. should be taken as the representative point indicating the arrival of excitation wave.The author has had recourse to Prof. Maekawa's views discussed in his "Chain-Doublet Theory".According to his theory, it is defined that the time of arrival of activation to the muscle region underlying electrode to lead is represented by the point where the downward deflection following initial positive peak crosses the zero-line in clinical E.C.G. In the simultaneously recorded E.C.G. above mentioned, the author calculated the activation times at different points on the atrial surface, taking for the activation times to lead points what were expended between the initial point of the P wave led from the sinus venosus and where the intrinsic deflection of the P wave led from the atrial surface crosses the zero-line. The summery and conclusion of this study are as follows.1) When stimulus is conducted from sinus venosus to atrium it is first conducted in a diffusing manner around the border between the sinus venosus and the right atrium.2) Stimulus conduction into the left atrium is performed a little later than in the former case but it is conducted in the same diffusing manner around the border between the sinus venosus and the left atrium. Moreover, it should be noted that conduction in the latter case is carried out not through the right atrium but directly from the sinus venosus.3) Stimulus conduction in the atria seems generally to propagate in a radial manner travelling towards the atrioventricular border, the rate of time expended being in proportion to the distance. So I think that there is not specific pathway of stimulus conduction in the atrium. Both the atria, however, seem to undergo conduction independently of the other with the septum intervening them and each of them is seen to contract by its own accord.4) It is observed that the time of arrival of activation differs considerably as the points on the atrioventricular border where the conduction take place vary. This is thought to be due to the fact that the distance between these points and the sinus venosus anatomically differs.