實驗的脚ブロック時の心室内興奮伝播に關する研究

概要

論文の詳細を見る
Studies on intraventricular conduction in the presence of bundle branch blocks by using direct leads have been carried out by the investigators such as Sodi-Pallares, Prinzmetal and Scher. In spite of the bulk of data, they are far from completeness in explaining the detailed mechanism of the modification in conduction which occurs in these conditions.It is essential to obtain the over-all picture of the mechanism of conduction in bundle branch blocks for the refinement of theoretical explanations of the ECG patterns of clinical bundle branch blocks.Such a knowledge should offer an important clue to the function and its peculiarity of the specialized conducting muscle fibers. Thus, conductions in the ventricular free walls as well as the interventricular septum in experimentally produced B. B. B. in the canine heart were investigated in this study.Three types of electrodes for direct leads were employed, i. e., one for multiple lead recordings, one for contiguous bipolar leads, and one for unipolar leads, all of which were specially designed for the purposes of this study.The electrodes which were provided with arrowheads were pierced through the cardiac muscle while protected with an injection needle; this technique and the design of the electrodes permitted to fix the electrodes at one site without risk of shift during the experiment.The locations of the electrodes were checked after each experimental animal was dead.To produce B. B. B. experimentally, a sickleshaped scalpel was introduced into the cardiac cavity through the ventricular free wall to incise the portion of the septal muscle close inferiorly to the bifurcation of His' bundle.R.B.B.B. was obtained by cutting at a relatively small area in the anterior portion of the right septal surface, while L.B.B.B. was produced by cutting from the extreme front to the back at a level of 1 cm below the aortic valve; this difference may be due to the difference in the anatomical structures of the two B.B.An eight-channel direct-writing electrocardiograph and a two-beam cathode ray oscilloscope were used for recording.The paper in the electrocardiograph was run with a speed of 150 cm/sec.; the photographic paper of a continuous recording unit to record the waves on the oscilloscope was run with a speed of 20 cm/sec. Such high speeds were mandatory to register minute differences in time accurately.The peak of the main deflection of the contiguous bipolar lead was accepted as the indicator of the arrival time of activation; in unipolar lead ECGs, the onset of the steepest portion of their downward deflection was used. The time was measured from the earliest QRS onest of the multiple simultaneous recordings. These two indicators coincided each other very well as Durrer's observations.Results Incontrast to the conduction in the non-blocked side which remains the same as before, the conduction in the blocked side exhibits drastic changes.A) R.B.B.B.1. Epicardial surface of the right ventricular free wall In R.B.B.B., the excitation started at the portion of the posterior wall adjoining the septum, then the portion of the anterior wall adjoining the septum, spread from posterior to anterior, from below upward, and ended at the basal portion of the antero-lateral wall, while in the normal, the conduction started at the central lower area of the anterior surface, and ended at the basal portion of the portero-lateral or lateral wall.2. Endocardial surface of the right ventricular free wall.In R.B.B.B., the excitation started at the area adjoining the septum of the posterior wall and ended at the basal portion of the antero-lateral wall, similarly to in the epicardial surface, while in the normal, the excitation started at the lower portion of the antero-lateral wall, and ended at the basal portion of the lateral wall.The time required for the excitation spread the entire areas of the endo-and epi-cardial surfaces was considerably prolonged after the blocking as compared with the time required in the normal excitation.The portion which excites earliest in the normal canine hearts varied and was either in the anterior wall or in the posterior wall; however, after the block was made, the posterior wall excited always earlier than the anterior wall.B) L.B.B.B.3. Epicardial surface of the left venticular free wall In L.B.B.B., the excitatory wave started at the area adjoinning the septum of either the anterior or posterior walls, ended at the basal portion of the lateral wall; the arrival times delayed proportionately to the distance from the septum, while in the normal, the excitatory wave started at the area adjoining the septum in the lower portion of the anterior wall of the apex, and ended at the basal portion of the lateral wall.4. Endocardial surface of the left ventricular free wall In L.B.B.B., similarly to in the epicardial surface, the wave started at the lower portion of the wall adjacent to the septum, and ended in a manner as surrounding the basal portion of the lateral wall, while in the normal, the excitation started at the basal portion of the anterior and posterior papillary muscles, spread to the apex a little later, then gradually progressed upward and ended at the antero-lateral wall or the posterolateral wall.In both the endocardium and epicardium, the time required for the completion of excitation was considerably prolonged as compared to the normal.5. Intramural lead ECG's in the left ventricular free wall In the anterior surface of the left ventricle adjoining the septum, the subepicardial side excited earlier than the subendocardial side in the reverse order of the normal, while in the lateral basal area, the excitation proceeded from the subendocardium to the subepicardium similarly to the normal.6. Transseptal activation As the septum receives the dual control of bilateral bundle branches in the normal condition, the excitation makes a double invasion from the bilateral endocardium interiorly towards the center of the septal mass; after a block was made, a considerable delay of conduction in the blocked side was noticed and therefore the conduction in this side must be made by the proper cardiac muscle.In the posterior upper area of the septum the conduction in the normal spreads from the left to the right through the whole thickness of the septum; no delay occurred after cutting the right bundle branch in this area. This portion must belong to the left ventricular muscle mass and be controlled by the branches of the left bundle branch, in accordance with Sodi-Pallares' statement.The fact that the posterior wall of the right ventricle excites, after blocking the right bundle branch, earlier than the anterior wall may possibly be expained by the influence of these branches of the left bundle branch which have the shortest access to the right ventricular muscle.In conclusion, from the above findings, the delayed and abnormal conduction in the blocked side was interpreted to indicate that the conduction was done by the proper cardiac muscle in the septum, and also in the free walls at least in the initial phase after the excitation arrived. The specialized conducting tissue does not play a major role in the conduction of the excitation in the blocked side free walls, if any, only the network of the Purkinje fibers is involved in the conduction.
社団法人日本循環器学会の論文
1959-08-20

實驗的脚ブロック時の心室内興奮伝播に關する研究

スポンサーリンク

概要

著者

関連論文

スポンサーリンク