Abstract
We have noted the association of definite peculiarities in the electrocardiogram, indicative of disturbed intraventricular conduction, with such clinical conditions as are usually accompanied by myocardial involvement.
The normal electrocardiogram is to be considered the result of the passage of an impulse at a normal velocity through the usual channels, i. e., node of Tawara, main stem, bundle branches and arborizations which consist of the so-called Purkinje fibers. The latter form a network covering practically the entire endocardial surface of the ventricles. The velocity of the impulse through Purkinje fibers is at least ten times faster than its rate through ordinary ventricular musculature. The impulse reaches the ventricle normally through the Purkinje fibers, stimulating the ventricular walls practically as a whole. An experimental injury to the Purkinje fibers delays the propagation of the impulse. A lesion only partially involving either bundle branch or an extensive lesion of the arborizations of a branch would cause a delay in the transmission of the excitation wave over the area supplied or damaged. An experimental block of either right or left main branch completely interrupts the passage of the impulse over normal channels to the corresponding ventricle, the spread then occurring through ordinary muscular connections. This gives a characteristic electrocardiogram differing in many respects from those to be described here which we believe to be intermediate forms between the normal and those due to bundle branch block. It is possible that some of the clinical records interpreted as bundle branch block may be instances of only partial blocks or rather of lesions beyond in the arborizations. Our gross pathological specimens tend to support this view.
The criteria in the electrocardiograms which we have used are in general as follows:
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