Conduction disturbances due to enhanced phase 4 depolarization of automatic cells

Singer, Donald H.; Lazzara, Ralph; Hoffman, B. F.

doi:10.1016/0002-9149(66)90331-6

Cited by 7 publications

(1 citation statement)

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“…This finding localizes its origin at a point within the fascicles of the left bundle-branch system from which the impulse propagates both antegradely toward the myocardium and simultaneously retrogradely toward the main His bundle, reaching both destinations within a period of time which is necessarily shorter than the His-Q interval of the conducted beats. As was demonstrated in a previous study,7 impulses arising from the fascicles of the left bundle depolarize the right ventricle last and, therefore, display complete or incomplete RBBB and also axis deviation-left if they originate from the 11, II, and V1. Frontal-plane mean QRS vectors are depicted both for sinus beats (left) and ectopic beats with narrow QRS (right).…”

Section: Report Of Casessupporting

confidence: 64%

Paradoxic Phenomenon of Premature Beats with Narrow QRS in the Presence of Bundle-Branch Block

et al. 1973

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In contrast to the functional bundle-branch block (BBB) which is frequently rate-related and disappears when heart rate slows, we have encountered seven cases of a paradoxic disappearance of an existing, ischemia-induced BBB in premature beats. Supernormal conduction within the blocked bundle branch was not present in any of the cases. His bundle electrography in three of the cases demonstrated His spikes before each of the narrow-QRS premature beats. The His-Q intervals of the premature beats were considerably shorter than those of the control sinus beats. This finding clearly indicated an ectopic origin midway between the ventricular myocardium and the His bundle, i.e., within the ischemic fascicles of the left bundle, or the ischemic right bundle. From their points of origin such fascicular impulses propagate antegradely toward the respective area of the ventricular myocardium, and retrogradely toward the main His bundle, and at the same time down the remaining two fascicles. The antegrade conduction time in the short pathway down the ischemic fascicle is equaled by the faster conduction through the longer pathways of the remaining, uninjured fascicles, thereby accounting for the almost simultaneous activation of the myocardium of the two ventricles and the resultant narrow-QRS complexes. ectopic beats approaching normal QRS duration.

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Section: Report Of Casessupporting

confidence: 64%