Peripheral Heart Blocks Associated with Myocardial Infarcts: Clinical Diagnosis Based on Experimental Findings

Gustavo Medrano,Alfredo Micheli,Pedro Iturralde

doi:10.2174/157340308784245784

Gustavo Medrano, Alfredo Micheli + Show 1 more

Open Access

https://doi.org/10.2174/157340308784245784

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Abstract

Septal necrosis + peripheral left blocks. Because of an extensive septal necrosis, the manifestation of the initial ventricular activation forces decreases in the precordial leads. With left bifascicular block (LASB + LPSB), the first ventricular activation forces become more evident and the electrical signs of septal necrosis can be concealed. In the presence of a trifascicular block, manifestation of the first ventricular electromotive forces diminishes again and the electrical signs of septal necrosis become evident once more. Small Q waves are present in leads V1 to V4.Extensive anterior necrosis + peripheral blocks. This necrosis is manifested by QS complexes from V2 to V6. An associated left bifascicular block reduces the electrical manifestation of dead tissue: QS complexes persist only in V3 and V4. In turn, a coexisting trifascicular block causes the presence of QS complexes from V2 to V5. Posteroinferior necrosis + peripheral blocks. Electromotive forces of the ventricular activation shift upward, due to a posteroinferior necrosis and QS or QR complexes are recorded in leads aVF, II and III. An associated left bifascicular block displaces the main electromotive forces downward, posteriorly and to the left, due to a delay of the posteroinferior activation fronts. The ventricular complexes become positive and wider in all leads, reflecting the potential variations of the inferior portions of the left ventricle: aVF, II, III, sometimes V5 and V6. Consequently, the electrical signs of necrosis are reduced or abolished. Due to a trifascicular block, wide and slurred QS complexes are recorded in aVF, II, III and sometimes in V5 and V6.

Highlights

Fascicular or peripheral blocks can be diagnosed, based on two types of data: morphologically by the slurred vertex of the R wave only in leads exploring the affected regions and chronologically by the prolonged time of onset of the intrinsicoid deflection (TOID) in these leads
We investigated the bases for diagnosing right peripheral blocks experimentally [8] and clinically [9,10]
When the septal inactive myocardium is associated with a left bifascicular block (LBFB), the activation process is delayed in the posterior and the anterosuperior portions of the interventricular septum [14]

Summary

INTRODUCTION

Fascicular or peripheral blocks can be diagnosed, based on two types of data: morphologically by the slurred vertex of the R wave only in leads exploring the affected regions and chronologically by the prolonged time of onset of the intrinsicoid deflection (TOID) in these leads. The main resultant vectors of ventricular activation, in the presence of left bifascicular block [13], are represented. When the septal inactive myocardium is associated with a left bifascicular block (LBFB), the activation process is delayed in the posterior and the anterosuperior portions of the interventricular septum [14]. The electromotive forces directed forward are increased, probably due to a greater manifestation of those originating in undamaged regions of the mid third of the interventricular septum and in the trabecular zone of the right ventricle. Because of this association, the delay in the activation of the free left ventricular wall due to both left peripheral blocks, can balance again the electromotive forces of the ventricular depolarization [17]. The small slurred Q waves in aVF, lasting 40 msec, suggest the presence of inactive myocardium in the diaphragmatic left ventricular wall

TRIFASCICULAR BLOCK

Clinical Example