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Slow antegrade excitation and delayed retrograde activation through an “inexcitable zone”: A basis for arrhythmia formation in infarcted myocardium ex vivo
Author(s) -
Patterson Eugene,
Scherlag Benjamin J.
Publication year - 2017
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1111/jce.13268
Subject(s) - medicine , cardiology , reentry , sinus rhythm , atrial fibrillation
The electrophysiologic mechanism for rate‐dependent PVBs associated with double potentials (DPs) was investigated in infarcted canine hearts using bipolar and intracellular microelectrode recordings. Methods and results Dogs exhibiting rate‐related ventricular ectopic beats (coupling interval, 390 ± 54 milliseconds) during sinus rhythm or atrial pacing were studied 4–5 days (N = 63) or 25 days (N = 16) following anterior descending coronary artery ligation. Sites of DP and rate‐dependent arrhythmia formation were identified in vivo using bipolar recordings for subsequent ex vivo studies. Rate‐dependent conduction delays with increasing duration isoelectric intervals representing very slow conduction were observed at sites of DP formation, frequently provoking both manifest and concealed reentry (non‐stimulated beats) over a narrow range of paced cycle lengths. Both slow antegrade and retrograde activation across an inexcitable gap (reflection) were integral components of extrasystole formation. Retrograde reflection to a region of very slow conduction (mid‐potential) during antegrade activation was routinely observed at 4–5 days (42 of 63 preparations, 67%) and 25 days (22 of 26 preparations, 85%) postcoronary artery ligation. Reflection and premature re‐activation of the proximal site was then observed in 6 of 63 (9%), and 3 of 26 preparations (12%). Conclusion The present experiments demonstrate DP formation and rate‐dependent constant‐coupled late epicardial premature beats in infarcted dog hearts. Microelectrode recordings at DP sites demonstrating prolonged isoelectric intervals display very slow conduction preceding distal activation and “reentrant” re‐activation of more proximal sites, representing reflection as an arrhythmia mechanism in ischemically injured epicardium during subacute myocardial infarction.