Slow conduction through an arc of block: A basis for arrhythmia formation postmyocardial infarction

• Published in: Journal of cardiovascular electrophysiology Vol. 28; no. 10; pp. 1203 - 1212
• Main Authors: Patterson, Eugene, Scherlag, Benjamin J., Berbari, Edward J., Lazzara, Ralph
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.10.2017
• Subjects: Activation; Animals; Arrhythmia; arrhythmia formation; Arrhythmias, Cardiac - etiology; Arrhythmias, Cardiac - physiopathology; Conduction; Coronary artery; Coronary Artery Disease - physiopathology; Dogs; EKG; Electrocardiography; Electrophysiological Phenomena; Epicardial Mapping; Epicardium; Heart Block - complications; Heart Block - physiopathology; Heart Conduction System - physiopathology; Heart Rate; Infarction; Male; Myocardial infarction; Myocardial Infarction - complications; Myocardial Infarction - physiopathology; myocardial reentry; Occlusion; Sinus; Tachycardia, Ventricular - complications; Tachycardia, Ventricular - physiopathology; Ventricle; ventricular arrhythmia; ventricular premature beats; Ventricular Premature Complexes - etiology; Ventricular Premature Complexes - physiopathology; ventricular arrhythmia; ventricular premature beats; arrhythmia formation; myocardial infarction; myocardial reentry
• ISSN: 1045-3873; 1540-8167
• DOI: 10.1111/jce.13300

Introduction The electrophysiologic basis for characteristic rate‐dependent, constant‐late‐coupled (390 + 54 milliseconds) premature ventricular beats (PVBs) present 4–5 days following coronary artery occlusion were examined in 108 anesthetized dogs. Methods and results Fractionated/double potentials were observed in injured zone bipolar and composite electrograms at prolonged sinus cycle lengths (1,296 ± 396 milliseconds). At shorter cycle lengths, conduction of the delayed potential decremented, separating from the initial electrogram by a progressively prolonged isoelectric interval. With sufficient delay of the second potential following an isoelectric interval, a PVB was initiated. Both metastable and stable constant‐coupled PVBs were associated with Wenckebach‐like patterns of delayed activation following an isoelectric interval. Signal‐averaging from the infarct border confirmed the presence of an isoelectric interval preceding the PVBs (N = 15). Pacing from the site of double potential formation accurately reproduced the surface ECG morphology (N = 15) of spontaneous PVBs. Closely‐spaced epicardial mapping demonstrated delayed activation across an isoelectric interval representing “an arc of conduction block.” Rate‐dependent very slow antegrade conduction through a zone of apparent conduction block (N = 8) produced decremental activation delays until the delay was sufficient to excite epicardium distal to the original “arc of conduction block,” resulting in PVB formation. Conclusion The present experiments demonstrate double potential formation and rate‐dependent constant‐coupled late PVB formation in infarcted dog hearts. Electrode recordings demonstrate a prolonged isoelectric period preceding PVB formation consistent with very slow conduction (<70 mm/s) across a line of apparent conduction block and may represent a new mechanism of PVB formation following myocardial infarction.