Re-entrant ventricular arrhythmias in the late myocardial infarction period. 2. Patterns of initiation and termination of re-entry.
The electrophysiologic mechanisms for the initiation and termination of re-entrant ventricular arrhythmias (RVA) were critically analyzed in dogs 3-7 days following ligation of the anterior descending coronary artery, utilizing direct recordings of the re-entrant pathway (RP) from the epicardial surface of the infarction zone. Re-entry could occur during a regular cardiac rhythm if the heart rate is within the narrow critical range during which conduction in a potentially RP exhibits a Wenckebach-like (W) pattern with a beat-to-beat increment of conduction delay until the activation waveform is sufficiently delayed to re-excite normal myocardium. If a regular cardiac rhythm is associated with limited conduction delay in a potentially RP, premature beats within a critical range of coupling intervals could result in sufficient conduction delay to induce re-entry. Re-entrant ventricular arrhythmias may be unmasked on abrupt termination of a critical fast rate of cardiac pacing only if pacing was terminated during those beats of a W pattern associated with marked conduction delay in a RP. RVA could be ended by one or more properly timed premature beats that would pre-excite part of the RP. An electrophysiologic mechanism for R-on-T and its relationship to onset of ventricular fibrillation was shown, based on markedly delayed RP conduction of the beat prior to the one apparently coupled to the premature beat.
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology* / Q000503:physiopathology; D002036:Bundle of His / Q000503:physiopathology; D004285:Dogs; D004558:Electric Stimulation; D004562:Electrocardiography; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D008722:Methods; D009203:Myocardial Infarction / Q000150:complications* / Q000503:physiopathology; D013610:Tachycardia / Q000209:etiology / Q000503:physiopathology; D014693:Ventricular Fibrillation / Q000209:etiology / Q000503:physiopathology