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Circulation, Vol 56, 225-234, Copyright © 1977 by American Heart Association

ARTICLES

Re-entrant ventricular arrhythmias in the late myocardial infarction period. 3. Manifest and concealed extrasystolic grouping

N El-Sherif, R Lazzara, RR Hope and BJ Scherlag

Re-entrant beats with regular extrasystolic grouping were seen in 44- of dogs 3--7 days following ligation of the anterior descending coronary artery. Utilizing direct recording of the re-entrant pathway (RP) from the epicardial surface of the infarction zone, we found extrasystolic grouping to be based on the infarction tachycardia- dependent conduction disorders in a potentially RP. Trigeminy and quadrigeminy were related, respectively, to a 3:2 and 4:3 Wenckebach- like conduction cycle in a RP. However, quadrigeminy could also be due to an underlying bigeminal rhythm with concealment of alternate re- entrant beats, i.e., concealed bigeminy. A bigeminal rhythm was the result of a 2:1 conduction pattern in a re-entrant pathway with a sufficient degree of conduction delay during the conducted beat of the 2:1 cycle to result in re-entry. A trigeminal or quadrigeminal rhythm could change to a bigeminal rhythm on critical shortening of the cardiac cycle. Fixed and variable coupling were related, respectively, to stable and changing conduction pattern in a re-entrant pathway. On the other hand, extrasystolic grouping could be concealed due to either block in the re-entrant pathway or entrapment in a small area of the closely bordering normal zone.