Triggered activity due to delayed afterdepolarizations in sites of focal origin of ischemic ventricular tachycardia

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 287; no. 5; pp. H2078 - H2084
• Main Authors: Xing, Dezhi, Martins, James B
• Format: Journal Article
• Language: English
• Published: United States 01.11.2004
• Subjects: Action Potentials; Animals; Dogs; Electrocardiography; Electrophysiology; Endocardium - physiopathology; Female; Male; Myocardial Ischemia - complications; Purkinje Fibers - physiopathology; Reaction Time; Tachycardia, Ventricular - etiology; Tachycardia, Ventricular - physiopathology
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00027.2004

Division of Cardiovascular Diseases, Department of Internal Medicine, University of Iowa College of Medicine and Veterans Affairs Medical Center, Iowa City, Iowa 52242 Submitted 12 January 2004 ; accepted in final form 25 June 2004 This study for the first time systematically evaluated the site of origin of focal ventricular tachycardia (VT) induced 1–3 h after acute coronary artery ligation in dogs. We determined whether delayed afterdepolarizations (DADs) and triggered activity (TA) are more often recorded from ischemic endocardium excised from focal sites of VT origin. A total of 145 -chloralose-anesthetized dogs were studied: in 54 dogs without inducible VT, normal or ischemic endocardium was investigated in vitro; in 91 dogs, inducible VT was studied by three-dimensional activation mapping, with in vitro study of 51 endocardial foci compared with 40 endocardial ischemic sites not of VT origin. Incidence of DADs (71% vs. 33%, P < 0.05) and TA (32% vs. 11%, P < 0.05) was greater in ischemic than in normal Purkinje tissues. Purkinje sites of origin of focal VT demonstrated the greatest frequency of DADs (92%, P < 0.05) and TA (75%, P < 0.05), with repetitive TA predominating. Similar results were obtained in endocardial sites of origin. Action potentials were mildly depolarized and prolonged in the focal sites of origin. These abnormalities were stable up to 2.5 h of recording. This study demonstrated that DADs and TA may underlie a majority of focal VTs in ischemic endocardium and Purkinje tissue. ventricles; myocardial infarction; endocardium Address for reprint requests and other correspondence: J. B. Martins, Div. of Cardiovascular Diseases, Dept. of Internal Medicine, Univ. of Iowa College of Medicine, 200 Hawkins Dr., E318-3 GH, Iowa City, IA 52242 (E-mail: james-martins{at}uiowa.edu )