Document Detail


An evaluation of automaticity and triggered activity in the canine heart one to four days after myocardial infarction.
MedLine Citation:
PMID:  3888438     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Both abnormal automaticity and triggered activity induced by delayed afterdepolarizations have been proposed as the primary mechanism for ventricular tachycardia (VT) occurring in dogs 24 hr after ligation of the left anterior descending coronary artery. Because of this controversy, we studied the effects of ventricular pacing and therapeutic concentrations of lidocaine and ethmozin on sustained rhythmic activity of isolated subendocardial preparations excised from the infarct, and on VT in conscious dogs. There were differences in the sustained rhythmic activity cycle length of isolated preparations and the VT cycle length that were attributable to the absence of sympathetic input in the former and its presence in the latter. In isolated tissues, pacing for 1 or 10 beats reset the sustained rhythmic activity and pacing for 1 min induced overdrive suppression. Lidocaine (5 micrograms/ml) had no effect on sustained rhythmic activity but ethmozin (2 micrograms/ml) suppressed it. Delayed afterdepolarizations occurred but appeared to be induced by pacing or by the hyperpolarization associated with recovery. Although delayed afterdepolarizations were infrequent at 24 hr, their frequency increased with the hyperpolarization of the membrane that occurred at 48 to 96 hr after infarction. Delayed afterdepolarizations also occurred more readily when superfusate temperature was lowered. In conscious dogs, pacing the VT for 1 or 10 beats or 1 min had no effect. Lidocaine (2 to 10 micrograms/ml) did not affect the VT but ethmozin (2 to 5 micrograms/ml) increased VT cycle length significantly. Pacing for 1 min in the presence of ethmozin, but not lidocaine, converted VT to sinus rhythm. Our results suggest that although delayed afterdepolarizations occur at 24 hr after infarction in the standard Harris preparation, they are most readily seen as an accompaniment of hyperpolarization, pacing, or lowering of bath temperature. The predominant rhythm at 24 hr appears to be automatic.
Authors:
H le Marec; K H Dangman; P Danilo; M R Rosen
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Circulation     Volume:  71     ISSN:  0009-7322     ISO Abbreviation:  Circulation     Publication Date:  1985 Jun 
Date Detail:
Created Date:  1985-07-16     Completed Date:  1985-07-16     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0147763     Medline TA:  Circulation     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1224-36     Citation Subset:  AIM; IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Cardiac Pacing, Artificial
Dogs
Electrophysiology
Lidocaine / therapeutic use
Moricizine
Myocardial Infarction / drug therapy,  physiopathology*,  therapy
Phenothiazines / therapeutic use
Tachycardia / drug therapy,  physiopathology,  therapy
Temperature
Grant Support
ID/Acronym/Agency:
1-KO4-HL00853/HL/NHLBI NIH HHS; HL-24354/HL/NHLBI NIH HHS; HL-28223/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
0/Phenothiazines; 137-58-6/Lidocaine; 31883-05-3/Moricizine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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