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Enhancement of triggered activity in ischemic purkinje fibers by ouabain: A mechanism of increased susceptibility to digitalis toxicity in myocardial infarction
- Source :
- Journal of the American College of Cardiology; March 1985, Vol. 5 Issue: 3 p672-679, 8p
- Publication Year :
- 1985
-
Abstract
- Enhanced susceptibility to toxic arrhythmias by digitalis administration has been reported in clinical and experimental myocardial infarction. To investigate the mechanism responsible for this phenomenon, the effects of superfusion with normal Tyrode's solution and super-fusion with Tyrode's solution containing 4 × 10−8Mof ouabain in ischemic Purkinje fibers were compared. Ischemic Purkinje fibers of small endocardial preparations from 1 day old myocardial infarcts in 18 dogs were used for the study. During control conditions, these endocardial preparations demonstrated delayed afterde-polarizations and triggered activity. Superfusion with normal Tyrode's solution resulted in a gradual increase in maximal diastolic potential and action potential amplitude, a decrease in delayed afterdepolarization amplitude and slowing and termination of triggered activity. Superfusion for 90 minutes with Tyrode's solution containing ouabain resulted in: 1) an increase in the magnitude of delayed afterdepolarizations in preparations demonstrating subthreshold delayed afterdepolarizations, 2) sustainment of triggered activity in preparations showing nonsustained triggered activity, and 3) shortening of cycle lengths of the triggered activity in preparations demonstrating sustained triggered activity before superfusion with ouabain. These effects occurred despite the gradual increase in maximal diastolic potential and action potential amplitude. Superfusion of normal Purkinje fibers with Tyrode's solution containing 4 × 10−8Mof ouabain for 90 minutes did not result in delayed afterdepolarizations or triggered activity. Thus, ouabain at a concentration that has no toxic effect on normal Purkinje fibers may enhance arrhythmias in ischemic Purkinje fibers by increasing the magnitude of delayed afterdepolarizations and enhancing triggered activity.
Details
- Language :
- English
- ISSN :
- 07351097 and 15583597
- Volume :
- 5
- Issue :
- 3
- Database :
- Supplemental Index
- Journal :
- Journal of the American College of Cardiology
- Publication Type :
- Periodical
- Accession number :
- ejs39666088
- Full Text :
- https://doi.org/10.1016/S0735-1097(85)80393-4