| Modulation of cardiac impulse generation and conduction by nifedipine and verapamil analyzed by a refined surface ECG technique in Langendorff perfused guinea pig hearts. | |
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MedLine Citation:
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PMID: 3395317 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Using a modified Langendorff system, a special ECG recording technique and appropriate placement of two silver wire electrodes, early atrial and His bundle activity can be detected continuously from the surface of intact and spontaneously beating guinea pig hearts. This new method was applied to measure the direct and inhibitory effects of nifedipine and verapamil on impulse generation and conduction in isolated and perfused guinea pig hearts. Depression of sinoatrial conduction was the most prominent effect of nifedipine. In all concentrations applied (10(-7) M, 10(-6) M, 10(-5) M) nifedipine predominantly led to sinoatrial blocks of different degrees. Heart rate decreased slightly in a dose-dependent manner. PQ and HV duration remained essentially constant. In the highest concentration of nifedipine (10-5) M), sinus node activity was so depressed that AV dissociation or ventricular rhythm developed. Only in one out of eight experiments with cumulative increase of nifedipine concentrations to 10(-5) M was the AV node affected by nifedipine and a second-degree AV block developed (10(-6) M). Verapamil's inhibitory effects on the rate of impulse initiation in the sinus node were more pronounced than those of nifedipine, but the inhibition of sinoatrial conduction by verapamil was less marked. At 10(-6) M verapamil, the incidence of sinoatrial blocks and of ventricular rhythm was similar to the incidence of first degree AV blocks. PQ time (+14%) but also HV time (+12%) were prolonged under the influence of this concentration of verapamil. At the highest concentration of verapamil (10(-5) M) applied for 10 min, ventricular rhythm developed in five out of eight experiments, as well as one second and two third-degree AV blocks. The results confirm that the simultaneous measurements of sinus node activity of sinoatrial and atrioventricular conduction and of HV duration is feasible with this ECG technique, to evaluate the inhibitory effects of Ca-antagonists on sinus and AV node activity in the intact heart. |
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Authors:
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G Stark; U Stark; H A Tritthart |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Basic research in cardiology Volume: 83 ISSN: 0300-8428 ISO Abbreviation: Basic Res. Cardiol. Publication Date: 1988 Mar-Apr |
Date Detail:
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Created Date: 1988-08-25 Completed Date: 1988-08-25 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0360342 Medline TA: Basic Res Cardiol Country: GERMANY, WEST |
Other Details:
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Languages: eng Pagination: 202-12 Citation Subset: IM |
Affiliation:
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Institute of Medical Physics and Biophysics, University of Graz, Austria. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Atrioventricular Node / physiopathology Electrocardiography* Electrophysiology Female Guinea Pigs Heart Conduction System / drug effects* Heart Rate / drug effects Male Nifedipine / pharmacology* Perfusion Sinoatrial Node / physiopathology Verapamil / pharmacology* |
| Chemical | |
Reg. No./Substance:
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21829-25-4/Nifedipine; 52-53-9/Verapamil |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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