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  • 1
    Electronic Resource
    Electronic Resource
    Modulation of cardiac impulse generation and conduction by nifedipine and verapamil analyzed by a refined surface ECG technique in Langendorff perfused guinea pig hearts (1988)
    Springer
    Basic research in cardiology 83 (1988), S. 202-212 
    Details
    ISSN: 1435-1803
    Keywords: sinoatrial blocks ; atrioventricular blocks ; Ca-antagonists ; HV duration ; PQ duration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 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 dosedependent 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 measurement 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01907274
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Comparison of acute electrophysiological effects of amiodarone and its metabolite desethylamiodarone in Langendorff perfused guinea pig hearts (1991)
    Springer
    Basic research in cardiology 86 (1991), S. 136-147 
    Details
    ISSN: 1435-1803
    Keywords: amiodarone ; desethylamiodarone ; cardiacconduction andrefractoriness ; isolated guinea pigheart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary During long-term treatment with amiodarone, slowing of conduction through the atrioventricular node, a prolongation of the QT-interval, and a prolongation of the atrial and ventricular myocardial refractoriness always developed. During short-term treatment, these effects were not found, except for depression of the AV-nodal conduction. This led to the suggestion that the electrophysiological effects of amiodarone during long-term treatment might be partly the result of the accumulation of its metabolite desethylamiodarone. Therefore, we examined the electrophysiological effects of amiodarone and desethylamiodarone on conduction and refractoriness in isolated spontaneously beating guinea pig hearts perfused by the method of Langendorff. Within 1 h of perfusion, desethyl-amiodarone caused a more pronounced prolongation of the AV-nodal, His-bundle, and intraventricular conduction intervals than did amiodarone. Desethylamiodarone, but not amiodarone led to a prolongation of the QT-interval. The refractoriness of sinoatrial-, AV-nodal conduction, and of the atrial myocardium were significantly more prolonged by amiodarone than by desethylamiodarone. Both compounds showed a comparable strong rate-dependent effect on AV-nodal refractoriness. The ventricular refractoriness was similarily prolonged by either compound. These results show that for the class-III effects (i.e., prolongation of repolarization period) observed under chronic treatment of amiodarone the metabolite desethylamiodarone may be responsible. Desethylamiodarone also exerts more pronounced effects on the fast-channel-dependent parts of the conduction system than does amiodarone, a fact indicated by a higher prolongation of His-bundle and intraventricular conduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02190546
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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