Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Stark, G; Kasper, K; Schulze-Bauer, C; Stark, U; Decrinis, M; Tritthart, HA.
How to measure AV nodal refractoriness in the presence of verapamil, amiodarone, digoxin, and diltiazem.
Pacing Clin Electrophysiol. 1996; 19(2):157-164
Doi: 10.1111/j.1540-8159.1996.tb03307.x
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PubMed
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- Co-Autor*innen der Med Uni Graz
- Tritthart Helmut
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- Abstract:
- On the AV node the negative dromotropic action of verapamil, amiodarone, digoxin, and diltiazem is known to be rate dependent. The effective refractory period of the AV node (AV-ERP) at a short cycle length is related to the AV conduction at that cycle length. We investigated how the number of stimuli during the conditioning train (S1) (during measurement of refractoriness at a high pacing rate [cycle length = 180 ms]) might influence the AV-ERP in isolated guinea pig hearts in a Langendorff preparation. Verapamil (10 nM), amiodarone (10 microM), digoxin (0.6 nM), and diltiazem (30 nM) caused a comparable prolongation of the AV conduction time (AVCT). All four drugs caused a significant prolongation of the AV-ERP when evaluated by a standard stimulation protocol with a conditioning train of 10 stimuli (10 S1) at a pacing cycle length of 180 ms followed by the test stimulus (S2). When the number of stimuli during the conditioning train (S1) was increased (> 10), until the prolongation of AVCT reached steady state, the AV-ERP in the presence of verapamil (132 +/- 4 vs 141 +/- 3 ms; P < 0.05, mean +/- S.E.M.) and diltiazem (143 +/- 3 vs 151 +/- 3 ms; P < 0.05) was prolonged significantly further. These results indicate that the effect of drugs on AV-ERP should be measured with a modified stimulation protocol, whereby the number of conditioning stimuli is comparable to the time constant characterizing the prolongation of AVCT at fast pacing rates.
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