Cardiac electrophysiological effects of two class III antiarrhythmic agents, tedisamil and D-sotalol: DISCUSSION (part 3)


The benefit of the combined effects of class I and class III properties was first discussed by Hondeghem and Snyders . Conduction velocity and ERP determine the maximal tachycardia rate of a reentry arrhythmia. Although action potential duration is an important parameter of the ERP, the availability of the sodium currents is also a major concern. Recovery from sodium channel block occurs primarily at negative potentials and, therefore, starts mainly after repolarization. Hence, its contribution to lengthening of refractoriness is added to that resulting from prolongation of the action potential duration.
Thus, prolongation of action potential duration and sodium channel block that, by themselves, were not able to prolong the ERP adequately to prevent or terminate tachyarrhythmias, might in combination be successful.

In conclusion, tedisamil exerts stronger class III effects on cardiac electrophysiological parameters than D-sotalol. For tedisamil at high concentrations, an additional influence on the sodium-dependent parts of the conduction system (ie, His bundle, intraventricular conduction) was found. Therefore, a reverse use-dependent effect on the ventricular myocardial refractoriness did not develop under the influence of te-disamil. Whether this effect is sufficient to provide a benefit in prevention or termination of tachyarrhythmias warrants further evaluation, especially in clinical studies.

ACKNOWLEDGEMENTS: This work was supported by Grant No P10239 from the Austrian Research Foundation, Vienna, Austria and Aktion Osterreich-Slowakische Republik: Wissen-schafts- und Erziehungskooperation, Grant No 5SR9. Online shopping will cost you less – find Symbicort Dosage click here and enjoy the experience.

Category: Cardiology

Tags: Conduction, D-sotalol, Guinea pig, Refractoriness, Repolarization, Tedisamil

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