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Lidocaine does not affect myocardial electrical heterogeneity: implications for low proarrhythmic actions
J J Sims1, A P Winecoff, M R Ujhelyi
1University of Georgia College of Pharmacy, Augusta Veterans Affairs Medical Center, USA.
Pharmacotherapy
|December 17, 1997
Summary
Lidocaine did not alter myocardial electrical heterogeneity, unlike other sodium channel blockers. This uniform effect across the heart may explain its lower proarrhythmic potential in preventing reentrant arrhythmias.
Area of Science:
- Cardiac electrophysiology
- Arrhythmia mechanisms
- Pharmacology of antiarrhythmic drugs
Background:
- Reentrant arrhythmias require unidirectional conduction block.
- Drug-induced block is often caused by dispersion in repolarization and refractoriness.
- Understanding drug effects on myocardial electrical heterogeneity is crucial.
Purpose of the Study:
- To assess lidocaine's effects on spatial dispersion of myocardial repolarization and refractoriness.
- To investigate lidocaine's impact on myocardial electrical heterogeneity in an intact heart model.
- To explore the electrophysiological basis for lidocaine's antiarrhythmic properties.
Main Methods:
- Intact porcine heart model.
- Measurement of monophasic action potential duration, effective refractory period (ERP), and ventricular fibrillation cycle length (VFCL) at multiple myocardial sites.
- Calculation of dispersion as the difference between maximum and minimum values across sites.
- Comparison between D5W (control) and lidocaine treatment groups.
Main Results:
- Lidocaine significantly altered ERP, VFCL, paced QRS duration, and intraventricular conduction time.
- Lidocaine did not significantly change basal dispersion in repolarization or refractoriness.
- Electrophysiological changes induced by lidocaine were uniform across the myocardium.
Conclusions:
- Lidocaine treatment did not increase myocardial electrical heterogeneity.
- The uniform electrophysiological effects of lidocaine may contribute to its reduced proarrhythmic potential compared to other sodium channel blockers.
- This study provides insights into the mechanism of lidocaine's antiarrhythmic action and safety profile.