Related Experiment Videos
Effect of amiodarone in the Wolff-Parkinson-White syndrome
Abstract:
The effect of amiodarone in the Wolff-Parkinson-White syndrome was studied with programmed electrical stimulation of the heart in 15 patients. All 15 patients had circus movement tachycardias; 7 also had atrial fibrillation. Programmed electrical stimulation was performed before and after 14 days of oral administration of amiodarone. The effective refractory period of the accessory pathway lengthened in an atrioventricular direction in all patients and in a ventriculoatrial direction in eight patients. The effective refractory period of the atrium and ventricle lengthened in 14 and 12 patients, respectively. After administration of amiodarone, circus movement tachycardia could no longer be initiated in five patients. The zone of tachycardia narrowed in four patients, did not change in two and increased in seven. The effect of amiodarone on initiation of circus movement tachycardia could be related to differences in effect of the drug and in the mechanism of tachycardia in individual patients. In all patients in whom tachycardias could still be initiated after treatment with amiodarone the heart rate during tachycardia was slower than before treatment. This slowing was caused by a decrease in conduction velocity of the circulatory wave in different parts of the tachycardia circuit. The effect of amiodarone in prolonging the refractory period of the accessory pathway makes this drug especially useful in patients with the Wolff-Parkinson-White syndrome and atrial fibrillation.
Insights
Amiodarone effectively treats Wolff-Parkinson-White syndrome by lengthening the refractory period of accessory pathways, preventing tachycardia initiation in some patients. This antiarrhythmic drug slows heart rates during tachycardia, proving beneficial for patients with atrial fibrillation.
Area of Science:
- Cardiology
- Electrophysiology
- Pharmacology
Background:
- Wolff-Parkinson-White syndrome is characterized by accessory pathways causing tachycardias.
- Atrial fibrillation is a common comorbidity in WPW patients.
- Amiodarone is an antiarrhythmic drug with broad electrophysiological effects.
Purpose of the Study:
- To evaluate the efficacy of amiodarone in patients with Wolff-Parkinson-White syndrome.
- To assess the electrophysiological effects of amiodarone on accessory pathways and tachycardia circuits.
- To determine amiodarone's impact on tachycardia initiation and heart rate.
Main Methods:
- Programmed electrical stimulation of the heart was used in 15 WPW patients.
- Stimulation was performed before and after 14 days of oral amiodarone.
- Measurements included effective refractory periods and tachycardia induction/characteristics.
Main Results:
- Amiodarone significantly lengthened accessory pathway refractory periods (AV and VA directions).
- It increased atrial and ventricular refractory periods in most patients.
- Tachycardia could not be initiated in 5 patients; heart rates slowed in others due to decreased conduction velocity.
Conclusions:
- Amiodarone effectively prolongs accessory pathway refractoriness in WPW syndrome.
- The drug demonstrates utility in managing WPW-associated tachycardias, particularly in patients with atrial fibrillation.
- Amiodarone's effects on tachycardia initiation and rate are patient-specific, related to drug action and tachycardia mechanisms.