Related Experiment Videos
Electrophysiologic effects of chronic amiodarone therapy in patients with ventricular arrhythmias
Insights
Amiodarone therapy effectively treats chronic ventricular arrhythmias by significantly altering heart electrophysiology. The drug slows heart rate and conduction, prolonging refractory periods across the atria, AV node, and ventricles.
Area of Science:
- Cardiology
- Electrophysiology
- Pharmacology
Background:
- Chronic refractory ventricular arrhythmias pose significant clinical challenges.
- Amiodarone is a widely used antiarrhythmic drug with complex electrophysiologic effects.
- Understanding amiodarone's impact on cardiac conduction and refractoriness is crucial for patient management.
Purpose of the Study:
- To investigate the electrophysiologic effects of chronic oral amiodarone therapy in patients with refractory ventricular arrhythmias.
- To assess changes in sinus node function, intra-atrial and AV nodal conduction, and ventricular repolarization.
Main Methods:
- Detailed electrophysiologic studies were conducted in nine patients before and after 7-20 weeks of amiodarone treatment.
- Patients received amiodarone doses ranging from 400-800 mg/day.
- Measurements included sinus rate, conduction times, refractory periods, and intervals like HV and QT.
Main Results:
- Amiodarone significantly reduced sinus rate and prolonged sinoatrial conduction time.
- Anterograde AV nodal conduction and Wenckebach cycle length were significantly prolonged.
- HV interval, QRS width, and QT interval were prolonged, alongside significant increases in atrial, AV nodal, and ventricular refractory periods.
Conclusions:
- Chronic oral amiodarone therapy exerts significant electrophysiologic effects throughout the heart.
- These effects support its clinical efficacy in managing atrial and ventricular arrhythmias.
- Amiodarone can be cautiously used in patients with intraventricular conduction defects, despite its effects on HV interval and QRS width.
Abstract:
Detailed electrophysiologic studies were performed in nine patients with chronic refractory ventricular arrhythmias before and after 7 to 20 weeks (mean 11 weeks) of amiodarone therapy. The amiodarone dose at the time of the repeat study ranged from 400 to 800 mg/day. The drug reduced the sinus rate (p less than 0.001) and prolonged the sinoatrial conduction time (p less than 0.05) with some prolongation of the corrected sinus node recovery time. Intra-atrial conduction was slightly prolonged both in sinus rhythm and during atrial pacing. Anterograde conduction through the AV node was significantly prolonged both in sinus rhythm (p = 0.001) and during atrial pacing (p less than 0.005), and Wenckebach AV block was seen at significantly lower atrial pacing rates after the drug (p less than 0.005). The HV interval was prolonged both in sinus rhythm (p less than 0.05) and during atrial pacing (p = 0.001), and so was the QRS width during atrial pacing (p less than 0.005) and the QT interval in sinus rhythm (p less than 0.005) and during atrial pacing (p less than 0.005). Significant prolongation of the refractory periods in the atrium, AV node, and ventricular muscle were also seen following the drug. We concluded that the significant electrophysiologic effects of this drug throughout the heart during chronic oral use attest to its clinical effectiveness in patients with atrial and ventricular arrhythmias. With due care and despite its effects on the HV interval and QRS width, it can be used in patients with intraventricular conduction defects complicating severe organic heart disease.