Related Experiment Videos
[Anti-arrhythmia effect of long-term encainide in chronic ventricular extrasystole]
Insights
Encainide effectively reduced ventricular extrasystoles (VES) and ventricular tachycardia over six months. However, side effects like vertigo and headaches occurred, and some patients experienced aggravated arrhythmias.
Area of Science:
- Cardiology
- Clinical Pharmacology
Background:
- Chronic ventricular extrasystoles (VES) pose a significant clinical challenge.
- Assessing long-term antiarrhythmic drug efficacy and tolerance is crucial for patient management.
Purpose of the Study:
- To evaluate the long-term efficacy and tolerance of encainide in patients with chronic VES.
- To determine the optimal dosing strategy based on individual patient response.
Main Methods:
- A 6-month study involving 48 patients with chronic VES treated with encainide.
- Holter monitoring was used for efficacy assessment at various time points.
- Plasma concentrations of encainide and its metabolites were analyzed.
Main Results:
- Significant reduction in the average number of VES/hour (from 480.6 to 2.0).
- Decreased frequency of ventricular tachycardia episodes.
- Common side effects included vertigo, visual disturbances, and headaches; 6 patients discontinued treatment.
Conclusions:
- Encainide demonstrates significant long-term efficacy in reducing ventricular arrhythmias.
- Individual variations in plasma concentrations and metabolism suggest a complex pharmacokinetic-pharmacodynamic relationship.
- Potential for aggravated arrhythmias in a subset of patients warrants careful monitoring.
Abstract:
The long term efficacy and tolerance of encainide were studied in 48 patients with chronic/ventricular extrasystoles (VES) treated for 6 months. Holter monitoring was performed before treatment and at each dose increment (75 mg/day; 150 mg/day and 225 mg/day) during the first week of titration, and then after 1 month and 6 months of treatment. The dose administered in the long-term study corresponded to the minimum effective dose during the titration phase (the dose which reduced the number of VES/24 hours by at least 75%). The average number of VES/hour decreased significantly from 480.6 before treatment to 2.0 at the end of the study. The frequency of episodes of ventricular tachycardia decreased significantly during treatment. The commonest side effects were vertigo, visual disturbances and headaches. Treatment was interrupted because of side-effects or inefficacy in 6 patients. The surface ECG showed significant lengthening of the PR, QRS and QTc periods and encainide appeared to have aggravated the ventricular arrhythmias of 4 patients receiving 200 mg/day. The plasma concentrations of encainide and its two principal metabolites were measured during the titration phase, at 1 month and after 6 months of treatment. 15.6 per cent of patients were slow and 84.4% of patients were rapid metabolizers. The wide individual variations of plasma concentrations and the absence of correlation between the plasma concentrations of encainide and its metabolites and the antiarrhythmic effect suggest that the compound and its metabolites play a role in the antiarrhythmic effect of the drug.