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[Effect of mexiletine on human atrial vulnerability]
Abstract:
The effect of mexiletine on human atrial vulnerability was investigated in 14 subjects (8 with paroxysmal atrial fibrillation, 2 with paroxysmal atrial tachycardia, 2 with ventricular tachycardia, 1 with sick sinus syndrome and 1 with Wolff-Parkinson-White syndrome). During the electrophysiologic study, after 8 consecutive stimuli (A1) were delivered through the electrode catheter positioned at high right atrium, premature stimulus (A2) was introduced, and following measurements were made; 1) Aw: atrial activity width of A1, 2) maximum atrial fragmentation (MAF): the longest atrial activity width of A2, which was expressed by the relative value against Aw, 3) fragmented atrial activity zone (FAZ): the zone of the coupling interval (A1A2) with the prolongation of the atrial activity width at A2 more than 150% against Aw, 4) conduction delay zone (CDZ): the zone of A1A2 with the prolongation more than 20 msec of the intraatrial conduction time at A2 from high right atrium to coronary sinus or low right atrium against the intraatrial conduction time at A1, and 5) right atrial effective refractory period (RAERP). These measurements were repeated after the intravenous administration of mexiletine (2 mg/kg/10 min). 3 cases (case 12, 13 and 14), whose FAZ and CDZ were 0 msec, were excluded from the following evaluation. Mexiletine showed little effect on Aw and RAERP, but significantly shortened MAF and FAZ (p less than 0.001 and p less than 0.05, respectively). CDZ were also reduced in 3 cases and remained unchanged in 6 cases, though no statistical difference of CDZ was recognized between before and after the administration of mexiletine.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Mexiletine significantly reduced atrial fragmentation (maximum atrial fragmentation and fragmented atrial activity zone) in patients undergoing electrophysiologic studies. This antiarrhythmic effect suggests potential benefits for managing atrial vulnerability.
Area of Science:
- Electrophysiology
- Pharmacology
- Cardiology
Context:
- Atrial vulnerability contributes to arrhythmias like atrial fibrillation.
- Electrophysiologic studies are crucial for assessing cardiac electrical activity.
- Mexiletine is a Class Ib antiarrhythmic agent.
Purpose:
- To investigate the impact of intravenous mexiletine on human atrial vulnerability.
- To quantify changes in atrial activity width, fragmentation, conduction delay, and refractory period.
- To evaluate mexiletine's efficacy in patients with various atrial and ventricular arrhythmias.
Summary:
- Mexiletine administration led to a significant reduction in maximum atrial fragmentation (MAF) and fragmented atrial activity zone (FAZ).
- While mexiletine showed minimal effect on atrial activity width (Aw) and right atrial effective refractory period (RAERP), it reduced conduction delay zone (CDZ) in some cases.
- The study excluded cases with zero FAZ and CDZ, focusing the analysis on patients exhibiting measurable atrial vulnerability parameters.
Impact:
- Mexiletine demonstrates antiarrhythmic properties by reducing atrial electrical instability.
- Findings suggest mexiletine may help mitigate the risk of atrial arrhythmias.
- Further research could explore mexiletine's role in preventing or treating atrial fibrillation and other related conditions.