Tricyclic antidepressants and cardiac conduction: changes in ventricular automaticity

Area of Science:

• Cardiology
• Pharmacology
• Electrophysiology

Background:

• Ventricular dysrhythmias stem from altered cardiac automaticity or conduction.
• Tricyclic antidepressants are known to induce ventricular dysrhythmias in various models.

Purpose of the Study:

• To investigate the direct effects of tricyclic antidepressants on ventricular automaticity.
• To elucidate the dose-dependent influence of these drugs on cardiac rhythm generation.

Main Methods:

• Anesthetized dogs were used to model ventricular rhythm by blocking atrioventricular conduction.
• Specific tricyclic antidepressants (imipramine, amitriptyline, nortriptyline) were administered at varying doses.

Main Results:

• Low doses of imipramine, amitriptyline, and nortriptyline caused minor but statistically significant increases in ventricular automaticity.
• Higher doses of these tricyclic antidepressants led to a pronounced suppression of ventricular automaticity.

Conclusions:

• Tricyclic antidepressants exhibit a dose-dependent effect on ventricular automaticity.
• These observed changes in automaticity may contribute to the arrhythmogenic potential of tricyclic antidepressants.