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[The effects of tolamolol on excito-conduction in men (author's transl)]
Abstract:
The electrophysiologic effects of tolamolol (UK-6558-01), a new beta-adrenergic blocking agent, were studied using the endocavitarian electrocardiography and the extrastimulus method. The drug was infused intravenously in the dose of 20 mg (0,23-0,36 mg per kilogram). Tolamolol resulted in: -- prolongation of sinus cycle length in 17 patients (P less than 0.001); -- prolongation of correct sinus node recovery time in 16 patients (P less than 0.001); -- there was no significant modification in intra-atrial conduction (P less than 0.3), while atrail effective refractory period was slightly lengthened (P less than 0.03); -- in A-V node conduction was prolonged in 17 patients (P less than 0.001) and the effective functional refractory periods were prolonged in all patients (P less than 0.001); -- a A-V block of 2 degrees grade appears in 17 patients at a more prolonged cycle length (P less than 0.001). Tolamolol had no effect on His-Purkinje system conduction time as well as the relative refractory period, measured before and after the drug in 2 patients. In 6 patients, during the induction of extrastimuli an "echo zone" appeared; after tolamolol its duration was reduced in 4 patients, in one unchanged and in one abolished. The therapeutical properties of this drug are discussed on the basis of such experimental data.
Insights
Tolamolol, a beta-adrenergic blocking agent, significantly prolonged sinus node recovery time and AV node conduction. It also induced AV block, suggesting potential therapeutic applications in cardiac electrophysiology.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Beta-adrenergic blocking agents are crucial in managing cardiovascular conditions.
- Understanding the electrophysiologic effects of new agents like tolamolol is essential for clinical application.
Purpose of the Study:
- To investigate the electrophysiologic effects of tolamolol, a novel beta-adrenergic blocker.
- To assess tolamolol's impact on cardiac conduction and refractoriness using endocavitary electrocardiography.
Main Methods:
- Intravenous infusion of tolamolol (20 mg) in patients.
- Utilized endocavitary electrocardiography and the extrastimulus method.
- Measured sinus cycle length, sinus node recovery time, and refractory periods.
Main Results:
- Tolamolol significantly prolonged sinus cycle length and sinus node recovery time (P < 0.001).
- It prolonged AV node conduction and effective functional refractory periods (P < 0.001), inducing AV block in some patients.
- No significant effect on His-Purkinje system conduction; reduced "echo zone" duration in some patients.
Conclusions:
- Tolamolol exhibits significant electrophysiologic effects on the sinus and AV nodes.
- The observed effects, including AV block induction, warrant further investigation for therapeutic potential.
- Tolamolol's impact on cardiac refractoriness may be relevant for antiarrhythmic strategies.