Related Experiment Videos
[Myocardial excitability under the influence of digitalis glycosides and anti-arrhythmia agent]
Abstract:
Using the technical procedure of transvenous cardiac pacing right ventricular myocardium was stimulated with various pulse duration (voltage-duration curves) and with paired stimuli utilizing double pacing technique, to determine diastolic threshold profile up to the absolute refractory period. Two kinds of cardiac drugs were tested: Digitalis glycosides increase distolic excitability and shorten refractory period. Anitarrhythmic drugs have different effects: Lidocaine and Phenytoine in several cases decrease slightly the stimulatory threshold and can shorten the refractory period. Procainamide and Ajmaline prolong the refractory period and increase the stimulatory threshold. Propranolol and Verapamil have no significant effect. Their major action is supraventricular. The results are important in view of clinical pharmacology of cardiac drugs and of long term cardiac pacemaker therapy.
Insights
This study investigated how cardiac drugs affect the heart's electrical properties during pacing. Findings reveal distinct drug impacts on diastolic excitability and refractory periods, crucial for pacemaker therapy.
Area of Science:
- Cardiovascular Physiology
- Cardiac Electrophysiology
Context:
- Understanding myocardial response to electrical stimulation is vital.
- Assessing drug effects on cardiac excitability and refractoriness is clinically significant.
Purpose:
- To determine the diastolic threshold profile up to the absolute refractory period using transvenous cardiac pacing.
- To evaluate the effects of specific cardiac drugs on these electrophysiological parameters.
Summary:
- Right ventricular myocardium was stimulated via transvenous pacing to map diastolic thresholds and refractory periods.
- Digitalis glycosides increased excitability and shortened refractoriness.
- Antiarrhythmic drugs showed varied effects: Lidocaine/Phenytoin slightly decreased thresholds and shortened refractoriness, while Procainamide/Ajmaline prolonged refractoriness and increased thresholds.
- Propranolol and Verapamil had minimal impact on these specific parameters, with primary supraventricular action.
Impact:
- Provides insights into the clinical pharmacology of cardiac drugs.
- Informs long-term cardiac pacemaker therapy by detailing drug-electrophysiology interactions.