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Electrophysiological effects of edrophonium in the innervated and the transplanted denervated human heart
Insights
Edrophonium affects the heart's electrical system by influencing autonomic nerves. This drug impacts cardiac conduction in normally innervated hearts but not in transplanted ones, showing nerve dependency.
Area of Science:
- Cardiology
- Autonomic Nervous System Pharmacology
Background:
- Edrophonium is a drug used to diagnose and treat certain conditions.
- Its precise effects on the cardiac conduction system require further elucidation.
Purpose of the Study:
- To investigate the electrophysiological mechanism of action of edrophonium on the cardiac conduction system.
- To determine the role of autonomic innervation in mediating edrophonium's cardiac effects.
Main Methods:
- His bundle recording and pacing techniques were employed.
- Electrophysiological parameters were measured in patients with normally innervated hearts and cardiac transplant recipients before and after edrophonium infusion.
Main Results:
- In normally innervated patients, edrophonium significantly increased sinus cycle length, AH interval, and AV nodal functional refractory period.
- In cardiac transplant recipients, edrophonium only increased recipient atrial cycle length, with no significant effect on other measured parameters.
Conclusions:
- The electrophysiological effects of edrophonium on the human cardiac conduction system are primarily mediated by autonomic innervation.
- Edrophonium's action is dependent on the presence of functional cardiac autonomic nerves.
Abstract:
In order to determine the mechanism of action of edrophonium on the cardiac conduction system, we used His bundle recording and pacing techniques to examine the electrophysiological effect of edrophonium in 6 patients undergoing diagnostic evaluation for coronary artery disease and in 9 cardiac transplant recipients who were free of acute graft rejection. After control measures were made of sinus cycle length, conduction intervals, and conduction system refractory periods, edrophonium was administered by constant intravenous infusion, and all electrophysiological measurements were repeated. In the normally innervated patients, edrophonium significantly increased sinus cycle length from 778 +/- 21 ms to 883 +/- 36 ms (P less than 0.01), AH interval from 88 +/- 11 ms to 100 +/- 12 ms (P less than 0.01), and AV nodal functional refractory period from 351 +/- 44 ms to 391 +/- 36 ms (P less than 0.05). In the patients with transplanted hearts, edrophonium had no electrophysiological effect other than increasing the cycle length of the remnant recipient atrium from 722 +/- 21 ms to 798 +/- 31 ms (P less than 0.01). We conclude that the electrophysiological effects of edrophonium in man are mediated primarily through autonomic innervation of the heart.