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[Electrophysiological effects of the combined administration of digoxin and propranolol in man]
Insights
Digoxin and propranolol combined significantly impact cardiac electrophysiology, affecting sinus node function and atrioventricular node conduction. Propranolol potentiates digoxin
Area of Science:
- Cardiology
- Electrophysiology
- Pharmacology
Background:
- Digoxin and propranolol are commonly used cardiac medications with known electrophysiological effects.
- Understanding their combined effects is crucial for managing patients with cardiac conduction abnormalities.
- Previous studies have investigated their individual impacts, but combined effects require further elucidation.
Purpose of the Study:
- To investigate the electrophysiological effects of combined digoxin and propranolol administration.
- To compare these effects with digoxin alone.
- To analyze the influence of pre-existing conduction pathway anomalies on drug responses.
Main Methods:
- Electrophysiological study in 40 patients.
- Administration of digoxin alone and in combination with propranolol.
- Assessment of sinus node function, sino-atrial and atrioventricular conduction intervals, and refractory periods.
Main Results:
- Combined digoxin and propranolol prolonged sinus node cycle length and sinus node recovery time.
- The AH interval was increased by digoxin and further potentiated by propranolol, especially in patients without supra-His block.
- Effective refractory periods of the atrium and AV node were increased by the combination, with notable exceptions in patients with supra-His block.
Conclusions:
- Combined digoxin and propranolol significantly alter cardiac electrophysiology, affecting sinus node and AV node function.
- Propranolol potentiates the electrophysiological effects of digoxin, particularly on AV nodal conduction.
- Patients with supra-His block exhibit altered responses to the combined drug regimen, necessitating careful consideration.
Abstract:
The electrophysiological effects of the combined administration of digoxin and propranolol were studied in 40 patients, compared with the effects of digoxin alone and considered in relation to anomalies of the conduction pathways. The cycle of the sinus node was only lengthened by digoxin in patients who had an anomaly of sinus node function. In contrast the addition of propranolol always increased it (from 1 109 +/- 53 ms to 1 232 +/- 58 ms). Sinus node recovery time was only increased by combined administration (from 1 331 +/- 101 ms to 1 450 +/- 68 ms). Changes in sino-atrial conduction intervals were not very marked. The AH interval was increased by digoxin (from 97 +/- 4 ms to 109 +/- 6 ms), with propranolol exerting a synergistic effect (119 +/- 6 ms). When there was pre-existing supra-His block only combined administration increased the conduction defect. The HV interval and QRS duration were not altered. The effective atrial refractory period was increased by combined administration (from 264 +/- 10 ms to 304 +/- 14 ms) except in subjects who had supra-His block. The effective refractory period of the AV node (385 +/- 26 ms) was increased by digoxin (450 +/- 37 ms). This effect was potentiated by propranolol (478 +/- 34 ms) except in those subjects who had supra-His block. In three cases in which there were two conduction pathways at A V node level the refractory periods of the rapid and slow pathways were increased by digoxin, with a synergistic effect from propranolol. The ventriculo-atrial conduction time changed from 151 +/- 24 ms to 172 +/- 22 ms following digoxin, then to 193 +/- 34 ms after the addition of propranolol.