EFFECT OF AUTONOMIC BLOCKADE ON DIGOXIN-INDUCED ECG-CHANGES AT REST AND DURING EXERCISE IN HEALTHY-SUBJECTS

The effect of pharmacological autonomic blockade on digoxin-induced el ectrocardiographic changes at rest and during exercise was studied in nine healthy men. The subjects performed bicycle exercise tests on fou r occasions after: (1) intravenous injection of sodium chloride, (2) i ntravenous injection of propranolol and atropine, (3) oral ingestion o f digoxin 0.5 mg daily for 2 weeks and intravenous injection of sodium chloride, and (4) oral ingestion of digoxin 0.5 mg daily for 2 weeks and intravenous injection of propranolol and atropine. The ST-T segmen t was significantly depressed after digoxin plus sodium chloride and d igoxin plus propranolol and atropine in comparison with sodium chlorid e only and propranolol and atropine only. The digoxin-induced ST-T cha nges after sodium chloride and propranolol-atropine injections were no t significantly different. Thus, judging from the results of this stud y, an effect mediated via the autonomic nervous system is an unlikely explanation of digitalis-induced ST-T changes.