Heart Ventricular Fibrillation

The earlier clinical features of over dosage are anorexia, nausea and headache, followed by vomiting, occasionally diarrhea and blurring of vision. The pulse rate may become unduly slow (fewer than 60 beats per minute). Ventricular extra systoles are a common occurrence and a warning to stop treatment for 24 hours. Coupled beats i.e. alternate extra systoles pulses bigamous are characteristic of digitalis poisoning. It is important to listen to the apex beat because the presence of extra systoles may be missed at the wrist. Before giving digitalis by injection or in large doses by mouth it is important to ensure that the patient has not been taking the drug within the previous 14 days, or serious toxicity may result. Hypocalcaemia may be responsible for hypersensitivity to digitalis. If administration of the drug is continued after toxic effects have developed any degree of heart block may follow, and there is a risk of ventricular tachycardia. Occasionally ventricular fibrillation occurs and is one cause of sudden death.