Propranolol induced bradycardia in tetralogy of Fallot.

Abstract

SUMMARY When an 18 month old girl who had tetralogy of Fallot and episodes of severe cyanosis with loss of consciousness was treated with propranolol there was some improvement. But when the dose was increased she had further episodes of near syncope. Holter monitoring showed extreme intermittent bradycardia with pauses of up to 2-6 seconds. The episodes of near syncope and the bradycardia resolved after propranolol was stopped.Apparent failure of propranolol treatment may on rare occasions be related to drug induced bradycardia rather than to continued episodes of severe cyanosis.Propranolol is widely accepted as an effective palliation for tetralogy of Fallot complicated by episodes of severe cyanosis.' Side effects of propranolol, such as bradycardia, congestive heart failure, bronchospasm, and hypoglycaemia, are well recognised in adults but seem to be rare in infancy even at high doses.2 We report the case of a child with tetralogy of Fallot who was treated with propranolol and in whom continued episodes of pallor and near syncope seemed to be caused by propranolol induced bradycardia. Case reportAn 18 month old Asian girl with tetralogy of Fallot had typical episodes of severe cyanosis during which she became distressed and then limp. Sometimes she lost consciousness for up to 10 minutes. She weighed 8 kg and she was treated with propranolol 5 mg three times a day. This seemed to abolish the attacks. During a subsequent outpatient visit, however, she had a prolonged episode of severe cyanosis and lost consciousness. She was admitted to hospital and the dose ofpropranolol was increased to 8 mg three times a day. After this she had several episodes each day when she became pale and suffered near syncope. Unlike her usual episodes these attacks were not associated with preceding cyanosis or distress. Because she had intermittent sinus bradycardia during a 12 lead electrocardiogram, 24 hour Holter

At what age should tetralogy of Fallot be corrected?

“…22 The possibility of severe hypoglycaemia must always be considered and checked, 27,28 and occasionally severe bradycardia leads to withdrawal of the drug. 29 Apart from these problems, in a minority of patients, propranolol does improve arterial oxygen saturation and reduces or abolishes hypercyanotic spells. The big unanswered question is whether the added months of growth make reconstruction of the outflow tract easier.…”