The congenital type of atrial flutter has a poor prognosis when unresponsive to digoxin (Moller, Davachi, and Anderson, 1969). Recorded experience with cardioversion is limited but it has been suggested that this type of flutter is refractory to electric countershock (Rodriguez-Coronel, Sueblingvong, and Hastreiter, 1968).We report an infant with congenital heart defects and congenital atrial flutter who appeared resistant to digoxin and ,B-blockade (practolol) but readily reverted to sinus rhythm with direct current (DC) cardioversion.Case Report This was the second pregnancy of a 25-year-old whose health was good until mild hypertension developed at term. Labour was induced at 40 weeks, and the fetal heart was noted to be rapid and irregular. A mature female infant weighing 3 * 8 kg was delivered by emergency caesarean section. No meconium staining was evident, and the Apgar score at one minute was 9. The infant remained active, sucked well, and was pink breathing air.The apex beat was consistently 180-200/minute. No cardiac murmurs were heard at this time and there were no signs of respiratory distress. X-ray showed slight cardiomegaly and clear lung fields. ECG showed atrial flutter with varying AV block and a ventricular rate around 180/minute.An attempt was made to control the ventricular rate using digoxin orally. A total dose of 0 3 mg over the first 24 hours was given, and 0 075 mg daily thereafter. After 3 days there was no change in the underlying arrhytnmia or the ventricular rate (Fig.). At this time a soft systolic murmur became audible at the left sternal edge.At the age of 4 days cardiac catheterization revealed an atrial septal defect with a pulmonary-systemic flow ratio of 2: 1 and a minor degree ofaortic coarctation. During the procedure the atrial flutter reverted to sinus rhythm for two short periods.At 5 days digoxin was stopped. After 24 hours, and with continuous ECG monitoring, practolol was given twice within one hour by slow i.v. injection in a dose of 05 mg diluted in 10 ml saline. No effect was noted on the heart rate or rhythm. Oral practolol 2-2 mg/kg twice daily was given and increased to four times daily without effect on rate or rhythm (Fig.).By 10 days the baby's condition was deteriorating with tachypnoea and feeding difficulty. The liver was palpable two fingers' breadth below the costal margin. X-ray revealed increasing cardiomegaly. DC cardioversion was, therefore, attempted.No anaesthetic was given. Adult electrodes (9 cm diameter) were placed on the right midsternal border and on the apex with about nine-tenths of the surface area of the paddles masked by insulating tape. A shock of 10 watt-seconds was given from a Lown cardiorater.
