In 1943 an otherwise healthy girl aged 3 developed measles encephalitis with an accompanying mild left hemiparesis. At this time a persistent tachycardia of 140 beats per minute was noted, and she was referred to Sir John Parkinson at the National Heart Hospital. He made a diagnosis of atrial tachycardia. A trial of digoxin and quinidine proved ineffective, but she remained symptomatically well...