Fifty years of tachycardia.

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 throughout her childhood and teen years. At the age of 22 she was admitted under the care of Dr Paul Wood because of atypical chest pain; however, persistent tachycardia was again noted. Over subsequent years she was treated with digoxin, practolol, propranolol, and verapamil-all without effect. She remained completely symptom free, tolerating four pregnancies without complication. Her electrocardiogram has been reviewed annually since 1962 and has always shown a narrow-complex tachycardia of 140-160 beats per minute with a long RP interval. Echocardiography in 1993 showed normal left and right ventricular size and function. The figure shows the effect of intravenous adenosine (6 mg) on the tachycardia. The tachycardia terminated transiently before starting again a few seconds later. The last complex of the tachycardia is a P wave, indicating either termination of a junctional tachycardia at the level of the atrioventricular node or coincidental termination of atrial tachycardia at exactly the same time as the production of atrioventricular nodal blockade. Examination of events post-termination