Electrocardiographic changes in paroxysmal supraventricular tachycardia after administration of adenosine

Three sets of simultaneous electrocardiographic rhythms in a 2-month-old baby with signs and symptoms of mild heart failure and in whom ice-cold wet cloth failed to convert the PSVT of 293 bpm (cycle length of 205 msec). Adenosine successfully converted the PSVT to sinus rhythm with an intravenous bolus dose of 150 microgram/kg (panel C) after failure at lower doses. The prediction of an orthodromic reciprocating tachycardia mechanism by noting P waves in the ST-T segments during tachycardia is supported by the finding of Wolff-Parkinson-White syndrome during sinus rhythm after conversion (panel C).