Postoperative narrow complex tachycardia presenting with low cardiac output

A 6-month-old child was diagnosed as a case of complete balanced atrioventricular (AV) canal defect and underwent intracardiac repair. His baseline ECG is shown in figure 1. Soon after shifting from the operating room, he developed a narrow complex tachycardia (shown in figure 2) with a rate between 180 and 210 per minute. His inotropic support, which consisted of low-dose intravenous milrinone, was soon stopped. He started to show signs of low cardiac output with hypotension and reduced urine output, despite fair left ventricle (LV) systolic function. The tachycardia was not responsive to beta blockers, direct …