Newborn in cardiogenic shock.

CLINICAL INTRODUCTION: A 2-month-old baby boy was referred to our centre due to tachycardia and acute heart failure. The ECG showed a narrow complex tachycardia with a heart rate of 300 beats per minute (Figure 1). Echocardiographically, a patent foramen ovale and a parachute mitral valve with mild regurgitation were diagnosed; cardiac function was highly impaired.heartjnl;104/6/467/F1F1F1Figure 1ECG (50 mm/s) showing the small complex tachycardia.

QUESTION: Which of the following is the most likely diagnosis?Ectopic atrial tachycardiaAtrial flutterChaotic atrial tachycardiaFocal micro re-entrant tachycardiaAtrial fibrillation.