Wide QRS Complex Tachycardia in a Young Healthy Man

Abstract

A 22-year-old man presented to the emergency room with palpitation. He had been suffering palpitations several times per year since the age of 17. Recently, the frequency of palpitations had increased to twice per week. The palpitation attacks usually lasted for one hour and terminated spontaneously. However, the present attack had been persisting for more than five hours. His pulse was 170/min and BP was 110/70 mmHg, and his general condition was good. A physical examination showed no abnormality except for rapid pulse. A chest X ray was normal without cardiomegaly. Echocardiography performed three months ago showed normal left ventricular contraction without any structural abnormality. Twelve-lead ECG showed wide QRS complex tachycardia (duration of 0.14 sec) with a right bundle branch block and left axis configuration (Figure 1).What is your diagnosis of the tachycardia?