A 60-year-old man with known coronary artery disease is admitted to the CCU with unstable angina. On the way to the hospital he had 2 episodes of paroxysmal palpitation of 5-10 minutes duration, associated with severe dyspnea and lightheadedness. Palpitation recurred shortly after admission, while this ECG was being recorded:

• Sinus rhythm followed by ventricular tachycardia

At the beginning of the ECG tracing there is a wide QRS complex followed by two sinus beats and a run of ventricular tachycardia.
The sinus beats show 1st degree AV block and left axis deviation. During ventricular tachycardia the rate is 156/min.
The QRS duration is markedly prolonged (275 msec) and there is “positive concordance” in the chest leads (positive QRS from V1 to v6).
This episode of ventricular tachycardia lasted 10 minutes.