A 53 year old man with a history of palpitations from his teenage years presents to the Emergency Department with an episode of sustained palpitations. ECG is shown below:

• Supraventricular tachycardia, likely atrioventricular reentrant tachycardia (AVRT), ventricular rate 194/min 
• Possible inferolateral ischemia (may be rate related) 

Comment: Negative P-waves (labeled ‘P’) in lead II are likely retrograde and the timing of the relationship between the P-wave and QRS is most compatible with AVRT as the cause of this arrhythmia.