PSVT

A 21-year old female came with history of palpitation on and off since last five year. 

ECG 1 (Click on the image to enlarge it)

ECG is showing narrow qrs complex regular tachycardia. I can not see any clear P wave or probably few doubtful P wave merged in the qrs complex seen at the end of qrs in lead II. So it is a short RP tachycardia. There were no ST- T wave changes.

ECG after giving adenosine injection (Click on the figure to enlarge it)

ECG is showing normal sinus rhythm at 75 beats per minutes, PR interval 130 msec, no evidence of any delta wave or any pre-excitation any where seen in the ecg. There are no ST-T wave changes.
So the final diagnosis of this patient is Short RP tachycardia and differential could be AVNRT, Atrial tachycardia or AVRT. Because P wave are merged into the qrs complex or very near the QRS complex(if i take negative complex seen in figure 1 in lead II), then the RP interval is less than 70 msec so most likely diagnosis is AVNRT.

Patient underwent Electrophysiological study and it show dual AV node physiology with AVNRT. Patient underwent successful radiofrequency ablation of slow pathway. Post ablation there is no evidence of any tachycardia. Patient was discharged in stable condition.

Let's discuss how to approach in a case of Narrow QRS complex tachycardia.

Thank you.