Which SVT?

Came in due to palpitations.

Image 1

What is the rhtyhm?

This is a narrow complex tachycardia at a rate about 167 bpm. In leads II, III aVF and V1, there is a distortion in the early part of the ST segment. So it looked like a supraventricular tachycardia (SVT) that has a short RP. Tachycardia can can be classified based on the relationship of the RP inteval to the PR interval. Thus, this case is a regular, narrow complex, short RP tachycardia.

Here is the strip after adenosine.

Image 2

There are upright or positive P waves in II, III and aVF and looked biphasic in V1. The atrial rate is about 167 bpm (9 small squares) There is also a clear isoelectric interval between P waves. Later part of the strip showed 1:1 conduction with a ventricular rate of 167 bpm. So, this is atrial tachycardia.