The patient is a 40 year old male who presented with dizziness and palpitations. He isn’t having any chest pain or trouble breathing. He was able to speak in full sentences, had clear lungs and tachycardia on the monitor.
This is his EKG: 20170717
The answer is atrial flutter with a 2:1 conduction, one of the supraventicular tachycardias. The atrial flutter conduction loop usually moves COUNTER-clockwise around the tricuspid valve and up the septum. This circles around at around 300 beats per minute so the 2:1 conduction into the ventricles clocks in at 150 beats per minute. It is difficult to distinguish from PSVT.
Here’s a nice diagram from ECGpedia.org.
You can recognize it by the narrow QRS complexes (indicating ventricular conduction is going through the bundle His and left and right bundle branches), regular rate (unlike atrial fibrillation) and the flutter waves if you can see them.