There is clearly a tachycardia with narrow QRS complexes indicating a supraventricular rhythm. The clues to the aetiology are the heart rate of almost exactly 150 / min and the saw tooth waves seen ...
Narrow-complex tachyarrhythmias are rapid heart rhythms originating in the upper heart chambers, characterized by a QRS duration of less than 120 milliseconds on an EKG. These arrhythmias can be ...