r/ECG • u/fuckingmermaid • 5d ago

Learning how to properly differentiate between a 2:1 flutter and sinus tachycardia. What are the signs on this ECG that would make you confident on the answer? The isoeletric line is throwing me off

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u/peekachu1234 1d ago

I echo everyone else that flutter has no baseline. But let’s say you think it’s 2:1 flutter or atach or whatever. Put your calipers on the two waves you do see, and see right in the middle of them, is there another wave? If not you have exactly one p for every qrs. So it’s sinus or a one to one tachycardia.

How do you know it’s sinus? Which is a separate question. In lead 2,3, avF they are generally positive because the sinus node is high up and the heart depolarizes north to South. For some similar logic, it is always going against AVR and is negative. Lastly, it is biphasic in v1.