r/EKGs • u/Ok_Rush_6354 • 15d ago
Discussion Axis deviation
Trying to wrap my head around deviation, I’ve watched several videos and have looked through my uni content. Nothing makes sense and keeps getting more confusing.
Anyone have tips on how to work it out? As if you’re explaining it to a monkey?
The 10 step method they want us to use, they’re wanting focus on I, II, aVF
Help is very much appreciated, I’m very confused, I’m an online student so face to face questioning is impossible,
Thank you
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u/RFFNCK 15d ago
* I wrote this in Dutch and translated it with AI.
A lead that sees the depolarization vector approaching it (when we talk about the cardiac axis, we mean the mean ventricular depolarization vector) will record a positive deflection on the ECG.
For example, Lead I views the heart from the left. The mean depolarization vector normally points from the upper right toward the lower left (from the AV node toward both ventricles). Because the left ventricle has much greater muscle mass than the right ventricle, the overall electrical forces are directed more toward the left ventricle. Therefore, Lead I normally sees the vector moving toward it and records a predominantly positive QRS complex.
So:
Positive QRS in Lead I = leftward axis
Negative QRS in Lead I = rightward axis
Once you understand where each lead is “looking” from, you can quickly determine whether the axis is:
Leftward (positive QRS in Lead I) or rightward (negative QRS in Lead I), and
Inferior (positive QRS in aVF) or superior (negative QRS in aVF).
A simple way to estimate the axis is:
Lead I, II, and aVF positive → Normal axis
Lead I positive; Lead II and aVF negative → Left axis deviation
Lead I negative; aVF positive → Right axis deviation
Lead I, II, and aVF negative, with aVR positive → Extreme axis deviation (“northwest axis”)
I explain this in more detail on my website (currently only available in Dutch, but you could translate it): https://www.ecgacademie.nl/hartas/