Differentiating normal early ST repolarization versus left anterior STEMI

Healthy young patients often present to the Emergency Department with chest pain. These patients often have EKGs that show early repolarization, AKA J-point elevation. ST elevation can also mean STEMI – and so while it’s almost never a STEMI in the Pediatric Emergency Department, it could be one – and it’s important to be able to differentiate between the two.

What does a left anterior STEMI look like on EKG?

You can check out this fantastic resource from LifeInTheFastLane.com. In general elevation of the ST segment in the following leads may suggest the location of the MI – but be warner that this correlation is often subject to error and is not always exactly what is seen on cath or autopsy:

Septal = V1-2
Anterior = V2-5
Anteroseptal = V1-4
Anterolateral = V3-6, I + aVL
Extensive anterior / anterolateral = V1-6, I + aVL

Since the left anterior descending artery in in the anterior portion of the heart then the precordial leads show elevation of the ST segments. Check out these sample EKGs and see if you can figure out where the ST changes are.

Anterolateral STEMI: ST elevation in V2-6, I and aVL.Reciprocal ST depression in III and AVF.

Hyperacute Anterior STEMI: There are hyperacute T-waves in V2-6 (most marked in V2 and V3) with loss of R wave height.The rhythm is sinus with 1st degree AV block.There are premature atrial complexes (beat 4 on the rhythm strip) and multifocal ventricular ectopy (PVCs of two different types), indicating an “irritable” myocardium at risk of ventricular fibrillation.

Anteroseptal STEMI: ST elevation is maximal in the anteroseptal leads (V1-4).Q waves are present in the septal leads (V1-2).There is also some subtle STE in I, aVL and V5, with reciprocal ST depression in lead III.There are hyperacute (peaked ) T waves in V2-4.These features indicate a hyperacute anteroseptal STEMI

How can we tell the difference?

Since both can be seen in young patients, this handy dandy Paucis Verbis card from Academic Life in Emergency Medicine does a great job in distilling down the main differences between the two.