ECG Solution: Mirror on the wall

Did you pick the right treatment plan based off the patient's ECGs?

Editor’s Note:

Editor's note: We asked columnist Tom Bouthillet to pick a winner to this month's contest, and he wrote: "I must have really stumped readers this month! I was expecting to break 100 comments because this is one of my favorite cases of all time.

On the bright side, it gave me the opportunity to pass along a very important tip on ECG interpretation. Namely, that ST-depression and T-wave inversion in leads V1-V3 is more likely to be acute posterior STEMI than anterior ischemia (or NSTEMI). When you see this pattern it's a good idea to check modified leads V7-V9 for evidence of ST-elevation.

For this month I picked Bryan Laviolette as my favorite response, whose answer can be seen in the comment block. He correctly picked up the acute posterior STEMI, recommended emergent transport to a PCI center, and prudently stated that he would exercise caution in doing anything to convert atrial fibrillation to sinus rhythm without knowing the time of onset (due to the risk of embolitic stroke).

-->  Haven't read the initial case presentation? Read: Mirror on the wall

Let's take another look at the 12-lead ECG.

What is your interpretation of this ECG? The patient's heart rhythm is atrial fibrillation with rapid ventricular response.

The ST-segment depression and T-wave inversion in the right precordial leads (V1-V3) is concerning and likely represents acute posterior STEMI. In fact, an ECG finding like this should be considered acute STEMI until proven otherwise.

One trick to help identify the STEMI is to "flip" the ECG and hold it up to a light. What you end up looks like this.

Now it's easy to see the STEMI.

Some might argue that the ST-segment depression and T-wave inversion in the right precordial leads might represent anterior subendocardial ischemia (and probable NSTEMI).

When maximal ST-segment depression is in the right precordial leads (V1-V3) as opposed to the left precordial leads (V4-V6) acute posterior STEMI is far more likely.

However, we don't want this patient's reperfusion to be delayed for any reason! It is therefore prudent to capture posterior chest leads V7-V9.

Alternatively (as this crew did) you can capture a 15-lead ECG with leads V4, V5 and V6 in the positions of V4R, V8 and V9.

Now we have hard evidence that the patient is experiencing acute posterior STEMI. Note the ST-elevation in leads V8 and V9.

The paramedics can now proceed confidently in activating the cardiac cath lab from the field and transporting the patient directly to a PCI center.

Treatment for this patient consisted of 324 mg of aspirin and a 250 ml bolus of 0.9% normal saline. After a short stop in the emergency department the patient was sent to the cardiac cath lab where angiography revealed 100% occlusion of the circumflex artery.

About the author

Tom Bouthillet is a Fire Captain/Paramedic with Hilton Head Island Fire & Rescue, Editor-in-Chief of the, Chief Content Architect of, host of the Code STEMI web series at First Responders Network, a member of the Editoral Advisory Board of EMS World Magazine, and developer of the 12-Lead ECG Challenge smartphone app. He has taught nationally in the Critical Care Transport (CCEMT-P) program out of UMBC and his writings have been referenced in the American Heart Journal, the Journal of the American College of Cardiology: Cardiovascular Interventions and the EP Lab Digest. Contact Tom at

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