This ECG is Waiving a Flag; Did you Catch it?

“Hey guys! What’s going on? I heard the STEMI call and came right over.” You hear one of the friendly interventional cardiologists say to your resident team.

“Oh good! I’m so glad it’s you on call today, you taught me so much on my CCU rotation,” the intern tells the interventionalist. “We have Mrs. Bronston in bed 7. A 57-year-old female with known coronary artery disease, hyperlipidemia, hypertension and diabetes. She’s complaining of intense chest pressure for the past 2 hours. Initially thought it was indigestion, but her daughter, who’s a nurse, convinced her to come in and get checked out. Here’s the ECG, we’re worried about a lateral STEMI:

Rate: 108 beats

Rhythm: Atrial fibrillation. It’s irregularly irregular, pretty good baseline fibrillations in the V1 rhythm strip

Axis: Normal

Intervals: Narrow QRS complexes, no PR interval, QTc looks reasonable

Morphology: Large ST segment elevation in leads I and aVL, also in V2. There is ST segment depression in lead III. There’s also some STE in lead V5 (but that isn’t a part of the pattern we’re going to cover today)

Final read: ST segment elevation in the high lateral leads (I and aVL) but also in V2? With ST depression in III. I’d activate the cath lab over this, but it doesn’t exactly follow traditional “STEMI Teaching”

“Oh! This ECG is quite exciting!” The interventionalist says. “Let me see. My team is in house, but they’re going to need about 2-3 more minutes to prep the lab and come down to get Mrs. Bronston. That gives us a few brief minutes for some bonus education. Did you know that this ECG tells me where the lesion is most likely going to be?”

“Well… Um.. It’s a lateral STEMI, right? So, the lesion is classically the left circumflex artery?” the intern asks.

“A great thought! But not quite. This ECG is showing a pattern known as the South African Flag Sign, classically associated with an occlusion of the first diagonal branch (D1) of the left anterior descending artery (LAD),” he explains.

“The South what sign?” The intern asks.

“The South African Flag Sign! Again, it’s an ECG pattern classically signifying occlusion of the first diagonal branch (D1) of the LAD. The ECG shows ST elevation in leads I, aVL, and V2 with a reciprocal ST depression in III. It’s named the South African Flag Sign due to the resemblance of the green portion of the South African Flag corresponding to the layout of the leads of an ECG printed in standard format. Here, take a look at the Flag of South Africa,” he says, pulling out his phone to google a quick picture:

“Now, imagine this flag on top of the ECG:”

“Following the green portion of the flag, notice the ST segment elevation in I, aVL, and V2 with ST segment depression in III. Of note, aVF may often have ST depression; however, this doesn’t fit the pattern of the flag, so think of it as a bonus if it’s there. I marked up the flag with some reminders of where to expect ST segment elevation (STE) and ST segment depression (STD):”

“Excuse me, Sir, the cath lab is calling for you, they’re almost ready for you to begin,” your clerk calls out.

“Yes, yes, just 30 more seconds for a history lesson. Uh… tell them I’m on my way!” he responds. “Anyway, this pattern signifying a D1 occlusion was first published in the American Journal of Emergency Medicine in 2015 by Drs. Edward Durant and Amandeep Singh, however Dr. Laszlo Littmann published a follow up article later in 2015 that coined the term SAFS to remember this ECG pattern, as it does not follow traditional STEMI criteria. These patients should be treated with the same rapid clinical course as traditional STEMI criteria findings, which means I need to be heading upstairs to the cath lab. Nice pick up, young intern! I will text you after the cath and let you know how it goes!” he says, hurrying off.

Case Wrap Up:

“Hey, did I hear one of the interventionalists doing some teaching about that STEMI case we had earlier today?” you ask the intern.

“Yeah! It was great! He was my attending on my CCU rotation earlier this year and is such a great teacher. Makes everything so easy to understand, not condescending at all! He said he’d call with results after the cath, so we should know what happened to Mrs. Bronston soon!” he says.

“Cath lab on the phone for you on line 2” the clerk tells the intern.

“Hello! My intern friend! Hope the ER is going well. Good news. Mrs. Bronston is going to be just fine. As expected, there was an acute D1 occlusion which I have successfully stented. She’s now in the CCU recovering. Great work with her!” the interventionalist says. “Ok, back to the cath lab. Catch you later!”

Recap:

1. The South African Flag Sign on ECG is one of the many patterns concerning for acute coronary occlusion mentioned in the 5^th Universal Definition of Myocardial Infarction
2. This pattern sticks out because it follows the green portion of the South African Flag
3. Look for:
   1. ST Segment Elevation in I, aVL, and V2
   2. ST Segment Depression in III
4. This pattern is significant for an acute D1 occlusion (the first diagonal branch off of the LAD)

Hit me up with any questions,

Lloyd