Pericarditis vs STEMI

So what is a STEMI?
STEMI criteria:
The ST segment of an EKG will be elevated by more than 3 mm in the precordial leads and by more than 1 mm in the limb leads. Further, in the precordial leads, the shape should be convex up (like a tombstone). The shape matters more than the amount of elevation in some cases. You may have minimal elevation, but the shape is convex up, that could be considered a STEMI.
In the limb leads, the shape does not matter, just the elevation. Anything more than one small box, and you have a STEMI! Pretty straight forward. Unless, of course, it is an early repol!

So why do people get confused? And what is Early Repolarization?
There is an entity known as normal variant early repolarization that can give you ST segment elevation. But this is not a STEMI. It is a normal finding.
So how can you tell the difference? Look at the shape of the ST segment take off (the J point), it will usually be a notch and does not take off flat across. See the example below.

Above you see the first example on the right. The notch on the J point gives it away as early repol. In the far left example, you see the notch again in one of the precordial leads, usually V2 or V3. This is early repol, not a STEMI.
Here is an Early Repol EKG:


So what about pericarditis?
Pericarditis ST elevations look like the concave upwards ST elevations of early repol, but do not have the notch. Further, you may have PR segment depression in lead II. There will be no reciprocal changes or ST depressions anywhere.
 Good example of pericarditis EKG:
 
Notice the ST elevations all over the place with no reciprocal changes.
 Below is a good example of an Inferior STEMI.
 
Notice the reciprocal changes in the anterior leads. You see depressions. While it is not necessary to have reciprocal changes, they can happen, and it helps clinch your diagnosis.
Below is an anterior STEMI, without reciprocal changes.

 Below is another Anterior STEMI with the perfect tombstone pattern. No reciprocal changes.

 Here is a nice table comparing the various EKG findings in STEMI, early repol, and pericarditis.

Comparison of ECG Changes Associated with Acute Pericarditis, Myocardial Infarction and Early Repolarization
ECG finding	Acute pericarditis	Myocardial infarction	Early repolarization
ST-segment shape	Concave upward	Convex upward	Concave upward
Q waves	Absent	Sometimes Present	Absent
Reciprocal ST-segment changes	Absent	Sometimes Present	Absent
Location of ST-segment elevation	Limb and precordial leads	Area of involved artery	Limb and Precordial leads
ST/T ratio in lead V6*	>0.25	N/A	<0.25
Loss of R-wave voltage	Absent	Present	Absent
PR-segment depression	Sometimes in Lead II	Absent	Absent

If you are unsure if it is a STEMI or not, KEEP GETTING EKGs! PLASTER THE WALLS WITH EKG PAPER! STEMIs evolve! They don't look the same. If you have 10 EKGs in the last hour, and they all look the same.... it's not a STEMI!

EKG challange 2

Let's take another look at the rhythm strip. 

This ECG shows 3rd degree AV block with a junctional escape rhythm at 40 beats/min.

Let's march out the P-waves.

When a bradycardia presents with more P-waves than QRS complexes, we know there is a block of some kind.

Because the PR-interval is variable we know this is either 2nd degree AV block type I (Wenckebach) or 3rd degree AV block.

So which one?

With 2nd degree AV block type I there will be clustering of QRS complexes because of the "dropped" P-waves.

This ECG shows a constant R-R interval.Therefore, it is reasonable to assume it is 3rd degree AV block.

So, is the escape rhythm junctional or ventricular?

The QRS complex is "narrow" at 92 ms (0.092 s) according to the computerized measurement.

Hence, it is junctional and not ventricular.

Now let's look at the 12-lead ECG.

This 12-lead ECG shows acute inferior ST-elevation myocardial infarction (STEMI).

Note the ST-elevation in lead II, III and aVF and reciprocal ST-depression in leads I and aVL.

(Note: The precordial leads aren't pretty either. There is subtle ST-depression in lead V2 and R-wave progression is absent in the right precordial leads (V1-V3). The ST-segments and T-waves are flat in leads V5 and V6.)

This 12-lead ECG is also very suspicious for right ventricular infarction because the ST-elevation in lead III is greater than the ST-elevation in lead II.

Regardless, the patient's blood pressure is 80/40 so nitroglycerin is contraindicated.

The patient needs fluid. Lots of fluid!

You might argue that the patient should receive atropine or transcutaneous pacing (TCP).

That might prove to be therapeutic, but it's important to remember that the most important determinant of myocardial oxygen demand is heart rate.

Correcting the heart rate could reverse shock and improve coronary perfusion. Or it could increase myocardial demand to the point where it worsens ischemia/injury.(  hypotension and bradycardia in the setting of acute inferior STEMI is often a manifestation of the Bezold-Jarisch reflex (hypervagotonia))

To me it makes more sense to try fluid first.

The other important thing, of course, is to call a "STEMI Alert" and get this patient to a cardiac cath lab or fibrinolytic therapy depending on transport time!

Remember, time is therapy for STEMI patients!

Treatment:  beginning a fluid bolus with the IV start and early use of atropine (w. the requisite med control), followed by TCP if no effect is seen, and finally dopamine at as low of a dose as I can muster (MAP of 70-80 if I can titrate well enough, higher if she has baseline hypertension)

EKG challange 1

I was just going thru few ECG and found this one very interesting...


If you see carefully-----there is ST depression in V1-v5....you might argue that its Anterior Subendocardial Ischemia or 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.

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.


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.