Wednesday, 15 September 2010

76 year old female CC: Chest pain - The case for this being an acute anterior STEMI

I find this case to be extremely interesting for a variety of reasons. (Click HERE to see the original post).

As many of you pointed out, the history and clinical presentation isn't exactly screaming "Acute Coronary Syndrome!"

But then, as others have pointed out, the elderly often have atypical or vague symptoms.

Let's look at the 12-lead ECG itself (I will post the serial ECGs to the original case study so you can see those, too).

First question, does it meet the ACC/AHA STEMI criteria (imperfect though it may be). I have to admit, when I first reviewed this case I didn't see it, but the answer is, "Yes."



Hyperacute T-wave are visible in several leads, the most noticeable of which are leads V4 and V5.

Here's an important teaching point, courtesy of Dr. Smith from Dr. Smith's ECG Blog in reference to this case.

"The T-wave is the best indicator of viable myocardium at risk."

Is ST-elevation also present?



Some of you have been taught that 2 mm of ST-elevation is required in two contiguous precordial leads. That is only the case for leads V2 and V3. This is probably due to the fact that leads V2 and V3 often have deep S-waves.

In this case, lead V4 has about 2 mm of ST-elevation and lead V5 has 1 mm of ST-elevation.

Couldn't this be benign early repolarization? In theory, yes, although BER is not particularly common in elderly female patients.

There's also another way to tell. Look at the R-wave progression in leads V1-V4. It's non-existent, which points away from benign early repolarization.

Do any other leads show ST-elevation?

As some of you mentioned in the comments, ST-elevation is present in the high lateral leads I and aVL. However, it's less than 1 mm. So it's not significant. Right?

Wrong.

It's significant due to the low amplitude of the QRS complex! You have to consider proportionality.

To illustrate this point consider the following graphics that "stretch" leads I and aVL vertically while preserving the ST/QRS ratio.



This is the same image side-by-side but the image on the right has been "stretched" vertically. It's a single cardiac cycle in lead I. It looks much worse when it's stretched, doesn't it? But the ST/QRS ratio is exactly the same!



Here's another example of lead I.



Here's lead aVL, normal on the top and "stretched" vertically on the bottom.

If only there were reciprocal changes to firm up the diagnosis!



You will notice a flattening of the ST-segment in leads III and aVF that by itself would not seem particularly significant in a 76 year old female with a history of emphysema. However, it's all about context! Over and over again I have preached Tomas Garcia, MD's admonition to "consider the company" that any ECG abnormality keeps.

A flattening of the ST-segments in the inferior leads when the anterior and high lateral leads are suspicious for acute STEMI should be considered reciprocal changes.

Now what do you think? Are you sold or do you still have doubts?