Saturday, 20 November 2010

63 year old male CC: Syncope - Conclusion

Here is the conlcusion to 63 year old male CC: Syncope.

First, let's take another look at the 12-lead ECG.



This 12-lead ECG shows poor data quality.

This is a problem because the ECG is abnormal and suspicious for acute anterior STEMI.

We need to consider whether or not this could be benign early repolarization or a strain pattern from left ventricular hypertrophy.

This ECG does not meet the voltage criteria for LVH and does not have the general appearance of a "strain pattern" (but it would be nice to be able to take a nuanced look at the ST-segments and T-waves in leads I and aVL).

Could it be benign early repolarization?

Stephen Smith MD from Dr. Smith's ECG Blog has come up with two different decision rules to help distinguish acute anterior STEMI from benign early repolarization.

Here they are in Dr. Smith's own words:

Decision rule #1

If the mean R-wave amplitude from V2-V4 is less than 5 mm, then it is almost certainly MI. If greater than 5 mm, it is probably BER. A cutoff of 5 mm gives a sensitivity for MI of about 70%, but a specificity of greater than 95%.

In this case the first decision rule favors BER.

Decision rule #2

If 2 of the following 3 questions are answered "yes", then it is MI with an accuracy of about 85%: 1) is the QTc > 392 ms? 2) Is the ST elevation at 60 ms after the J-point in lead V4 > 2mm? 3) Is the R-wave in V4 < 13 mm?

In this case the second decision rule favors acute anterior STEMI.

Do you see why this is such a difficult case?

I've said it before and I'll say it again.

Sometimes the "go or no go" decision for the cardiac cath lab comes down to fractions of millimeters!

I really liked the way Tim Phalen explained the importance of serial 12-lead ECGs when we appeared together on the MedicCast at EMS Today 2010. He compared it to taking a single photograph of Old Faithful.

"Maybe it's a geyser. Maybe it's a hole in the ground."

In this case a single 12-lead ECG was captured by the EMS crew. They did, however, obtain another rhythm strip as they were pulling into the hospital.



It appears as though this might show a change from the initial rhythm strip but we're in monitor mode and a diagnostic quality 12-lead ECG should be used to observe changes on serial ECGs.

Let's move on because poor data quality is about to rear its ugly head again. This time inside the hospital.

Here is the 12-lead ECG captured on arrival at the hospital.



Now we have a 12-lead ECG with excellent data quality.

When the medical chart was pulled it was discovered that the patient had a history of "remote inferior wall myocardial infarction".

It was the next ECG that led to the patient becoming a "Code STEMI".



You will note that someone has drawn brackets around the ST-segments in leads II and III.

This problem is, this isn't ST-depression. This is artifact.

The ST-depression is not present in the first cardiac cycle. In addition, the baseline is shifted upwardly prior to the P-wave, marking this as some kind of wandering baseline or loose lead artifact.

Poor data quality continues in the right precordial leads.

From the cath report:
"The initial ECG in the emergency department was of concern because of ST-elevation in the anterior septal leads. This was not clear-cut acute myocardial injury-type ST-elevation. A follow-up ECG revealed the same findings and also non-specific inferior T-wave changes, possibly representing reciprocal changes. These changes were different in comparison with the previous ECG from our office in 2004. Therefore, ER physician's consultation with me, we elected to treat this as a Code STEMI event."
The patient was sent to the cardiac cath lab where angiography revealed no acute lesions.

Serial cardiac biomarkers came back negative.

The patient ruled out for acute myocardial infarction.

Please don't think that I believe I'm perfect. I know that I'm not. All human beings make mistakes and that's why patient safety experts like Peter Pronovost advocate designing systems that help minimize the impact of human error.

The first 12-lead ECG captured in the emergency department might have been reason enough to cath this patient (I am not in possession of the 12-lead ECG from 2004 so it's difficult to speculate).

I also know that emergency physicians are under tremendous pressure not to delay care for acute STEMI patients.

It is impossible to identify acute STEMI with perfect sensitivity and specificity.

Having said that, poor data quality should not enter into the equation.