There’s an important caveat when it comes to the GE-Marquette 12SL interpretive algorithm.
It’s highly susceptible to errors when it interprets ECGs with poor data quality.
Consider the following example.
I don’t know anything about the history or clinical presentation. For my purposes here, I’m only interested in the interpretive statements.
First, the rhythm strip.
The rhythm is borderline sinus bradycardia with 1°AVB. The QRS complex appears to be “wide” and QRS morphology in lead II looks very much like RBBB is supposed to look like in lead I.
When I see something like this, I immediately check the leads to make sure the red and black electrodes are not switched.
Now the first 12 lead ECG.
I suspect this ECG was captured in the back of a moving ambulance. Note that the rhythm strip was captured at 0222 and the first 12 lead ECG was captured at 0255.
In the first place, had this been a STEMI, that’s 33 minutes of time during which the hospital could have been calling in the cath team from home (nights, weekends, holidays). This is sometimes referred to as “parallel processing” and it’s a key concept for prehospital 12 lead ECG programs and regional STEMI systems.
In addition, sometimes you will get wandering baseline artifact in the back of a moving ambulance.
All the more reason to capture your 12 lead ECG on scene with the first set of vital signs.
I cringe when I see an ECG like this on the Lifenet Receiving Station (all too often). This gives ammunition to ED physicians who don’t support prehospital 12 lead ECGs and are adamantly opposed to activating the cardiac cath lab while a STEMI patient is still in the field.
What does this ECG tell us?
In the first place, the heart rate is slower than in the rhythm strip. We also see obvious RBBB morphology in lead V1. Beyond that, the only leads we can really interpret are lead II and the right precordial leads.
The interpretive statement mentions “premature ectopic complexes with ventricular escape complexes”. It also says “lateral infarct, age undetermined.” Both of these statements should be completely ignored because of the poor data quality.
Let’s look at the third and final 12 lead ECG.
The GE-Marquette 12SL interpretive algorithm gets a bad rap, and those of you who have followed my blog from the beginning (or know me from the EKG Club and other internet forums) know that I have defended its capabilities from time to time.
It’s true that the computer has a high specificity when it gives the ***ACUTE MI SUSPECTED*** message, but only when it interprets an ECG with excellent data quality.
That point cannot be overemphasized.
The specificity can be improved even more if the patient’s chief complaint is chest pain and heart rate is less than 100.
The take-home point is this. If you get the ***ACUTE MI SUSPECTED*** message but your ECG is showing poor data quality, you should completely ignore the interpretive statement and capture another 12 lead ECG with excellent data quality.
Under no circumstances should you transmit an ECG with poor data quality to the emergency department for physician interpretation.
Earlier today I Googled “12 lead data quality” and found a document about the ZOLL M-series monitor called 12-Lead ECG Monitoring that says, “The 12SL analysis results can be affected by poor ECG data quality. If poor data quality is flagged by the system, the interpretation statements will be preceded by the statement, “Poor data quality, interpretation may be adversely affected.”
This feature must be unique to ZOLL, because I’ve never seen a similar message on the LP12.
How do you capture a 12 lead ECG with excellent data quality?
- Undress the patient from the waist up, including the bra if it’s a female.
- Prep the skin (shave the skin if necessary and use benzoin tincture if the patient is diaphoretic).
- Strand out each lead individually and don’t wrap the ECG leads around the O2 or IV tubing.
- If possible place your patient in a comfortable semi-Fowlers position.
- Make sure the patient is not holding him/herself up with his/her arms.
- Once the leads are placed, cover the patient with a sheet to prevent shivering.
- Have the patient breathe normally.
- Capture the ECG.
It’s really not that hard.
You should orchestrate all of this with the first set of vital signs.
You should also consider grabbing yourself a few gowns next time you’re at the hospital. The nurses will love you when you bring in a gowned patient with the ECG leads perfectly placed, an IV established, and the first set of labs drawn.