If I show this 12-lead to a group of paramedics, I would wager close to 100% would accurately identify it as an inferior MI and call in a STEMI alert if the 50 year old male patient in front of them was clutching his chest.
Now, if I have the same patient and the 12-lead shows this;
How many paramedics are going to say this is a STEMI?
It is not a STEMI, it is a Left Ventricular Hypertrophy.
In a recent study published in the April 2013 issue of Prehospital Emergenncy Care, 63.3% of paramedics identified this ECG as a STEMI.
The study, PARAMEDIC ABILITY TO RECOGNIZE ST-SEGMENT ELEVATION MYOCARDIAL INFARCTION ON PREHOSPITAL ELECTROCARDIOGRAMS, by Mencl, et al, goes against the findings of prior studies that have shown paramedics can identify STEMIs with a high degree of accuracy. The limitations of the other studies have been that they have used paramedics right after training classes and in many cases had them evaluate only a small number of relatively obvious ECGs. The 12-leads used in this study I believe offer a more realistic test of a paramedic’s interpretation abilities.
In this study they had 472 paramedics from 30 different EMS services in five counties with 15 different medical directors read 10 different ECGs and were asked to either identify the strip as a STEMI or not.
Here’s how they did:
The number indicates the percentage of paramedics who correctly identified the rythm as a STEMI or not a STEMI.
Inferior STEMI 96.0%, Anterior STEMI 78.0%, Lateral STEMI 51.1%
Normal 1 97.3%, Normal 2 100%
RBBB 79.2%, LBBB 39.0%, Ventricular pacing 52.8%, LVH 36.7% , SVT 65.3%
The study concludes: “Despite training and a high level of confidence, the paramedics in our study were only able to identify an inferior STEMI and two normal ECGs. Given the paramedics’ low sensitivity and specificity, we cannot rely solely on their ECG interpretation to activate the cardiac catheterization laboratory. Future research should involve the evaluation of training programs that include assessment, initial training, testing, feedback, and repeat training.”
I took the 10 ECGs from this study and gave them as a test to a large group of paramedics ranging from twenty-year veterans to new paramedics and found similar results. These results square with my observations of paramedics bringing possible STEMI patients into our hospital.
Here’s what I take from it:
Paramedics can identify inferior STEMIs with a high degree of reliability. Lateral and Anterior STEMIs can be more difficult. Left bundle branch and LVH can particularly cause confusion in some paramedics.
My experience with field STEMI alerts is that paramedics tend to by shy about calling for STEMI alerts, and thus have fewer false activations than this study, if extrapolated, would suggest. In other words, if a paramedic is sure it is a STEMI, such as an inferior, the paramedic will call in a STEMI alert. But while the paramedic might guess a 12-lead is a STEMI such as the LVH ECG above, the paramedic might be less likely to call in a STEMI alert with it.
Despite this well done study, I continue to support field activation of the cath lab through paramedic interpretation alone, but I do believe we need to increase our 12-lead training efforts.
I believe that with frequent training and regular competency checking, paramedics can indeed identify STEMIs with a high degree of reliability. But if you don’t do the training and keep it up, the results will not be as high.
In a future post – What about computer interpretation?