Let’s take another look at the ECG from Part II.
I asked you to look carefully at this ECG, and then using the concept of appropriate T-wave discordance, see if anything bothers you.
Does anything stand out?
How about lead V4?
Here you can see the terminal deflection (blue arrow) is positive, and so is the T-wave (inappropriate T-wave concordance). There is also at least 1 mm of ST segment elevation. That’s definitely abnormal!
Now let’s look in the inferior leads. They all look abnormal, but I’m going to use lead aVF as the example.
The terminal deflection is negative (blue arrow) and the T wave is also negative (inappropriately concordant T-wave). The inferior leads are reciprocal to the anterior leads. Could this represent reciprocal changes? Absolutely!
It is sometimes said that reciprocal changes are of no value in the presence of bundle branch blocks. That’s not entirely true! You just have to interpret them within the context of appropriate T-wave discordance.
In other words, in the presence of bundle branch block, if the terminal deflection of the QRS complex is negative in lead III and positive in lead aVL, then you will have pseudo reciprocal changes (positive in lead III and negative in lead aVL). This is a normal finding in left bundle branch block, for example.
If, however, the terminal deflection of the QRS complex is negative in lead III (as in this ECG) and the same lead is showing inappropriately concordant ST-segment depression or T-wave inversion, then it’s probably not a pseudo reciprocal change. Why? Because it’s opposite the expected pattern.
I’d also like to point out that leads V2 and V3 look really strange in this ECG. Why? Because there’s a merging together of the S-wave and T-wave (sometimes seen in severe hyperkalemia). This is a really ugly T-wave abnormality, especially since we would normally expect a terminal R wave in lead V2 with right bundle branch block.
Something’s going on here!
Let’s look at some serial ECGs. This one was taken just 4 minutes later.
Now what do you see?
*** Update 07/13/09 ***
Here’s the final ECG in the series, recorded as the ambulance arrived at the hospital.
Quite a difference! Once again, it’s easy to see the value of serial ECGs.
Let’s take a look at lead V2 and see how it changed from the first ECG to the last.
The problem (or perhaps the challenge) is that this final piece of the puzzle wasn’t present until arrival at the hospital. Fortunately, it was one of 17 PCI hospitals in the State of South Carolina!
This is why paramedics need to be able to interpret a 12 lead ECG at a high level. Every Patient Counts! We need to make sure that STEMI patients are delivered to the right hospital!
QRS confounders like right and left bundle branch block can make the ECG diagnosis of STEMI more difficult, but these are the patients who receive the most benefit from reperfusion therapy, and prompt, expertly performed primary PCI is the preferred strategy!
We shouldn’t delay a high risk patient’s care because we can’t read their ECG. Unfortunately, it happens every day all over the country.
That’s assuming the EMS system has 12 lead ECG monitors in the first place.
See also:
Right bundle branch block – Part I
Right bundle branch block – Part II
Right bundle branch block – Part III
Increase in inferior reciprocal changes along with changes in the ST segment in V2, V3, I, and aVL. Delta of the two 12-leads.
C. Watford – I wasn't sure what "delta of the two 12-leads" meant, but that was really cool!
You'd think the good folks at Physio would include something like that as a product update.I've had similar ideas before, but I like the overlay concept.Nice work!Tom
Thanks, I was a software engineer long before a paramedic student, so this sort of thinking comes naturally. The only difficulty with taking a "delta" and doing "differential debugging" (to borrow a software term) on these 12-leads is rate changes. However, it is easy enough to pull a representative complex from each lead and superimpose it (I used Paint.Net).
That's true! I know from consulting for a certain implantable device company that changes in heart rate create problems for ST segment analysis, and not always for the reasons you might think! The biggest problem is rate-related changes in the QT interval, which changes the measured value for ST-segment deviation.As the heart rate increases, the QT interval shortens, so if you're measuring the ST-segment a prescribed distance away from the J-point (or R wave) then your measurement point creeps toward the T-wave.If the ST segment is upwardly concave (as it usually is) then as the heart rate increases, the ST-segment elevates, which can cause false positives.Tom
Tom,Again I just want to say amazing. What a great clarification of RBBB. I was just berated by a "colleague" for calling a Code STEMI on a RBBB (Despite ACEP making a statement that patient's with BBB should err on the side of cuation). I wish I could have went back with this information in hand. Thanks for writing this stuff.- Ken
Ken -Thanks for the positive feedback! I'm glad you're finding the Prehospital 12 Lead ECG blog to be useful.Tom
These ECG's show the absolute importance of performing serial tracings! You said 'fortunately' this patient was delivered to a PCI hospital!? Did the paramedic not call a cardiac alert for the patient? Looking at the initial 12-lead I may be hard pressed as well to activate the cath lab from the field, but there is definitely cause for concern with this patient. The presentation along with the abnormal ECG findings would make me hit '12 lead' on the monitor like every two seconds! The second tracing gives us enough 'at least in the system I work in' to activate the cath lab from the field. Our protocols state that there must be 1mm of STE in two anatomically contiguous leads (I am sure similar to most other systems.) The receiving PCI hospitals really don't look at sending a patient off for intervention until there is at leas 2mm of STE in the precordial leads. Enough going on….This is a great blog and I truly enjoy stopping in to progress my knowledge.
Thanks for all of your hard work on this!
i just wish our service had 12 lead but it dosent have to rely on lead 2 and MCL not good enough for this day and age