Wednesday, November 28, 2012

How to cure incomplete RBBB.

I had an interesting sign-out yesterday. The patient was a 30-ish year old woman with some vague complaint that localized to somewhere between her eyes and her knees. The off-going physician is a model of thoroughness, and they mentioned that the patient was getting, amongst other tests, a CT for pulmonary embolism.

"I wasn't really thinking PE at first," they explained to me, "but after I saw the incomplete RBBB on the ECG, I sent a D-dimer." The D-dimer, of course, came back trivially elevated, and the CT had been ordered.

Ah, the scourge of the IRBBB. It typically take the appearance of an rSR' pattern in V1 and V2 with a narrow QRS, although the AHA takes a dim view of this colloquial definition.

This seemingly "hard" element of evidence, however, can be surprisingly malleable!

I cured the patient's IRBBB!
The patient was already off at CT, so I looked at the ECG myself. It looked pretty darn normal, except for the right-precordial leads:


V2 shows an rSR' pattern, clearly.

The patient returned from CT scan, and I awaited the results. In the meantime, however, I re-interviewed an examined the patient, and convinced myself that she was low risk for all of the "bad actors." The IRBBB stuck in my craw, however, and after some fiddling around, I aquired a new ECG.

Sweet. It's not up there with sinking a difficult tube, or threading a pacer wire, but it makes for a cleaner chart!

What did I do?
I put V1 and V2 where they are supposed to go.

For a fuller explanation of the background here, please check out The most difficult step in obtaining an ECG. It's a post I wrote for paramedics about the importance, as well as the common difficulty, of placing the precordial leads in the correct locations. It's written in a conversational and witty tone, with plenty of illustrations - you'll like it!

Suffice it to say, though, that V1 and V2 are usually placed far too high on the chest. This produces a number of artifacts, including pseudo-infarction patterns and, yes, IRBBB.

I took a picture (with the patient's knowledge and permission - she believes in education!) of the actual lead placements on the patient's chest. The electrode wires are attached to the proper locations, at the 4th intercostal spaces, just to the right and left of the sternum.

Thank you Ms Anonymous!
The other electrode stickers are located only about 5-7 cm higher, around the 2nd or 3rd intercostal spaces, but it was enough to produce the spurious IRBBB.

The Bottom Line
Learn where to put the leads yourself.

If the diagnosis is going to rely critically on the ECG, you ought to check out where the electrodes were placed by the nurse, tech, or paramedic. Certainly, if there are abnormalities isolated to the precordial leads you should go back and do this, especially if the ECG doesn't match the patient's age or presentation.

BONUS QUESTION: For major extra points at the "Port, tell me what electrophysiologic diagnosis may rely on placing V1 and V2 higher than usual.

(Answer can be found by checking my self-aggrandizing link.)

*******
Added post-publication.

Mr Várhegyi points out a similar example, elsewhere on the web, of an IRBBB. Oddly, that example seemed to show some QRS prolongation in V2 that was not appreciated in the other leads.

Source

So, I took another look at my patient's initial ECG:


Darned if it doesn't seem to also have an isolated, minor (< 0.02 seconds), QRS prolongation in V2.

I'm going to defer providing an explanation until I have some idea about why this occurs, or even declaring that this is a reliable feature of improperly placed precordial leads. But it's apparent in these two examples. I'll look into it - anyone else with a better idea write in!


3 comments:

  1. Great post!

    Placing V1 and V2 higher than usual may help identify the Brugada pattern.

    ReplyDelete
  2. Excellent! Grabbing the early-morning bonus points.

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  3. Dear Dr. Walsh!

    Yesterday on one of the ECG pages on Facebook a similar case was posted. Maybe you have already read that.
    The ECG is here (with my modification):
    http://kepfeltoltes.hu/view/121222/Brugada_or_too-high-lead-placement_www.kepfeltoltes.hu_.jpg

    I was totally certain that this is not RBBB, because:

    1. There is no deep and wide S wave in left sided leads.

    But more interesting:

    2. There is an isolated QRS prolongation in V1-2 (QRS is 120 ms wide in V1-2, but about 90-100 ms in other leads). On the ECG linked above I put a vertical line through the J point of V3, and so one can see that the QRS ends at the top of the R' wave in V1-2, so these are not R' waves actually, and that is why the top of them is the J point itself, and the QRS is not 120 ms wide as we think if we only see V1-2, but 90-100 ms (as in V3 and other leads).
    And if that is the J point then the ST segment is by definiton elevated (so it is a downsloping ST elevation).

    That's (downsloping ST elevation) why I thought it is Brugada pattern which was supported by the patients history of cocaine abuse (which - as far as I know - can mimick or trigger the appearance of Brugada pattern). However, not so typical Brugada pattern, as the ST segment is only elevated for 20 ms.

    BUT:

    The admin then wrote the solution: V1 and V2 were placed too high.

    I know this can cause RBBB-like pattern, but I think it won't cause QRS prolongation, especially isolated QRS prolongation in V1-2. So I'm a bit skeptic:-)

    In your example here the QRS is not prolonged (comparing the wrong and the right lead placement strip, the QRS is about 80 ms in both).

    What do you think?
    Thanks for your answer!

    Best regards,

    Márton Várhegyi
    5th year medical student
    Semmelweis University, Hungary
    (interested in electrocardiography and emergency medicine)

    ReplyDelete