Wednesday, February 11, 2015

New Left Bundle Branch Block (LBBB) and Dyspnea

It is important to remember that the latest (2013) ACC/AHA STEMI guidelines removed New Left Bundle Branch Block (LBBB) as an indication for emergent reperfusion because there are too many false positives.

A reader sent this:

An elderly female presented with dyspnea, nausea, diaphoresis, and indigestion at 2am.  She had a history of CAD with stents, and no history left bundle branch block.
There is sinus rhythm and Left Bundle Branch Block.  There is not a lot of ST elevation, nowhere near 5 mm.  Lead V5 possibly has some concordant STE, but there is a wandering baseline and it certainly does not come to 1 mm.
However, the ST/S ratio in V2 is high in spite of only 3 mm of STE, and it thus meets the Smith-modified Sgarbossa criteria

The physician wrote to me that he was suspicious of LAD occlusion, based on the modified Sgarbossa criteria, and called the interventionalist, who said, “It doesn’t meet Sgarbossa criteria.”

The emergency physician continued: "I didn’t mention your study directly but expressed my concern that this was a STEMI. We activated the cath lab.  She had a totally occluded LAD with thrombus."

Here is a suggested algorithm by Cai and Sgarbossa, using the Modified Criteria (full text and algorithm copied below).

See two figures below:


  1. THANK YOU for posting this Steve! That said - all it takes is one glance at this tracing in an older woman with new-onset dyspnea and no prior history of LBBB to know that there is acute evolving anterior STEMI. Lead V5 is the KEY - as there is subtle-but-real primary ST elevation. Neighboring leads V2,3,4 just look off (marked J-point ST elevation in V2,3 - and a hyperacute looking T in V4 despite the LBBB) - all supported by your modified Smith-Sgarbossa criteria for disproportionate J-point ST elevation in V2,V3.

    Frankly - I am amazed that the Interventionalist Cardiologist in this case is still clinging to number scales (that he and others apparently do not yet understand how to read ...) - rather than assessing the ECG as an entire entity in context with the clinical situation.

    THANK YOU once again for ALL of your great work in this area!

    1. Ken, as always, this post is not to instruct ECG experts, but to guide those who are NOT experts. I can't just say to anyone "just take one look, it's obvious." Even though it is obvious to you and me. If the interventionalist can't see it, how many clinicians can? Not many. They need help. Rules help. That's why there was the original Sgarbossa criteria.
      As for V5, we looked at concordant ST elevation less that 1 mm, and it was very NONSPECIFIC. Many patients without MI had less than 1 mm of concordant STE. This surprised me, because I thought, like you, that it would be very sensitive (it is) and specific (it is not).
      Proportionally excessive discordant ST elevation (as in V2) was far more specific than less than 1 mm of concordant ST elevation!

    2. Hello!
      Concerning the concordant ST change in V5, is it not that in LBBB the lead at or before transition often gives us the wrong information, that is, even though there is concordance it doesnt mean it is a STEMI?

      Thank you both for your comments.

    3. Not sure why you say so. It is true that the lead at transition may have an equally positive or negative QRS. In that case, there should be no expected discordant ST segment, so any ST deviation is likely ischemia, no matter the direction, and any ST elevation will be ischemic ST elevation.

    4. I think the problem with lead V5 in this tracing is that there are only 4 beats in this lead. Three of these beats ( = the 1st, 2nd and 4th beats in V5) show a concordant ST segment, but no more than minimal ST elevation. That is not diagnostic of a STEMI. In contrast, the 3rd beat in lead V5 clearly looks to have significant ST elevation, as well as a concordant ST-T wave. Which of the 4 beats in lead V5 is “real”? I would think that if it is indeed the 3rd beat in V5 that is the “real beat” — that this picture would then be diagnostic of acute STEMI in this patient with LBBB. But if it is the other 3 beats — then, that alone would not be diagnostic. For this particular case, given associated findings in other leads — I gave additional “weight” to the picture I saw of the 3rd beat in lead V5 in my synthesis interpretation.

  2. Steve,
    Do you know if there are any prospective studies that aim to validate the modified Sgarbossa rule?

    1. Peter,
      We are trying now, but it's not easy. I don't know of any others.
      It's not easy to get a consecutive group of LBBB with coronary occlusion. they are an uncommon group!

  3. Thanks Dr. Smith for your great Job!

  4. Hi Dr Steve,

    I've been following your blog for many years but this is my first post here. I've read the lbbb article few times and i am confused with the diagram and it's explanation.

    In the diagram, if a patient is suspected AMI with LBBB + hemodynamic instability, the management pathways is either pci or fibrinolytics without using the modified Sgarbossa rule.

    However, in the text (I copy & paste)

    "If patients present with hemodynamic instability or acute heart failure, ischemia should be strongly suspected, and
    primary PCI should be considered. The Sgarbossa criteria are particularly helpful in this setting, due to their high
    specificity and positive predictive value. Clinicians can confidently treat for STEMI when a Sgarbossa score of 3 is

    It is recommended to use the rule before the definitive management. Can you help me with this.

    Thank you

    1. Andey,
      Good question. It is a general principle that if a patient has ACS with hemodynamic instability of acute heart failure, they should go the cath lab regardless of the ECG. That said, the crucial part is "if the patient has ACS." Many unstable patients are unstable for other reasons (COPD exacerbation, GI bleed, sepsis, etc.) and those must be ruled out or managed first.
      If the patient is stable, then consider ECG characteristics, including Sgarbossa.
      Steve Smith


Recommended Resources