"New" LBBB – What's the big deal?

In the January 2010 EMCast at EMedHome.com, Amal Mattu MD reviews Chang AM, Shofer FS, Tabas JA, et al. Lack of association between left bundle-branch block and acute myocardial infarction in symptomatic ED patients. Am J Emerg Med 2009;27:916-921.

His comments confirm what I have suspected for a long time with regard to LBBB in the setting of suspected ACS.

“This is a really interesting and provocative article that may bust the traditional myth that we should be thrombolysing or cathing everybody with chest pain who presents with a new left bundle branch block.”

“They found that there was no significant difference in the rate of acute myocardial infarction between patients that were presenting with a new, or presumed new left bundle branch block pattern versus patients with a known old left bundle branch block pattern […] In other words, when patients presented with a new left bundle branch pattern, those patients did not rule-in at any greater increased frequency compared to the other patients, and based on this data the argument is certainly made that when patients have chest pain and they present with the left bundle branch block pattern, there’s not necessary a need purely based on the presence of a new left bundle to assume that that patient is having an acute MI, and therefore that patient needs to get thrombolytics or go immediately to the cath lab.”

“As I mentioned before, there is reasonable data to indicate that if the patient has a left bundle branch block – whether it’s new or old – and they demonstrate Sgarbossa criteria, then those patients do end up ruling-in for acute myocardial infarction […] Simple presence of a new left bundle branch block pattern does not appear to warrant immediate activation of the cath lab or immediate thrombolytics according to this study.”

Amal Mattu MD does add the caveat that the guidelines still state that patients with new LBBB are supposed to get reperfusion therapy.

See also:

80 year old male CC: Chest pain

Excessive discordance as a marker of acute STEMI in LBBB

80 year old male CC: Chest pain – Conclusion

58 year old female CC: Chest pain

58 year old female CC: Chest pain – Conclusion (meets all 3 of Sgarbossa’s criteria)

62 year old male CC: Chest pain (LBBB with ST-elevation > 0.2 the QRS complex)

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part I

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part II

Discordant ST-segment elevation in LBBB or paced rhythm

Sgarbossa’s Criteria – New Graphic

Found on the Lifenet Receiving Station (LBBB with concordant ST-depression in leads V3 and V4)

11 Comments

  • Christopher says:

    Sgarbossa's criteria wasn't mentioned in my paramedic class, and it was touched on briefly in Tim Phalen's course (i.e. there is a way to figure it out, but that's left for another time). I get the feeling it is being left out currently perhaps due to the high number of false positives people think it could cause. Although, you could look at it from the other direction that by arming people with the tools to differentiate then you would have less false positives.

  • Tom B says:

    C.Watford – If anything Sgarbossa's Criteria would eliminate (or dramatically reduce) false positives. Is that what you meant? I don't understand the first part, but I agree with the second part! Sgarbossa's criteria is not an "entry level" ECG skill. I'm not at all convinced that the majority of ED physicians are fluent with it.Tom

  • Christopher says:

    Basically I was alluding to the fact that because it is seen as difficult, it is left out of our education in order to reduce confusion.Basically we're taught: "LBBB != STEMI" and to leave it be. I had supposed this to be an attempt to limit false positives because the criteria for differentiation is potentially confusing (Personally, I always have to look it up).

  • Tom B says:

    I think I see the source of our misunderstanding now, but you'll have to correct me if I'm mistaken.Teaching paramedics that "LBBB not known to be old = STEMI" would actually reduce false negatives, because it teaches paramedics to cast as wide a net as possible.In other words, it increases sensitivity at the cost of specificity.Tom

  • Christopher says:

    Correct, and the Cath lab then complains about the lack of specificity.

  • Tom B says:

    I don't know that it's the cath lab that's complaining. It's important to clarify what we mean when we say "false positive" because there are conflicting definitions.Requiring angiography that shows "no culprit artery" and negative cardiac biomarkers is the most stringent criteria.I think we're all united in our belief that we should not subject patients to potentially risky procedures if they do not stand to benefit.I also think most people agree that some "false positive" cath lab activations are inevitable but should be minimized to the extent possible.One way to do that is to have physicians "over-read" the ECG and "stand down" the STEMI Alert if they do not agree with the paramedic's interpretation.Another way is to question things like the presumption that a LBBB "not known to be old" is automatically "new" and suggests that the patient should be emergently cathed.I can't help but think of the Larson study that showed almost half of patients with LBBB had no culprit artery.I think this article sheds light on the problem. Adding Sgarbossa's criteria to the equation should pinpoint exactly which patients with LBBB (new or old) should be rushed to the cath lab.Can paramedics be taught Sgarbossa's criteria? Well, I think so. EM physicians can be taught Sgarbossa's criteria, too! Tom

  • Jesse says:

    Let me see if Im following this correctly. According to one of the graphs youve previously posted, those most in need of pci were pts with ami and a new bbb.What Im taking from this post, is that that statement should be modified to "those most in need of pci are pts with a bbb (old or new) that rule in for ami using sgarbossas criteria."That sound about right?

  • Tom B says:

    Jesse -We know that patients with bundle branch block have the highest mortality based on the FTT data, but those are patients who "ruled in" for AMI based on a rise and fall of cardiac biomarkers.Based on that, it seemed logical to give thrombolytics to "new" LBBB. The problem is, it turns out that many of them do not "rule in" for AMI (either because the angiography is negative or because there's no rise and fall of cardiac biomarkers).So yes, your modified statment makes sense, but a patient with a preexisting LBBB who presents with acute inferior STEMI as evidenced by Sgarbossa's criteria, while they need emergent reperfusion therapy, may not have as much myocardium at risk as a patient with acute anterior STEMI that causes the "new" LBBB.It's also worth mentioning that a rise and fall of cardiac biomarkers could be NSTEMI as opposed to STEMI (which is an imperfect surrogate to indicate an acute thrombosis in an epicardial coronary artery).If I were an emergency physician (which of course I am not) I would want a patient with LBBB to 1.) meet Sgarbossa's critera, 2.) show changes on serially obtained ECGs, or 3.) show wall motion abnormalities on a bedside echo prior to activating the cardiac cath lab.It seems to me that would prevent what happened in the Larson study where almost 50% of patients with LBBB had no culprit artery.Tom

  • Jesse says:

    As always, thank you for your wisdom master jedi.It would be interesting to find out if the 50% that did have a culprit artery met Sgarbossas criteria..

  • Tom B says:

    Jesse – It would very interesting! I suspect they did meet Sgarbossa's criteria (or at least the modified form) based on Dr. Smith's views on the topic, since he works at Hennepin County Medical Center (which is in Minneapolis).Tom

  • Baren says:

    Hi Tom, Jesse and Christopher. I agree with Tom in that too much time has been spent worrying about LBBB or RBBB with ACS and that the Sgarbossas criteria could only benefit our industry. South Africa has recently taken a step forward in allowing Pre-Hospital Emergency Care Practitioners(Paramedics with a four year degree or higher) to fibrinolyse very specific cases only after 12 lead ECG/ EKG interpretation and cardiologist consultation both agree. Our pre-hospital criteria differs in that we prefer to fibrinolyse younger patients without inferior infarcts and more specifically those who cannot recieve PCI within 90 minutes of symptom onset, not EMS arrival. This has come about mainly due to our large distances to emergency departments and cath labs. It is well known that biomarkers are renowned for only elevating close to 3 hours after the myocardium has sustained ischaemia or infarction making this a confirmation tool later on. A high suspician and good patient Hx and Assesment are always key to Dx the correct cause of chest pain. Our main indication is a symptomatic STEMI with or without BBB. The LATE, MINAP and GREAT studies show incredible data to support this. BBB was never been a primary concern. Hope this helps. Keep up the amazing work

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