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Ordinarily I like to write a conference follow up on the same day as conference to review clinical information or research relevant to the topics that were covered that day. Yesterday, however, I was working overnight and just didn’t have the time to put anything together. As fate would have it, I saw something during that very shift that was very apropos to our cardiology board review. There is no better way to learn something in medicine that to review it and then see it clinically, which is what happened in this case.

As you may recall, I mentioned numerous times during the board review that a new left bundle branch block in patients with no prior EKG and symptoms of acute coronary syndrome should be treated as an STEMI and receive treatment with thrombolytics or mobilization of the cath lab (owing to journal club yesterday, I’ll say either-or since we all seemed to agree that doing both is not yet supported by the evidence).

Well, at the end of my shift, a 58 yo smoker with DM and HTN happened to come in with chest pain and SOB for the last 75 minutes upon awaking. The pain was in the left chest without radiation, pressure-like. Vital signs were HR 120, BP 176/98, O2 sat 100% on RA, RR 18. The initial EKG while having pain was:

Note the LBBB with the wide QRS, notched R waves in I, V5, V6 with deep S waves in the early precordium V1-V3. The patient denied prior history of heart disease or myocardial infarction and had never been to this facility before. At this point, the patient was moved into the Resus area and the cardiac cath team was called. Aspirin, beta-blocker, and nitro were administered. Shortly thereafter, the patient reported being pain-free. A repeat EKG was obtained:

Whoa!?! What is going on here? Where’s the bundle? Is this the same patient? If it is, this would seem to be reassuring since the pain is now gone and the left bundle has resolved. Just get two sets and stress or even send for follow up as an outpatient, right?

Actually no. This is what is known as having “dynamic EKG changes” and is very concerning and would seem to indicate that the LBBB is indeed new and is related to a dynamic lesion in the heart. Presumably, the pain and LBBB resolved because the 100% stenosis auto-lysed (or maybe with the help of the aspirin) and the patient’s underlying, native rhythm can be seen on the second EKG. So this is worrisome and indicates that this patient should be evaluated urgently for a critical lesion. In this case, the cath was performed and the patient was found to have a single-vessel coronary disease with 60-70% stenosis in the LCx. Again, presumably no 100% lesion was found in any vessel owing to the pre-cath lysis of the clot which was causing the LBBB.

So in summary, new LBBB is bad and should be treated with the same urgency as an STEMI. It also highlights the importance of the repeat EKG. No matter how tedious it may seem, you can’t see dynamic EKG changes without repeats.

Posted on Thursday, July 19th, 2007 at 9:52 pm by Sohan. Filed under ACS, Conduction Blocks.
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