Friday, May 14, 2010

Atypical Left Bundle Branch with acute RCA occlusion

This 70 year old woman with a history of left bundle branch block presented with 10 hours of dyspnea.

Notice there is QRS widening with a wide upright R wave in lead V6. That the QRS is not similar to V6 in leads I and aVL makes this an atypical LBBB. Nevertheless,, the same rules of concordance and discordance apply: the ST-T complex should go the opposite, or discordant, direction of the majority of the QRS.

Notice there is concordant ST elevation in inferior leads.

In addition, there is less discordant ST elevation in leads V1--V3 than is normal for LBBB. A normal amount of discordant ST elevation almost always produces an ST to S ratio of less than 0.20. The mean of normal LBBB is 0.09 to 0.11, but ratios of 0.07 to 0.15 may be seen. Thus, with a 26 mm S-wave in V2, the minimum amount of normal ST elevation is 26 x 0.07 or 1.8 mm. However, there is only 1 mm of ST elevation in V1 because of relative ST depression in leads V1 to V3.

This is infero--posterior STEMI in the context of old atypical LBBB.


  1. its not inferior MI sir. because ST in avf within normal right ? but why u called it inferior. and how we can explained the st elevation in v1 and st depression in v2 v3 and st depression in v2 more obvious. is it MI ? or not ?why those elevation and depression ?

  2. Yes, this is infero-posterior STEMI in the setting of LBBB. Perfect ECG for it and proven by immediate angiogram. The ST depression in V2 and V3 are because of posterior ST elevation. The ST elevation in V1 is normal discordant ST elevation of Left Bundle.

  3. sorry i have 2 check strip again ... there is an slight st-elevation v1 v2 v3 . aVF and II its not obvious if there st elevation. lead III good st elevation. you mean when there is LBBB the st elevation will be samll right. but why its infrerior not septal for example plz i want some clues ....

  4. You must remember that the normal condition in LBBB is discordance: the inferior ST segments should be in the opposite direction of the QRS, in this case depressed. But instead they are elevated, though not a full millimeter. Given that they should have at least 1 mm of depression, they now have at least 1.5 mm of relative ST elevation. OK?

  5. how the clinical sir??? and what next plan and treatment??

  6. she went for PCI of the RCA. (Occluded)

  7. Sir, I don't find P wave in this ECG, could it be atrial fibrillation with 3rd AV block and junctional rhythm?


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