Friday, December 17, 2010

ECG Interpretation Review - #3 (BBB, Wide QRS, BBB with ST Changes, Ischemia, RBBB vs LBBB)

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QUESTION: Interpret the 12-lead ECG below.
  • What type of conduction defect is present?
  • Are ST-T waves doing what you'd expect given the presence of this conduction defect?
  • Clinically - What else may be going on?
Figure 1 (ECG reproduced from ECG-2014-ePub )
- Note - Enlarge by clicking on Figures -


         











INTERPRETATION:  The rhythm is sinus. The rate is slow (~50-55/minute) - with slight irregularity making this sinus bradycardia and arrhythmia. The PR interval is normal. The QRS is obviously long.  Recognition of QRS widening at this point is indication to STOP - and figure out WHY the QRS is wide before going on:
  • Assessment of QRS Widening:  - The 3 KEY leads to assess in order to determine the reason for QRS widening are leads I, V1, and V6.  Right-sided Lead V1 shows an rSR' complex (with a taller right rabbit ear).  Left-sided Leads I and V6 both have a relatively wide terminal S wave (albeit the S in lead I is modest in size).  QRS morphology is therefore consistent with complete RBBB = Right Bundle Branch Block (Figure 2).
Figure 2 - Typical Morphology for RBBB.
(ECG reproduced from ECG-2014-ePub )
Returning to Our Systematic Approach: The QT interval is less relevant in the setting of BBB (BBB by itself may prolong the QT). Regarding Axis - there is no hemiblock (Other than the presence or absence of associated left anterior or posterior hemiblock - the concept of axis means little in the setting of BBB).  There is no chamber enlargement.
  • Q-R-S-T Changes - There are some relatively larger-than-expected Q waves in the lateral leads (I,V5,V6 - and especially aVL) - which could reflect infarction of uncertain age.  The tall R wave in lead V1 is from RBBB. An important finding in Figure 1 is that ST-T waves are not as one would expect for simple BBB (Figure 3).
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KEY Rule - Normally when there is typical RBBB or LBBB - the ST segment and T wave should be oriented opposite to the last QRS deflection in the 3 KEY leads (arrows in Figure 3). Deviation from this pattern in any of the 3 KEY leads (I, V1 or V6) is abnormal - and indicates a primary ST-T wave change (suggesting ischemia or infarction may be occurring).  
Figure 3ST-T Wave Changes Expected with BBB.
(ECG reproduced from ECG-2014-ePub )
Note - The above KEY Rule for ST-T wave direction works only for RBBB and LBBB (but not for IVCD).
  • In Figure 1 - One would expect ST-T waves to be opposite to the last QRS deflection in the KEY leads (ie, negative in V1 - and upright in I,V6).  Instead - there is ST flattening in leads I and V1, and a negative T wave in lead V6.  Deep, symmetric T wave inversion in leads V2 thru V6 is also clearly more than what one should see with simple RBBB.
CLINICAL IMPRESSION:  We interpret this ECG as showing sinus bradycardia and arrhythmia with complete RBBB and primary ST-T wave changes.  In addition - there are Q waves in multiple leads with a clearly deeper-than-expected Q wave in lead aVL. We worry about infarction/ischemia in addition to RBBB, which could be recent or even acute. Clinical correlation is urged.
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   - See also ECG Blog Review #11 - and Review #13 -
   - For more on BBB please see our ECG Video on BBB BASICS -
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12 comments:

  1. hi doctor
    the Q wave in avl is suspected to be ischemic not a normal variant according to the overwhelmingly positive QRS in avl ?

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  2. Thank you for your comment Lot Ben. As stated - the Q in lead aVL is clearly much deeper-than-expected! There are other deeper than expected Q waves on this tracing (in leads I, V5,V6) - and in the context of clearly abnormal T inversion for RBBB - I am highly suspicious of infarction of uncertain age in lateral lead areas. Note also the subtle-but-real ST coving in lead aVL.

    There is some semantics in terminology - but rather than "ischemia" - I say the abnormal Q in aVL suggests infarction of uncertain age. This certainly could be recent given all of the T wave changes we see. Hope that explains your question.

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  3. Your interpretation is excellent !

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  4. Your interpretation is excellent !

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  5. Since your interpretation includes myocardial ischenia and infarction of uncertain age, should it be treated as a stemi (immediate cathlab if the patient complains of chest pain), or we should go with the nstemi guideline?
    Many thx

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    1. @ Tamas — As always, one needs the clinical history for optimal correlation. That said, there is NO ST elevation here — so this should not be treated as a STEMI ...

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    2. Dear Ken, Thx for your answer. I was thinking of whether we should go to the cathlab ASAP if the patient has tight chest, distress etc.
      For example: a patient with symptoms and de Winter's T-waves we should go straight to tha lab, since it is a STEMI-equivalent case.

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    3. @ Tamas — There ARE times when acute cardiac cath may be indicated even though the patient is not having a STEMI. Unrelieved chest pain with ischemia as is suggested on this tracing might be one of those indications — but then the reason for cath would be to define the anatomy in a case not responding to medical therapy. That said, I would emphasize my original answer to your question — which is that the tracing above is not suggestive of a stemi; and immediate cath would not be indicated unless there were unusual circumstances (such as persistent pain despite full medical therapy). Hope that answers your question.

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    4. Many thx. It was satisfying. Hope you to write this blog for a long time :)

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  6. There is ST depression in lead v4v5v6 with T wave inversion (assymetric)
    In the right clinical settings(asymptomatic, older age) can those changes be attributed to underlying LVH with strain obscured by RBBB??

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    1. One would expect more voltage if the ST-T changes in V4,5,6 were due to strain ... That said, it's often hard to exclude the possibility of some "strain" — but the main point of this case is that the appearance seen here looks ischemic.

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