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Right Bundle Branch Block

Wed, 12/24/2014 - 21:21 -- Dawn

This is an example of right bundle branch block - with a couple of twists.  It has the usual ECG characteristics of right bundle branch block:  widened QRS (154 ms), supraventricular rhythm (sinus bradycardia), and an rSR' pattern in V1.  In addition, wide little S waves are clearly seen in Leads I and V6.  This secures the diagnosis of right bundle branch block (RBBB).  Each QRS complex in every lead starts off with a very normal appearance, or morphology.  Then, as the right ventricle is depolarized late, an additional wave is "added on".  This is the R-Prime (R') in V1 and the S wave in Leads I and V6.

In most examples of RBBB, you will see the T wave point in the OPPOSITE direction of the terminal wave.  So, V1 should have a NEGATIVE T wave.  In this example, V2 and V3 should have also had negative T waves.  The upright T waves could be considered to have the same significance as inverted T waves in a normal ECG.  

Another interesting aspect to this ECG is the unusual morphology of the terminal S wave in most of the leads.  There appears to be a slight notch.  Lead V2 even appears to have ST elevation.  Perhaps some of our Gurus would comment on this.

This is a good ECG to use to show how the terminal R' and S waves can sometimes be confused with ST elevation and depression.  Lead III has a very flat T wave, and one might make the mistake of calling the R' wave "ST elevation".  The R' does not have the sloping shape of a normal ST segment and T wave.  Also, all the channels on the ECG are run simultaneously.  One needs only to look up at Leads I and II to see where the true T waves are - Lead III's T wave is directly under them.

This is a very good teaching ECG.  We look forward to hearing your comments.

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Comments

ekgpress@mac.com's picture
 
Interesting example of complete RBBB with the 2 unusual features Dawn mentions.
  • Notching in the S Wave: At 1st (and even 2nd) glance - I took the notching in the S waves seen in leads I, II, aVF; V3,V4,V5 to be retrograde P waves. But on closer analysis - this notching is all part of the QRS complex. Lead V1 gives us the best perspective of how wide the QRS complex really is. If one drops an imaginary vertical line from the end of the R' in V1 down to lead V3 - we can easily discern that the terminal notching is part of the QRS complex. If such notching was retrograde atrial activity - then this would almost certainly reset the SA node and produce a significantly longer delay before the next sinus beat. So the notching is all part of the QRS complex ...
  • Upright T Waves in Leads V2,V3: The direction of ST-T waves with typical bundle branch block (either RBBB or LBBB) should be opposite to the last QRS deflection in the 3 key leads (ie, in leads I,V1,V6). Preservation of this opposite direction for ST-T waves is not necessarily guaranteed in the remaining 9 leads. Thus, the fact that the T wave is upright in leads V2,V3 is not necessarily indicative of ischemia. In fact, the shape of the ST-T wave in these leads is more characteristic of a normal repolarization variant - given asymmetric (slower) ascent and a rounded peak - rather than the more isoelectric (equal ascent and descent) T wave with more pointed peak that is characteristic of ischemia. Given the absence of other ST-T wave abnormality on this tracing - ischemia is even less certain (though it cannot be ruled out)
BOTTOM LINE: As per Dawn - this tracing shows sinus bradycardia with complete RBBB. The unusual QRS morphology (with notching in many S waves) suggests the possibility of underlying structural heart disease. I believe the upright T waves in leads V2,V3 are either related to such underlying heart disease and/or represent a repolarization variant. CLINICAL HISTORY would be key to accurate interpretation.

Ken Grauer, MD  www.kg-ekgpress.com   [email protected] 

Submitted by frbreijo on

Has anyone noticed a QT-interval prolonged?

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