Bundle branch blocks Flashcards
Which leads look towards the left and right bundle branches?
V6 looks towards the left bundle branch, while V1 looks towards the right bundle branch.
What is the definition and cause of a bundle branch block?
A bundle branch block is the interruption of the normal transmission of depolarisation through the bundle branches. It can be caused by defects such as infarctions, structural changes, pressure or trauma.
How can you recognise a RBBB through an ECG?
Changes include an RSR pattern forming in the QRS complex in leads V1 and V2 (an “M” shaped mark) and a slurred S-wave in leads V5, V6 and aVL. A broad, monophasic R-wave in V1 can also indicate an RBBB, and can be useful as the RSR pattern may not be present.
How can you recognise a LBBB through an ECG?
Changes include a dominant S-wave in leads V1 and V2 and broad monophasic R waves and/or an absence of Q-waves in leads V5, V6 and aVL
What evidence of appropriate discordance can be viewed in and ECG for either a LBBB or a RBBB?
In leads with a dominant S-wave, you would often see ST elevation and positive T-waves, while in leads with tall broad R-waves, you would often see ST depression and T-wave inversion.
What is the Modified Sgarbossa Criteria?
A criteria used to identify through ECG features whether or not an individual with a known LBBB or pacemaker is also experiencing a STEMI.
What are the criteria within the Modified Sgarbossa Criteria?
Concordant ST elevation of more than 1mm in leads with a positive QRS complex, concordant ST depression of more than 1mm in V1, V2 or V3, or proportionately excessive discordant ST elevation in more than 1 lead with more than 1mm of ST elevation (as defined by the depth of the preceding S-wave).
