Bundle Branch Blocks• Right Bundle Branch Block (RBBB) – The single right fascicle is blocked.• Left Bundle Branch Block (LBBB) – Both left fascicles are blocked.• Non-Specific Intraventricular conduction delay (IVCD) – BBB that doesn’t meet RBBB or LBBB criteria.
Bundle Branch Blocks• May mimic an MI• The side that is blocked conducts last and takes longer.
Bundle Branch Blocks Mean vector• Normal conduction 4 Cardiac vector without a block. 1 3 3 2 2
Bundle Branch Blocks • With a RBBB, the right fascicle is blocked, so the left ventricle is1 conducted first and 2 then the impulse 3 returns to the right.
Bundle Branch Blocks • With a LBBB, the right ventricle is conducted first, and the impulse1 travels back to the 2 left. 3
Right Bundle Branch BlockI V1 aVR V4 II aVL V2 V5 V6 III aVF V3
Right Bundle Branch Block Slurred S-Wave I & V6
Right Bundle Branch Block + + A B A + BMean vector moves towards positive electrode = positive QRSMean vector moves away from positive electrode = negative QRSMean vector is perpendicular to positive electrode = equiphasic QRS
Intraventricular Conduction Delay• A Non-specific IVCD is less common than a RBBB or LBBB• They are wide, atrial rhythms that usually look like a left or right BBB in V1, but do not match the criteria in I & V6.
Non-Specific IVCDI I V1 aVR V4 II aVL V2 V5 V6 III aVF V3