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
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
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
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.
Ventricular Enlargement• Left Ventricular Hypertrophy (LVH) – The left ventricle is enlarged – Probably due to left-sided heart failure• Right Ventricular Hypertrophy (RVH) – The right ventricle is enlarged – Probably due to right sided heart failure – May be due to pulmonary disease
Ventricular Enlargement• Left Ventricular Hypertrophy (LVH) – May cause left axis deviation – May cause a left ventricular strain pattern • Often mimics an anterior MI• Right Ventricular Hypertrophy (RVH) – May cause right axis deviation – May cause a right ventrcular strain pattern • May mimic a inferior or posterior wall MI
RVH• Right Ventricular Hypertrophy – Criteria = R:S ration > 1 in V1/V2 • This means that the R-wave is bigger than the S- wave in V1 or V2. • The QRS complex should be narrow • P-Pulmonale may be present. • Right axis deviation is common.
RVHV1 or V2 R = 9mm V1/V2: R > S = RVH •QRS < 120ms (0.12 sec) S = 6mm