bundle branch blocks

Question 1

what is the direction of the electrical current in the ventricles normally

Answer 1

from left (V6 closest) to right (V1), as LV significantly more muscular

Question 2

normally on an ecg, the QRS in V1 is predominately….

Answer 2

negative

Question 3

on a normal ECG the V6 QRS is predominately……

Answer 3

positive

Question 4

characteristics of a RBBB

Answer 4

wide QRS
V1, rSR ( small R then big R)
V1,big negative deflection between the Rs
V6 or lateral leads, slurred S wave, tall R wave
BOTH LEADS: T wave in the opposite direction of the QRS

Question 5

how to tell if its a left anterior fascicular block

Answer 5

wide QRS, T wave discordance

V1-2,3: negative QRS, slurred long S wave

V6 and lateral leads: large positive QRS with slurred, discordant ST segment

Question 6

how to tell if its a left posterior fascicular block

Answer 6

RBBB with right axis deviation ( negative in I and positive in AVF)

Question 7

cause of RBBB

Answer 7

RVH, pulmonary HTN, ischemic heart disease

Question 8

Q
what causes a LBBB

Answer 8

the left anterior descending

Question 9

Q
why is the QRS slurred in RBBB

Answer 9

RBB blocked, RV will depol after the LV, and it occurs slowly, muscle fibre to muscle fibre, thus a slur that draws it out