Bundle branch blocks Flashcards
Contractile cells
Cells which contract to move blood in the heart, slow transmission of impulses between cells.
Conduction cells
Make up the conduction system including Bachmann’s bundle, bundle of his, left and right bundles, purkinje fibres.
Lead V6
looks towards left ventricle and left bundle branch
lead V1
looks towards right ventricle and right bundle branch
Q wave
Septal depolarisation, normally left to right.
R wave
Ventricular depolarisation, electricity is moving towards the lead creating a positive inflection.
S wave
Ventricular depolarisation, electricity is moving away from the lead creating a negative deflection.
Bundle branch block pathophysiology
Damage to left or right bundle branch of conduction system due to ischaemia or infarction. Impulse cannot travel down one bundle so opposing bundle contracts first. Slower conduction of impulse in impacted side occurs via contractile cells causing delayed contraction.
RBBB causes
normal variant
MI
myocarditis
cardiomyopathy
PE causing fluid back up and ventricular stretching.
RBBB ECG changes
QRS duration > 0.12 seconds
RSR shaped QRS complex in leads v1,v2,v3, aVL and lead 1.
Slurred S waves in leads V5 and V6
Broad monophasic R waves
RSR mechanism
Electricity travelling towards V123, blocked by damaged bundle, alternative conduction route moves electricity away, eventual movement back towards lead.
LBBB causes
MI
cardiomyopathy
endocarditis
valvular disease
congenital defect
LBBB ECG changes
QRS> 0.12 seconds
Dominant S waves in lead V123
Absent Q waves in lead V5 and 6
Broad monophasic R waves
Absent Q waves mechanism
Septal depolarisation is normally left to right creating a negative deflection, reversal due to left bundle damage removes negative Q wave.
