bundle branch blocks and abberation Flashcards
what are bundle branch blocks caused by?
lesions or pathologic conditions in the HIS bundle fibres as they join into the bundle branches or more commonly, in the bundle branches themselves.
myocardial ischemia, infarctions or fibrosis. can occur in either branch
what are the bundle branches also referred to as ? how many branches on each side?
fascicles.right has a single fascicle and left has 2, referred to as the anterior and posterior fascile
are bundle branch blocks temporary or perm?
permanent intraventricular (within the vesicles) conduction problem or delays
what gives us clues regarding which bundle branch is blocked?
certain leads.
how would the QRS look if there is a BBB
wide QRS cause impulse is delayed.
do BBB occur in any rhythm?
any supra ventricular rhythm such as SR or afib so SR with BBB. so normal p wave an wide QRS
how would afib with BBB look
usual clues with afib (fib line w irregular R-R intervals) and wide QRS
what is the 3 fascicle intraventricular conduction system also called?
trifasciular
where is the left (superior division) and right bundle branch located?
what does this mean for MIs
both anterior structures so vulnerable to anteroseptal MI
the posterior division of the LBB is supplied by what coronary artery?
right
what are some ECG clues for BBB
QRS .12 or greater and wide QRS can also occur w any supra ventricular rhythm
t wave opposite to terminal wave of fQRS
perm
right BB QRS morphology in V1 rSr and V6 qRs
left BB QRS morph . V1 mainly neg complex QS or rS
V6 always positive
causes of BBB?
myocardial ischemia/infarct
drugg iduced
fibrosis
RBBB usually associated with anterior MI (left anterior descending- LAD vessel feeds the r. bundle)
LBBB associated with inferior or anterior MI (right coronary artery feeds thicker posterior fascicle of left bundle)
LAD coronary artery feeds thiner anterior fascicle of left bundle
what are the hemodynamic effects of BBB
dep on underlying rate or rhythm
if rate inc e.g. sinus tach - less time for filling so dec SV, CO, BP
if afib then loss of atrial kick so dec SV, BP, and CO
if rate slow same as above
treatment for BBB
pacemaker if signs of intermittent or perm conduction failure
if no conduction failure then treatment is aimed at underlying rhythm as nec
what is aberration?
term used to describe a supra ventricular beat that finds one of the bundle branches not ready to conduct.
abberant means ‘straying away from the right way or wandering’
what do aberrant beats produce?
changing QRS complexes which are wide and appear in ventricular in origin
what is a non-conducted PAC?
abberation betts are commonly premature supraventricular impulses (usually PACs) that have deviated from normal ventricular conduction. normally when a PAC reaches the ventricles, it is uniformly conduced down he BB and there is a normal QRS but if the PAC is very premature, bundle branches may be refractory (not ready to conduct) and PAC will not be conduced at all and no QRS is produced
what happens if the PAC finds the BB partially refractory? what is this called?
impulse may be conduced with delay, deviation or both.
abberant conduction
what BB has the longest refractory period? what does this mean for conduction? what is it called
right BB so aberrantly conducted PAC usually find the right BB refractory or unable to conduct so impulse travels down the LBB and then back up the right (now no longer refractory)
called right bundle branch block pattern (RBBB) bc makes fun pattern
is aberration pathological?
no usually temporary or transient and often rate related
is there usually a p wave before the beat or no? what does this mean for PJCs?
yes usually before the aberrant beat although the PJCs can be conducted aberrantly as well
are QRS complexes wide in BBB and aberration beats?
yes because intraventriclar conduction is delayed
are both ventricles conducted at the same time in aberration and BBB?
no at different times which is not normal so depolarization is also abnormal . so t wave will be opposite QRS
what lead gives you the best picture with wide QRS patients?
MCL1 or V1. allows you to differentiate between BBB, aberration and PVCs
ECG clues with aberration?
wide WRS between .12-.14 usually
premature atrial contractions
sudden onset of SVT afib
can be rate related
t wave opposite to terminal wave of QRS
tends to be transient or temp
RBBB and LBBB same as previous
possible causes of aberration?
sudden or premature stimulation of bundle branches while one bundle is still depolarizing (phase 3)
long pause in conduction (slow rate) where the beat finds the bundle already depolarized
retrograde concealed conduction (common cause in afib) integrate or normal conduct is blocked for example in left bundle so next beat goes back up left bundle once it is ready (retrograde)
hemodynamic effects of aberration?
dep or underlying supraventrcular rythym
if rate inc or atrial kick lost then dec SV, CO, BP
tx for aberration?
12 lead
treat underlying rhythm with med
