ConductionBlocks Flashcards
define conduction block
delay or disruption in transmission of an impulse from atria to ventricle
What are the types of AV conduction blocks and describe them?
- 1st degree: AV synchrony is maintained (every p goes with a QRS)
- 2nd degree: intermittent loss of AV conduction (not every p has a QRS)
- 3rd degree: complete AV dissociation
etiology of AV conduction blocks
- MC = progressive heart conduction disease
- incr. vagal tone
- ischemic heart dz
- infiltrative process (amyloid/sarcoid)
- myocarditis
- congenitl heart dz
- familial dz
- malignancies
- drugs
- heart surgery
define 1st degree AV conduction block
- prolonged PR interval (greater than 0.2s)
- every p goes with every QRS
- not likly to progress to 2nd degree
etiology of 1st degree AV conduction block
- structural abnormalities
- increased vagal tone
- drugs that impair/slow AV conduction
epidemiology of 1st degree AV conduction block
increased in trained athletes
clinical presentation of 1st degree AV conduction block
ususally asx
management of 1st degree AV conduction block
- if PRI under 300ms ==> no intervention
- if wide QRS ==> refer
- tx underlying cause
- avoid AV nodal blocking meds
define 2nd degree AV conduction block (generally speaking)
- not every QRS has a p
- two types
epidemiology of 2nd degree AV conduction block
increased in trained athletes
etiology of 2nd degree AV conduction block
- heart drugs
- lithium
- inflammatory dz
- infiltrative dz
- malignancies
- collagen vascular dz
diagnostics for 2nd degree AV conduction block
- EKG
- electrolytes
- digoxin
- biomarkers
- Lyme titers
- echo
define type I 2nd degree AV conduction block
- progressive slowing of subsequent AV node impulses until node fails to conduct
- cycle repeats
- Wenchback Walk
clinical presentation of type I 2nd degree AV conduction block
- asx
- decr CO = fatigue, lightheadedness, syncope, angina, heart failure
treatment of type I 2nd degree AV conduction block
- tx underlying cause
- no specific tx when asx
- monitor EKG
- refer when sxatic
define type II 2nd degree AV conduction block
- PR interval remains equal until dropped beat
- no change in PR interval
- frequently progresses to 3rd degree
clinical presentation of type II 2nd degree AV conduction block
- ranges from asx to many
- if decr HR or many dropped beats = decr. CO ==> fatigue, lightheadedness, syncope
treatment of type II 2nd degree AV conduction block
- tx underlying cause
- avoid AV blocking drugs
- pacemaker
define 3rd degree AV conduction block
- complete failure of AV node to conduct any impulse from atria to ventricles
- variable PR interval
- with escape rhythm
possible sites of 3rd degree AV conduction block
- AV node = narrow QRS
- Bundle of His = narrow QRS
- Proximal (B) Bundle Branches = wide QRS
- R bundle w/ L fasicles = wide QRS
clinical presentation of 3rd degree AV conduction block
- more distal block = decr. rate
- distal blocks = syncope
- chest pain (in MI)
- lightheadedness
- DOE
- bradycardia
- vtach/fib/ventricular brady
- asystole
diagnostics for 3rd degree AV conduction block
same as 2nd degree
- EKG
- electrolytes
- digoxin
- cardiac biomarkers
- Lyme titers
- echo
- CBC & blood cx to r/o endocarditis
treatment of 3rd degree AV conduction block
- temporary then pacemaker
- refer
- treat underlying cause
- avoid rx that block AV node
define LBBB
- wide QRS (greater than 0.12s)
- broad R waves in V1-6 & broad S waves in AVR
LBBB is difficult to ddx with _____ d/t _____.
- myocardial ischemia & infarction
- ST-T abnormalities
New LBBB is _____ until proven otherwise.
MI
diagnostics for LBBB
- echo
- stress testing (CAD)
treatment for LBBB
- if young + asx w/o CAD ==> no tx
- tx underlying condition
- reduce risks
- consider pacemaker
clinical presentation of RBBB
asx
associated conditions of LBBB
- HTN
- CAD
- valve dz
- cardiomyopathies
associated conditions of RBBB
- cor pulmonale
- PE
diagnostics for RBBB
- no further needed
treatment of RBBB
- pacemaker if syncope occurs
