17 BBB
- AP can only go from SA to ventricle from AV node
- PR: electrical activity pass through all these things before ventricular depolarize
- severe block: does not generate QRS, does not conduct to ventricle
- can be caused by any portion of AV conduction system
- clinically divided into two causes
- AV node: fewer dropped beats, less bradycardia, improve with exertion (increased sympathetic activity)
1st Degree
- should be under 1 box
- all followed by QRS
- AV node: good prognosis
- atheletes: high parasympathetic tone
- no symptoms for condition. All P conducted, no bradycardia
- fibrosis: occurs with aging. Older pts have advanced types of AV block, pacemaker
2nd Degree
Mobitz 1
- like 1st degree, but gets worse with each beat until no conduction
- find non-conducted P, find one before and one after, see length differences
- BB, CCB, atheletes
- regularly irregular pulse, different from afib
- asymptomatic, goes away with exertion
- different lengthed PR
- grouped beating
- irregular RR interval
- fibrosis: occurs with aging. Older pts have advanced types of AV block, pacemaker
Mobitz II
- no progressive prolongation: 2 conducted P, same length, then 2 non conducted P
- HIS purkinje: hanging on barely, can conduct 2, then can't conduct for next 2
- high risk to complete heart block
- often with BBB: HIS purkinje includes BB, wide QRS
3rd Degree
- no conduction from A to V
- some lower rate pacemaker in AV or V depolarizing the V at slower rate
- may look similar to Mobitz type 1, difference: RR interval completely regular
stage 2:
- heart shield: Heart block caused by Myocarditis
- bells on both side: Bilateral Bell's palsy
AV Dissociation
- AV dissociation but still has P, not caused by AV block
- escape rhythm generated by lower pacemaker
- lower pacemaker cannot increase rate like SA
Pacemaker
BBB
- when AP reach BB, one is not blocked, starts QRS on time (normal PR) but take longer to depolarize (wide QRS)
- RBBB: V1 pointing up
- LBBB: V1 pointing down
- RBBB: impulse travels to left, depolarize, then send electricity slowly to RV, takes longer, thus prolonged QRS
- LBBB: electrical activity go towards left, away from V1, negative V1
- RBBB: go towards right, towards V1, positive V1
- result: different QRS
- underlying structural problems that may cause problems
- biggest problem: interfere with ischemia detection
- underlying diseases that can result in BBB
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