17 BBB

Overview

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• 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

• symptoms: low CO

• 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)

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• type 1: no dropped beats

1st Degree

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• 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

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• 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

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• 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

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• 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

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• AV dissociation but still has P, not caused by AV block

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• escape rhythm generated by lower pacemaker

• lower pacemaker cannot increase rate like SA

Pacemaker

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BBB

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• 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

• rSR': rabbit ears

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• underlying structural problems that may cause problems

• biggest problem: interfere with ischemia detection

• underlying diseases that can result in BBB