av nodal blocks(hb)
Post on 01-Mar-2016
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AV Nodal BlocksAV Nodal Blocks
Lancashire & South Cumbria Cardiac Network
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AV NodeAV NodeAV nodal conduction time is represented AV nodal conduction time is represented on the ECG as the PR segment. on the ECG as the PR segment.
But But -- we always measure the PR interval. we always measure the PR interval.
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AV Nodal Blocks (heart blocks)AV Nodal Blocks (heart blocks)
Disturbances of the conduction through Disturbances of the conduction through the heart, occurring at the AV Nodethe heart, occurring at the AV Node
AV Node AV Node damaged/diseased damaged/diseased delay or delay or total block of impulses at the AV Nodetotal block of impulses at the AV Node
This conduction defect can be seen on the This conduction defect can be seen on the ECGECG
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CausesCauses
Increased vagal tone (parasympathetic Increased vagal tone (parasympathetic nervous system)nervous system)IHD (MI)IHD (MI)EndocarditisEndocarditisDegeneration (age)Degeneration (age)Sclerosis (Aortic)Sclerosis (Aortic)Cardiac surgery traumaCardiac surgery trauma
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First Degree Heart Block (1First Degree Heart Block (1))
SA Node SA Node normalnormalNormal P waveNormal P wave
AV Node conducts more slowly than AV Node conducts more slowly than normalnormal
Prolonged PR IntervalProlonged PR Interval
Rest of conduction is normalRest of conduction is normalNormal QRSNormal QRS
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First Degree Heart Block (1First Degree Heart Block (1))
PR Interval > 0.2 seconds (5 small sq)PR Interval > 0.2 seconds (5 small sq)
Note Note the PR Interval is constant the PR Interval is constant
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Clinical significanceClinical significanceNoneNone
TreatmentTreatmentNoneNone
Note Note this can progress to 2this can progress to 2 or 3or 3 heart heart blockblock
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Second Degree Heart Block (2Second Degree Heart Block (2))
Mobitz Type I (Mobitz Type I (WenkebachWenkebach))
Mobitz Type IIMobitz Type II
2 : 12 : 1
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Second Degree Heart Block (2Second Degree Heart Block (2))Mobitz Type IMobitz Type I((WenkebachWenkebach))
Conduction through the AV Node Conduction through the AV Node progressively delayed until a drop beat is progressively delayed until a drop beat is seenseen
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Second Degree Heart Block (2Second Degree Heart Block (2))Mobitz Type IMobitz Type I((WenkebachWenkebach))
PR PR PR DROPPED BEAT
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Second Degree Heart Block (2Second Degree Heart Block (2))Mobitz Type IMobitz Type I((WenkebachWenkebach))
PR Interval prolongs with each beat until a PR Interval prolongs with each beat until a dropped beat is seendropped beat is seenThe PR Interval is NOT constantThe PR Interval is NOT constantAfter each dropped beat, the PR interval is After each dropped beat, the PR interval is normal and the cycle starts again normal and the cycle starts again
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Clinical SignificanceClinical SignificanceSlight symptoms Slight symptoms egeg. Lethargy,Confusion. Lethargy,Confusion
TreatmentTreatmentPacemaker if during day &/or symptomsPacemaker if during day &/or symptomsNo treatment if at nightNo treatment if at night
Note Note this can progress to 3this can progress to 3 Heart BlockHeart Block
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Second Degree Heart Block (2Second Degree Heart Block (2))Mobitz Type IIMobitz Type II
Conduction through the AV node is Conduction through the AV node is constant but dropped beats are seenconstant but dropped beats are seen
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Second Degree Heart Block (2Second Degree Heart Block (2))Mobitz Type IIMobitz Type II
PR PR DROPPED BEAT PR
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Second Degree Heart Block (2Second Degree Heart Block (2))Mobitz Type IIMobitz Type II
PR Interval normal & constantPR Interval normal & constant
Occasionally a dropped beat is seenOccasionally a dropped beat is seen
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Clinical significance Clinical significance this is more this is more significant disease significant disease
Treatment Treatment pacemakerpacemaker
Note Note this can progress to 3this can progress to 3 Heart BlockHeart Block
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Second Degree Heart Block (2Second Degree Heart Block (2))2 : 12 : 1
Unable to strictly classify as Mobitz Type I Unable to strictly classify as Mobitz Type I or IIor II
Particular type of second degree Heart Particular type of second degree Heart BlockBlock
Ratio 2 P waves : 1 QRS Ratio 2 P waves : 1 QRS
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Second Degree Heart Block (2Second Degree Heart Block (2))2 : 12 : 1
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Clinical significance Clinical significance unable to classify as unable to classify as Mobitz type I or IIMobitz type I or II Will be associated with symptoms, dizziness, Will be associated with symptoms, dizziness,
lethargy etc.lethargy etc.
Treatment Treatment pacemakerpacemaker
Note Note this can deteriorate to 3this can deteriorate to 3 Heart Heart BlockBlock
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Third Degree Heart Block (3Third Degree Heart Block (3))(Complete)(Complete)
Complete failure of the AV NodeComplete failure of the AV Node
No impulses from Sinus Node will pass No impulses from Sinus Node will pass through to the ventriclesthrough to the ventricles
Some part if the conducting system will Some part if the conducting system will take over as pacemaker of the heart (even take over as pacemaker of the heart (even a myocardial cell 10a myocardial cell 10--15 bpm)15 bpm)
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Third Degree Heart Block (3Third Degree Heart Block (3))(Complete)(Complete)
P wave rate P wave rate normalnormal
Ventricular rate Ventricular rate slowslow
Ventricular complex may be broadVentricular complex may be broadIdioventricularIdioventricular rhythmrhythm
Complete dissociation between P waves & Complete dissociation between P waves & QRSQRS
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Third Degree Heart Block (3Third Degree Heart Block (3))(Complete)(Complete)
P P P P P
QRS QRS
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clinical significanceclinical significanceSymptoms LOC, Confusion, Dizziness, Low Symptoms LOC, Confusion, Dizziness, Low BPBPCan lead to standstill, VT or VF (stokes Can lead to standstill, VT or VF (stokes Adams)Adams)
Treatment Treatment -- pacemakerpacemaker
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SummarySummary11 -- prolongation of PR Intervalprolongation of PR Interval
22 -- Mobitz I Mobitz I Increasing PR Interval until Increasing PR Interval until dropped beat is seen dropped beat is seen Mobitz II Mobitz II Constant PR Interval with Constant PR Interval with more P more P waves to QRS waves to QRS 2 : 1 2 : 1 Constant PR Interval with more Constant PR Interval with more P waves to QRSP waves to QRS
33 -- Complete dissociation between P Complete dissociation between P waves & QRS waves & QRS
AV Nodal BlocksAV NodeAV Nodal Blocks (heart blocks)CausesFirst Degree Heart Block (1)First Degree Heart Block (1)Second Degree Heart Block (2)Second Degree Heart Block (2)Mobitz Type I(Wenkebach)Second Degree Heart Block (2)Mobitz Type I(Wenkebach)Second Degree Heart Block (2)Mobitz Type I(Wenkebach)Second Degree Heart Block (2)Mobitz Type IISecond Degree Heart Block (2)Mobitz Type IISecond Degree Heart Block (2)Mobitz Type IISecond Degree Heart Block (2)2 : 1Second Degree Heart Block (2)2 : 1Third Degree Heart Block (3)(Complete)Third Degree Heart Block (3)(Complete)Third Degree Heart Block (3)(Complete)Summary
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