AV Blocks Artificial Pacemakers Terry White, RN, EMT-P

AV Blocks AV Blocks Artificial PacemakersArtificial Pacemakers

Terry White, RN, EMT-PTerry White, RN, EMT-P

AV BlocksAV Blocks

Disorders of conduction at AV Disorders of conduction at AV JunctionJunction

CategoriesCategories– First degree (1° AV Block)First degree (1° AV Block)– Second degree (2° AV Block)Second degree (2° AV Block)

Type IType I Type IIType II

– Third degree (3° AV Block or Complete Third degree (3° AV Block or Complete AV Block)AV Block)

Analyze the RhythmAnalyze the Rhythm

AV BlocksAV Blocks

First DegreeFirst Degree– Prolonged AV conduction timeProlonged AV conduction time– PR interval > 0.20 secondsPR interval > 0.20 seconds– Characteristics of that of any other Characteristics of that of any other

rhythm with a SINGLE sinus or atrial rhythm with a SINGLE sinus or atrial pacemaker sitepacemaker site

– Associated with an underlying sinus Associated with an underlying sinus or atrial rhythm!!!or atrial rhythm!!!

AV BlocksAV Blocks

First DegreeFirst Degree– CausesCauses

AV node ischemia/hypoxiaAV node ischemia/hypoxia Increased vagal or decreased sympathetic Increased vagal or decreased sympathetic

tone tone Drug effectsDrug effects

– DigitalisDigitalis– Beta blockersBeta blockers– Calcium channel blockersCalcium channel blockers– QuinidineQuinidine– PronestylPronestyl

AV BlocksAV Blocks

First DegreeFirst Degree– ManagementManagement

Usually requires no specific treatmentUsually requires no specific treatment Treat the patient!!!Treat the patient!!! Monitor for progression to higher degree Monitor for progression to higher degree

blockblock

AV BlocksAV Blocks

Second DegreeSecond Degree– DefinitionDefinition

More Ps than QRSsMore Ps than QRSs Every QRS caused by a PEvery QRS caused by a P

– The pattern determines the type of 2° The pattern determines the type of 2° AV blockAV block

– Since requires presence of P waves, it Since requires presence of P waves, it also requires an underlying sinus or also requires an underlying sinus or atrial rhythmatrial rhythm

AV BlocksAV Blocks

Second DegreeSecond Degree– TypesTypes

Type IType I– VariableVariable– Wenckebach phenomenonWenckebach phenomenon

Type IIType II– FixedFixed– ClassicalClassical


AV BlocksAV Blocks

Second DegreeSecond Degree– Type IType I

DefinitionDefinition– PR interval lengthensPR interval lengthens– Beat dropsBeat drops

PathophysiologyPathophysiology– Usually physiologicUsually physiologic

Increased vagal tone (Acute inferior MI, RVI)Increased vagal tone (Acute inferior MI, RVI) Drug effects (digitalis, beta blockers, CCBs)Drug effects (digitalis, beta blockers, CCBs)

– Frequently resolvesFrequently resolves

AV BlocksAV Blocks

Second DegreeSecond Degree– Type IType I

Good prognosisGood prognosis Specific therapy usually not necessarySpecific therapy usually not necessary

– therapy, if indicated, most likely targeted therapy, if indicated, most likely targeted towards bradycardiatowards bradycardia

Treat the patient!!!Treat the patient!!!


AV BlocksAV Blocks

Second DegreeSecond Degree– Type IIType II

DefinitionDefinition– P waves fail to conduct without warningP waves fail to conduct without warning– PR interval does not lengthenPR interval does not lengthen

CharacteristicsCharacteristics– Atrial rate > Ventricular rateAtrial rate > Ventricular rate– QRS QRS usuallyusually longer than 0.12 sec longer than 0.12 sec– Usually 4:3 or 3:2 conduction ratio (P:QRS Usually 4:3 or 3:2 conduction ratio (P:QRS

ratio)ratio)

AV BlocksAV Blocks


PathophysiologyPathophysiology– Organic lesions in bundle branchesOrganic lesions in bundle branches

Usually occurs below bundle of His in the Usually occurs below bundle of His in the bundle branches (infranodal AV block)bundle branches (infranodal AV block)

Intermittent block of conduction through Intermittent block of conduction through one bundle and complete block in otherone bundle and complete block in other

Usually caused by Acute anterior or Usually caused by Acute anterior or anteroseptal MIanteroseptal MI

AV BlocksAV Blocks


OutlookOutlook– Not goodNot good– Usually associated with anterior or Usually associated with anterior or

anteroseptal MIanteroseptal MI– Frequent progression to complete AV blockFrequent progression to complete AV block

Requires pacemakerRequires pacemaker Worsened by digitalis, procainamide, Worsened by digitalis, procainamide,

lidocaine, propranolol, TCAslidocaine, propranolol, TCAs


AV BlocksAV Blocks CompleteComplete

– DefinitionDefinition No conduction through AV nodeNo conduction through AV node Independent atrial and ventricular rhythmsIndependent atrial and ventricular rhythms Ventricular depolarization dependent on Ventricular depolarization dependent on

automaticity of ventricular pacemaker sitesautomaticity of ventricular pacemaker sites

– PathophysiologyPathophysiology AV node hypoxia/ischemiaAV node hypoxia/ischemia Myocardial infarctionMyocardial infarction Increased vagal or decreased sympathetic tone Increased vagal or decreased sympathetic tone

AV BlocksAV Blocks CompleteComplete

– CharacteristicsCharacteristics Atrioventricular dissociationAtrioventricular dissociation Regular P-P and R-R but without Regular P-P and R-R but without

association between the twoassociation between the two Atrial rate > Ventricular rateAtrial rate > Ventricular rate QRS > 0.12 secQRS > 0.12 sec

AV BlocksAV Blocks

CompleteComplete– OutlookOutlook

Junctional escape rhythm: goodJunctional escape rhythm: good Ventricular escape rhythm: badVentricular escape rhythm: bad

– WarningWarning Do NOT give lidocaine or other ventricular Do NOT give lidocaine or other ventricular

antidysrhythmics!!!antidysrhythmics!!!

AV BlocksAV Blocks ManagementManagement

– Treatment based on Sx/SxTreatment based on Sx/Sx– Most common complication = BradycardiaMost common complication = Bradycardia

IV/OIV/O22/ECG Monitor/12 lead ECG/ECG Monitor/12 lead ECG Atropine (not useful in 2° Type II or 3° AV Block)Atropine (not useful in 2° Type II or 3° AV Block) TCP (bridge to transvenous pacer)TCP (bridge to transvenous pacer) Catecholamine dripCatecholamine drip

– Prophylactic pacer application (standby)Prophylactic pacer application (standby) 2° Type II AV block2° Type II AV block 3° AV Block3° AV Block


Cardiac PacemakersCardiac Pacemakers

DefinitionDefinition– Delivers artificial stimulus to heartDelivers artificial stimulus to heart– Causes depolarization and contractionCauses depolarization and contraction

UsesUses– BradyarrhythmiasBradyarrhythmias– AsystoleAsystole– Tachyarrhythmias (overdrive pacing)Tachyarrhythmias (overdrive pacing)

Cardiac PacemakersCardiac Pacemakers TypesTypes

– FixedFixed Fires at constant rateFires at constant rate Can discharge on T-waveCan discharge on T-wave Very rareVery rare

– DemandDemand Senses patient’s rhythmSenses patient’s rhythm Fires only if no activity sensed after preset Fires only if no activity sensed after preset

interval (escape interval)interval (escape interval)

– Transcutaneous vs Transvenous vs Transcutaneous vs Transvenous vs ImplantedImplanted



Demand Pacemaker TypesDemand Pacemaker Types– VentricularVentricular

Fires ventriclesFires ventricles

– AtrialAtrial Fires atriaFires atria Atria fire ventriclesAtria fire ventricles Requires intact AV conductionRequires intact AV conduction


Demand Pacemaker TypesDemand Pacemaker Types– Atrial SynchronousAtrial Synchronous

Senses atriaSenses atria Fires ventriclesFires ventricles

– AV SequentialAV Sequential Two electrodesTwo electrodes Fires atria/ventricles in sequenceFires atria/ventricles in sequence


ProblemsProblems– Failure to captureFailure to capture

No response to pacemaker artifactNo response to pacemaker artifact Bradycardia may resultBradycardia may result Cause: high “threshold”Cause: high “threshold” ManagementManagement

– Increase amps on temporary pacemakerIncrease amps on temporary pacemaker– Treat as symptomatic bradycardiaTreat as symptomatic bradycardia


ProblemsProblems– Failure to senseFailure to sense

Spike follows QRS within escape intervalSpike follows QRS within escape interval May cause R-on-T phenomenonMay cause R-on-T phenomenon ManagementManagement

– Increase sensitivityIncrease sensitivity– Attempt to override permanent pacer with Attempt to override permanent pacer with

temporarytemporary– Be prepared to manage VFBe prepared to manage VF


ProblemsProblems– Inappropriate absence of pacer artifactInappropriate absence of pacer artifact

CausesCauses– Depleted batteryDepleted battery– Circuit malfunctionCircuit malfunction– OversenseOversense

ManagementManagement– Decrease sensitivityDecrease sensitivity– Treat bradycardiaTreat bradycardia– Replace pacemakerReplace pacemaker

Cardiac PacemakersCardiac Pacemakers ProblemsProblems

– Runaway pacemakerRunaway pacemaker Rates of up to 400/minuteRates of up to 400/minute Increasing rate = EmergencyIncreasing rate = Emergency CausesCauses

– Component failureComponent failure– Battery depletionBattery depletion

ManagementManagement– TransportTransport– Enter site surgically, cut leadEnter site surgically, cut lead– Some may be turned “off” by donut-shaped magnetSome may be turned “off” by donut-shaped magnet


Special ConsiderationsSpecial Considerations– Pacemaker does NOT affect treatment Pacemaker does NOT affect treatment

of cardiac arrestof cardiac arrest– Do NOT fire defibrillator directly over Do NOT fire defibrillator directly over

pacemaker generatorpacemaker generator– Pacemakers may keep AEDs from Pacemakers may keep AEDs from

advising shockadvising shock

Cardiac PacemakersCardiac Pacemakers Transcutaneous PacingTranscutaneous Pacing

– Electrical vs Mechanical captureElectrical vs Mechanical capture– Tips for improving electrical captureTips for improving electrical capture

Ensure adequate conductanceEnsure adequate conductance Increase current (mA)Increase current (mA)

– Tips for improving mechanical captureTips for improving mechanical capture Ensure the “tank” is topped offEnsure the “tank” is topped off Increase the electrical rateIncrease the electrical rate Increase peripheral vascular resistanceIncrease peripheral vascular resistance


Transcutaneous Pacing RealizationsTranscutaneous Pacing Realizations

It is much easier to increase the electrical rate of depolarization than it is to increase the

mechanical rate of contraction!

You can’t create mechanical capture in dead muscle!

Implanted DefibrillatorsImplanted Defibrillators

AICDAICD– Automated Automated

Implanted Cardio-Implanted Cardio-DefibrillatorDefibrillator

UsesUses– TachyarrhythmiasTachyarrhythmias– Malignant Malignant

arrhythmiasarrhythmias VTVT VFVF

Implanted DefibrillatorsImplanted Defibrillators

Programmed at insertion to deliver Programmed at insertion to deliver predetermined therapies with a set order predetermined therapies with a set order and number of therapies including:and number of therapies including:– pacingpacing– overdrive pacingoverdrive pacing– cardioversion with increasing energiescardioversion with increasing energies– defibrillation with increasing energiesdefibrillation with increasing energies– standby modestandby mode

Effect of standby mode on Paramedic Effect of standby mode on Paramedic treatmentstreatments

Implanted DefibrillatorsImplanted Defibrillators Potential ComplicationsPotential Complications

– Fails to deliver therapies as intendedFails to deliver therapies as intended worst complicationworst complication requires Paramedic interventionrequires Paramedic intervention

– Delivers therapies when NOT appropriateDelivers therapies when NOT appropriate broken or malfunctioning leadbroken or malfunctioning lead parameters for delivery are not specific enoughparameters for delivery are not specific enough

– Continues to deliver shocksContinues to deliver shocks parameters for delivery are not specific enough and parameters for delivery are not specific enough and

device senses a resetdevice senses a reset may be shut off (not standby mode) with donut-may be shut off (not standby mode) with donut-

magnetmagnet

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AV Blocks Artificial Pacemakers Terry White, RN, EMT-P