principles of cardiac pacing for paramedics · pdf fileprinciples of cardiac pacing ......

Principles of Cardiac Pacing Principles of Cardiac Pacing

Miguel Leal, MDMiguel Leal, MD

Assistant Professor of Medicine, University of WisconsinAssistant Professor of Medicine, University of Wisconsin

Director, Cardiac Electrophysiology, VA Hospital Director, Cardiac Electrophysiology, VA Hospital -- MadisonMadison

PacemakersPacemakers

Implantable CardioverterImplantable Cardioverter--DefibrillatorsDefibrillators

Advances in Device (ICD) Implantation

Implanting physicianImplanting physician Cardiac surgeonCardiac surgeon EP or surgeonEP or surgeon

Device size (volume)Device size (volume) 120 120 -- 140 mL140 mL << 40 mL40 mL

Implant site Implant site AbdominalAbdominal PectoralPectoral

ProcedureProcedure Median sternotomyMedian sternotomy Skin incisionSkin incisionLateral thoracotomyLateral thoracotomy

Procedure timeProcedure time 2 2 -- 4 hours4 hours 1 hour1 hour

PerioperativePerioperative 2.5%2.5% < 0.5%< 0.5%mortalitymortality

PostPost--implant implant 3 3 -- 5 days5 days 1 day1 dayhospitalization hospitalization

Battery longevityBattery longevity 18 months18 months Up to 9 yearsUp to 9 years

# Implants# Implants 00--2,000/yr2,000/yr 80,000 / year80,000 / year

1980 - 1999 2000 - date

Morgan Stanley Dean Witter. Investors Guide to ICDs. 2000.

Number of Worldwide ICD Implants Per Year

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

1980 1985 1990 1995 2000 E

Evolution of ICD Therapy

19801980•• First HumanFirst Human

ImplantImplant

19851985•• FDA ApprovalFDA Approval

of ICDsof ICDs

19991999•• MUSTTMUSTT

19931993•• SmallerSmaller

DevicesDevices

19961996•• SteroidSteroid

LeadsLeads

•• MADITMADIT

19891989•• TransvenousTransvenous

LeadsLeads

•• BiphasicBiphasic

WaveformWaveform

1997/981997/98•• DC ICDsDC ICDs

•• AT TherapiesAT Therapies

•• AVIDAVID

•• CASHCASH

•• CIDSCIDS

19881988•• TieredTiered

TherapyTherapy

20002000•• CRTCRT--DD

External Defibrillator

Pacemaker ECG StripsPacemaker ECG Strips

•• Assessing Paced ECG StripsAssessing Paced ECG Strips

–– Identify intrinsic rhythm and clinical conditionIdentify intrinsic rhythm and clinical condition

–– Identify pacer spikesIdentify pacer spikes

–– Identify activity following pacer spikesIdentify activity following pacer spikes

–– Failure to captureFailure to capture

–– Failure to senseFailure to sense

•• EVERY PACER SPIKE SHOULD HAVE A EVERY PACER SPIKE SHOULD HAVE A

PP--WAVE OR A QRSWAVE OR A QRS--COMPLEX COMPLEX

FOLLOWING IT.FOLLOWING IT.

Pacemaker CodesPacemaker Codes

PositionPosition

FunctionFunction

11

Chambers Chambers

PacedPaced

22

Chambers Chambers

SensedSensed

33

Response to Response to

Sensed Sensed

StimulusStimulus

44

Rate Rate

Modulation?Modulation?

O (none)O (none) OO OO O (nonO (non--rate rate

responsive)responsive)

A (atrium)A (atrium) AA T (triggered)T (triggered) R (rate R (rate

responsive)responsive)

V (ventricle)V (ventricle) VV I (inhibited)I (inhibited)

D (both atrium & D (both atrium &

ventricle)ventricle)

Principles of PacingPrinciples of Pacing

•• Commonly used modes:Commonly used modes:

–– AAI AAI –– atrial demand pacingatrial demand pacing

–– VVI VVI –– ventricular demand pacingventricular demand pacing

–– DDD DDD –– atrial/ventricular demand pacing, atrial/ventricular demand pacing,

senses & paces both chambers; trigger senses & paces both chambers; trigger

or inhibitor inhibit

–– AOO AOO –– atrial asynchronous pacingatrial asynchronous pacing

–– VOO VOO –– ventricular asynchronous pacingventricular asynchronous pacing

Normal PacingNormal Pacing

•• Atrial pacingAtrial pacing

–– Atrial pacing spikes followed by PAtrial pacing spikes followed by P--waveswaves


•• Ventricular pacingVentricular pacing

–– Ventricular pacing spikes followed by wide, Ventricular pacing spikes followed by wide,

bizarre QRSbizarre QRS--complexescomplexes


•• Sequential AV pacingSequential AV pacing

–– Atrial & ventricular pacing spikes followed by Atrial & ventricular pacing spikes followed by

atrial & ventricular complexesatrial & ventricular complexes


•• PP--wave synchronous mode of pacingwave synchronous mode of pacing

–– Ventricle paced at sensed atrial rateVentricle paced at sensed atrial rate

Abnormal PacingAbnormal Pacing

•• Atrial nonAtrial non--capturecapture

–– Atrial pacing spikes are not followed by PAtrial pacing spikes are not followed by P--waveswaves


•• Ventricular nonVentricular non--capturecapture

–– Ventricular pacing spikes are not followed by Ventricular pacing spikes are not followed by

QRSQRS--complexescomplexes

Failure to CaptureFailure to Capture

•• CausesCauses

–– Insufficient energy delivered by pacerInsufficient energy delivered by pacer

–– Low battery voltageLow battery voltage

–– Dislodged, loose, fibrotic, or fractured Dislodged, loose, fibrotic, or fractured

electrodeelectrode

–– Electrolyte abnormalitiesElectrolyte abnormalities

•• AcidosisAcidosis

•• HypoxemiaHypoxemia

•• HyperkalemiaHyperkalemia

Failure to CaptureFailure to Capture

•• SolutionsSolutions

–– View rhythm in different leadsView rhythm in different leads

–– Change electrodesChange electrodes

–– Check connectionsCheck connections

–– Increase pacer outputIncrease pacer output

–– Change battery, cables, pacer Change battery, cables, pacer

–– Reverse polarityReverse polarity


•• Atrial undersensingAtrial undersensing

–– Atrial pacing spikes occur irregardless of PAtrial pacing spikes occur irregardless of P--

waveswaves

–– Pacemaker is not Pacemaker is not ““seeingseeing”” the intrinsic activitythe intrinsic activity


•• Ventricular undersensingVentricular undersensing–– Ventricular pacing spikes occur regardless of Ventricular pacing spikes occur regardless of

QRSQRS--complexescomplexes

–– Pacemaker is not Pacemaker is not ““seeingseeing”” the intrinsic activitythe intrinsic activity

Failure to SenseFailure to Sense

•• CausesCauses

–– Pacemaker not sensitive enough to detect Pacemaker not sensitive enough to detect the patientthe patient’’s intrinsic electrical activity s intrinsic electrical activity (mV)(mV)

–– Insufficient myocardial voltageInsufficient myocardial voltage

–– Dislodged, loose, fibrotic, or fractured Dislodged, loose, fibrotic, or fractured electrodeelectrode

–– Electrolyte abnormalitiesElectrolyte abnormalities

–– Low battery voltageLow battery voltage


•• Danger Danger –– potential (low) for paced potential (low) for paced

ventricular beat to land on T wave ventricular beat to land on T wave

(R(R--onon--T phenomenon)T phenomenon)





–– Check connectionsCheck connections

–– Increase pacemakerIncrease pacemaker’’s sensitivitys sensitivity

–– Replace cables and/or batteryReplace cables and/or battery


–– Check electrolytesCheck electrolytes

–– Unipolar settingUnipolar setting

OversensingOversensing

•• Pacing does not occur when intrinsic Pacing does not occur when intrinsic

rhythm is inadequaterhythm is inadequate


•• CausesCauses

–– Pacemaker inhibited due to sensing of Pacemaker inhibited due to sensing of

““PP”” waves & waves & ““QRSQRS”” complexes that do complexes that do

not existnot exist

–– Pacemaker too sensitivePacemaker too sensitive

–– Possible wire fracture, loose contactPossible wire fracture, loose contact

–– Pacemaker failurePacemaker failure

•• Risks: heart block, asystoleRisks: heart block, asystole





–– Check connections Check connections

–– Decrease pacemaker sensitivityDecrease pacemaker sensitivity

–– Change cables and/or batteryChange cables and/or battery


–– Check electrolytesCheck electrolytes

–– Unipolar pacing with subcutaneous Unipolar pacing with subcutaneous ““ground ground wirewire””

CompetitionCompetition

•• AssessmentAssessment

–– Pacemaker & patientPacemaker & patient’’s intrinsic rates are similars intrinsic rates are similar

–– Pacer spikes unrelated to PPacer spikes unrelated to P--waves and/or QRSwaves and/or QRS--complexescomplexes

–– Fusion/pseudoFusion/pseudo--fusion beatsfusion beats

Magnet modeMagnet mode

•• Pacemakers: asynchronous pacingPacemakers: asynchronous pacing

•• Defibrillators: suspended detection of Defibrillators: suspended detection of

arrhythmiasarrhythmias

Assessing Underlying RhythmAssessing Underlying Rhythm

•• Carefully assess underlying rhythmCarefully assess underlying rhythm

–– Right way: slowly decrease pacemaker rateRight way: slowly decrease pacemaker rate

Assessing Underlying RhythmAssessing Underlying Rhythm

•• Assessing Underlying RhythmAssessing Underlying Rhythm

–– Wrong way: pause pacer or unplug cablesWrong way: pause pacer or unplug cables

Pacemaker WenckebachPacemaker Wenckebach

•• AssessmentAssessment

–– Appears similar to 2Appears similar to 2ndnd degree heart blockdegree heart block

–– Occurs with intrinsic tachycardiaOccurs with intrinsic tachycardia

•• CausesCauses

–– DDD mode safety featureDDD mode safety feature

–– Prevents rapid ventricular pacing Prevents rapid ventricular pacing

impulse in response to rapid atrial rateimpulse in response to rapid atrial rate

•• Sinus tachycardiaSinus tachycardia

•• Atrial fibrillation, flutterAtrial fibrillation, flutter

•• Prevents pacemakerPrevents pacemaker--mediated tachycardiamediated tachycardia

•• Upper rate limit may be inappropriateUpper rate limit may be inappropriate


•• SolutionSolution

–– Treat cause of tachycardiaTreat cause of tachycardia

•• Fever: CoolingFever: Cooling

•• Atrial tachycardia: AntiAtrial tachycardia: Anti--arrhythmicarrhythmic

•• Pain: AnalgesicPain: Analgesic

•• Hypovolemia: Fluid bolusHypovolemia: Fluid bolus

–– Adjust pacemaker upper rate limit as appropriateAdjust pacemaker upper rate limit as appropriate


Special scenarios Special scenarios –– MVPMVP

(Managed Ventricular Pacing)(Managed Ventricular Pacing)

Practice Strip #1Practice Strip #1

AAI: normal atrial pacing


Sinus rhythm: no pacing;

possible back-up settings are AAI, VVI or DDD


DDD: failure to sense ventricle; increase ventricular sensitivity


VVI: ventricular pacing


DDD: failure to capture atria or ventricle;

increase atrial & ventricular output


DDD: normal atrial & ventricular pacing


DDD: normal atrial sensing, ventricular pacing


DDD: failure to sense P-waves; increase atrial sensitivity


DDD: ventricular oversensing; decrease ventricular sensitivity

Thank you!Thank you!

Questions?Questions?

principles of cardiac pacing for paramedics · pdf fileprinciples of cardiac pacing ......

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