TemporaryTemporary PacemakersPacemakers - drstultz.comdrstultz.com/Presentations/2007 11 14 Temporary Pacemakers - VVI.pdf · Failure of output (Failure of output (oversensingoversensing))

TemporaryTemporaryPacemakersPacemakers

November 14, 2007November 14, 2007

David Stultz, MDDavid Stultz, MD

Southwest Cardiology, Inc.Southwest Cardiology, Inc.

(c) 2000-2008 David Stultz, MD

Topics to be coveredTopics to be covered

IndicationsIndications

Pacemaker nomenclaturePacemaker nomenclature

Insertion TechniqueInsertion Technique

ComplicationsComplications

Orientation toOrientation to ““the boxthe box”” (Pacemaker)(Pacemaker)

TroubleshootingTroubleshooting

Questions?Questions?


General indications for a temporaryGeneral indications for a temporarypacemakerpacemaker

Heart rate is slow, causingHeart rate is slow, causing hemodynamichemodynamic compromisecompromise Sick sinus syndromeSick sinus syndrome

SinusSinus bradycardiabradycardia or atrial fibrillation with slow heart rateor atrial fibrillation with slow heart rateresponse (generally <40response (generally <40 bpmbpm))

Heart blockHeart block 33rdrd degreedegree 22ndnd degree type 2 (degree type 2 (MobitzMobitz))

Malignant Tachyarrhythmia caused byMalignant Tachyarrhythmia caused by bradycardiabradycardia TorsadesTorsades de Pointesde Pointes


Clinical settings for temporaryClinical settings for temporarypacemakerpacemaker

SyncopeSyncope

Myocardial infarctionMyocardial infarction

Especially inferiorEspecially inferior

Shock due toShock due to bradycardiabradycardia

MyocarditisMyocarditis

LymeLyme diseasedisease


22ndnd Degree AV block type 1Degree AV block type 1WenkebachWenkebach –– not a reason for pacemakernot a reason for pacemaker


22ndnd Degree AV block type 2Degree AV block type 2((MobitzMobitz))


Inferior/Lateral/Posterior InfarctInferior/Lateral/Posterior Infarctwith 2:1 blockwith 2:1 block


33rdrd degree heart blockdegree heart block


Another 3Another 3rdrd degree heart blockdegree heart block


Atrial fibrillationAtrial fibrillation AsystoleAsystole


NSRNSR 20 second20 second asystoleasystole


Pacemaker NomenclaturePacemaker Nomenclature

Common ModesCommon Modes VVIVVI –– Single chamber (ventricle)Single chamber (ventricle)

DDDDDD –– Dual chamberDual chamber

AAI (uncommon)AAI (uncommon) –– Single chamber (atrium)Single chamber (atrium)

11stst Letter is chamber PACEDLetter is chamber PACED

22ndnd Letter is chamber SENSEDLetter is chamber SENSED

33rdrd Letter is responseLetter is response I = InhibitI = Inhibit

T = Triggered (Unusual)T = Triggered (Unusual)

D = Dual (Inhibit or Pace)D = Dual (Inhibit or Pace)

44thth LetterLetter –– R = Rate responsive (permanent pacers)R = Rate responsive (permanent pacers)


Components of a pacemaker systemComponents of a pacemaker system

LeadLead

Wire connects to heartWire connects to heart

PercutaneousPercutaneous

Ventricular wire sits in RV apexVentricular wire sits in RV apex

EpicardialEpicardial (post surgery)(post surgery)

http://www.oscor.com/images/lead%20pics/RU-STR-Polaris%20lead2%20copy.jpg


The CanThe CanAKAAKA ““Pulse Generator,Pulse Generator,”” ““BatteryBattery””

http://upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Pacemaker_GuidantMeridianSR.jpg/549px-Pacemaker_GuidantMeridianSR.jpg

http://www.staff.vu.edu.au/CriticalCare/Critical%20Care/Images%20_l1/spacer.gif

http://intensivecare.hsnet.nsw.gov.au/five/images/generator.jpg

Single chamber Dual chamberPermanent single chamber

Temporary


http://www.hgcardio.com/HRhythm/Treatments/a_pacemaker_schematic.jpg


Sites of insertion for a temporarySites of insertion for a temporarypacemakerpacemaker

Right internal jugularRight internal jugular

LeftLeft subclaviansubclavian veinvein

RightRight subclaviansubclavian veinvein

Either femoral vein (Fluoroscopy required)Either femoral vein (Fluoroscopy required)

Left IJ is possible but very difficultLeft IJ is possible but very difficult


SeldingerSeldinger techniquetechniqueforfor percutaneouspercutaneous vascular accessvascular access

ICU Book (Marino)

General steps•Trendelenberg position or leg elevation canfacilitate access to IJ and subclavian veins•Sterile Field•Anesthetize skin with lidocaine•Access vein with Cook needle•Insert guidewire•Remove needle•Consider making a skin nick with scalpel•Insert 6-8F introducer sheath with dilator overguidewire•Remove dilator and guidewire•Flush sheath using side port•Advance temporary pacemaker to rightventricle


Complications of temporaryComplications of temporarypacemaker insertionpacemaker insertion

Blood loss/Blood loss/hematomahematoma

InfectionInfection

Arrhythmia (especially during insertion)Arrhythmia (especially during insertion) PVCPVC’’s are commons are common

Heart blockHeart block Especially in patients with underlying LBBBEspecially in patients with underlying LBBB

Bundle branch blockBundle branch block

PneumothoraxPneumothorax (about 1+% when(about 1+% when subclaviansubclavian accessaccessused)used)

Cardiac perforationCardiac perforation TamponadeTamponade


PneumothoraxPneumothorax of Left Lungof Left Lungh

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Functions of a pacemakerFunctions of a pacemaker

SensingSensing

The deviceThe device ‘‘seessees’’ a native heart beata native heart beat

PacingPacing

The device delivers a shock to stimulate a heart beatThe device delivers a shock to stimulate a heart beat


VVI ExplainedVVI Explained

A VVI pacemakerA VVI pacemaker

Paces the ventriclePaces the ventricle

Senses the ventricleSenses the ventricle

In response to a sensed event it INHIBITS theIn response to a sensed event it INHIBITS thepacing responsepacing response

So if it doesnSo if it doesn’’t SENSE a native heart beat in a specifiedt SENSE a native heart beat in a specifiedperiod, it will deliver a pace.period, it will deliver a pace.


Timing cyclesTiming cycles

VVI pacemakerLR = lower rate limitVRP = ventricular refractory periodNote that a sensed QRS starts the VRP and resets the LR

Braunwald, 7th ed.


The dials on the TemporaryThe dials on the Temporarypacemakerpacemaker

RateRate

Determines the lower rate limit of the deviceDetermines the lower rate limit of the device

Heart rate should not go lower than the set rateHeart rate should not go lower than the set rate

OutputOutput

In milliamps, the amount ofIn milliamps, the amount of ‘‘juicejuice’’ the devicethe deviceoutputs with each pacer spikeoutputs with each pacer spike


SensitivitySensitivity

SensitivitySensitivity asynchronousasynchronous InIn millivoltsmillivolts, the amount of energy that has to be, the amount of energy that has to be

detected in order for the device todetected in order for the device to ‘‘sensesense’’ a beata beat

HigherHigher millivoltsmillivolts = less sensitive= less sensitive More likely for the pacemaker to pace at the lower rateMore likely for the pacemaker to pace at the lower rate

regardless of what the heart does on its ownregardless of what the heart does on its own

LowerLower millivoltsmillivolts = more sensitive= more sensitive More likely to pick up noise, andMore likely to pick up noise, and ‘‘sensesense’’ a ventricular beata ventricular beat

even though nothing actually happenedeven though nothing actually happened



http://www.univie.ac.at/cga/courses/BE513/EKG/qrs.gif

0 mV

Async

Sensitivity low –Everything (QRS, T, U)can be sensed by thepacemaker as a QRS




0 mV

Async

Sensitivity low –QRS and some T waves will besensed by pacemaker as a QRS




0 mV

Async

Sensitivity just rightQRS will be sensed,T waves will not




0 mV

Async

Sensitivity too highNothing will be sensed


Testing thresholdsTesting thresholds

Output ThresholdOutput Threshold Set Sensitivity toSet Sensitivity to ‘‘asynchronousasynchronous’’

Set Rate just above the native heart rateSet Rate just above the native heart rate 6060--8080 bpmbpm

Start output at 5Start output at 5--1010 mAmA, and gradually turn down, and gradually turn downuntil ventricular capture is lostuntil ventricular capture is lost

The last point before losing capture is the thresholdThe last point before losing capture is the threshold

Pacemaker output should be set at 2Pacemaker output should be set at 2--3x the3x thethresholdthreshold


Testing ThresholdsTesting Thresholds

Sensitivity ThresholdSensitivity Threshold Not always necessaryNot always necessary Testing the amplitude of native QRS complexes as seen byTesting the amplitude of native QRS complexes as seen by

the canthe can Set Rate just below native heart rateSet Rate just below native heart rate Set Output at 2Set Output at 2--3x the Pacing threshold3x the Pacing threshold StartStart asynchonrousasynchonrous, then slowly turn dial down. Pacemaker, then slowly turn dial down. Pacemaker

spikes will disappear when the sensitivity threshold isspikes will disappear when the sensitivity threshold isreached. The pacemaker can nowreached. The pacemaker can now ‘‘seesee’’ the native QRSthe native QRScomplexes.complexes.

The pacemaker should be set at a sensitivity 1/3 to 1/2 theThe pacemaker should be set at a sensitivity 1/3 to 1/2 thesensitivity thresholdsensitivity threshold


Troubleshooting PacemakersTroubleshooting Pacemakers

Normal behavior that looks strangeNormal behavior that looks strange

Failure to CaptureFailure to Capture

UndersensingUndersensing

OversensingOversensing

Cross Talk (Dual Chamber only)Cross Talk (Dual Chamber only)


Normal behavior of VVI pacemakerNormal behavior of VVI pacemaker

Native QRS



Paced beat with capture



Fusion beat – combination of native QRS and paced beat



Pseudofusion – pacing spike, normal QRS


Failure to CaptureFailure to Capture

Atrial pacing with intermittent ventricular captureBraunwald, 7th ed.


Failure of output (Failure of output (oversensingoversensing))

VVI pacemaker sensing artifact as ventricular contractions (oversensing)As a result, the pacemaker does not output

Braunwald, 7th ed.


UndersensingUndersensing

VVI pacemaker3rd ventricular beat is a PVC, but it is followed by a pacemaker spike4th beat is a probably a normal ventricular beat, but it is also followed by a pacer spike

Braunwald, 7th ed.


Cross TalkCross Talk

Dual chamber pacemaker in DDD mode3rd atrial pacing spike is not followed by ventricular spikeVentricular lead detects the atrial spike as a ventricular depolarization,So the pacemaker fails to deliver a ventricular spike

Braunwald, 7th ed.


Documents

TemporaryTemporary PacemakersPacemakers - drstultz.comdrstultz.com/Presentations/2007 11 14 Temporary Pacemakers - VVI.pdf · Failure of output (Failure of output (oversensingoversensing))