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Anesthesia for Lithotripsy in Patients with Pacemaker

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Carlos J Estrada, MD

Annals of Cardiac Anaesthesia 2005; 8: 21–32 Rastogi et al. Patients with Pacemakers & Defibrillators 21

Anaesthetic Management of Patients with Cardiac Pacemakers andDefibrillators for Noncardiac Surgery

Sh iv a n i Ra sto g i, M D , Sa n j a y G o e l, M D , D e e p a k K Te m p e , M D ,Sa n ju l a V ir m a n i, D A , DNB

Department of Anaesthesiology and Intensive Care, GB Pant Hospital, New Delhi

REVIEW ARTICLES

Introduction

Patients with cardiac disease presenting fornoncardiac surgery pose a considerable

challenge to the anesthesiologists. With theavailability of better medical facility andsophisticated diagnostic methods, many patientsespecially of the elderly age group, are detected tohave electrophysiological disorders. Pacemakersare being used with greater frequency for bothconduction and arrhythmia problems in suchpatients. Currently more than 5,00,000 patients inthe United States have pacemakers and nearly1,15,000 new devices are implanted each year.1

Although, no definite figures are available thenumber is also increasing in India. These patientsmay require one or more surgical procedures afterreceiving the pacemaker.2 Care of the pacemakerduring surgery as well as understanding itsanesthetic implications is crucial in themanagement of these patients. The perioperativemanagement of patients with permanentpacemaker undergoing noncardiac surgery isdiscussed.

Cardiac pacing is one of the most reliabledocumented treatment for various cardiacarrhythmias, especially bradyarrhythmias since1950.3 The initial pacing system consisted of asingle lead asynchronous pacemaker, which pacedthe heart at a fixed rate. Over the years, thetechnological advances have revolutionised thepacemakers and currently more sophisticatedmultiprogrammable devices are available. In

addition, automated implantable cardioverterdefibrillators (AICD) have been designed to treatfatal tachyarrhythmias.4 With the availability ofpacing devices to suit many conditions, potentialindications for pacing are expanding. TheAmerican College of Cardiology /American HeartAssociation (ACC/AHA) established indicationsfor permanent pacemaker or antitachycardiadevices in 2002, which are depicted in table 1.5

Address for Correspondence: Dr. Deepak K. Tempe, Director - Professorand Head, Department of Anaesthesiology and Intensive Care, GB PantHospital, New Delhi – 110002. Phone: 91-11- 23232877.Email: [email protected]

Annals of Cardiac Anaesthesia 2005; 8: 21-32

Key Words:- Equipment, Defibrillator; Equipment, Pacemaker

Table 1. Indications of permanent pacemakerlmplantation.5

1) Acquired AV block:A) Third degree AV block

Bradycardia with symptomsAfter drug treatment that cause symptomaticbradycardiaPostoperative AV block not expected to resolveNeuromuscular disease with AV blockEscape rhythm <40 bpm or asystole > 3s

B) Second degree AV blockPermanent or intermittent symptomatic bradycardia

2) After Myocardial infarction:Persistent second degree or third degree blockInfranodal AV block with LBBBSymptomatic second or third degree block

3) Bifascicular or Trifascicular block:Intermittent complete heart block with symptomsType II second degree AV blockAlternating bundle branch block

4) Sinus node dysfunction:Sinus node dysfunction with symptoms as a result oflong term drug therapySymptomatic chronotropic incompetence

5) Hypertensive carotid sinus and neurocardiac syndromes:Recurrent syncope associated with carotid sinusstimulationAsystole of >3s duration in absence of any medication

AV: atrioventricular, LBBB: Left bundle branch block,

Technique of Permanent Pacing

In permanent pacing, leads are usually insertedtransvenously through the subclavian or cephalic

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22 Rastogi et al. Patients with Pacemakers & Defibrillators Annals of Cardiac Anaesthesia 2005; 8: 21–32

Mercury–Zinc batteries that were used in the earlydays had a short useful life (2-3 yrs). CurrentlyLithium-iodine batteries are being used which havelonger shelf life (5-10 yrs) and high energy density.

Leads

These are insulated wires connecting the pulsegenerator.

Electrode

It is an exposed metal end of the lead in contactwith the endocardium or epicardium.

Unipolar Pacing

There is one electrode, the cathode (negativepole) or active lead. Current flows from the cathode,stimulates the heart and returns to anode (positivepole) on the casing of pulse generator via themyocardium and adjacent tissue to complete thecircuit. Unipolar sensing is more likely to pick upextracardiac signals and myopotentials.

Bipolar Leads

They consist of two separate electrodes, anode(positive pole) and cathode (negative pole), bothlocated within the chamber that is being paced. Asthe electrodes are very close, the possibility ofextraneous noise disturbance is less and the signalsare sharp.

Endocardial Pacing

It is also called as transvenous pacing whichimplies that the leads/ electrodes system has beenpassed through a vein to the right atrium or rightventricle. It can be unipolar or bipolar.

Epicardial Pacing

This type of pacing is accomplished by insertingthe electrode through the epicardium into themyocardium. This can also be unipolar or bipolar.

Pacing Threshold

This is the minimum amount of energy required

vein with the leads positioned in the right atrialappendage for atrial pacing and right ventricularapex for ventricular pacing. The leads are thenattached to the pulse generator, which is insertedinto the subcutaneous pocket below the clavicle.Epicardial lead placement is used when eithertransvenous access cannot be obtained or if thechest is open during cardiac operations.

Generic Codes of Pacemaker

To understand the language of pacing, it isnecessary to comprehend the coding system thatwas developed originally by the internationalconference on heart disease and subsequentlymodified by the NASPE/BPEG (North Americansociety of pacing and electrophysiology/Britishpacing and electrophysiology group) alliance. TheNASPE/BPEG code consists of a five positionsystem using a letter in each position to describethe programmed function of a pacing system (Table2).3 The first letter indicates the chamber beingpaced, the second letter designates the chamberbeing sensed, third position designates responseto sensing (I and T indicates inhibited or triggeredresponses, respectively). The fourth and fifthpositions describe programmable andantitachyarrhythmia functions, but these two arerarely used. An R in fourth position indicates thatthe pacemaker incorporates a sensor to modulatethe rate independently of intrinsic cardiac activitysuch as with activity or respiration.

Table 2. Generic codes for pacemaker.3

I II III IV VPacing Sensing Response Programmability Tachycardia

O-None O- None O-None O-None O- NoneA-Atrium A-Atrium I-Inhibited C-Communicating P-Pacing

V-Ventricle V-Ventricle T-Triggered P-simple S-Shocksprogrammable

D-Dual D-Dual D-dual M-multi D-Dual(A+V) (A+V) (I+T) programmable (P+S)

S-Simple S-Simple R-Rate(A or V) (A or V) modulation

Important Definitions

Pulse Generator

It includes the energy source (battery) andelectric circuits for pacing and sensory function.

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to consistently cause depolarization and thereforecontraction of the heart. Pacing threshold ismeasured in terms of both amplitude and durationfor which it is applied to the myocardium. Theamplitude is programmed in volts (V) or inmilliampers in some devices, and the duration ismeasured in milliseconds. Factors affecting themyocardial pacing threshold are listed in table 3.6

However, only those factors important from theanaesthesia point of view will be discussed.

pacing rate (e.g.72 beats/min). It is particularlyuseful in patients with sick sinus syndrome.

Runaway Pacemaker

It is the acceleration in paced rates due to agingof the pacemaker or damage produced by leakageof the tissue fluids into the pulse generator.Treatment with antiarrhythmic drugs orcardioversion may be ineffective in such cases. Itis necessary to change the pacemaker to anasynchronous mode, or reprogram it to loweroutputs. If the patient is haemodynamicallyunstable temporary pacing should be donefollowed by changing of pulse generator.

Types of Pacing Modes

Asynchronous: (AOO, VOO, and DOO)

It is the simple form of fixed rate pacemakerwhich discharges at a preset rate irrespective of theinherent heart rate. It can be used safely in caseswith no ventricular activity. However, the problemsassociated with asynchronous pacemaker are thatit competes with the patient’s intrinsic rhythm andresults in induction of tachyarrythmias.Continuous pacing wastes energy and alsodecreases the half-life of the battery.7

Single Chamber Atrial Pacing (AAI, AAT)

In this system atrium is paced and the impulsepasses down the conducting pathways, thusmaintaining atrioventricular synchrony. A singlepacing lead with electrode is positioned in the rightatrial appendage, which senses the intrinsic P waveand causes inhibition or triggering of thepacemaker. This is useful in patients with sinusarrest and sinus bradycardia providedatrioventricular conduction is adequate. It isinappropriate for chronic atrial fibrillation and longventricular pauses.

Single Chamber Ventricular Pacing (VVI, VVT)

VVI is the most widely used form of pacing inwhich ventricle is sensed and paced. It senses theintrinsic R wave and thus inhibits the pacemakerfunction. This type of pacemaker is indicated in a

Table 3. Factors affecting pacing thresholds.6

Increase Decrease

1-4 weeks after implantation Increased catecholaminesMyocardial ischaemia/infaction Stress, anxietyHypothermia, hypothyroidism Sympathomimetic drugsHyperkalaemia, acidosis/alkalosisAnticholinergicsAntiarrythmics (class Ic,3) GlucocorticoidesAntiarrythmics ( class IA/B,2)* HyperthyroidismSevere hypoxia/hypoglycaemia Hypermetabolic statusInhalation-local anaesthetics**

*possibly increase threasholds**conflicting evidence, probably dose-related

R Wave Sensitivity

It is the measure of minimal voltage of intrinsicR wave, necessary to activate the sensing circuit ofthe pulse generator and thus inhibit or trigger thepacing circuit. The R wave sensitivity of about 3mV on an external pulse generator will maintainventricle inhibited pacing.

Resistance

It can be defined as impedance to the flow ofcurrent. In the pacemaker system it amounts to acombination of resistance in lead, resistancethrough the patient’s tissue and polarization thattakes place when voltage and current are deliveredinto the tissues. Abrupt changes in the impedancemay indicate problem with the lead system. Veryhigh resistance can indicate a conductor fractureor poor connection to the pacemaker. A very lowresistance indicates an insulation failure.

Hystersesis

It is the difference between intrinsic heart rate atwhich pacing begins (about 60 beats/min) and

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patient with complete heart block with chronicatrial flutter, atrial fibrillation and long ventricularpauses. Single chamber ventricular pacing is notrecommended for patients with sinus node disease,as these patients are more likely to develop thepacemaker syndrome.

Dual Chamber AV Sequential Pacing (DDD, DVI,DDI, and VDD)

Two leads that can be unipolar or bipolar areused, one for the right atrial appendage and theother for right ventricular apex. The atrium isstimulated first to contract, then after an adjustablePR interval ventricle is stimulated to contract. Thesepacemakers preserve the normal atrioventricularcontraction sequence, and are indicated in patientswith AV block, carotid sinus syncope, and sinusnode disease. In DDD system, both the atrium andventricle can be sensed and paced. The advantagesof dual chamber pacemaker are that they are similarto sinus rhythm and are beneficial in patients,where atrial contraction is important for ventricularfilling (e.g. aortic stenosis). The disadvantage ofdual chamber pacing is the development of apacemaker-mediated tachycardia (PMT) due toventriculoatrial (VA) conduction in whichventricular conduction is conducted back to theatrium and sensed by the atrial circuit, whichtriggers a ventricular depolarization leading toPMT. This problem can be overcome by carefulprogramming of the pacemaker.

Programmable Pacemaker

This is being used since 1980. It providesflexibility to correct abnormal device behavior andadapt the device to patient’s specific and changingneeds. The various factors, which can beprogrammed are pacing rate, pulse duration,voltage output, R wave sensitivity, refractoryperiods, PR interval, mode of pacing, hysteresis,and atrial tracking rate.

In patients with normal cardiac contractility, thestroke volume increases to its maximal point whenonly 40% of maximal activity is performed. Thusan increase in heart rate is important duringexercise to achieve the peak cardiac output. Patientswith fixed stroke volume such as those with dilated

cardiomyopathy are not able to effectively increasecardiac output by increase in contractility. Theydepend entirely on their heart rate. Similarly,patients on pacemaker need to change the pacedrate in proportion to the metabolic demand so asto normalize the haemodynamic status. Patientswith “chronotropic incompetence” (atrialfibrillation, complete heart block) are unable tochange the heart rate according to their metabolicdemands. DDD, VVI, and AAI modes also cannotincrease heart rate according to the metabolicdemands in these patients. In such cases, rateresponsive pacemakers (i.e. pacemakers, which notonly sense the atrial or ventricular activity but alsosense various other stimuli and thus, increase thepacemaker rate) are helpful. Various types ofsensors have been designed which respond to theparameters such as vibration, acceleration, minuteventilation, respiratory rate, central venouspressure, central venous pH, QT interval, pre-ejection period, right ventricular stroke volume,mixed venous oxygen saturation, and right atrialpressure.8 Out of these, sensors capable of detectingbody movements (vibrations), changes inventricular repolarisation, central venoustemperature, central venous oxygen saturation,respiratory rate and depth, and right ventricularcontractility are commonly used in clinical practice.

Pacemaker Syndrome

Most individuals can compensate for thereduction in cardiac output due to loss of atrialsystole by activation of baroreceptor reflexes thatincrease peripheral resistance and maintainsystemic blood pressure. Some individuals,particularly those with intact retrograde VAconduction, may not tolerate ventricular pacingand may develop a variety of clinical signs andsymptoms resulting from deleterioushaemodynamics induced by ventricular pacingtermed as pacemaker syndrome. These includehypotension, syncope, vertigo, light-headedness,fatigue, exercise intolerance, malaise, weakness,lethargy, dyspnoea, and induction of congestiveheart failure. Cough, awareness of beat-to-beatvariation of cardiac response from spontaneous topaced beats, neck pulsation or pressure sensationin the chest, neck, or head, headache, and chest painare the other symptoms.9 Symptoms may vary

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from mild to severe, and onset may be acute tochronic. The pathophysiology of pacemakersyndrome results from a complex interaction ofhaemodynamic, neurohumoral and vascularchanges induced by the loss of AV synchrony.Patients with retrograde VA conduction are in astate of constant AV dys-synchrony. Retrograde VAconduction is present in about 15% of patients withcomplete antegrade AV block and in about 67% ofpatients with intact antegrade AV conduction pacedfor sinus node disease.

Pacemaker Failure

It may be due to generator failure, lead failure,or failure to capture. Failure to capture owing to adefect at the level of myocardium (i.e. the generatorcontinues to fire but no myocardial depolarizationtakes place) remains the most difficult problem totreat.10

Haemodynamic Changes During Pacing

In single chamber pacemaker, atrial pacingincreases the cardiac output by about 26% incomparison to ventricular pacing, as atrialcontraction contributes 15 to 25% of preload toventricles. Also atrial systole increases the coronaryblood flow and decreases the coronary resistance.

The new AV sequential pacing results in 35 %increase in cardiac output in comparison to thesingle chamber pacing. This is achieved by the atrialsystolic boost (atrial kick) to ventricular filling.While matching pacemaker to a patient, severalfactors need to be taken into consideration such aspatient’s age, symptoms, cardiac rhythm, presenceof underlying heart disease, ventricular function,and response of sinus node to activity (chronotropicresponse). BPEG have issued guidelines on therecommended pacing modes for all types ofbradyarrhythmias requiring pacing (Table 4).11

In patients with atrioventricular block, the ventriclemust be paced. Ventricular pacing should followatrial pacing or sensing to maintain atrioventricularsynchrony and cardiac output. If the patient isphysically active and sinus node is chronotropicallyincompetent, a rate responsive system isadvisable.

Factors Important from AnaesthesiaPoint of View

Physiological

During the first two weeks, there is an initialsharp increase in the pacing threshold i.e. up to tentimes the acute level because of the tissue reactionaround the electrode tip. Then it decreases to twoto three times the acute level because of the scarformation. In chronic state, it reaches the initial levelin 80% of patients. But this has become far less of aproblem with the introduction of steroid-elutingleads and other refinements in the lead technology.1

Potassium

Its equilibrium across the cell membranedetermines the resting membrane potential (RMP).In certain clinical situations, the RMP becomes lessnegative and approaches the membrane’s thresholdpotential so that less current density at the electrodetissue interface is required to initiate an actionpotential, making capture by the pacemaker easier.If the RMP becomes more negative, an increased

Table 4. British pacing and electrophysiology grouprecommended pacemaker modes.11

Sinus node disease

Optimal AAIRAlternative AAIInappropriate VVI, VDDAtrioventricular blockOptimal DDDAlternative VDDInappropriate AAI, DDISinus node disease with atrioventricular blockOptimal DDDR, DDIRAlternative DDD, DDIInappropriate AAI, VVIChronic atrial fibrillation with atrioventricular blockOptimal VVIRAlternative VVIInappropriate AAI, VVI, VDDCarotid sinus syncopeOptimal DDIAlternative DDD, VVI (with

hysteresis)Inappropriate AAI, VDDMalignant vasovagal syndromeOptimal DDIAlternative DDDInappropriate AAI, VVI, VDD.

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current density would be required to raise the RMPto the membrane threshold potential, making itmore difficult for the pacemaker to initiatemyocardial contraction. An acute increase inextracellular potassium concentration as in patientswith myocardial ischaemia, rapid potassiumreplacement in chronic hypokalaemic patients oruse of depolarising muscle relaxants in patientswith burns, trauma or neuromuscular disease mayincrease the RMP to less negative value, thusmaking the capture easier. Similarly, decrease inextracellular potassium (in patients on diuretictherapy or those undergoing hyperventilation suchas neurosurgical patients) leads to more negativeRMP making the pacemaker capture difficult.7,9,12

Myocardial Infarction

Its scar tissue is unresponsive to electricalstimulation and may cause loss of pacemakercapture.7

Antiarrhythmic Drug Therapy

Class Ia (quinidine, procainamide), Ib (lidocaine,diphenylhydrantoine), and Ic (flecainide,encainide, propafenone) drugs have been found toincrease the pacing threshold.13,14

Acid Base Status

Alkalosis and acidosis both cause increase inpacing threshold.14

Hypoxia

It causes increase in pacing threshold.12

Anaesthetic Drugs

These drugs are not likely to change the pacingthreshold. It is notable that addition of equipotenthalothane, enflurane, or isoflurane to opiate basedanaesthesia after cardiopulmonary bypass did notincrease pacing threshold.14

Preoperative Evaluation

Preoperative evaluation is an important aspectof the anaesthetic management of a patient with

permanent pacemaker undergoing noncardiacsurgery. It includes evaluation of the patient andthe pacemaker. It should include not only detailedevaluation of the underlying cardiovascular diseaseresponsible for the insertion of pacemaker, but alsoother associated medical problems. Sincesubstantial number of these patients suffers fromcoronary artery disease (50%), hypertension (20%)and diabetis (10%),7 one should know the severityof the cardiac disease, the current functional status,and medication of the patient. The patient shouldalso be questioned about the initial indication forthe pacemaker and preimplantation symptomssuch as lightheadedness, dizziness or fainting. Ifthese symptoms occur even after the pacemakerinsertion, cardiology consultation should beobtained.9 The general physical examinationshould be done to rule out the presence of anybruits, and signs of congestive heart failure. Thelocation of the pulse generator should be noted.Generally, generator for the epicardial electrodesis kept in the abdomen and over one of the pectorismuscles for the endocardial electrodes.7 Routinebiochemical and haematological investigationsshould be performed as indicated on an individualbasis. A 12 lead electrocardiogram, X–ray chest (forvisualization of continuity of leads) andmeasurement of serum electrolytes (especially K+)should be performed.

Pacemaker Evaluation

It is equally important to evaluate the functionof pacemaker in the preoperative period. Assistancefrom the cardiologist and the manufacturer’srepresentative may be obtained for the purpose.Most of the information about the pacemaker, suchas type of pacemaker (fixed rate or demand rate),time since implanted, pacemaker rate at the timeof implantation, and half-life of the pacemakerbattery can be taken from the manufacture’s bookkept with the patient.

Ten percent decrease in the rate from the time ofimplantation indicates power source depletion. Inpatients with VVI generator, if intrinsic heart rateis greater than pacemaker set rate, evaluation ofpacemaker function can be done by slowing downthe heart rate by carotid sinus massage, whilethe patient’s ECG is continuously monitored.15

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Carotid sinus massage should be done cautiouslyin patients with a history suggestive ofcerebrovascular disease or carotid artery disease,because the atherosclerotic plaque may emboliseto the cerebral circulation. Other methods to slowthe heart rate are Valsalva manoeuvre and use ofedrophonium (tensilone 5-10 mg).6

Reprogramming the pacemaker is generallyindicated to disable rate responsiveness. The AICDalso needs to be disabled before anaesthesia. ACC/AHA guidelines advise that all antitachycardiatherapy should be disabled before anaesthesia. Ifthe risk of electromagnetic interference (EMI) ishigh, such as, when the electricity is in closeproximity to the generator, alternative temporarycardiac pacing device should be available. The useof magnet may also be necessary.

Effect of the Magnet Application on Pacemaker Function

Magnet application is an extremely importantfunction. The magnet is placed over the pulsegenerator to trigger the reed switch present in thepulse generator resulting in a non-sensingasynchronous mode with a fixed pacing rate(magnet rate). Magnet operated reed switches wereoriginally incorporated to produce pacemakerbehaviour that would demonstrate remainingbattery life and sometimes pacing thresholds.16

Activation of the reed switch shuts down thedemand function so that the pacemaker stimulatesasynchronous pacing. Thus, magnets can be usedto protect the pacemaker dependent patient duringEMI, such as diathermy or electrocautery. However,not all pacemakers switch to asynchronous modeon the application of magnet. The response varieswith the model and the manufacturer and may bein the form of no apparent change in rate or rhythm,brief asynchronous pacing, continuous or transientloss of pacing, or asynchronous pacing without rateresponse. It is advisable to consult the manufacturerto know the magnet response before use. Thepatient must be connected to an electrocardiographrecorder before the magnet is applied and, remainconnected, until after the magnet is removed. Thefirst few paced complexes after magnet applicationprovide information regarding the integrity of thepulse generator and its lead system. A 10% decreasein magnet rate from the time of implantation

indicates power source depletion and is anindicator of end of life requiring electivereplacement of battery.17

If no information is available from the patientabout the pacemaker, magnet may identify theparticular model with the help of magnet rate,which varies among different manufacturers andthus provide clue for its identification.

Despite the previous recommendations to havea magnet available in the operating room, routineuse of magnet during surgery is not without riskand at times may be unjustified. Switching toasynchronous pacing may trigger ventricularasynchrony in patients with myocardial ischaemia,hypoxia, and electrolyte imbalance.12 The newgeneration pacemakers are relatively immune tomagnet application and may not convertpacemaker to asynchronous mode.10 Constantmagnet application over the pacemaker may alterthe programming leading to either inhibited ortriggered pacing, or may cause continuous ortransient loss of pacing.18 It has also been seen thatif a magnet is placed over a programmablepacemaker, in the presence of EMI, the pulsegenerator may become inadvertently andunpredictably reprogrammed. This new ‘surprise’programme may not be evident until after themagnet is removed. A further problem withmagnetic application is the variability of responsebetween devices, as there is no universal standard.Thus, the use of magnet may be safe in non-programmable pacemaker, however, the mostcurrent devices should be consideredprogrammable unless known otherwise.9

Intraoperative Management

Intraoperative monitoring should be based onthe patient’s underlying disease and the type ofsurgery. Continuous ECG monitoring is however,essential to monitor pacemaker functioning. Inaddition, both electrical and mechanical evidenceof the heart function should be monitored bymanual palpation of the pulse, pulse oximetry,precordial stethoscope and arterial line, ifindicated.10,19 Presence of pacemaker is not anindication for insertion of pulmonary artery (PA)or central venous catheter.7 If these are indicated,

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care should be taken during insertion of the guidewire or central venous catheter as they arepotentially arrhythmogenic.4,12 In a patient in whomthe pacemaker or AICD has been recentlyimplanted, while passing the PA catheter, careshould be taken as it can easily dislodge the freshlyplaced transvenous endocardial electrode. It is bestto avoid the insertion of PA catheter or usealternative site of insertion in such patients.Multipurpose PA catheter with pacing facilities canalso be used.20

The anaesthetic technique should be usedaccording to the need of the patient. Both narcoticand inhalational techniques can be usedsuccessfully. These anaesthetic agents do not altercurrent and voltage thresholds of the pacemaker.14

Skeletal myopotentials, electroconvulsive therapy,succinylcholine fasciculation, myoclonicmovements, or direct muscle stimulation caninappropriately inhibit or trigger stimulation,depending on the programmed pacing modes.6 Themuscle fasciculation induced by succinylcholinecan be avoided by using nondepolarizing musclerelaxant or defasiculating with nondepolarizingmuscle relaxant before giving succinylcholine.Etomidate and ketamine should be avoided asthese cause myoclonic movements.12 Pacemakerfunction should be verified, before and afterinitiating mechanical ventilation, as there may bedislodgement of pacemaker leads by positivepressure ventilation,21 or nitrous oxide entrapmentin the pacemaker pocket.22 In patients with rateresponsive pacemakers, rate responsive modeshould be deactivated before surgery. If this is notpossible for some reason, the mode of rate responsemust be known so that conditions causing changesin paced heart rate can be avoided. For example,shivering and fasciculations should be avoided ifthe pacemaker is ‘activity’ rate responsive,ventilation (respiratory rate and tidal volume)should be kept controlled and constant in case of‘minute ventilation’ rate responsive, andtemperature must be kept constant in ‘temperature’rate responsive pacemakers.9

Electromagnetic Interference

Most pacemakers are sensitive to direct orindirect EMI. Strong ionizing beams of radiation,

nuclear magnetic resonance imaging, surgicalelectrocautery23 or dental pulp vitality tester are themost common direct sources of EMI that couldinterfere with pacemaker.6 The indirect sources ofEMI include radar, orthopaedic saw, telemetricdevices, mechanical ventilators, lithotriptors,cellular telephones, and whole body vibrations arethe potential sources of mechanical interferencesthat could affect pacemaker. Diagnostic radiologyand computed tomographic (CT) scans do not affectthe function of the pacemaker. Amongst these,electrocautery is the most important source of EMI.It involves radiofrequency current of 300-500 KHz.Fatal arrhythmias and deaths have been reportedwith the use of electrocautery leading to failure ofpacemaker. Between 1984-1997, the US-FDA wasnotified of 456 adverse events with pulsegenerators, 255 from electrocautery and significantnumber of device failures.10

One should apply the following measures todecrease the possibility of adverse effects due toelectrocautery.

1) Bipolar cautery should be used as much aspossible as it has less EMI.

2) If unipolar cautery is to be used duringoperation, the grounding plate should beplaced close to the operative site and as faraway as possible from the site of pacemaker,usually on the thigh and should have goodskin contact.

3) Electrocautery should not be used within 15cm of pacemaker. Frequency of electrocauteryshould be limited to 1-second bursts in every10 seconds to prevent repeated asystolicperiods. Short bursts with long pauses ofcautery are preferred.4,9,15

4) Pacemaker may be programmed toasynchronous mode by a magnet or by aprogrammer. Before using cautery, theprogrammer must be available in theoperation theatre (OT). During the use ofcautery, magnet should not be placed on pulsegenerator as it may cause pacemakermalfunction.

5) Provision of alternative temporary pacing(transvenous, noninvasive transcutaneous)should be ready in the OT.2

6) Drugs such as isoproterenol and atropine

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should be available.7) If defibrillation is required in a patient with

pacemaker, paddles should be positioned asfar away as possible from the pacemakergenerator. If possible, anterior to posteriorpositioning of paddles should be used.Although permanent pacemakers haveprotective circuits to guard against externallyapplied high voltage, pulse generatormalfunction has been reported.15 In electivecardioversion, the lowest voltage necessaryshould be utilized. However, even with theseprecautions, defibrillation may result in acuteincrease in the stimulation threshold, withresultant loss of capture. If this occurs,immediate reprogramming or temporarypacing should be done with increasedgenerator output.4,23

8) Careful monitoring of pulse, pulse oximetryand arterial pressure is necessary duringelectrocautery, as ECG monitoring can also beaffected by interference.

9) The device should always be rechecked afteroperation.

Specific Perioperative Considerations

Some procedures pose a greater risk ofpacemaker malfunction.

Transuretheral Resection of Prostate (TURP) andUterine Hysteroscopy

Coagulation current used during TURPprocedure has no effect, but the cutting current athigh frequencies (up to 2500 kc/sec) can suppressthe output of a bipolar demand ventricularpacemaker. Dresener et al reported a case in whichelectrosurgical unit (ESU) used during operationcaused pacemaker malfunction.25 Duringapplication of cutting current there was a loss ofpulsatile arterial flow, which returned withinterruption of ESU. Thus when ESU use isanticipated reprogramming of pacemakerpreoperatively to the asynchronous (fixed rate)mode should be performed.10

Electroconvulsive Therapy

ECT appears safe for patients with pacemakers,

since little current flows within the heart becauseof the high impedance of body tissue, but theseizure may generate myopotentials which mayinhibit the pacemaker. Thus ECG monitoring isessential and pacemakers should be changed tononsensing asynchronous mode (fixed mode).10

Radiation

Cases where radiation therapy is planned fordeep seated tumors, therapeutic radiation candamage the complementary metal oxidesemiconductors (CMOS) that are the parts of mostmodern pacemakers. Generally, doses in excess of5000 rads are required to cause pacemakermalfunction but as little as 1000 rads may inducepacemaker failure or cause runaway pacemaker. Ifpacemaker cannot be shielded from the field ofradiation, consideration should be given toreimplanting the pacemaker at a distant site.26

Temporary damage to pacemaker may recover afterreprogramming but there may be permanentdamage to the pacemaker as well.27 This effectcould be attributed to charge accumulation insideCMOS after radiation therapy leading to failure ofvarious components in the circuitry and therefore,cause pacemaker failure.28

Nerve Stimulator Testing or Transcutaneous ElectronicNerve Stimulator Unit (TENS)

TENS is now a widely used method for painrelief. TENS unit consists of several electrodesplaced on the skin and connected to a pulsegenerator that applies 20 µsec rectangular pulsesof 1 to 200 V and 0 to 60 mA at a frequency of 20 to110 Hz. This repeated frequency is similar to thenormal range of heart rates, so it can create a farfield potential that may inhibit a cardiac pacemaker.Adverse interaction between these devices has beenfrequently reported, so these patients should bemonitored during initial application of TENS.Pacemaker mediated tachycardia has been inducedby intraoperative somatosensory evoked potentialstimulation.29

Lithotripsy

Anaesthesia may be required in patientsundergoing extracorporeal shock wave lithotripsy

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(ESWL) for immobilisation and to avoid pain inflank at entry site of waves. There may be electricalinterference from hydraulic shock waves and cancause mechanical damage. High-energy vibrationsproduced by lithotripsy machine can cause closureof reed switch causing asynchronous pacing.‘Activity’ rate responsive pacemaker can beaffected due to the damage caused to thepiezoelectric crystals by ESWL. The shock wavescan produce ventricular extrasystoles, if notsynchronized with R wave.9 Thus, pacemakermalfunction can occur in patients undergoingESWL, requiring adequate preparation prior toprocedure. One should have cardiologist’s opinion,perioperative ECG monitoring, device programmerand a standby cardiologist to deal with any devicemalfunction. Rate responsive pacemaker shouldhave their activity mode deactivated. Focal pointof the lithotriptor should be kept at least six inches(15 cm) away from the pacemaker.30,31 Patient withabdominally placed pacemaker generators shouldnot be treated with ESWL. Low shock waves (<16kilovolts) should be used initially followed by agradual increase in the level of energy.32 Dualchamber demand pacemaker is especially sensitiveto shock waves and should be reprogrammed to asimpler mode (VOO, VVI ) preoperatively.

Magnetic Resonance Imaging (MRI)

MRI is an important diagnostic tool. But its usein patients with pacemaker is contraindicated dueto lethal consequences and mortality. Three typesof powerful forces exist in the MRI suite.33

Static Magnetic Field: An intense static field is alwayspresent even if the scanner is not imaging. Most ofthe pacemakers contain ferromagnetic material,which gets attracted to the static magnetic field inthe MRI and may exert a torque effect leading todiscomfort at the pacemaker pocket. The reedswitches used in the pacemaker are known to closeat very low magnetic field of 0.5-2 mT, thus reedswitch activation by high static field of 0.5-1.5 Tcan result in switching of pacemaker to a non-sensing asynchronous pacing.

Radiofrequency Field (RF): This field is switched onand off during magnetic resonance imaging and

has a frequency of 21-64 MHz depending on thestrength of magnetic field. The radiofrequencysignals can cause interference with pacemakeroutput circuits resulting in rapid pacing at multipleof frequency between 60-300 bpm causing rapidpacing rate. It may cause pacemakerreprogramming and destruction of electroniccomponents.34 It may also cause heating at theelectrode-tissue boundary, which may causethermal injury to endocardium and myocardium.35

Gradient Magnetic Field: used for spatial localizationchanges its strength along different orientationsand operates at frequencies in order of 1 kHz.Gradient magnetic field may also interact withreed - switch in pacemaker. Inappropriate sensingand triggering because of the induced voltages canoccur. It may induce negligible heating effect.14,36

The results of various studies done to evaluatethe safety and feasibility suggest that in the absenceof other alternative for getting diagnosticinformation, MRI can be done in the presence of acardiologist. However, appropriate patientselection should be done and equipment forresuscitation and temporary pacing should beavailable. Also patients should be closelymonitored with ECG and oxygen saturation.35

Further studies are necessary to refine theappropriate strategies for performing MRI safelyin a patient with implanted pacemaker. The risk-benefit ratio must be individually evaluated inevery patient with a pacemaker. Patients, whorequire head MRI scanning without alternativediagnostic possibilities, may be best served in acarefully monitored setting. Thus patients withpacemakers should not routinely undergo MRIscanning.35,37

Conclusion

Patients with implanted pacemakers can bemanaged safely for surgery and other non-surgicalprocedures. It requires thorough understandingabout indication of pacemaker insertion, variousmodes of pacing, and programming of pacemaker.A cardiologist should also be consulted for deviceevaluation regarding its proper function and life ofthe batteries. Anaesthetic management should be

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planned preoperatively according to patient’smedical status. Careful monitoring of ECG, pulseoximetry and arterial blood pressure should be done.While using electocautery, precaution for minimalEMI should be taken. Magnet should not be placedover pacemaker in the OT in presence of

1. Atlee JL, Bernstein AD. Cardiac rhythm managementdevices. (Part I) indications, device selection andfunction. Anesthesiology 2001; 95: 1265-1280

2. Levine PA, Balady GJ, Lazar HL, Belott PH, Robert AJ.Electrocautery and pacemakers: Management of thepaced patient subject to electrocautery. Ann Thorac Surg1986; 41: 313-317

3. Hayes DL, Zipes DP. Cardiac pacemakers andcardioverter-defibrillator. In: Braunwald E, Heart Disease6th edition, Philadelphia, WB Saunders, 2001; 7775-814

4. Mehta Y, Swaminathan M, Juneja R, et al. Noncardiacsurgery and pacemaker cardioverter-defibrillatormanagement. J Cardiothorac Vasc Anesth 1998; 12: 221-224

5. Gregoratos G, Abrams J, Epstein AE, et al. ACC/AHA/NASPE 2002. Guideline update for implantation ofcardiac pacemaker and Antiarrhythmia devices-Summary article (a report of the ACC/ AHA/NASPEcommittee to update the 1998 pacemaker guidelines) JAm Coll Cardiol 2002; 40: 1703-1719.

6. Atlee JL, Cardiac pacing and electroversion. In: KaplanJA, ed Cardiac Anesthesia, 4th edition Philadelphia, WBSaunders, 1999; pp 959-89

7. Zaidan JR. Pacemakers. Anesthesiology 1984; 60: 319-3348. Bourke ME. The patients with a pacemaker or related

device. Can J Anaesth 1996; 48: R24-R419. Chien WW, Foster E, Phillips B, Schiller N, Griffin JC.

Pacemaker syndrome in a patient with DDD pacemakerfor long QT syndrome. Pacing Clin Electrophysiol 1991;14: 1209-1212

10. Rozner MA. Intrathoracic gadgets: Update onpacemakers and implantable cardioverter–defibrillators,ASA refreshers course 1999, pp 212

11. Clarke M, Sutton R, Camm AJ, et al. Recommendationsfor pacemaker prescription for systematic bradycardia:report of a working part of the British Pacing and Electrophysiology group. Br Heart J 1991; 66: 185-91

12. Sethuran S, Toff WD, Vuylsteke A, Solesbury PM, MenonDK. Implanted cardiac pacemakers and defibrillatorsin anaesthetic practice. Br J Anaesth 2002; 88: 627-631

13. Bianconi L, Baccadamo R, Toscano S, et al. Effect of oralpropafenone therapy on chronic myocardial pacingthreshold. Pacing Clin Electrophysiol 1992; 15: 148-154

14. Atlee JL, Bernstein AD. Cardiac rhythm managementdevices. (Part II) perioperative management.Anesthesiology 2001; 95: 1492- 1506

15. Simon AB. Perioperative management of the pacemakerpatient. Anesthesiology 1977; 46: 127-131

16. Saluke TV, Dob D, Sutton R. Pacemakers and

defibrillators: Anaesthetic implications. Br J Anaesth2004: 93: 95-104

17. David LH, Strathmore NF. Electromagnetic interferencewith implantable devices, In Clinical cardiac pacing anddefibrillation, 2nd edition. Ellenbogen KA, Kay GN,Wilkoff BL, (eds) Philadelphia, WB Saunders 2000;939-952

18. Kleinman B, Hamilton J, Hariman R, et al. Apparentfailure of a precordial magnet and pacemakerprogrammer to convert a DDD pacemaker to VOOmode during the use of the electrosurgical unit.Anesthesiology 1997; 86: 247-50

19. Shapiro WA, Roizen MF, Singleton MA, Morady F,Bainton CR, Gaynor RL. Intraoperative pacemakercomplications. Anesthesiology 1985; 63: 319-322

20. Kemnitz J, Peters J. Cardiac pacemakers and implantablecardioverter defibrillators in the perioperative phase.Anesthesiol Intensiv Med Notfallmed Schmerzther 1993; 28:199-212

21. Thiagarajah S, Azar I, Agres M, Lear E. Pacemakermalfunction associated with positive pressureventilation. Anesthesiology 1983; 58: 565-566

22. Lamas GA, Rebecca GS, Braunwald NS, Antman EM.Pacemaker malfunction after nitrous oxide anesthesia.Am J Cardiol 1985; 56: 995

23. Mangar D, Atlas GM, Kane PB. Electrocautery-inducedpacemaker malfunction during surgery. Can J Anaesth1991; 38: 616-618

24. Finfer SR. Pacemaker failure on induction of anesthesia,Br J Anaesth 1991; 66: 509-512

25. Dresner DL, Lebowitz PW. Atrioventricular sequentialpacemaker inhibition by transurethral electrosurgery.Anesthesiology 1988; 68: 599-601

26. Souliman SK, Christie J. Pacemaker failure induced byradiotherapy. Pacing Clin Electrophysiol 1994; 17: 270-273

27. Muller-Runkel R, Orsolini G, Kalokhe UP. Monitoringthe radiation dose to a multiprogrammable pacemakerduring radical radiation therapy: a case report. PacingClin Electrophysiol 1990; 13: 1466-1470

28. Mitrani RD, Myerburg RJ, Castellanos A. Cardiacpacemakers. In: Fuster V, Alexander RW, O’Rourke RA10th (eds). Hurst’s The Heart, New york, McGraw-Hill,2001; 963-992

29. Philbin DM, Marieb MA, Aithal KH, Schoenfeld MH.Inappropriate shocks deliverd by an ICD as a result ofsensed potientials from a transcutaneous electronicnerve stimulation unit. Pacing Clin Electrophysiol 1998;21: 2010- 2011

30. Asroff SW, Kingston TE, Stein BS. Extracorporeal shock

References

electocautery. Rate responsive pacemakers shouldhave rate responsive mode disabled before surgery.Provision of temporary pacing should be availablein the OT to deal with emergency situation ofpacemaker malfunction. Pacemaker should berechecked after the procedure.

ACA-04-134 Review.p65 1/5/2005, 12:15 PM31


wave lithotripsy in patients with cardiac pacemaker inan abdominal location: case report and review of theliterature. J Endourol 1993; 7: 189-192

31. Albers DD, Lybrand FE 3rd, Axton JC, Wendelken JR.Shockwave lithotripsy and pacemakers: experience with20 cases. J Endourol 1995; 9: 301-303

32. Ganem JP, Carson CC. Cardiac arrhythmias withexternal fixed rate signal generators in shock wavelithotripsy with the Medstone lithotripter. Urology 1998;51: 548-552

33. Vahlhaus C, Sommer T, Lewalter T, et al. Interferencewith cardiac pacemakers by magnetic resonanceimaging: are there irreversible changes at 0.5 Tesla. PACE2001; 24: 489-495

34. Luechinger R, Duru F, Scheidegger MB, Boesiger P,

Candinas R. Force and torque effects of a 1.5 Tesla MRIscanner on cardiac pacemakers and ICDs. Pacing ClinElectrophysiol 2001; 24: 199-205

35. Sommer T, Vahlhaus C, Lauck G, et al. MR imaging andcardiac pacemakers: in-vitro. evaluation and in-vivostudies in 51 patients at 0.5 T. Radiology 2000; 215:869-879

36. Gimbel JR, Johnson D, Levine PA, Wilkoff BL. Safeperformance of magnetic resonance imaging on fivepatients with permanent cardiac pacemakers. Pacing ClinElectrophysiol 1996; 19: 913-919

37. Erlebacher JA, Cahill PT, Pannizzo F, Knowles RJ. Effectof magnetic resonance imaging on DDD pacemakers.Am J Cardiol 1986; 57: 437-440

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Managing patients with pacemaker or ICD

General Recommendations for management of patients with CRMD’s undergoing surgery 1. Determine presence and type of device 2. Obtain records from the device clinic that is monitoring the patient’s device 3. Determine original indication for device placement 4. Is patient pacer-dependent? 5. If pacer-dependent, has the device been evaluated during the 3 to 6 months prior to surgery 6. Determine device settings and program status

Appendix 2: Summary of Practice Advisory Preoperative Evaluation

x Establish whether a patient has a CRMD. o Conduct a focused history (patient interview, medical records review, review of available chest x-ray films, electrocardiogram, or

any available monitor or rhythm strip information). o Conduct a focused physical examination (check for scars, palpate for device).

x Define the type of CRMD. o Obtain manufacturer’s identification card from patient or other source. o Order chest x-ray studies if no other data are available. o Refer to supplemental resources (e.g., manufacturer’s databases).

x Determine dependency on pacing function of the CRMD. o History of symptomatic bradyarrhythmia resulting in CRMD implantation. o History of successful atrioventricular nodal ablation. o Inadequate escape rhythm at lowest programmable pacing rate.

x Determine CRMD function. o Interrogate device (consultation with a cardiologist or pacemaker–ICD service may be necessary). o Determine whether the device will capture when it paces (i.e., produce a mechanical systole with a pacemaker impulse). o Consider contacting the manufacturer for perioperative recommendations.

Preoperative Preparation x Determine whether EMI is likely to occur during the planned procedure. x Determine whether reprogramming pacing function to asynchronous mode or disabling rate responsive function is advantageous. x Suspend antitachyarrhythmia functions if present. x Advise individual performing the procedure to consider use of a bipolar electrocautery system or ultrasonic (harmonic) scalpel. x Temporary pacing and defibrillation equipment should be immediately available. x Evaluate the possible effects of anesthetic techniques and of the procedure on CRMD function and patient CRMD interactions.

Intraoperative Management x Monitor operation of the CRMD.

- Conduct electrocardiographic monitoring per ASA standard. - Monitor peripheral pulse (e.g., manual pulse palpation, pulse oximeter plethysmogram, arterial line).

x Manage potential CRMD dysfunction due to EMI. - Electrocautery.

� Assure that the electrosurgical receiving plate is positioned so that the current pathway does not pass through or near the CRMD system. Fo rsome cases, the receiving plate might need to be placed on a site different from the thigh (e.g., the superior posterior aspect of the shoulder contralateral to the generator position for a head and neck case).

� Advise individual performing the procedure to avoid proximity of the cautery’s electrical field to the pulse generator or leads.

� Advise individual performing the procedure to use short, intermittent, and irregular bursts at the lowest feasible energy levels.

� Advise individual performing the procedure to reconsider the use of a bipolar electrocautery system or ultrasonic (harmonic) scalpel in place of a monopolar electrocautery system, if possible.

- Radiofrequency ablation. � Advise individual performing the procedure to avoid direct contact between the ablation catheter and the pulse

generator and leads. � Advise individual performing the procedure to keep the radiofrequency’s current path as far away from the pulse

generator and lead system as possible. - Lithotripsy.

� Advise individual performing the procedure to avoid focusing the lithotripsy beam near the pulse generator. � If the lithotripsy system triggers on the R wave, consider preoperative disabling of atrial pacing.

- MRI. � MRI is generally contraindicated in patients with CRMDs. � If MRI must be performed, consult with the ordering physician, the patient’s cardiologist, the diagnostic radiologist,

and the CRMD manufacturer. - Radiation therapy.

� Radiation therapy can be safely performed in patients who have CRMDs. � Surgically relocate the CRMD if the device will be in the field of radiation.

- Electroconvulsive therapy. � Consult with the ordering physician, the patient’s cardiologist, a CRMD service, or the CRMD manufacturer.

x Emergency defibrillation or cardioversion. - For a patient with an ICD and magnet-disabled therapies:

� Advise individual performing the procedure to terminate all sources of EMI while magnet is removed. � Remove the magnet to reenable antitachycardia therapies. � Observe the patient and the monitors for appropriate CRMD therapy. � If the above activities do not restore ICD function, proceed with emergency external defibrillation or cardioversion.

- For a patient with an ICD and programming-disabled therapies:


� Advise individual performing the procedure to terminate all sources of EMI while magnet is removed. � Reenable therapies through programming if the programmer is immediately available and ready to be used. � Observe the patient and the monitors for appropriate CRMD therapy. � If the above activities do not restore ICD function, proceed with emergency external defibrillation or cardioversion.

- For external defibrillation: � Position defibrillation/cardioversion pads or paddles as far as possible from the pulse generator. � Position defibrillation/cardioversion pads or paddles perpendicular to the major axis of the CRMD to the extent

possible by placing them in an anterior–posterior location. � If it is technically impossible to place the pads or paddles in locations that help to protect the CRMD,

defibrillate/cardiovert the patient in thequickest possible way and be prepared to provide pacing through other routes.

� Use a clinically appropriate energy output. Postoperative Management

x Continuously monitor cardiac rate and rhythm and have backup pacing and defibrillation equipment immediately available throughout the immediatepostoperative period.

x Interrogate and restore CRMD function in the immediate postoperative period. - Interrogate CRMD; consultation with a cardiologist or pacemaker–ICD service may be necessary. - Restore all antitachyarrhythmic therapies in ICDs. - Assure that all other settings of the CRMD are appropriate.

Refer to Table 3 for an example of a stepwise approach to the perioperative treatment of the patient with a CRMD. ASA _ American Society of Anesthesiologists; CRMD _ cardiac rhythm management device; EMI _ electromagnetic interference; ICD _ implantable

Example of stepwise approach to the Periop Treatment of Patient with CRMD Perioperative Period Patient/CRMD Condition Intervention Preoperative evaluation Patient has CRMD Ɣ Focused history

Ɣ Focused physical examination

Determine CRMD type (pacemaker, Ɣ Manufacturer’s CRMD identification card ICD, CRT) Ɣ Chest x-ray studies (no data available)

Ɣ Supplemental resources*

Determine whether patient is CRMD Ɣ Verbal history dependent for pacing function Ɣ Bradyarrhythmia symptoms

Ɣ Atrioventricular node ablation Ɣ No spontaneous ventricular activity†

Determine CRMD function Ɣ Comprehensive CRMD evaluation‡ Ɣ Determine whether pacing pulses are present and create paced beats

Preoperative preparation EMI unlikely during procedure Ɣ If EMI unlikely, special precautions are not needed

EMI likely: CRMD is pacemaker Ɣ Reprogram to asynchronous mode when indicated Ɣ Suspend rate-adaptive functions§

EMI likely: CRMD is ICD Ɣ Suspend antitachyarrhythmia functions Ɣ If patient is dependent on pacing function, alter pacing functions as above

EMI likely: all CRMD Ɣ Use bipolar cautery; ultrasonic scalpel Ɣ Temporary pacing and external cardioversion–defibrillation available

Intraoperative physiologic changes Ɣ Plan for possible adverse CRMD–patient interaction likely (e.g., bradycardia, ischemia)

Intraoperative Monitoring Ɣ Electrocardiographic monitoring per ASA standard Management Ɣ Peripheral pulse monitoring

Electrocautery interference Ɣ CT/CRP—no current through PG/leads Ɣ Avoid proximity of CT to PG/leads Ɣ Short bursts at lowest possible energy Ɣ Use bipolar cautery; ultrasonic scalpel

Radiofrequency catheter ablation Ɣ Avoid contact of radiofrequency catheter with PG/leads Ɣ Radiofrequency current path far away from PG/leads Ɣ Discuss these concerns with operator

Lithotripsy Ɣ Do not focus lithotripsy beam near PG Ɣ R wave triggers lithotripsy? Disable atrial pacing_


Perioperative Period Patient/CRMD Condition Intervention MRI Ɣ Generally contraindicated

Ɣ If required, consult ordering physician, cardiologist, radiologist, and manufacturer

RT Ɣ PG/leads must be outside of RT field Ɣ Possible surgical relocation of PG Ɣ Verify PG function during/after RT course

ECT Ɣ Consult with ordering physician, patient’s cardiologist, a CRMD

service, or CRMD manufacturer

Emergency defibrillation– ICD: magnet disabled Ɣ Terminate all EMI sources Cardioversion Ɣ Remove magnet to reenable therapies

Ɣ Observe for appropriate therapies

ICD: programming disabled Ɣ Programming to reenable therapies or proceed directly with external cardioversion–defibrillation

ICD: either of above Ɣ Minimize current flow through PG/leads Ɣ PP as far as possible from PG Ɣ PP perpendicular to major axis PG/leads Ɣ To extent possible, PP in anterior–posterior location

Regardless of CRMD type Ɣ Use clinically appropriate cardioversion/defibrillation energy

Postoperative Immediate postoperative period Ɣ Monitor cardiac R&R continuously Management Ɣ Backup pacing and cardioversion/defibrillation capability

Postoperative interrogation and Ɣ Interrogation to assess function restoration of CRMD function Ɣ Settings appropriate?#

Ɣ Is CRMD an ICD?** Ɣ Use cardiology/pacemaker–ICD service if needed

* Manufacturer’s databases, pacemaker clinic records, cardiology consultation. † With cardiac rhythm management device (CRMD) programmed VVI at lowest programmable rate. ‡ Ideally CRMD function assessed by interrogation, with function altered by reprogramming if required. § Most times this will be necessary; when in doubt, assume so. _ Atrial pacing spikes may be interpreted by the lithotriptor as R waves, possibly inciting the lithotriptor to deliver a shock during a vulnerable period in the heart. # If necessary, reprogram appropriate settings. ** Restore all antitachycardia therapies. CRP _ current return pad; CRT _ cardiac resynchronization therapy; CT _ cautery tool; ECT _ electroconvulsive therapy; EMI _ electromagnetic interference; ICD _ internal cardioverter– defibrillator; MRI _ magnetic resonance imaging; PG _ pulse generator; PP _ external cardioversion– defibrillation pads or paddles; R&R _ rhythm and rate; RT _ radiation therapy. References: “Practice Advisory for the Perioperative Management of Patients with Cardiac Rhythm Management Devices: Pacemakers and Implantable Cardioverter—Defibrillators.” Anesthesiology 2005;103(1):186-98 Fleischer et al. “ACC/AHA Guidelines on Perioperative Cardiovascular Evaluation and Care for Noncardiac Surgery: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.” J Amer Coll Cardiology 2007;50(17):e159-241

Rev 05/06

Extracorporeal Shock Wave Lithotripsy (ESWL) Shock wave lithotripsy is a medical procedure which uses a spark gap or electromagnetic transducer to produce a shock wave for patients with renal calculi (kidney stones). Lithotripters radiate an electrical signal which could potentially be sensed as intrinsic heart activity by the pacemaker and cause a single beat inhibition of the ventricular output pulse. In general, single beat inhibition is not noticed by the patient. Cardiac pacemakers are electronic devices with sensing circuits designed to detect small electrical signals from inside the heart. Pacemakers are designed to inhibit their output when sensing these intracardiac signals. Pacemakers can occasionally sense extraneous electromagnetic signals from sources other than the patient and can incorrectly interpret these signals as intrinsic activity of the heart. The medical literature suggests potential inhibition could be minimized by timing shock wave delivery synchronously with the patient's R-wave. ESWL therapy should therefore be performed in the R-wave triggered mode. Dual chamber pacemakers should be programmed to the VVI, VOO or DOO mode prior to ESWL to prevent ESWL triggering off of the atrial output pulse and subsequent inhibition of the following ventricular pulse. Taping a magnet over the device will also force asynchronous pacing and can be used in lieu of mode programming. ESWL also has the potential to permanently damage the piezo crystal in an activity sensor based pacemaker if the pulse generator if the ESWL focal point is directed towards the pacemaker. Therefore, the beam should be focused at least six inches away from the implanted pulse generator. Activity sensor based pacemakers should be programmed to a non-rate responsive pacing mode prior to ESWL therapy. A thorough assessment of pulse generator should be performed immediately prior to and again following exposure to ESWL to rule out the possibility of damage to the device.

Sensor function should be assessed after an ESWL procedure with activity sensor based pacemakers. A copy of the programmer printouts should be included in the patient's record documenting proper pacer function after the therapy. Enclosed is a sheet detailing a variety of considerations and recommendations regarding lithotripsy. Also enclosed is a bibliography of articles on this important topic that may be of interest.

ANESTHESIA FOR LITHOTIRPSY IN PATIENTS WITH PACEMAKERS

Technical Services

Rev 05/06

LITHOTRIPSY AND PACEMAKERS

WARNINGS The use of lithotripsy with a pacemaker patient may cause one or more of the following: 1. Temporary single beat pacemaker inhibition with each ESWL shock 2. Circuit damage causing erratic or cessation of pacemaker function if the ESWL

transducer is placed near the pacemaker. RECOMMENDATIONS The following steps should be taken to minimize the potential for complications: 1. Pacemakers should be programmed to the VVI, VOO or DOO mode. DOO/VOO

pacing can also be achieved with use of a magnet securely placed over the device. 2. The lithotriptor focal point should be kept at least 15 cm (6 inches) away from the

pacemaker especially in activity sensor based pacemakers. 3. Where possible the shock wave delivery should be timed synchronously with the

patient's R wave 4. Monitor the patient's heart rate during the procedure 5. Following the procedure, reprogram the pacemaker to the initial parameters. If an

activity sensor pacemaker is present, thorough evaluation of the sensor function should be assessed.

Rev 05/06

BIBLIOGRAPHY

1. Cooper, Daniel et al.: Effects of Extracorporeal Shock Wave Lithotripsy on Cardiac

Pacemakers And Its Safety in Patients with Implanted Cardiac Pacemakers, Daniel Cooper et al, NASPE ABSTRACTS, PACE Vol.11, April 1988, p.483

2. Garza, J., et al. : The Effect of Extracorporeal Shock Wave Lithotripsy On Implantable

Cardiac Pacemakers, NASPE ABSTRACTS, PACE Vol 10, May-Jun 1987, Part II, p.675

3. Irnich, W.: Pacemaker Patients and Extracorporeal Shock Wave Lithotripsy. Cardiac

Pacing and Electrophysiology – R&L Creative communications Ltd., Pub. Jerusalem 1987: p221-226

4. Lanberg, Jonathan, et al.: The Effects of Extracorporeal Shock Wave Lithotripsy on

Pacemaker Function, PACE, Vol. 10, Sep-Oct 1987, p1142 5. St. Jude Medical, Cardiac Rhythm Management: Users Manual, Affinity DR – Model

5330, Document 9191977-001 6. Ellenbogen, Kenneth et al.: Clinical Cardiac Pacing. Philadelphia: W.B. Saunders

Company, 1995.

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