Manejo perioperatorio de dispositivos electrnicos cardiacos implantables

Camilo Ernesto Argoty IncaResidente de AnestesiologaUniversidad del ValleFebrero de 2012Manejo perioperatorio de dispositivos electrnicos cardiacos implantables

Contenido antecedentesHistoria 18991926 1932 19571958Furman y cols.Estimuo temporal transvenosa1959

En 1899, J. A. McWilliam report en el British Medical Journal sus experimentos en los cuales la aplicacin de un impulso elctrico al corazn humano en estado asistlico causaba una contraccin ventricular y que un ritmo de 60-70 pulsos por minuto poda ser evocado por impulsos elctricos aplicados a espacios iguales a 60-70 por minuto.1En 1926, el Doctor Mark C. Lidwell en el hospital Royal Prince Alfred de Sydney, apoyado por el fsico Edgar H Booth de la Universidad de Sdney, inventaron un dispositivo porttil que se conectaba a un "punto de disparo" en el corazn, y que consistia en dos electrodos; uno era una almohadilla empapada en solucin salina aplicada sobre la piel y otro era una aguja aislada excepto la punta que se clavaba en la cmara cardaca apropiada. El ritmo del marcapasos era variable desde 80 hasta 120 pulsos por minuto y de la misma manera, el voltaje variaba desde 1.5 hasta 120 voltios. En 1928, este dispositivo fue usado para revivir un nio que haba nacido muerto en el hospital materno Crown Street en Sydney, cuyo corazn continu latiendo "por voluntad propia" despus de 10 minutos de estimulacin.2 3En 1932, el fisilogo americano Albert Hyman, trabajando de forma independiente, invent un instrumento electro-mecnico que desarroll con un motor elctrico de manivela. Hyman se refera a su invento como "marcapasos artificial", trmino que se usa hoy en da. Hyman prob su invento en animales y logr revivir 14 de 43 animales de laboratorio.4 5Entre los inicios de la dcada de 1930 y laSegunda Guerra Mundialsucedi una aparente interrupcin de publicaciones de investigacin sobre marcapasos tal vez por la percepcin pblica de que se estaba "interfiriendo con la naturaleza" al "revivir a los muertos". Por ejemplo, "Hyman no public datos sobre el uso de su marcapasos en humanos por la mala publicidad, tanto de sus colegas mdicos como de los reportes en peridicos de la poca. Lidwell pudo haberse dado cuenta de eso y no procedi con experimentos en humanos".3Un marcapasos externo fue diseado y construido por el ingeniero electricista canadiense John Alexander Hopps en 1950 basado en las observaciones del cirujano cardio-torxico Wilfred Gordon Bigelow en el hospital Toronto General. Un aparatoso dispositivo externo que utilizaba tecnologa detubos de vacopara suministrar estimulacin cardaca transcutanea, era imprctico y doloroso para el paciente que lo tena que usar y siendo alimentado por corriente alterna del tomacorriente, conllevaba un riesgo potencial de electrocucin.En los aos siguientes, innovadores como Paul Zoll, hicieron cada vez mas pequeos los dispositivos de estimulacin transcutnea usando grandes bateras recargables como fuente de energa.6En 1957, el Doctor William L. Weirich public los resultados de una investigacin desarrollada en laUniversidad de Minnesota. Los estudios demostraron la restauracin del ritmo cardaco, presin artica media y gasto cardaco en animales con bloqueo cardaco mediante el uso de un electrodo en elmiocardio. Este efectivo control de bloqueos cardacos post-quirrgicos prob ser una contribucin significativa a la disminucin de lamortalidaden cirugas a corazn abierto durante ese perodo.7El desarollo deltransistordesilicioy su disponibilidad comercial en 1956, fueron hechos cruciales que encaminaron un rpido avance en la tecnologa de los marcapasos cardacos.En 1957,el ingenieroEarl Bakkende Minneapolis, Minnesota, construy el primer marcapasos externo que poda llevarse puesto un paciente del doctorC. Walton Lillehei. Este marcapasos transistorizado, acomodado en una pequea caja de plstico, tena controles que permitian el ajuste del ritmo y voltaje, y estaba conectado a cables que transpasaban la piel del paciente para terminar en unos electrodos fijados a la superficie delmiocardio.En 1958 el ingeniero electrnico ColombianoJorge Reynolds Pomboinventara el primer marcapasos externo,con electrodos internos mientras que la primera implantacin clnica de un marcapasos interno en un humano fue hecha por el cirujanoke Senningese mismo ao en elInstituto Karolinskaen Slona, Suecia, usando un marcapasos diseado porRune Elmqvist. Se conectaron los electrodos al miocardio mediante unaToracotoma. El dispositivo fall tres horas despus. Un segundo dispositivo fue implantado y dur dos das. El primer paciente en el mundo con marcapasos interno, Arne Larsson, recibi 26 marcapasos diferentes a lo largo de su vida. Muri en 2001 a la edad de 86 aos.8En 1959, la tcnica de la estimulacin temporal transvenosa fue demostrada por primera vez por Furman y otros. Un electrodo-catterse insert en lavena baslicadel paciente.9El 3 de febrero de 1960, se implant enMontevideo,Uruguayuna versin mejorada del marcapasos del sueco Elmqvist en el Hospital Casmu 1 por los doctoresOrestes FiandrayRoberto Rubio. Fue el primer implante de un marcapasos en Amrica. El dispositivo dur hasta que el paciente muri de otras dolencias 9 meses ms tarde. El precoz diseo sueco con bateras recargables haca necesario el uso de una bobina de induccin para su recarga desde el exterior del cuerpo del paciente.

4Historia 19711962-631980 - Actual

Los marcapasos implantables construidos por el ingenieroWilson Greatbatchse empezaron a usar desde abril de 1960 despus de numerosas pruebas en animales. La innovacin de Greatbatch sobre los primeros dispositivos suecos consista en el uso de bateras de mercurio como fuente de energa. El primer paciente en recibir uno de estos marcapasos vivi mas de 18 meses.La primera vez que se us la estimulacin transvenosa en conjunto con un marcapasos implantado fue en 1962-63 y llevado a cabo por Parsonnet en los Estados Unidos,101112Lagergren en Suecia1314y por Jean-Jaques Welti en Francia.15El procedimiento transvenoso o perivenoso involucra la incisin en una vena por la cual se inserta el electrodo y se gua mediante fluoroscopia hasta el punto dentro de la trabcula delventrculo derechodonde se va a alojar. Este mtodo se convirti en el mtodo por excelencia hacia mediados de la dcada de 1960.Primer marcapasos con celda de yoduro de litio. Cardiac Pacemakers Inc. 1972Hasta esta poca todos los marcapasos sufrian por la falta de confiabilidad y cortos perodos de vida de las bateras que principalmente eran bateras de mercurio.Hacia finales de la dcada de 1960, muchas compaas en los Estados Unidos desarrollaron marcapasos accionados por ungenerador termoelctrico de radioistopos, pero fueron sobrepasados por el desarrollo en 1971 de la celda de yoduro de litio porWilson Greatbatch. Las celdas de yoduro de litio o nodo de litio se convirtieron en el estndar para futuros diseos de marcapasos.Un impedimento adicional a la confibilidad de los primeros dispositivos era la difusin de vapor de agua de los fluidos corporales a travs de la resina que encapsulaba los circuitos electrnicos. Este fenmeno se super forrando el marcapasos con una cubierta de metal hermticamente sellada, inicialmente porTelectronicsde Autralia en 1969 seguida por Cardiac Pacemakers Inc de Minneapolis en 1972. Esta tecnologa, que usa titanio en la cubierta se convirti en estndar hacia mediados de la dcada de 1970.Otros que contribuyeron significativamente al desarrollo tecnolgico de los marcapasos en los inicios fueron Bob Anderson deMedtronicMinneapolis, J.G (Geoffrey) Davies de St George's Hospital Londres, Barouh Berkovits y Sheldon Thaler de American Optical, Geoffrey Wickham deTelectronicsAustralia, Walter Keller deCordisCorp. en Miami, Hans Thornander quien se uni aRune Elmquistde Elema-Schonander en Suecia, Janwillem van den Berg de Holanda y Anthony Adducci de Cardiac Pacemakers Inc.Guidant. En 2011Jorge Reynolds Pomboanunci el lanzamiento de un dispositivo del tamao de un tercio de grano de arroz que no necesita baterias, y que puede ser monitoreado por internet desde cualquier parte del mundo, este adems puede implantarse mediante ciruga ambulatoria y usa la propia energa del corazn para recargarse.

5Historia Bases y clasificacin de dispositivosPartes de marcapasos

Sistemas de codificacin

Sistemas de codificacin

Interferencia electromagnetica (IEM)11Interferencia electromagnticaMaxwell, Faraday, Hertz

Interferencia electromagnticaReportes de caso y estudios descriptivosElectrocauterioAblacin por radiofrecuenciaResonancia magnticaTerapia de radicacinLitotripsiaTerapia Electroconvulsiva?

Interferencia electromagntica

EMI and CIEDsEMI causing malfunction of pacemakers and defibrillatorsis well-described.3The perioperative period is particularlyproblematic as patients are exposed to a number of energysources and machinery that may generate EMI and interactwith a CIED, ranging from transient effects such as pacinginhibition, inappropriate tracking of electrical noise, dam-age at the lead-tissue interface, pulse generator damage, andthe induction of an electrical reset mode. EMI can alsointerfere with rate responsive algorithms and can rarelycause pulse generator damage. The significance and extentof abnormal behavior seen in CIEDs when exposed to EMIdepends on the strength, duration, and particular type ofinterference. The clinical impact of EMI on the patientdepends upon clinical indications for their CIED, the pa-tients intrinsic rate and rhythm, the pacing mode, as well asthe functioning of protective circuitry engineered to filterout extraneous electrical currents, and manufacturer-spe-cific algorithms designed to minimize adverse clinical ef-fects14Interacciones usualesElectrosurgical energyElectrosurgery involves the application of focused radiofrequency electrical current to produce tissue desiccation,cutting or coagulation. Electrical current can be deliveredin bipolar or monopolar configurations, and with a vari-ety of power waveforms to produce these tissue effects.For bipolar electrosurgery (e.g. ophthalmic and micro-surgery) there appears to be minimal chance for an ad-verse CIED interaction.4,5Bipolar electrosurgery is usedfar less commonly than monopolar electrosurgery be-cause, unlike monopolar electrosurgery, bipolar electro-surgery is useful only for coagulation and not dissection.Bipolar surgery involves the use of electrical forcepswhere each limb is an electrode. Monopolar electrosur-gery is utilized for most surgical procedures. In mono-polar electrosurgery, electrical current is applied via asmall active electrode pen or stylus to the operativesite, and then flows though the patients body to a largesurface area return electrode. Monopolar electrosurgeryis the most common source of EMI and CIED interactionin the operating room. These interactions include inhibi-tion, triggering unneeded tachyarrhythmia therapy, andTable 2 Problems that can occur during medical procedures Bipolar electrosurgery does not cause EMI unless it is applied directly to a CIED EMI from monopolar electrosurgery is the most common problem incurred during surgical procedures- Pacemakers may have oversensing and be inhibited when exposed to EMI- ICDs and pacemakers with antitachycardia function may be inhibited or may falsely detect arrhythmias when exposed to EMI- Device reset occurs infrequently with electrosurgery- Electrosurgery applied below the umbilicus is much less likely to cause PM or ICD interference than when applied above theumbilicus- Pulse generator damage from electrosurgery can occur, but is uncommon- Impedance based rate responsive systems may go to upper rate behavior with electrosurgery exposure- Risk mitigation strategies can be effective- Keeping the current path away from CIED diminishes the potential for adverse interaction with the CIED- Using bipolar electrosurgery whenever possible- Minimizing the length of monopolar electrosurgery bursts to 5 seconds or less Lead tissue interface damage from external current is considered an unlikely risk Cardioversion can cause reset of the CIED RF ablation can cause all of the interactions that monopolar electrosurgery can cause but may have a more significant risk profiledue to the prolonged exposure to current Therapeutic radiation is the most likely source of EMI to result in CIED reset ECT has rarely been reported to cause EMI during the stimulus, but the more common problem with EMI may be the extreme sinustachycardia that occurs with the seizure, prompting a need to review tachycardia therapy zones in ICDs GI procedures that use electrosurgery may result in interference TENS units can result in EMI1117 Crossley et al Perioperative Management of Patients With Devicesmore serious ones such as causing electrical reset of thepulse generator. When appropriate precautions are taken,these serious reactions are infrequent.While there have been many older reports of variousuntoward responses to EMI, including failure to pace, sys-tem malfunction and even inappropriate life-threatening re-programming resulting in uncontrolled pacing activity,6-16most recent reports suggest little effect on CIED function.17Advances made in lead and generator design and in EMIresistance, as well as the development of newer surgicaltools18,19have made these events, including reset, much lesscommon in modern-day systems.Those possible interactions of CIED with EMI can begrouped by effects on oversensing of the electrosurgeryenergy, initiation of noise-reversion mode, initiation of elec-trical reset mode, permanent damage to or failure of theCIED pulse generator, and damage to the lead-myocardialinterface causing an increase of pacing thresholds.11Thelatter two interactions are exceedingly rare unless the en-ergy is applied directly to the pulse generator or systemelectrode. Experience has shown that if the distance fromthe electrosurgery current path to the pulse generator andleads is greater than 6 inches, damage to or interaction withthe pulse generator is unlikely.20Each of these possibleinteractions is discussed separately.15Sobresensado

Coagulacion OversensingBy far, the most frequent CIED interaction with EMI isoversensing. The result of oversensing on the pacing func-tion of a CIED is inappropriate inhibition of pacing output.As discussed below, continuous ventricular sensing of EMImay rarely initiate temporary noise reversion mode21seebelow for details. Oversensing by an ICD has the additionalproblem of false detection of a tachyarrhythmia, possiblyleading to inappropriate CIED therapy.The consequences of oversensing are determined by anumber of patient- and device-related factors, such as theduration of exposure to the radiofrequency current, the pathof the current and the patients underlying rhythm. Implant-able defibrillators require a certain duration of continuoushigh-rate sensing (typically several seconds or more) tofulfill arrhythmia detection criteria. Therefore, short burstsof electrosurgery that are punctuated by several-secondpauses in electrosurgery application are less likely to resultin false tachyarrhythmia detection than in long continuousapplications. For a patient with a robust underlying rhythm,pacing inhibition may be inconsequential; while a pacemaker-dependent patient may experience a hemodynamically un-stable underlying rhythm with prolonged pacing inhibition,short electrosurgical bursts limited to 4 to 5 seconds areunlikely to result in significant hemodynamic compromisefor the majority of patients. Therefore, in many instances, anapproach that limits electrosurgery usage to short burstsmay be a safer approach to patient-CIED management thaneither reprogramming the CIED or placement of a magnetover the pulse generator.16Sobresensado

OversensingBy far, the most frequent CIED interaction with EMI isoversensing. The result of oversensing on the pacing func-tion of a CIED is inappropriate inhibition of pacing output.As discussed below, continuous ventricular sensing of EMImay rarely initiate temporary noise reversion mode21seebelow for details. Oversensing by an ICD has the additionalproblem of false detection of a tachyarrhythmia, possiblyleading to inappropriate CIED therapy.The consequences of oversensing are determined by anumber of patient- and device-related factors, such as theduration of exposure to the radiofrequency current, the pathof the current and the patients underlying rhythm. Implant-able defibrillators require a certain duration of continuoushigh-rate sensing (typically several seconds or more) tofulfill arrhythmia detection criteria. Therefore, short burstsof electrosurgery that are punctuated by several-secondpauses in electrosurgery application are less likely to resultin false tachyarrhythmia detection than in long continuousapplications. For a patient with a robust underlying rhythm,pacing inhibition may be inconsequential; while a pacemaker-dependent patient may experience a hemodynamically un-stable underlying rhythm with prolonged pacing inhibition,short electrosurgical bursts limited to 4 to 5 seconds areunlikely to result in significant hemodynamic compromisefor the majority of patients. Therefore, in many instances, anapproach that limits electrosurgery usage to short burstsmay be a safer approach to patient-CIED management thaneither reprogramming the CIED or placement of a magnetover the pulse generator.unctional pacemaker dependence can also influence he-modynamic stability in the operating room and should beconsidered in some patients with cardiac resynchronizationdevices (CRT). Most CRT patients are not pacemaker de-pendent, and they will not experience hemodynamic diffi-culties if biventricular pacing is interrupted. However, a fewCRT patients do suffer acute decompensation of their con-gestive heart failure when CRT is inhibited for long periodsof time because of reversion to a dyssynchronous electricalactivation of the heart. This is the type of information thatcould only be provided by the CIED team managing thepatient, where a comprehensive understanding of the pa-tient, their particular CIED and the surgical environmentwill be considered when offering prescriptive recommenda-tions.17

Modo reversin ruidoPrograma para minimizar impacto de IEMActivacin con estmulos en periodo refractarioResponden a IME continua

Sometimes the generator detects significant EMI and begins pacing asynchronously at the programmed lower rate. This behavior is called noise reversion mode pacing, even though the PM does not actually change modes. Noise reversion is not present in some ICDs and is programmable in others.

18Algoritmos especiales

Modo Reinicio InfrecuenteRadiacin ionizanteCorrupcin de la memoria del circuitoSobrecarga en el generadorProgramacin de fabrica

ResetDevice reset mode occurs infrequently, and is more com-monly caused by therapeutic ionizing radiation rather thanEMI.23,24Resetting of pacemakers has been rarely reportedafter exposure to electrosurgery.25This reset mode is a typeof safety backup in case of catastrophic failure. There isconsensus that the two most common precipitants of this are(1) corruption of the memory in the circuitry which isusually caused by therapeutic radiation and rarely caused byambient radiation, and (2) a surge of energy coursingthrough the pulse generator that simulates the initial con-1118 Heart Rhythm, Vol 8, No 7, July 2011nection of the power source at the time of manufacture. Thisis one of the purposes of this reset mode. In the reset mode,pacing and antitachycardia therapy parameters are unique toeach manufacturer and are summarized in Appendix 4Aand4B. These settings are not necessarily optimal for any givenpatient, but neither are they likely to be unsafe for thepatient. The CIED programmer is required to restore pro-gramming from reset mode back to the original pacing andarrhythmia detection/therapy parameters. If reset mode isdetected, we recommend contacting the technical supportservice of the manufacturer, since recommendations foractions vary greatly.Some newer Boston Scientific ICDs have Safety Core,and it is planned for future pacemakers. Safety Core is aback-up mode intended for major hardware failures thatprovides high-voltage therapy with a simple unipolar VVIpacing. If Safety Core occurs while the ICD Tachy Mode isOFF, the device returns to MonitorTherapy. If there areadditional high voltage faults while the device is in SafetyCore, the Tachy Mode will be set to Tachy Therapy NotAvailable. This situation has not been reported, but couldfor instance, occur with multiple direct exposures to thera-peutic radiation. If this were to occur, the device can bereturned to Monitor Therapy by toggling Tachy ModeOFF then back to MonitorTherapy. Tachy Mode pro-grammability is the only programming available while inSafety Core. The pulse generator must then be replaced.This reversion to Safety Core has been rarely reported tooccur during electrosurgery.20Marcapasos

Cardiodesfibriladores ResetDevice reset mode occurs infrequently, and is more com-monly caused by therapeutic ionizing radiation rather thanEMI.23,24Resetting of pacemakers has been rarely reportedafter exposure to electrosurgery.25This reset mode is a typeof safety backup in case of catastrophic failure. There isconsensus that the two most common precipitants of this are(1) corruption of the memory in the circuitry which isusually caused by therapeutic radiation and rarely caused byambient radiation, and (2) a surge of energy coursingthrough the pulse generator that simulates the initial con-1118 Heart Rhythm, Vol 8, No 7, July 2011nection of the power source at the time of manufacture. Thisis one of the purposes of this reset mode. In the reset mode,pacing and antitachycardia therapy parameters are unique toeach manufacturer and are summarized in Appendix 4Aand4B. These settings are not necessarily optimal for any givenpatient, but neither are they likely to be unsafe for thepatient. The CIED programmer is required to restore pro-gramming from reset mode back to the original pacing andarrhythmia detection/therapy parameters. If reset mode isdetected, we recommend contacting the technical supportservice of the manufacturer, since recommendations foractions vary greatly.Some newer Boston Scientific ICDs have Safety Core,and it is planned for future pacemakers. Safety Core is aback-up mode intended for major hardware failures thatprovides high-voltage therapy with a simple unipolar VVIpacing. If Safety Core occurs while the ICD Tachy Mode isOFF, the device returns to MonitorTherapy. If there areadditional high voltage faults while the device is in SafetyCore, the Tachy Mode will be set to Tachy Therapy NotAvailable. This situation has not been reported, but couldfor instance, occur with multiple direct exposures to thera-peutic radiation. If this were to occur, the device can bereturned to Monitor Therapy by toggling Tachy ModeOFF then back to MonitorTherapy. Tachy Mode pro-grammability is the only programming available while inSafety Core. The pulse generator must then be replaced.This reversion to Safety Core has been rarely reported tooccur during electrosurgery.21Dao del generador

Pulse generator damageCIEDs are rigorously engineered for protection from elec-trical energy sources such as electrosurgery, which are rou-tinely encountered in the operating room. However, it ispossible to cause failure or permanent damage to a CIEDfrom application of electrosurgery either in immediate closeproximity or directly to the pulse generator. In older-modelpacemakers (with voltage-controlled oscillators), failurewas more likely to occur near or at the battery end-of-life.26,27Devices with these types of oscillators are nolonger manufactured, and it is unlikely that any patientscurrently still have one of these types of devices. Applica-tion of monopolar electrosurgery close to the pulse gener-ator or electrodes may cause current entry with damage tothe pulse generator, and should be avoided. ICDs may besomewhat more resistant to the effects of electrosurgery;however, electrical energy can still enter the pulse generatorthrough any breach of lead insulation or through corruptionof the sealing rings with conductive fluid bridge to the leadconnector. Therefore, surgeries close to the CIED (such asbreast, shoulder, head and neck, pulse generator replace-ment, or carotid procedures) should be done with bipolarrather than monopolar electrosurgery whenever that is pos-sible. Also, strategic positioning of the electrosurgery returnelectrode such that the predicted current path avoids theCIED coupled with working at a lower electrosurgerypower setting may reduce exposure of the CIED to theeffects of electrosurgical energy. An example is that if apatient is having surgery on the ipsilateral hand, the returnelectrode should be on the ipsilateral arm.22Dao interface tejido electrodoLead tissue interface damageElectrosurgical collateral damage to the lead-myocardialinterface is possible, although generally thought to occurrarely with current-generation CIEDs. Monopolar electro-surgery pathways that cross or come close to a pulse gen-erator can produce enough voltage to activate the Zenerdiodes and create a unipolar current path of least resistancefrom the pulse generator case to a pacing electrode incontact with myocardium, and then on to the return elec-trode. This has been rarely reported to result in damage tothe tissue at that electrode surface, resulting in an increasein pacing threshold or loss of capture or induction of ar-rhythmias23magnetoMagneto

Magnet responseMagnet application is often used in the perioperative period tochange the behavior of CIEDs. Appendix 5A and 5B displays thenature of the magnet response for currently implanted CIEDs. It isrecognized that magnet features may change as manufacturersrelease new devices and that CIED teams will need to apprisethemselves continually of these differences. A simple doughnutmagnet (typically 90 Gauss) is the standard magnet used forinhibiting tachyarrhythmia detection in CIEDs. A magnet will notrender the pacemaker function in an ICD asynchronous. Thismagnet should be in the room with any patient undergoing aprocedure that involves the potential for EMI. A magnet applied toa pacemaker will avoid inhibition by initiating asynchronous pac-ing, as well as gain control of inappropriate tracking or rateresponse operation with the device in the operating room.87How -ever, there are exceptions when CIED magnet functions are pro-grammed differently by virtue of manufacturer, and device func-tion is either transiently or completely unaffected by magnetapplication. It is important for the CIED team to notify the surgicalteam if this is the case.3.10.1.1. Pacemakers.For pacemakers, the magnet gener-ally causes asynchronous pacing by closing a magneticswitch. Older pulse generators used a mechanical reed1123 Crossley et al Perioperative Management of Patients With Devicesswitch, while newer generators either employ a Hall sensoror giant magneto resistive (GMR) sensor, neither of whichhave moving parts and are therefore more robust. The pulse-generator-specific magnet behavior (i.e., magnet pacing rateand whether the device responds with unique characteristicsto placement of a magnet) should be known to the operatingroom staff to ensure appropriate application of the magnet.Some antitachycardia pacing devices (e.g. Medtronic AT500)do not convert to an asynchronous pacing mode in thepresence of a magnet; however, atrial antitachycardia pac-ing is suspended.25Magneto Magneto

Magneto It is important to realize that in some casesan unnecessary and inappropriate use of a magnet can beassociated with significant untoward hemodynamic effects;for example, because the magnet rate may compete with thepatients own heart rate resulting in competing rhythms. Ordue, for example in a dual chamber pacemaker, to a magnetdetermined A-V delay which may be shorter than the pa-tients intrinsic AV conduction resulting in undesirable ven-tricular pacing. Rarely, asynchronous pacing in a patientwith a competing intrinsic rhythm can also potentially in-duce an atrial or ventricular arrhythmia. Many current pace-makers have an autocapture algorithm, at least in the ven-tricular chamber and often also the atrial chamber. Whenthese functions are operating, the programmed device am-plitude output may be re-set above the autocapture thresh-old. Placing the magnet over a pacemaker will alter thepacing amplitude in several manufactures devices while inothers it will continue to pace at the last programmedoutput.With BIOTRONIK, Boston Scientific and Medtronicpace-makers, placing a magnet will not alter the programmedamplitude (which will be the last autocapture determinedoutput if that feature is enabled). In St. Jude and ELA/Sorinpacemakers, magnet placement temporarily changes theoutput to a higher output settingImplantable cardioverter-defibrillators (ICDs). Forimplantable cardioverter defibrillators (ICDs), tachycardia de-tections can be disabled by magnet application without havingan effect on pacing mode or rate (see Appendix 5B). SomeBoston Scientific (Guidant) ICDs may be permanently deacti-vated by magnet application, necessitating reprogramming ofthe pulse generator prior to the patient being removed from acardiac monitor.88In most CIEDs, however, arrhythmia detec -tion will be automatically re-enabled when the magnetic fieldis removed. An important feature unique to ICDs is that mag-net response will not affect ICD antibradycardia pacing func-tions. Permanent reprogramming can also be used in lieu of amagnet to suspend ICD arrhythmia detection. However, re-sumption of therapy to treat spontaneously occurring ventric-ular tachycardia (VT) or VF will not occur unless the CIED isreprogrammed28Magneto

Test de margen de umbral, (SJM VARIO)

Taquicardia mediada por marcapasosMagneto

Fenomeno R en TMagneto Respuesta a magneto puede seleccionarse en la programacin

Valoracin preoperatoriaValoracin preoperatoria

Preoperative evaluation of a patientwith a CIEDTimely, thorough preoperative evaluation is essential for thesafe perioperative management of patients with CIEDs andshould include a multidisciplinary and systematic approach.The preoperative evaluation presents an opportunity for mutualunderstanding between the CIED team (cardiologist, cardiacelectrophysiologist, device clinic nurses and staff) and theperioperative team (anesthesiologist, surgeon, perioperative as-sessment team). We assert that the most effective prescriptionfor the perioperative care of a patient with a CIED will beobtained from the team that monitors that patient and devicecombined with an understanding of the procedure to be per-formed and risk for EMI. The general principles of the preop-erative evaluation are enumerated in Table 3 .4.1. Preoperative/preanesthesia assessment bythe perioperative teamDuring the preoperative evaluation of a CIED patient, sev-eral elements of the history need to be obtained beforecustomizing a perioperative management plan. History andphysical examination will determine the presence of aCIED. The perioperative management team should consultthe CIED managing team for recommendations regardingperioperative device management. This is true whether thepatient is having the surgical procedure in the same insti-tution where he/she received their CIED care as well as ifthe two sites are remote from each other. The consultationrequest should provide the elements in Table 4to the CIEDphysician/team to obtain informative and personalized rec-ommendations. These data will allow the CIED team togauge the risk of the planned procedure and provide rec-ommendations to the procedure team to help mitigate thoserisks.The patient should be queried to identify the CIED teamthat cares for them. If this is not available, then data regard-ing the make and model of the CIED can be obtained froma wallet-sized card that is given to the patient followingimplantation. If the patient cannot provide information andthe CIED management physician is unavailable or un-known, an identifier is located on the generator and can beviewed on a chest radiograph. This will allow for the iden-tification of the pulse generator. The patient registration1124 Heart Rhythm, Vol 8, No 7, July 2011department of each of the major manufacturers can bequeried by telephone to see if they have a record of thepatients most recent implant.It should be acknowledged that the CIED managementteam will provide advice about the pacemaker or defibril-lator system but will often not be the same health care teamthat provides for the patients usual cardiac clinical care andtherefore the perioperative cardiac risk assessment. If uponreview of the patients CIED interrogation and review of themedical record and or in-person evaluation, the CIED man-agement team identifies new or worsened arrhythmias ornew clinical symptoms, then there should be collaborationwith the patients clinical management team for furtherassessment as needed.34Valoracin preoperatoriaPurday JP, Towey RM: Apparent pacemaker failure caused by activation of ventricular threshold test by a magnetic instrument mat during general anaesthesia. Br J Anaesth 1992; 69:645 6 No valoracion completa: deci inhibido / asistolia, B335Valoracin preoperatoriaTiene un DECI?

During the preoperative evaluation of a CIED patient, sev-eral elements of the history need to be obtained beforecustomizing a perioperative management plan. History andphysical examination will determine the presence of aCIED. The perioperative management team should consultthe CIED managing team for recommendations regardingperioperative device management. This is true whether thepatient is having the surgical procedure in the same insti-tution where he/she received their CIED care as well as ifthe two sites are remote from each other. The consultationrequest should provide the elements in Table 4to the CIEDphysician/team to obtain informative and personalized rec-ommendations. These data will allow the CIED team togauge the risk of the planned procedure and provide rec-ommendations to the procedure team to help mitigate thoserisks.The patient should be queried to identify the CIED teamthat cares for them. If this is not available, then data regard-ing the make and model of the CIED can be obtained froma wallet-sized card that is given to the patient followingimplantation. If the patient cannot provide information andthe CIED management physician is unavailable or un-known, an identifier is located on the generator and can beviewed on a chest radiograph. This will allow for the iden-tification of the pulse generator. The patient registration1124 Heart Rhythm, Vol 8, No 7, July 2011department of each of the major manufacturers can bequeried by telephone to see if they have a record of thepatients most recent implant.It should be acknowledged that the CIED managementteam will provide advice about the pacemaker or defibril-lator system but will often not be the same health care teamthat provides for the patients usual cardiac clinical care andtherefore the perioperative cardiac risk assessment. If uponreview of the patients CIED interrogation and review of themedical record and or in-person evaluation, the CIED man-agement team identifies new or worsened arrhythmias ornew clinical symptoms, then there should be collaborationwith the patients clinical management team for furtherassessment as needed36Valoracin preoperatoria

RAMIREZ E, Pablo et al. Sndrome de Twiddler: una causa infrecuente de disfuncin de marcapaso definitivo. Caso clnico. Rev. md. Chile [online]. 2011, vol.139, n.7 [citado 2012-02-12], pp. 917-919 .Valoracin preoperatoria

The type of device should be identified: pacemaker (sin-gle or dual chamber), ICD (single or dual chamber), CRT-Por CRT-D, implantable loop recorders (ILR), or an implant-able hemodynamic monitor. The manufacturer and genera-tor model need to be noted.38

Valoracin preoperatoria

Valoracin preoperatoria

It is important to know if the patient is pacemaker de-pendent. Pacemaker dependence may be absolute or func-tional. Note that patients who are not usually pacemakerdependent may become pacemaker dependent intraopera-tively (e.g., with sedation, direct or indirect vagal stimula-tion, certain high potency opiates, other anesthetics or otherpharmacologic agents).92The underlying cardiac rhythm ,ifany, should be determined. This may be done by temporar-ily programming the CIED to the VVI mode at 40 beats perminute, or by completely inhibiting pacing.It should be noted whether any of the leads are new ( 3months old). Leads implanted within the last 3 months are atgreatest risk for dislodgement during cardiac surgery, centralline placement, or manipulation of intracardiac catheters.41Valoracin preoperatoria

5% de DECI valorados preoperatoriamente tienen indicacin de cambio de generadorThe battery longevity should be noted and determined ifit is adequate for the perioperative period. The estimatedbattery longevity ideally should be at least 3 months. If it isnot, there may be an increased sensitivity for pulse gener-ator damage from EMI. Also, the CIED team needs to takeinto account the expected postoperative course. For exam-ple, if there is an expectation of a prolonged period ofradiation and or chemotherapy after surgery, and the pulsegenerator has limited expected longevity, one might con-sider recommending that the pulse generator be replacedbefore surgery.42Programacin de DECIhe programmed pacing mode should be documented(e.g., VVI, VVIR, DDD, DDDR). This is important becausesome modern modes use atrial pacing only until a beat isdropped (AAI DDD), whereupon they switch to dualchamber-pacing, termed in one manufactures device asMVP mode (managed ventricular pacing). Withoutknowledge of these kinds of programming, pacemaker mal-function may be misdiagnosed. Seemingly innocent, pseu-do-malfunctions could delay surgery, cause inappropriatetherapy, or generate needless communications with CIEDmanagement personnel. For ICDs and antitachycardia en-abled pacemakers, it is important to document the lowestheart rate for which the CIED will deliver therapy, eitherantitachycardia pacing or shocks.It should be noted if the CIED is programmed forrate-responsive pacing and the untoward responses that theparticular sensor might create in the procedure room. Forexample, an impedance (minute ventilation) sensor mayexhibit faster than expected pacing rates when the patient isventilated, either mechanically or with a bag and mask.Artifacts from these sensors may also be detected on telem-etry monitoring systems. External respiratory impedancemonitors may stimulate the minute ventilation sensor toincrease paced rate. Thus, consideration could be given todisabling these sensors for the perioperative period. Like-wise, activity-based sensors may accelerate the heart ratewith moving the patient or with prepping of the skin.43Planeacin preoperatoriaPlaneacin preoperatoriaThe magnet response of the CIED should be documented(Appendix 5A and 5B). I n most pacemakers, a magnet willlead to asynchronous pacing at a rate that varies witheach manufacturer. In most ICDs, a magnet will lead tosuspension of tachyarrhythmia detection with inhibitionof tachycardia therapies but will not affect the pacingmode. Magnet application may reprogram some BostonScientific devices to permanently disable tachyarrhyth-mia detection after 30 seconds of application. There arealso some pacemakers where magnet application does notresult in asynchronous pacing if the magnet responseparameter had been reprogrammed.45Reduciendo el riesgoRisk mitigationOversensing is the adverse interaction most likely to occurwhen a CIED is exposed to EMI. The anatomical site ofelectrosurgery application, the duration of electrosurgeryapplication, and the position of the return electrode deter-mine the risk of oversensing. The risk is greatest if thecurrent path crosses the CIED and/or leads. The risk is lesswhen the presumed current path is kept at least 6 inchesaway from the CIED. For example, if surgery is being doneon the ipsilateral arm to the CIED, the return electrodeshould be placed on the same arm as opposed to placing iton the flank and exposing the CIED to all of the electrosur-gical energy.Experience has demonstrated, and literature suggests,that in a CIED implanted in the usual upper chest position,oversensing problems are unlikely for operative procedureswhere the application of electrosurgery will be inferior tothe umbilicus and the return electrode is placed on the lowerbody (thigh or gluteal area).29The use of monopolar elec-trosurgery involving the upper abdomen, chest, arms, headand neck pose more of a risk for oversensing and damage tothe CIED system46Interferencia electromagntica

Uso del magnetoInterferencia electromagntica

Uso del magneto504 horas de cirugaElectro bistur monopolar

73 eventos registrados

Uso del magnetoUso del magnetoUso del magneto

Uso del magneto

Manejo intraoperatorioManejo intraoperatorio

57Ciruga por debajo del ombligoManejo intraoperatorioCiruga por encima del ombligoUnderstanding the likelihood of oversensing (eitherpacing inhibition or false arrhythmia detection) can assistthe CIED professional in the development of reasonablerecommendations. For example, if monopolar electrosur-gery is applied below the umbilicus, inhibition of pacingis unlikely. The writing group feels that it is generallybest to make a pacemaker asynchronous only if signifi-cant inhibition is observed, even if the patient is pace-maker dependent. Similarly, oversensing in an ICD pa-tient is unlikely when monopolar electrosurgery isapplied below the umbilicus.Prophylactic magnet application in ICDs is an ap-proach the committee recommends as an alternative to nointervention for procedures below the umbilicus. Someoperators may be more comfortable with this approach.Magnet application will suspend arrhythmia detectionand protect the patient from inappropriate EMI sensing,1119 Crossley et al Perioperative Management of Patients With Deviceswhich would be interpreted incorrectly by the device asan arrhythmia. The CIED team should have informed thesurgical team ahead of time to the surgical team whetherthe patients particular device has the magnet functionprogrammed on as in a few devices this is a feature thatcan be programmed to off (see Appendix 5A and 5B).In that circumstance, the device would NOT respond to amagnet placed over the device and arrhythmia detectionwould NOT be suspended.While in general, reprogramming and magnet applicationare options that can be considered, these approaches maysimply be unnecessary for surgical procedures utilizing mo-nopolar electrosurgery below the umbilicus, and as with anyintervention, these actions should not be undertaken withouta thoughtful consideration of their value. An example wherereprogramming would be needed is a patient with an ICDwho is pacemaker dependent and their ICD is capable ofprogramming to asynchronous pacing. In this scenario, pro-longed inhibition of pacing could not be mitigated withmagnet use as an ICD will not revert to asynchronouspacing with magnet application.This risk for pacing inhibition or false tachyarrhythmiadetection is considered by the committee to be so low forsurgical procedures performed on the lower extremities thatneither re-programming nor magnet application is consid-ered mandatory regardless of PM or ICD and regardless ofpacemaker dependency. While this recommendation is notbased upon randomized trials, it is based on extensive per-sonal experiences of the committee and some descriptiveliterature.29,32In all cases, having a magnet immediately available iscritical in cases where re-programming is not chosen. WhenICDs are deactivated (detections turned off or therapiesturned off), patients should be monitored continuously forpossible spontaneous or surgical stress-induced ventriculararrhythmia. Equipment for urgent cardioversion or defibril-lation as well as emergent pacing must be immediatelyavailable.These examples illustrate the need for the CIED teamand the surgical team to communicate effectively regardingthe type of procedure, the potential for EMI and the poten-tial for patient harm. Only in this manner can the bestperioperative plan be designed for the patient.58Monitoria intraoperatoriaECGMonitoria del pulso perifrico continuoPulsioximetroLnea arterial (si procede)Desactivar monitoria de respiracin (impedancia)

Samain E, Marty J, Souron V, Rosencher N, Eyrolle L: Intraoperative pacemaker malfunction during a shoulder arthroscopy. Anesthesiology 2000; 93:306-7

The goal of intraoperative monitoring is to provide a safeenvironment for the patient with a CIED undergoing asurgical, interventional or diagnostic procedure where in-terference from EMI is likely to be present. This includesboth assuring rhythm stability and protection of the CIEDfrom damage related to the EMI, therefore providing patientsafety. See Table 7.To accomplish this goal requires knowledge of the po-tential risks to the patient and the CIED, appropriate prep-aration of the patient and the CIED, monitoring of thepatients rhythm throughout the procedure and emergencypreparedness. All operative team members should be awarethat a CIED is in place, should review the preoperativeassessment and the prescription provided by the CIED teammanaging the patient and should review the surgical and/orprocedural equipment for potential CIED interaction.Intraoperative monitoringMonitoring should be performed with techniques appropri-ate to the patients underlying medical condition and theextent of the surgery as well as monitoring of the patientsrhythm throughout the procedure regardless of whether theyare receiving general or regional anesthesia, sedation, ormonitored anesthesia care. Intraoperative monitoring in-cludes continuous electrocardiography as well as monitor-ing of the peripheral pulse (e.g., palpation of the pulse,auscultation of heart sounds, monitoring of a tracing ofintra-arterial pressure, ultrasound peripheral pulse monitor-ing, pulse plethysmography or oximetry).93Important inter-Table 7 Recommendations for the intraoperative monitoring of patients with CIEDs External defibrillation equipment is required in the OR and immediately available for all patients with pacemakers or ICDs havingsurgical and sedation procedures or procedures where EMI may occur All patients with ICDs deactivated should be on a cardiac monitor and during surgery should have immediate availability ofdefibrillation Some patients may need to have pads placed prophylactically during surgery (e.g. high-risk patients and patients in whom padplacement will be difficult due to surgical site All patients with pacemakers or ICDs require plethysmographic or arterial pressure monitoring for all surgical and sedationprocedures Use an ECG monitor with a pacing mode set to recognize pacing stimuli PMs may be made asynchronous as needed with either a magnet application or reprogramming, provided that the pulse generator isaccessible ICD detection may be suspended by either magnet application as needed or reprogramming, provided that the pulse generator isaccessible During the placement of central lines using the Seldinger technique from the upper body, caution should be exercised to avoidcausing false detections and/or shorting the RV coil to the SVC coil Because of interactions with monitoring, ventilation, and other impedance monitoring operative devices, inactivating minuteventilation sensors can be considered Keep a magnet immediately available for all patients with a CIED who are undergoing a procedure that may involve EMI1129 Crossley et al Perioperative Management of Patients With Devicesactions may occur between the heart rate monitoring systemand the CIED. The anesthesiologist should be aware ofpotential limitations of electrocardiographic monitoring.59Monitoria intraoperatoria

Interactions with OR monitoring equipmentThere may be difficulties in the identification of the pacedcomplex on the monitoring equipment. The pulse generatoroutput may not be visible as spikes in displayed leads due totypical low voltage outputs of bipolar pacing or due to a lowamplitude signal on the selected ECG lead. Also, moderndigital monitors filter high-frequency signals (between1,000 to 2,000 Hz) that include pacemaker spikes (thepacemaker signal is at about 2000 Hz), unless options ac-centuating display of pacing spikes are enabled in the mon-itor setup. It is important to recognize that this accentuationscheme occasionally goes awry and marks artifact as pacingspikes. Multiple vectors improve the likelihood of detectingchanges in the paced ECG. Because of these difficulties, itis vital that there be monitoring of the peripheral pulse,whether by contour display pulse oximetry, arterial wave-forms, or other appropriate methods, confirming adequatepulse and prevents confusion with ECG artifacts. This willavoid the misinterpretation of a noncaptured pacing stimu-lus for a QRS complex.The heart rate counting may be inaccurate, most oftenfalsely reporting a higher electrocardiographic heart rate bydouble counting the pacemaker spike and the QRS complex.Regardless of the situation, responding to erroneous heartrates could result in inappropriate use of anesthetic or chro-notropic medications. Conversely, rhythms such as atrialfibrillation may include nonperfused QRS complexes withundercounting of heart rate by pulse oximetry. For thesereasons, all monitoring equipment used on patients with aCIED should include an electrocardiographic monitor and aplethysmographic pulse measurement and display.When CIED rate-responsive sensors are not inactivatedeither by reprogramming or use of a magnet, the operativeteam needs to be aware that the paced heart rate couldincrease due to normal function of the sensor. It is importantto know what type of rate sensor is used in the patientsCIED. Most CIEDs use activity sensors that measure vibra-tion or pressure on the generator. Therefore, movement ofthe patient onto the surgical table, pressure placed over thedevice or motion of the ipsilateral arm may result in a pacedheart rate that could increase up to a maximum rate definedby the programming of the upper sensor rate in the device.Minute ventilation sensors use the measurement of thoracicimpedance. Current emitted by the CIED to measurechanges in thoracic impedance can be detected by monitor-ing equipment and appear to be rapid pacing without cap-ture. Also, electrosurgery may interfere with this measure-ment and cause pacing at the upper sensor rate.BIOTRONIK pacemakers have a rate algorithm based uponmeasurement of right ventricle (RV) lead tip impedancechanges with cardiac contraction. Interference with moni-toring equipment has not been reported.Occasionally, problems have been noted with monitorsthat measure electroencephalographic activity as an index ofsedation depth. These may sometimes report erroneous ac-tivity in the setting of CIED pacing. Unless dealt withappropriately by filtering, the new electrical signal of theCIED may be assumed biological in origin.60Accesos venosos centrales

Central venous accessWhen considering central venous access, caution should beused as a guide wire enters the heart in a patient with anactive ICD. Contact between wire and sensing electrodescan trigger antitachycardia therapy. A worse scenario existsif there is a defibrillator discharge and the guide wire hasshorted the proximal coil to the distal coil. Arrhythmiastriggered by the guide wire might also activate antitachy-cardia therapy. Caution is also advised when leads havebeen recently inserted (within 3 months) because of anincreased chance for dislodgement of the lead. In general, ifthe guide wire does not enter the ventricle, there will be noproblems.61Manejo de IEM / electrocauterio

Risk mitigationOversensing is the adverse interaction most likely to occurwhen a CIED is exposed to EMI. The anatomical site ofelectrosurgery application, the duration of electrosurgeryapplication, and the position of the return electrode deter-mine the risk of oversensing. The risk is greatest if thecurrent path crosses the CIED and/or leads. The risk is lesswhen the presumed current path is kept at least 6 inchesaway from the CIED. For example, if surgery is being doneon the ipsilateral arm to the CIED, the return electrodeshould be placed on the same arm as opposed to placing iton the flank and exposing the CIED to all of the electrosur-gical energy.Experience has demonstrated, and literature suggests,that in a CIED implanted in the usual upper chest position,oversensing problems are unlikely for operative procedureswhere the application of electrosurgery will be inferior tothe umbilicus and the return electrode is placed on the lowerbody (thigh or gluteal area).29The use of monopolar elec-trosurgery involving the upper abdomen, chest, arms, headand neck pose more of a risk for oversensing and damage tothe CIED system62Manejo de IEM / electrocauterioPeters RW, Gold MR: Reversible prolonged pacemaker failure due to electrocautery. J Interv Card Electrophysiol 1998; 2:343-4

Proper use of electrosurgeryThere have been reports of threshold rise after electrosur-gery where older, nonisolated earth-grounded electrosurgi-cal RF generators were used. Stray RF currents entering apacing lead can also induce ventricular fibrillation.95In theearth-grounded electrosurgical systems, failure of the returnelectrode connection resulted in shunting of current to al-Table 8 Specific procedures and writing committee recommendations on postoperative CIED evaluationProcedure RecommendationMonopolar electrosurgery CIED evaluated# within 1 month from procedure unless Table 9 criteria are fulfilledExternal cardioversion CIED evaluated# prior to discharge or transfer from cardiac telemetryRadiofrequency ablation CIED evaluated# prior to discharge or transfer from cardiac telemetryElectroconvulsive therapy CIED evaluated# within 1 month from procedure unless fulfilling Table 9 criteriaNerve conduction studies (EMG) No additional CIED evaluation beyond routineOcular procedures No additional CIED evaluation beyond routineTherapeutic radiation CIED evaluated prior to discharge or transfer from cardiac telemetry; remote monitoring optimal;some instances may indicate interrogation after each treatment (see text)TUNA/TURP No additional CIED evaluation beyond routineHysteroscopic ablation No additional CIED evaluation beyond routineLithotripsy CIED evaluated# within 1 month from procedure unless fulfilling Table 9 criteriaEndoscopy No additional CIED evaluation beyond routineIontophoresis No additional CIED evaluation beyond routinePhotodynamic therapy No additional CIED evaluation beyond routineXray/CT scans/mammography No additional CIED evaluation beyond routine#This evaluation is intended to reveal electrical reset. Therefore, an interrogation alone is needed. This can be accomplished in person or by remotetelemetry.1131 Crossley et al Perioperative Management of Patients With Devicesternative RF ground sites, including the pacing electrode,with resulting threshold increase or loss of capture.96Opti -mal grounding of the electrosurgical system involves theuse of a split foil return electrode, which allows for detec-tion of proper application to the patient.3As has beenpreviously discussed, the current from the electrosurgerysystem can be effectively managed by placing the returnelectrode in a position that directs the current away from theCIED. For example, if surgery is planned on the ipsilateralshoulder, the return electrode should be placed on the ipsi-lateral arm.63Litotripsia Reporte de caso, evento extremadamente raroRiesgo de dao es bajoDrach GW, Weber C, Donovan JM. Treatment of pacemaker patients with extracorporeal shock wave lithotripsy: experience from 2 continents. J Urol 1990;143:895 896

RMNEvidencia contradictoria de interferencia En general, RMN esta CONTRAINDICADA

Terapia de radiacin

Subito y errado estimulo, falla multiple del sistemaActualmente, si ocurre , la frecuencia es menor de 210 latidos minTherapeutic radiationWhile diagnostic radiography rarely interferes with CIEDfunction, therapeutic radiation can have several potentialdamaging effects on CIED function, especially when thebeam is directed onto the pulse generator.44-46ModernCIEDs utilize metal oxide semiconductors (CMOS) in theintegrated circuitry. These circuits may be more readilydamaged by lower levels of radiation than were older de-vices that were designed with discrete components. Whenthe semiconductors are exposed to ionizing radiation, dam-age occurs to the silicon and the silicon oxide insulatorswithin the semiconductor.47The mechanism of failure isunpredictable, since any part of the semiconductor can bedamaged. Sudden output failure or runaway pacing has beenreported23,24in older devices and remains at least a theo-retical concern with present CIEDs.48Reports in the litera-ture include damage from radiation doses as low as 10 Gy,while safe operation has been reported with accumulateddoses of 30 to 150 Gy.48Therefore, direct radiation ofpacemakers and ICDs should be strictly avoided and accu-mulated doses should generally not be allowed to exceed5 Gy66Terapia de radiacinSimulacin de dosis acumuladaDosis acumulada no mayor a 5 GyDispositivo fuera de campo (cambio Qx?)Chalecos RX no protegen al DECI

For all cases, shielding options should be discussed withthe radiation oncologist and physicist responsible for treat-ing the patient. For all therapeutic radiation, there should besophisticated modeling of the radiation that will be absorbedby the pulse generator. Each CIED manufacturer has rec-ommended tolerances for each pulse generator. If the mod-eling suggests that there will be an exposure that is at ornear the tolerance of that specific pulse generator, reposi-tioning of the generator to another site may be required.Risks and benefits of relocation will vary depending uponthe patient, radiation therapy plan, and the degree of pacingdependence. When a pulse generator is to be moved, somephysicians will extract the system and others will use leadextenders and move the pulse generator with a plan to putthe pulse generator back in its original location after thetherapy is completed.Electrical reset may occur as a result of scatter neutronexposure during conventional radiotherapy, and the proba-bility of scatter neutrons increases as the photon beamenergy increases. Importantly, the use of conventional x-rayshielding during radiotherapy does not protect the pulsegenerator from the effects of the scattered neutrons. If thephoton beam energy exceeds 10 MV, evaluation of CIEDfunction immediately after each radiotherapy treatmentmight be necessary. Electrical reset requires reprogrammingof device parameters. Electron beam therapy has not beenreported to cause electrical reset of presently used CIEDs.67Terapia electroconvulsivaGoldberg RJ, Badger JM: Major depressive disorder in patients with the implantable cardioverter defibrillator. Two cases treated with ECT. Psychosomatics 1993; 34:273-7Electroconvulsive therapyIn electroconvulsive therapy (ECT), an electric current isdelivered to the brain, triggering a brief seizure. This hasbeen associated with abnormal CIED function.51There areseveral small case reports spanning both older and modernday devices that illustrate the effects of ECT on pacemakerand ICD function. Despite the high amount of current usedin these procedures, no report demonstrated CIED malfunc-tion or reversion to a backup safety mode.51-53The noisereversion mode may also be triggered. An additional con-cern is myopotential oversensing from the resulting seizureactivity. Although transient, this can be a significant issue inpacemaker-dependent patients, especially those with unipo-lar lead configurations. Another clinical concern is the po-tential for marked sinus tachycardia, which could cause aninappropriate shock by an ICD.There are no reports of direct damage to CIED circuitryas a result of the electric current, although inhibition ofpacing is certainly possible. The duration of the electricalstimuli is typically quite brief (1 to 2 seconds). Thus, he-modynamically significant inhibition of pacing is unlikely.Similarly, with standard programming on ICDs, inappropri-ate shocks from this brief electrical therapy are also un-likely. If a prolonged stimulus is used, then there is somepotential for bradycardia or inappropriate ICD shocks.Pacemaker-dependent patients should not have devices pro-grammed with unipolar sensing and should have their de-vices be made asynchronous. When magnet responses isprogrammed ON in the appropriate device, placing a mag-net over the pacemaker rather than actual interrogation andreprogramming is reasonable. The physician needs to knowthe ICD tachycardia detection rate and should have a mag-net handy in case the sinus rate gets near that rate. Pretreat-ment with short-acting beta-adrenergic blockers might alsobe considered in such patients68Cardioversin / DesfibrilacinCardioversionExternal cardioversion was associated with transient dys-function of older CIEDs, particularly those that used uni-polar leads. Individual reports noted transient loss of captureand electrical reset, particularly when using an anterior-lateral electrode position.33,34The mechanism for thresholdchanges at the tissue-electrode interface is poorly under-stood, although, tissue edema or microcauterization fromexposure to high voltages have been suggested. With thewidespread use of bipolar leads and incorporation of sophis-ticated circuitry, abnormal function of CIEDs during car-dioversion is now rarely observed.34-37In a recent clinicalstudy of 44 patients with various types of CIEDs, no CIEDmalfunction was observed during cardioversion using ananterior-posterior electrode positioned with 8 cm betweenthe anterior electrode and the CIED. The pads were placedin the anterior-posterior position. No clinically importantproblems such as loss of capture or undersensing, wereidentified during interrogations 1 hour and 1 week aftercardioversion although a transient decrease in battery im-pedance and voltage was identified at 1 hour.36Although ithas not been evaluated in a randomized trial, an anterior-posterior electrode position, with the anterior pad placedaway from the pulse generator, has the theoretical advantageof creating an electrical field that is more likely to beperpendicular to the orientation of intracardiac ventricularlead electrodes. Rare reports exist that noted adverse inter-actions of cardioversion and CIEDs when using the antero-lateral electrode position.34In a case-series of three patients,high pacing thresholds developed several hours to one dayafter the cardioversion, requiring lead revision.35After aor-tic unclamping in cardiac surgery, defibrillation energies of10 to 30 Joules may be applied directly to the ventricles. Inthe experience of several committee members, occasionally,this has been associated with pulse generator reset.69Cardioversin / DesfibrilacinSituaciones clnicasPreparacin, Algoritmo sugerido

Disfuncin de marcapasosManejo POPPili-Floury S, Farah E, Samain E, Schauvliege F, Marty J: Perioperative outcome of pacemaker patients undergoing non-cardiac surgery. Eur J Anaesthesiol 2008; 25:514 6Aumento de umbral de marcapasospopo descritoReinicio de modo seguro por emi monopolarEffect of intraoperative procedures onpostoperative functionality of CIEDsThe rationale for postoperative interrogation of devices restsprimarily on 1) assuring that the device has not entered abackup safety mode, 2) functionality was not impaired and,3) restoring preprocedural programming settings if changeswere made prior to the procedure. The timing of postoper-ative assessment depends upon whether EMI exposure waspresent, the type of CIED, the type of procedure performedand whether preoperative reprogramming was performed.The recommendations for postoperative evaluation arelisted in Table 8 . The source of EMI and the degree to whichit may alter CIED functionality is a result of both theamount of EMI energy delivered as well as the procedureperformed. Patients who will require CIED evaluation priorto patient discharge or transfer from a cardiac telemetryenvironment include (1) those whose devices were repro-grammed prior to the procedure that left the device non-functional such as disabling tachycardia detection in anICD, (2) those undergoing hemodynamically embarrassingsurgeries such as cardiac surgery or significant vascularsurgery (e.g., abdominal aortic aneurysmal repair), (3) thosewho experienced significant intraoperative events includingcardiac arrest requiring temporary pacing or cardiopulmo-nary resuscitation and tachyarrhythmias requiring externalelectrical cardioversion, (4) those who are exposed to cer-tain types of procedures that emit EMI with a greater prob-ability of affecting device function and (5) those with lo-gistical limitations that would prevent reliable deviceevaluation within one month from their procedure. Thosepatients have a significant risk of entering the reset modeand may have some risk of changes in CIED function. SeeTable 9.In all other situations, there is little or no risk of a changein CIED function and there is only a small risk of enteringreset mode. In these patients it is reasonable to have theCIED interrogated no more than one month from the time ofthe procedure (see Table 8). An in-office evaluation is notnecessary and the evaluation may be performed with remoteCIED evaluation technologies. This one-month time wasempirically chosen and is intended to be a maximum inter-val. It may be altered in specific situations by the physiciansinvolved.

74Manejo POP

gracias