Perioperative management of patients with a pacemaker or implantable cardioverter-defibrillator

INTRODUCTION — More than three million people in the United States have a conventional pacemaker (PM) and more than 300,000 have an implantable cardioverter-defibrillator (ICD) with pacing capabilities [1,2]. Use of these cardiac implantable electronic devices (CIEDs) is increasing throughout the world, and these patients are presenting with increasing frequency for surgical and other interventional procedures [3].

Creation of perioperative care algorithms for patients with CIEDs is complicated by the diverse programming capabilities of currently manufactured devices, the presence of functioning older (legacy) devices in some patients, continuing evolution in CIED technology (eg, leadless PMs and subcutaneous ICDs), and confusion regarding the differences between PMs and ICDs, including variable responses to magnet application [4,5].

Perioperative advisories have been developed by four professional societies: the American Society of Anesthesiologists (ASA), the Heart Rhythm Society (HRS), the Canadian Anesthesiologists' Society (CAS) in conjunction with the Canadian Cardiovascular Society (CCS), and the Medicines and Healthcare products Regulatory Agency (MHRA), a British governmental agency [6-9]. The recommendations of these agencies differ with respect to intraoperative magnet use and the need for device interrogation and/or reprogramming for surgery (table 1).

This topic discusses management of patients with CIEDs during the preoperative, intraoperative, and immediate postoperative periods. Other aspects of CIED technology are discussed separately:

●(See "Implantable cardioverter-defibrillators: Overview of indications, components, and functions".)

●(See "Cardiac implantable electronic devices: Patient follow-up".)

●(See "Permanent cardiac pacing: Overview of devices and indications".)

●(See "Modes of cardiac pacing: Nomenclature and selection".)

ELECTROMAGNETIC INTERFERENCE — Electromagnetic interference (EMI) refers to the potential disruption of the operation of an electronic device when it is in the vicinity of an electromagnetic field generated by an external source. During surgical procedures, the function of a cardiac implantable electronic device (CIED) may be affected by EMI, most commonly due to use of an electrosurgery unit (ESU).

Modern transvenous leads can be programmed to either a unipolar or bipolar sensing configuration. With a bipolar configuration, two electrodes near the distal end of the lead serve as the cathode and anode, whereas with a unipolar configuration an electrode near the lead tip serves as the cathode while the pulse generator functions as the anode. CIEDs programmed to a unipolar sensing configuration are more susceptible to EMI than those programmed to a bipolar configuration [10].

Bipolar leads can have either a true bipolar or integrated bipolar sensing design. True bipolar leads have a lower risk of EMI due to the close spacing of their two electrodes (one for pacing and one for sensing) near the distal end of the lead tip, compared with integrated bipolar leads that use more widely spaced electrodes for pacing and sensing [11,12].

Risks of electromagnetic interference — EMI may cause:

●Inhibition of pacing due to ventricular oversensing of EMI. All CIEDs sense intracardiac signals (R and/or P waves) delivered through the electrodes. Oversensing leads to under-pacing when a device senses electrical signals that should be ignored (eg, myopotentials, T waves, artifact from a monopolar ESU), and interprets these signals as native R waves. Since these signals are interpreted by the device as R waves, no pacing is generated. This may result in profound bradycardia or asystole in a pacing-dependent patient (waveform 1).

●Misinterpretation of EMI as a tachyarrhythmia, resulting in delivery of inappropriate shock(s) or antitachycardia pacing by an ICD [13-20]. (See "Cardiac implantable electronic devices: Long-term complications", section on 'Inappropriate shocks'.)

●Direct damage to the CIED, altering its ability to deliver treatment for ventricular tachycardias or pacing.

An insertable cardiac monitor (ICM; also sometimes referred to as an implantable cardiac monitor or implantable loop recorder) is an electronic device designed to monitor cardiac rhythm and record pauses, bradycardia, and atrial and ventricular arrhythmias (image 1). Since an ICM delivers no therapy, EMI is unlikely to cause patient harm. However, preoperative interrogation of the device is necessary because all recorded data may be lost during exposure to monopolar ESU or other strong EMI.

Other adverse consequences of EMI are less likely but may lead to patient injury. These include:

●Misinterpretation of EMI as atrial signals, resulting in ventricular pacing at the maximum ventricular pacing rate in a dual-chamber PM, with consequent undesirable tachycardia.

●Stimulation of an active sensor for rate-responsive pacing, resulting in pacing at the upper sensor rate and undesirable tachycardia [21]. The sensor may be a mechanical sensor (eg, an accelerometer) or a physiologic sensor (eg, a minute ventilation sensor that increases heart rate when respiratory rate increases), or a combination of the two. Such sensors are used in some patients to temporarily increase the pacing rate to compensate for increased physiologic need during exercise. Physiologic sensors are more susceptible to the effects of EMI than are mechanical sensors.

●Activation of "power on reset" mode, causing the device to revert to its factory-programmed parameters. In an ICD, these parameters include a lower heart rate for initial treatment of ventricular arrhythmias and maximal energy shocks, as well as single-chamber (ventricular only; VVI) pacing at a rate of 60 to 72.5 beats/minute (bpm) [6,7]. In a PM, these parameters would include ventricular-only pacing at a rate of 60 to 72.5 bpm.

These settings are not optimal for many patients and may be dangerous for some. For patients who benefit from atrioventricular (AV) synchrony or cardiac resynchronization therapy (CRT), sudden loss of these specialized functions may precipitate acute heart failure.

●Total device failure with no output, which may occur with certain older devices [22]. When EMI is likely to occur for a pacing-dependent patient with an older device, an alternate pacing modality (eg, transvenous, transcutaneous, transesophageal) should be employed or be readily available as a backup. Of these backup options, transvenous pacing is the most reliable.

Sources of electromagnetic and other interference

●EMI caused by ESUs – During surgery, EMI is most commonly generated by an ESU. Monopolar electrosurgery is much more likely to cause EMI than bipolar electrosurgery [23,24]. The coagulation (high voltage) mode causes more EMI than the non-blended cutting (low voltage) mode. (See "Overview of electrosurgery", section on 'Clinical use'.)

Risk of EMI causing interference with a CIED is highest if an ESU will be used near the pulse generator or leads of an ICD or PM. Typically, this occurs during surgical procedures performed superior to the umbilicus. The farther away the CIED is from the electrosurgical instrument, the lower the risk of EMI [11,25-29]. In a prospective cohort study, use of a monopolar ESU caused clinically meaningful EMI (defined as interference that would have resulted in delivery of inappropriate antitachycardia therapy [antitachycardia pacing or shock] by an ICD had the device not been reprogrammed) in 20 percent (5/70) of patients during noncardiac surgery above the umbilicus, in 29 percent (10/34) of those undergoing intrathoracic cardiac surgery, but in 0 percent (0/40) if surgery was below the umbilicus [11].

●EMI caused by other surgical or anesthetic equipment – Other equipment may generate EMI in the perioperative period. Examples include nerve stimulators for nerve blocks or peripheral nerve stimulation [30-32], transcutaneous electrical nerve stimulation [TENS] units [33-35], radiofrequency scanners used to find retained surgical instruments [36,37], lithotripsy, electroconvulsive therapy [17], or radiofrequency ablation devices.

●Mechanical interference

•Guidewires used during central venous catheter insertion – During insertion of a central venous catheter (CVC), mechanical interference is caused by movement of the guidewire near the sensing electrodes of a CIED. This may result in ventricular oversensing, leading to delivery of an inappropriate shock in a patient with an ICD or inhibition of a necessary pacing function [7].

Also, atrial oversensing in a dual-chamber pacing mode may occur, which may lead to ventricular tracking and inappropriately rapid ventricular pacing.

Actual physical contact between the guidewire and the right ventricular rate sensor has been reported to cause an electrical short with irreversible damage to the CIED generator [38].

•Bone saws – Bone saws that vibrate can cause mechanical interference [39,40].

PREOPERATIVE ASSESSMENT — Prior to elective procedures, preoperative assessment includes consultation with the cardiology or institutional cardiac implantable electronic device (CIED) care team [41,42], as well as the anesthesiologist and surgeon (algorithm 1). Assessment will determine the type of CIED, manufacturer, model number, current settings, and proper functioning of the device.

Patients typically carry a manufacturer's identification card containing some of these details if they are not in the medical records. Procedures for perioperative management in cases of emergency surgery are discussed below. (See 'Emergency surgery' below.)

Device interrogation — The patient's underlying rhythm and appropriate function and programming of the CIED should be reconfirmed in the preoperative period [4-9,41,43,44]. In most patients, this can be accomplished by accessing the results of a recent interrogation of the CIED. The American Society of Anesthesiologists (ASA) Practice Advisory suggests that interrogation should occur within three to six months prior to scheduled surgery [6], while the Heart Rhythm Society (HRS) recommends interrogation prior to scheduled surgery [7], as follows:

●Within six months for an ICD

●Within 12 months for a conventional PM

●Within three to six months for any cardiac resynchronization therapy (CRT) device

This step is critical since subsequent steps for intraoperative management might be ineffective in a malfunctioning device [4,22].

Planning device management — Key management issues determined during the preoperative evaluation by the CIED care team include (table 2) [6-9,41]:

●Is the patient pacing-dependent? – Patients with either a PM or an ICD may be pacing-dependent (eg, history of symptomatic bradycardia, inadequate escape rhythm, or history of atrioventricular [AV] nodal ablation). Electromagnetic interference (EMI)-induced inhibition of pacing may result in severe bradycardia or asystole in such patients [16]. Thus, if EMI is likely and the patient is pacing-dependent, the PM or ICD should be reprogrammed to an asynchronous pacing mode by a programming machine (or in some cases by placement of a magnet). This is possible in all PMs and in most currently implanted ICDs; however, magnet placement will never alter the pacing mode of an ICD.

●Does the patient have an ICD? – When devices generating EMI will be used near an ICD (ie, a surgical procedure involving the use of electrosurgery superior to the umbilicus), the antitachycardia therapy must be suspended. This can be accomplished with a programming machine or, in some cases, by applying a magnet (table 3). (See 'Reprogramming with a programming machine' below and 'Magnet application' below.)

If EMI is not anticipated, ICD reprogramming may not be necessary. However, a magnet should be readily available in case of unanticipated EMI.

●If reprogramming is necessary, can a magnet be used for this purpose? – The decision to reprogram a CIED with a programming machine or to utilize a magnet for this purpose depends on the type of CIED and how it is programmed, the patient's underlying rhythm, likelihood of EMI, proximity of the CIED to the surgical field, and planned patient positioning during surgery. (See 'Magnet application' below.)

If magnet application is planned, the device's magnet response should be known. For most PMs, magnet application will initiate asynchronous pacing at a fixed rate with a fixed AV delay. For most ICDs, a magnet will suspend tachyarrhythmia detection and therapy. However, a magnet will never change the pacing mode of an ICD (ie, pacing inhibition may still occur).

Based on these key issues, the following specific goals for perioperative CIED management are communicated to the anesthesiologist and the surgeon:

●When EMI is likely (see 'Electromagnetic interference' above):

•The anti-tachyarrhythmia function of the ICD should be disabled to avoid inappropriate shocks or antitachycardia pacing [11,13,14].

•In patients who are pacing-dependent, the ICD or PM should be programmed to an asynchronous pacing mode to avoid oversensing and pacing inhibition.

●Regardless of the risk of EMI:

•If unwanted patient movement from an ICD shock would create a hazard to the patient (eg, intraocular surgery) or surgical personnel (eg, use of a scalpel), the anti-tachyarrhythmia function of the ICD should be disabled.

•If the CIED has an active sensor for rate-responsive pacing (eg, a mechanical sensor [accelerometer] or a physiologic sensor [minute ventilation sensor]), this function should be disabled during surgery to prevent undesirable tachycardia.

Reprogramming with a programming machine — We typically reprogram an ICD to suspend anti-tachyarrhythmia therapy (ie, delivery of shocks or antitachycardia pacing) by using a programming machine rather than a magnet. Transcutaneous pacing/defibrillator pads are placed on the patient when the anti-tachyarrhythmia functions are disabled. (See 'Placement of transcutaneous pacing/defibrillator pads' below.)

Advantages of reprogramming with a programming machine include (table 3) [6]:

●Programming an ICD to an asynchronous pacing mode can only be accomplished with a programming machine. The pacing mode of an ICD cannot be changed with a magnet. Likewise, disabling a rate-responsive sensor for rate-responsive pacing in an ICD can only be accomplished with a programming machine.

●Programming a PM with a programming machine allows options that are not available with magnet application; such alternative options are important for patients who would have suboptimal cardiac function in a magnet-driven asynchronous pacing mode [4] (see 'Magnet application' below). For example, the asynchronous pacing mode interferes with AV synchrony and CRT. Also, competition between the asynchronous pacing rate and the patient's intrinsic rate may occur if the intrinsic rate accelerates due to noxious stimuli during surgery.

Disadvantages of reprogramming with a programming machine rather than a magnet include:

●Trained personnel must be present for preoperative reprogramming, which may delay surgery. Personnel must also be available to reprogram the CIED after the procedure. If reprogramming and reactivation of CIED settings are forgotten, the patient could leave the hospital with disabled or altered ICD therapies [41].

●Changes are not as quickly reversible after reprogramming compared with applying or removing a magnet. Adjustments are delayed while the programmer or appropriately trained personnel return to the operating room, and the reprogramming process itself takes several additional minutes.

Thus, backup therapy should include placement of transcutaneous pacing/defibrillator pads on the patient and immediate availability of an external defibrillator with antibradycardia pacing capability at the bedside. (See 'Placement of transcutaneous pacing/defibrillator pads' below.)

Magnet application — Application of a magnet may be used to suspend anti-tachyarrhythmia therapy in an ICD or to produce asynchronous pacing in a PM. This alternative approach to reprogramming with a machine is recommended for selected patients by some agencies (eg, the Heart Rhythm Society [HRS] and Canadian Anesthesiologists' Society [CAS]/Canadian Cardiovascular Society [CCS]) in some settings (table 1) [7,8]. However, advisories and expert opinion statements caution against routine magnet use as a substitute for appropriate preoperative consultation and preparation [4-6,45].

Actual response to magnet application should be confirmed by the CIED care team during the preoperative evaluation of the device. For example, the device’s magnet function may be disabled so that the magnet application would have no effect; this is possible in Boston Scientific, St. Jude Medical, and Biotronik (PM only) devices [9]. Also, deactivation of the magnet mode can occur if the "power on reset" mode has been activated. Finally, some leadless PMs do not initiate asynchronous pacing in response to magnet application [46].

The expected responses to magnet application for PMs (table 4) or ICDs (table 5) include:

●For most PMs – Magnet application will initiate asynchronous pacing at a fixed rate, as well as a fixed AV delay, which varies by manufacturer (and sometimes model) (table 4).

●For most ICDs – Magnet application will suspend tachyarrhythmia detection and therapy but has no effect on the pacing mode [4]. Further details are found in the table (table 5).

Disadvantages of magnet application include:

●Magnet application does not result in asynchronous pacing in any ICD. In a pacing-dependent patient, profound bradycardia or asystole may still occur if pacing is inhibited by EMI.

●In patients who are obese or have a deep CIED implant (ie, a subcutaneous ICD), magnet application might fail to elicit the magnet response [15]. Two or more magnets can sometimes be used in a stacked configuration to increase the likelihood of eliciting the magnet response. However, confirmation of ICD response to the magnet is not possible in all devices (table 5).

●Location of the surgical procedure and patient positioning may create the following problems:

•It may be difficult to maintain the magnet in a stable position over the pulse generator of the device when the patient is in a lateral or prone position [16].

•Magnet application may jeopardize sterility of the surgical field if the incision is located near the device.

•Surgical drapes may preclude access to the magnet, as well as the ability to observe that it remains securely in place.

●In some patients with a PM, magnet-induced asynchronous pacing can compromise cardiac function [4,47]. For example, asynchronous pacing may result in loss of AV synchrony, loss of CRT, loss of capture, or competition between the PM and the patient's intrinsic rate due to acceleration of the intrinsic rate during a noxious stimulus such as surgical incision.

●Although some ICDs emit a diagnostic tone when a magnet is applied, whether any sound is emitted and its meaning depend on the device manufacturer and, in some cases, the model and/or how the device is programmed (table 5). As examples:

•Boston Scientific (including their legacy companies Guidant Medical and Cardiac Pacemakers, Inc.) manufactures transvenous ICDs that emit continuous diagnostic tones (ie, "beeping") indicating ongoing presence of a magnet and confirming the suspension of anti-tachyarrhythmia therapy. Boston Scientific also manufacturers subcutaneous ICDs that only emit a tone for 60 seconds with magnet application.

•Emission of a constant tone with magnet application in some legacy devices from these manufacturers indicates that tachyarrhythmia detection and anti-tachyarrhythmia therapy (but not antibradycardia pacing) have been deactivated, and removal of the magnet will not reactivate these functions. Reprogramming is required to reactivate ICD therapy.

•The absence of any tone from a Boston Scientific ICD upon magnet application indicates a problem with the device (eg, malfunction, magnet switch that has been programmed off, or loss of beeper volume following MRI scanning).

•Medtronic-manufactured ICDs emit a tone upon initial detection of a magnet, but the anti-tachyarrhythmia functions revert to active status as soon as the magnet is removed, even if the tone sound continues.

•St. Jude Medical and Biotronik-manufactured ICDs do not emit any sound or provide any confirmation that a magnet has been detected. St. Jude Medical ICDs do have a programmable magnet switch but do not provide any sound to confirm that the magnet switch function has been programmed off.

•Some Microport/Sorin/ELA-manufactured ICDs change the pacing rate to 90 when a magnet is detected without a change in mode and without emitting any sound.

Preanesthesia consultation — Communication with the CIED care team should provide important information about the type of device (PM, ICD, CRT, ICM), adequacy of function, current settings, specific recommendations for reprogramming with a programming machine or magnet application, and clinical implications of the expected response (table 2) [6-9,41].

During physical examination, pulse regularity and location of the device generator (incisional scar and palpation of the device) are assessed. A recent electrocardiogram (ECG) should be available. If appropriate CIED function has been confirmed, no other special laboratory tests are needed.

If a chest radiograph (CXR) is available, the CIED location is noted (image 2 and image 3 and image 4). Note that not all devices on a CXR are CIEDs (image 5). A CIED is typically in a pectoral position, with leads from the device following the great veins into the heart and terminating in the right ventricle, right atrium, and coronary sinus (depending on the device type). However, the pulse generator of a subcutaneous ICD is implanted in the left midaxillary line, with subcutaneous lead(s) positioned over the heart (image 6).

INTRAOPERATIVE MANAGEMENT — The presence of a cardiac implantable electronic device (CIED) necessitates (algorithm 1) [6-9,23,48,49]:

●Continuous electrocardiographic (ECG) and pulse oximetry or arterial pressure waveform monitoring in the operating room.

●Preparation for the possibility of urgent cardioversion, defibrillation, or transcutaneous pacing.

●Precautions when the use of an electrosurgery unit (ESU) or other device that generates electromagnetic interference (EMI) is planned.

The overall procedural risk may be increased [50,51].

Placement of transcutaneous pacing/defibrillator pads — Transcutaneous pacing/defibrillator pads are placed on the patient before or shortly after the anti-tachyarrhythmia functions of an ICD have been electively disabled and/or asynchronous pacing has been enabled to allow treatment of malignant arrhythmias [4,5,45,52-54]. An external defibrillator with pacing capability should be immediately available.

Ideal positioning of transcutaneous pacing/defibrillator pads minimizes damage to the ICD during external defibrillation. The pads should not be placed directly over any CIED. For most individuals with a left-sided CIED, standard anteroposterior pad position is preferred (figure 1). Anterolateral pad position is selected if the anteroposterior position is not feasible. Rarely, a defibrillator pad is positioned only on the back of the patient, and a sterile anterior pad is immediately available near the surgical field for emergency placement if needed. (See "Basic principles and technique of external electrical cardioversion and defibrillation", section on 'Electrode position'.)

Monitoring — During any procedure where an ESU or other device that generates EMI may be used, monitoring always includes both:

●Continuous electrocardiography – Most ECG monitors require reconfiguration of high-frequency filtering to clearly demonstrate pacing pulses. In general, selection of the "diagnostic" bandpass filter mode is preferred over the "monitor" or "filter" modes because it allows clear display of higher-frequency signals, including pacing spikes [55].

However, pacing artifacts may be visible but misinterpreted as QRS complexes by the ECG monitor and by the clinician (waveform 2) [9]. A false heart rate may be displayed on the ECG monitor, but other monitors such as pulse oximetry and arterial pressure waveforms will indicate the patient's true perfused heart rate. This scenario is more likely with unipolar than bipolar pacing.

In some cases, EMI may obscure clear, consistent display of both pacing spikes and QRS complexes on the ECG [48,56].

●Pulse oximetry or intra-arterial pressure waveform – Continuous display of either pulse oximetry plethysmography or an invasive intra-arterial pressure waveform is necessary throughout the perioperative period in order to directly detect mechanical systole and presence of an adequate arterial pulse [6,7]. In rare cases, false readings of pulse oximetry "systoles" may delay detection of cardiac arrest [57].

Management of the cardiac implantable electronic device — Either reprogramming of the CIED with a programming machine or application of a magnet is necessary before use of an ESU or another device generating EMI superior to the umbilicus. As noted above, anti-tachyarrhythmia therapy is suspended in an ICD, while asynchronous pacing is initiated in a pacing-dependent patient (table 3) [6]. (See 'Planning device management' above.)

Management of electromagnetic interference — The dispersive electrode pad for an ESU should be positioned so the current path from the ESU to the pad will not cross the CIED generator or leads (typically located in the chest) [11]. Similar considerations apply to the pads used for nerve stimulators or other devices which may generate EMI. (See 'Risks of electromagnetic interference' above and "Overview of electrosurgery", section on 'Avoid electromagnetic interference'.)

An underbody electrosurgery dispersive electrode that is incorporated into a pad and placed directly on the operating table is sometimes used instead of a conventional dispersive electrode. There is insufficient evidence to determine the impact of using an underbody dispersive electrode on the risk of electromagnetic interference for patients with a CIED, compared with use of a conventional dispersive electrode [6]. However, a prospective study [11], and case reports [19,20,58] suggest that risk of EMI with an underbody electrode might be higher than with a conventional electrode.

Central venous catheterization — During insertion of a central venous catheter (CVC), some clinicians suspend antitachycardia functions in a patient with an ICD; pacing-dependent patients might require reprogramming to an asynchronous pacing mode [7]. Guidewire movement may lead to inhibition of pacing function or delivery of an inappropriate shock (see 'Sources of electromagnetic and other interference' above). Continuous monitoring of ECG and pulse oximetry or an intra-arterial catheter waveform is necessary during insertion. (See 'Monitoring' above.)

Physical lead dislodgement is also possible during placement of the CVC. Risk is highest in the first three months after insertion of the CIED [7,59]. In these cases, the position of the coronary sinus lead on the chest radiograph (CXR) is noted prior to CVC insertion since this lead is most prone to dislodgement (image 2).

Anesthetic agents — Anesthetic agents do not affect CIED function.

For patients with bradycardia, high doses of anesthetics that exacerbate bradycardia are avoided (eg, dexmedetomidine [60] or fentanyl [61]) due to the theoretical risk of inducing pacing dependence [62].

For patients with long QT syndrome as the indication for CIED placement, agents that prolong the QT interval are typically avoided (eg, haloperidol, methadone, or high doses of the potent volatile inhalation agents) due to the theoretical increased risk of polymorphic ventricular tachycardia [63-67]. (See "Acquired long QT syndrome: Definitions, pathophysiology, and causes", section on 'Psychotropic medications'.)

Intraoperative emergencies — Before attempting emergency external defibrillation or cardioversion of a patient with a magnet applied to an ICD, the magnet should be removed to permit reactivation of the ICD's anti-tachyarrhythmia function. Also, all sources of EMI should be discontinued to ensure correct rhythm interpretation and appropriate therapy. If magnet removal does not immediately result in reactivation of the device with appropriate cardioversion or defibrillation, an external defibrillator should be employed using the previously applied transcutaneous pacing/defibrillator pads. (See "Advanced cardiac life support (ACLS) in adults", section on 'Management of specific arrhythmias'.)

During such events, chart paper recording of the ECG on the bedside monitor is initiated to allow later review of the cardiac rhythm and to confirm the presence of a ventricular arrhythmia. The actual ventricular rate should be noted and recorded since the ventricular response rate might be lower than the lowest setting for anti-tachyarrhythmia therapy, indicating a need for ICD reprogramming in the postoperative period.

Outright intraoperative failure of a CIED system is rare, even when older devices are exposed to strong EMI. Failure may manifest as absence of any response or as inappropriate therapy, such as repeated shock delivery or "runaway" high-rate pacing (typically 180 to 200 beats/minute [bpm]) [4,22]. Discovery or suspicion of inappropriate antitachycardia therapy requires cessation of surgery, withdrawal of all EMI sources, and urgent CIED evaluation. Improvements in newer CIED technology prevent runaway high-rate pacing.

Management of procedures involving magnetic resonance imaging — Management of patients who have a CIED is discussed separately [68]. (See "Patient evaluation for metallic or electrical implants, devices, or foreign bodies before magnetic resonance imaging", section on 'Cardiovascular implantable electronic device'.)

EMERGENCY SURGERY — Emergency circumstances complicate care of the patient with a cardiac implantable electronic device (CIED) because there is inadequate time for preoperative assessment by the in-hospital CIED service or communication with the anesthesiology and surgical teams. (See 'Preoperative assessment' above.)

Patients having procedures superior to the umbilicus are at greatest risk, particularly if monopolar electrosurgery unit (ESU) use is likely. (See 'Risks of electromagnetic interference' above.)

Evaluation — A scar at the CIED insertion site or a palpable pulse generator reveals the presence and location of the device. A manufacturer's identification card with the type of device, model number, and current settings may be available from the patient or a family member (or found by emergency department [ED] personnel).

If a chest radiograph (CXR) is available, the type of device (ICD versus PM) and often the generator manufacturer can be identified on the image (image 2 and image 3).

If a 12-lead electrocardiogram (ECG) was not obtained in the preoperative period, the anesthesia monitoring equipment and chart paper recorder in the operating room may be used to generate a rhythm strip in multiple leads. The anesthesia monitor should be configured in the "diagnostic" bandpass mode, with "pacing" selected to best display the high-frequency pacing spikes. The ECG is examined to determine if the patient has atrial and/or ventricular pacing spikes. Pacing dependence is assumed if all beats are paced. In the absence of identifiable pacing artifacts, a consistently regular rhythm at a rate of 60, 65, or 70 beats/minute (bpm) usually indicates pacing. A complete 12-lead ECG can be recorded by using the operating room monitor and recording individual precordial leads from each of the six standard electrode positions [55].

If time allows, a magnet is applied to the device before surgery begins to determine whether this will produce the desired effect. This may be accomplished in the operating room after continuous monitoring of ECG and pulse oximeter plethysmography has been established, ideally with the chart paper recorder running. After the magnet is applied, the ECG recording and the intra-arterial catheter waveform, if available, are compared with the expected response to magnet application in patients with a PM (table 4) or ICD (table 5). Magnet application does not always produce the desired or expected response due to previous elective disabling of the magnet switch or malfunction of the CIED [9]. If this is suspected, the CIED should be interrogated as soon as possible to ensure that it is functioning properly, that the battery status is adequate, and to determine whether the magnet response is programmed off.

Management — When there is inadequate time for preoperative device interrogation and reprogramming for an emergency case where electromagnetic interference (EMI) is likely (see 'Device interrogation' above and 'Planning device management' above), it is essential to place transcutaneous pacing/defibrillator pads and to ensure continuous ECG and pulse oximeter plethysmography monitoring (figure 1) (see 'Monitoring' above and 'Placement of transcutaneous pacing/defibrillator pads' above). Prior to use of an ESU or other device that may cause EMI, a magnet is applied. If necessary, a nonsterile magnet can be placed in a sterile plastic sleeve and positioned over the CIED to effect changes in the programming of the device, as described above. (See 'Magnet application' above.)

Other aspects of emergency management with a magnet include:

●PM – For patients with a PM, magnet application will almost always initiate asynchronous pacing at a fixed rate with a fixed atrioventricular (AV) delay (table 4). Careful observation of the ECG rhythm is important to ensure that asynchronous pacing is not competing with the patient's intrinsic rhythm. (See 'Magnet application' above.)

●ICD – For patients with an ICD, application of a magnet will almost always suspend tachyarrhythmia detection and anti-tachyarrhythmia therapy. However, EMI may still cause ventricular oversensing and pacing inhibition (table 5). Careful observation of the ECG rhythm is essential to ensuring that profound bradycardia or asystole does not occur. (See 'Magnet application' above.)

EMI may be minimized by use of bipolar instead of monopolar ESU, or use of monopolar ESU in short, intermittent, and irregular bursts at the lowest feasible energy levels. (See 'Sources of electromagnetic and other interference' above and "Overview of electrosurgery", section on 'Avoid electromagnetic interference'.)

EMI might also be minimized by use of an appropriately positioned conventional dispersive electrode as opposed to an underbody dispersive electrode. (See 'Management of electromagnetic interference' above.)

POSTOPERATIVE MANAGEMENT — Cardiac implantable electronic devices (CIEDs) that were reprogrammed before surgery require reactivation of the original settings in the postoperative period before the patient leaves an intensive care unit or other closely monitored setting such as the post-anesthesia care unit (PACU) (algorithm 2) [6]. In some cases, hemodynamic instability or other changes in the patient's condition may necessitate adjustments, such as selection of a higher-paced heart rate or a more optimal atrioventricular (AV) delay.

Until CIED settings are restored, the patient should remain continuously monitored with both electrocardiography (ECG) and pulse oximetry plethysmography, and the transcutaneous pacing/defibrillator pads should be left in place. An external defibrillator with pacing capability should remain immediately available. (See 'Preoperative assessment' above and 'Monitoring' above and 'Placement of transcutaneous pacing/defibrillator pads' above.)

We suggest that postoperative interrogation of the CIED be performed if:

●The patient underwent emergency surgery without appropriate preoperative CIED evaluation. (See 'Emergency surgery' above.)

●There is suspicion that anti-tachyarrhythmia therapy might have been permanently disabled rather than temporarily suspended (eg, due to magnet use in an older device or due to outright failure).

Examples include:

•Observed delivery of inappropriate shocks or multiple appropriate shocks that may deplete the battery [14].

•Intraoperative exposure to strong electromagnetic interference (EMI) near the pulse generator. (See 'Magnet application' above.)

This practice is based on case reports of morbidity and mortality with failure to perform a postoperative CIED evaluation in such situations [14,51,69,70].

These suggestions for postoperative CIED evaluation are similar to those in the American Society of Anesthesiologists (ASA) advisory (table 1) [6]. Other approaches include recommendations from the Heart Rhythm Society (HRS), which suggest that immediate postoperative interrogation is needed only for hemodynamically unstable patients or when a CIED is exposed to significant EMI (eg, monopolar electrosurgery superior to the umbilicus) [7]. The Canadian Anesthesiologists' Society (CAS) and Canadian Cardiovascular Society (CCS) CAS/CCS guidelines recommend monitoring the patient until hemodynamic stability is assured, and suggest that postoperative device interrogation is routinely required only after thoracotomy [8]. The British Medicines and Healthcare products Regulatory Agency (MHRA) recommends contacting the patient's CIED clinic for support in order to confirm device functionality shortly after surgery (timeframe unspecified) [9].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Perioperative cardiovascular evaluation and management" and "Society guideline links: Cardiac implantable electronic devices".)

SUMMARY AND RECOMMENDATIONS

●Risks of electromagnetic interference – Function of cardiac implantable electronic devices (CIEDs) may be affected by electromagnetic interference (EMI), causing (see 'Risks of electromagnetic interference' above):

•Inhibition of needed antibradycardia pacing in a pacing-dependent patient.

•Delivery of inappropriate shock(s) or anti-tachyarrhythmia pacing by an implantable cardioverter-defibrillator (ICD).

•Direct damage to the CIED, altering its ability to deliver pacing or shocks.

●Preoperative assessment – Prior to elective procedures, a preoperative assessment of the patient with a CIED is necessary to (table 2 and algorithm 1) (see 'Preoperative assessment' above):

•Check the CIED or determine that a recent check was completed to confirm appropriate function. (See 'Device interrogation' above.)

•Determine if the patient is pacing-dependent, since pacing may be inhibited by EMI. (See 'Planning device management' above.)

•Determine whether CIED reprogramming with a programming machine or magnet application is necessary for the planned surgical procedure (table 3). (See 'Planning device management' above.)

•If magnet use is planned, determine the actual response and clinical implications of magnet application (table 4 and table 5). (See 'Magnet application' above.)

●Reprogramming versus magnet application – EMI is likely when there is planned use of an electrosurgery unit (ESU). This is potentially problematic if EMI use is superior to the umbilicus in patients with an ICD or those who are pacing-dependent. In such circumstances, CIED reprogramming to suspend anti-tachyarrhythmia therapy and/or initiate asynchronous pacing is advised. This can always be accomplished with a programming machine and can sometimes be accomplished by applying a magnet. (See 'Planning device management' above.)

Situations that necessitate reprogramming with a programming machine rather than magnet placement include (table 3 and algorithm 1) (see 'Reprogramming with a programming machine' above and 'Magnet application' above):

•Reprogramming an ICD to an asynchronous pacing mode

•Reprogramming a CIED to optimal settings in a patient whose cardiac function would be compromised by the proprietary preprogrammed magnet rate and asynchronous mode.

•Reprogramming any CIED when a magnet would interfere with sterility of the surgical field, is inaccessible, or might move after patient positioning.

●Intraoperative management – Other aspects of intraoperative management of the patient with a CIED include:

•Positioning transcutaneous pacing/defibrillator pads on the patient before reprogramming (and, in some cases, before surgical prepping and draping) (figure 1). (See 'Placement of transcutaneous pacing/defibrillator pads' above.)

•Continuous monitoring with both electrocardiography (ECG) and direct detection of mechanical systoles with pulse oximetry plethysmography or intra-arterial pressure waveforms. (See 'Monitoring' above.)

•Positioning the current dispersion pad of the ESU so the current path does not cross the CIED. Also, monopolar ESU is avoided, if possible. (See 'Management of electromagnetic interference' above.)

•For intraoperative emergencies requiring defibrillation or cardioversion, if a magnet was placed over an ICD it should be removed to reactivate the ICD's anti-tachyarrhythmia therapy, and all sources of EMI should be discontinued before attempting external (transcutaneous) defibrillation or cardioversion. If magnet removal does not immediately result in reactivation of the device with appropriate cardioversion or defibrillation, an external defibrillator should be employed using the previously applied transcutaneous pacing/defibrillator pads. (See 'Intraoperative emergencies' above.)

●Considerations for emergency surgery – For emergency surgery with potential for EMI superior to the umbilicus, a magnet is placed over a PM in a pacing-dependent patient to initiate asynchronous pacing, or over an ICD to disable anti-tachyarrhythmia therapy. However, a magnet will never cause an ICD to pace asynchronously, and profound bradycardia or asystole may still occur due to EMI-induced pacing inhibition in a patient with an ICD who is pacing dependent. The risk of EMI can be minimized by using bipolar instead of monopolar ESU, or by using monopolar ESU in short, intermittent, and irregular bursts at the lowest feasible energy levels. (See 'Emergency surgery' above.)

●Postoperative management – Reactivation of CIED function should be accomplished in the immediate postoperative period if reprogramming with a machine was performed, and postoperative CIED interrogation should be performed after emergency surgery that proceeded without preoperative evaluation, or in any patient with suspected CIED malfunction (algorithm 2). We monitor the patient continuously with both ECG and pulse oximetry plethysmography and leave the transcutaneous pacing/defibrillator pads in place until reactivation and proper function are confirmed. (See 'Postoperative management' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Marc A Rozner, PhD, MD, who contributed to earlier versions of this topic review.