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Cardiac Implantable Electronic DevicesPeter M. Schulman, MDEric C. Stecker, MD, MPH


Key Points

  • 1.

    Transvenous cardiac implantable electronic devices (CIEDs) include pacemakers (PMs), implantable cardioverter defibrillators (ICDs), and cardiac resynchronization therapy pacemakers (CRT-Ps) and defibrillators (CRT-Ds). In addition to delivering antitachycardia therapy, all modern transvenous ICDs and CRT-Ds have antibradycardia pacing capability (ie also function as a PM).

  • 2.

    CIEDs now also include the subcutaneous ICD (S-ICD) and leadless PM, which both function and respond to magnet application differently than their transvenous counterparts.

  • 3.

    Although patients with CIEDs frequently present for surgery, CIEDs are sometimes ignored in the context of the overall perioperative care plan, as many clinicians erroneously assume that magnet application will prevent any perioperative problem and correct any adverse issue that might arise.

  • 4.

    CIEDs are generally very reliable, but they do occasionally malfunction. Electromagnetic interference (EMI) from monopolar electrosurgery is the most common cause of CIED malfunction during surgery. Consequences of EMI can be serious, and failure to mitigate this risk might lead to patient injury and CIED damage. Even when a properly functioning CIED is perceived to be malfunctioning (“pseudomalfunction”), harm to the patient and/or CIED can occur.

  • 5.

    Prior to scheduled surgery, key CIED-related information should be obtained (i.e., CIED type, manufacturer, indication for placement, current settings, patient’s underlying rhythm) and proper CIED function should be confirmed. A de novo CIED interrogation is not always needed, as it is often possible to obtain this information from the patient’s most recent interrogation report. However, a de novo interrogation should be performed if a recent interrogation report is not available, or there is any concern about proper CIED function.

  • 6.

    Intraoperative CIED management is predominantly dictated by the likelihood of EMI. The risk of EMI is greatest when monopolar electrosurgery is used superior to the umbilicus, and very low when monopolar electrosurgery is used inferior to the umbilicus, provided the electrosurgery dispersive electrode is appropriately positioned to divert the current return path away from the CIED generator and leads.

  • 7.

    Underbody dispersive electrodes, that are placed directly on the operating table rather than affixed to the patient’ skin, are being used with increasing frequency. Since mounting evidence suggests the risk of EMI might be increased with underbody electrode use, consideration should be given to conventional rather than underbody dispersive electrode use for CIED patients undergoing surgery.

  • 8.

    If EMI is likely (i.e., monopolar electrosurgery use is planned superior to the umbilicus), a CIED should be made to pace asynchronously if the patient is pacing dependent, and the antitachycardia therapy of an ICD should be suspended. Additional programming changes that might be warranted include programming rate responsiveness and other pacing features that can mimic pacing system malfunction to off, since inappropriate pacing rates can create confusion and lead to patient injury. For major surgery, it is also sometimes prudent to increase a patient’s paced lower rate limit to optimize systemic oxygen delivery.

  • 9.

    Magnet application can often be used in lieu of reprogramming to cause a PM to pace asynchronously or suspend the antitachycardia function of an ICD. However, magnet behavior remains nonstandardized across manufacturers, and when programming changes are warranted, reprogramming rather than magnet use is generally the most reliable option. A magnet will never alter the pacing mode of an ICD.

  • 10.

    Any CIED that was reprogrammed for surgery should have its original settings restored. In some cases, new programming changes, such as a higher-paced heart rate or a more optimal atrioventricular delay, may also be warranted. The patient should remain in a monitored setting until any needed reprogramming has been accomplished.

Acknowledgments

Marc A. Rozner, PhD, MD, authored the prior edition of this chapter. We are saddened by his untimely death and wish to acknowledge his extensive expertise and vast contributions on this subject matter.

The first implantable, battery-powered pacemaker (PM) was introduced in the late 1950s. This invention revolutionized the treatment of lethal electrical conduction abnormalities, and ultimately improved quality of life for people with conditions such as atrioventricular (AV) dyssynchrony, chronotropic incompetence, and atrial fibrillation (AF). The development of the implantable cardioverter defibrillator (ICD), which received the Food and Drug Administration (FDA) approval in 1985, extended this technology to patients who have experienced or are at risk for malignant ventricular arrhythmias or sudden cardiac death. By the late 1990s, in addition to delivering antitachycardia (i.e., high voltage) therapies, ICDs were also capable of performing the functions of a conventional PM (i.e., antibradycardia pacing).

Since 1958, more than 3000 PM models have been marketed in the United States alone. Although it is difficult to determine the current prevalence of these cardiac implantable electronic devices (CIEDs) (i.e., PMs, ICDs, cardiac resynchronization therapy [CRT] devices, implantable loop recorders), and the incidence of CIED use since the mid-2000s has not been extensively studied, in the United States, there are likely at least 3 million patients with a CIED, and recent data suggest that several hundred thousand CIEDs continue to be implanted annually. The incidence of patients with a CIED undergoing surgery is also unknown, but this number is likely also substantial, given the large number of these devices, that their incidence is highest in elderly patients with multiple comorbidities, and since more than 80 million surgical procedures are performed in the United States each year. ,

Despite their high prevalence, many factors conspire to create confusion regarding CIEDs and their perioperative management. During the last several decades, CIED complexity, features, data storage abilities, and size minimization have rapidly evolved. As this technology has advanced, the delineation between different types of CIEDs has become less clear. For example, every transvenous ICD (TV-ICD) currently implanted has robust antibradycardia pacing capability, and patients, the news media, and even physicians often misidentify a PM as an ICD, and vice versa. Although this mistake might seem innocuous, it can lead to adverse intraoperative events, since magnet application will cause most PMs to pace asynchronously, but will never change the pacing mode of an ICD. The more recent development of the subcutaneous ICD (S-ICD) and leadless PM have generated even more complexity and confusion. S-ICDs are larger than their transvenous counterparts, cannot provide antitachycardia or sustained antibradycardia pacing, and generally have higher defibrillation thresholds (DFTs). Leadless PMs also behave differently than their transvenous counterparts with respect to some key features and their response to magnet application. Implantable loop recorders might also create confusion as they are much less frequently encountered. Although these devices have no therapeutic capability (and thus will not be discussed further herein), their capability to detect both tachyarrhythmias and bradyarrhythmias remains underutilized when these patients are evaluated preoperatively.

Although patients with CIEDs frequently present for surgery, CIEDs are often ignored in the context of the overall perioperative care plan, as many clinicians erroneously assume that the mere application of a magnet will prevent any perioperative problem and correct any adverse issue that might arise. The preoperative consultation process can occasionally lead to improper advice as well, and a mounting number of publications suggest that adverse outcomes occur when patients with CIEDs receive suboptimal perioperative care.

Because of the complexity of these devices and the challenges they create during the perioperative period, advisories have been developed by professional societies including 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 British Heart Rhythm Society (BHRS). Table 3.1 compares and contrasts these statements.

TABLE 3.1
Comparison of Perioperative CIED Societal Recommendations
(Modified from Rozner MA. Implantable cardiac pulse generators: pacemakers and cardioverter-defibrillators. In: Miller RD, ed. Miller’s Anesthesia . 8th ed. Philadelphia: Saunders; 2015; Schulman, PM. Perioperative management of patients with a pacemaker or implantable cardioverter-defibrillator. In: Post TW, ed. UpToDate . Waltham, MA: UpToDate Inc.)
Preoperative Recommendation Intraoperative Magnet Use ESU Dispersive Electrode Placement Postoperative Recommendation Emergency Surgery
ASA De novo interrogation likely not needed provided CIED was interrogated within 3–6 months prior to scheduled surgery and shown to be functioning properly. When appropriate, altering the pacing function of a PM to an asynchronous pacing mode may be accomplished by applying a magnet. When appropriate, suspending the antitachycardia function of an ICD may be accomplished by applying a magnet; however, indiscriminate magnet use over an ICD is discouraged. Prevent presumed current path from passing through or near the CIED system. Insufficient evidence to determine impact of using an underbody dispersive electrode as compared with a conventional dispersive electrode on the risk of EMI. Postoperative interrogation may not be needed in low-risk situations (eg appropriate preoperative interrogation, no EMI-generating devices used during procedure, no perioperative reprogramming, and no problems identified during the procedure). Interrogation should occur within 30 days after surgery if not performed during the immediate postoperative period. Interrogate CIED after emergency surgery if preoperative interrogation was not performed.
HRS PM interrogation within 12 months, ICD interrogation within 6 months, and CRT interrogation within 3–6 months prior to scheduled surgery. CIED physician must provide prescription for perioperative care. Magnet use recommended to produce asynchronous pacing (where needed in pacing-dependent patients) and to disable ICD antitachycardia therapy (provided patient position does not interfere with magnet access or observation). Prevent presumed current path from crossing the chest/CIED system. For most cases involving EMI (especially those inferior to the umbilicus and where no preoperative reprogramming was performed), interrogation can occur within 1 month as an ambulatory procedure. For reprogrammed CIEDs, hemodynamically challenging cases, cardiothoracic surgery, RFA, and external cardioversion, interrogation needed prior to transfer from cardiac telemetry. Use 12-lead ECG to identify pacing need; presume dependence if 100% pacing.
Cardiac monitoring until postoperative interrogation.
Use magnet to produce asynchronous pacing (if PM), or to suspend antitachycardia therapy (if ICD).
CAS-CCS De novo interrogation likely not needed, but CIED physician must provide prescription for perioperative care. Where reasonable, magnet use suggested for asynchronous pacing (where needed in PM patients) and disabling ICD high-energy therapy. No mention. Clear plan for postoperative care established prior to elective case. Use 12-lead ECG to identify pacing need; assume pacing dependence if 100% paced; careful monitoring to determine if magnet application to a PM produces asynchronous pacing with an acceptable hemodynamic profile; asynchronous pacing might be indicated in a pacing-dependent patient if ESU interference is observed
If a reprogramming machine cannot be employed before or during surgery, EMI may be minimized by use of bipolar instead of monopolar ESU, with short, intermittent bursts at the lowest feasible energy levels.
BHRS Preoperative contact with the pacemaker/ICD follow-up clinic for evaluation and perioperative recommendations. Magnet use is only acceptable in emergency situations when deactivation with a programmer is not possible. Ensure the return electrode is anatomically positioned, so the current pathway between the diathermy electrode and return electrode is as far away from the generator and leads as possible. Follow-up clinic to prescribe postoperative follow-up. Attempt to follow routine steps; postoperative interrogation as soon as possible.
Magnet might create asynchronous pacing.
Magnet might prevent ICD inappropriate discharge.
ASA , American Society of Anesthesiologists Perioperative Advisory; BHRS , British Heart Rhythm Society; CAS-CCS , Canadian Anesthesiologists’ Society/Canadian Cardiovascular Society Joint Position Statement; CIED , cardiac implantable electronic device; CRT , cardiac resynchronization therapy (any CIED that has right and left ventricular pacing capability); ECG , electrocardiogram; EMI , electromagnetic interference; ESU , electrosurgical unit (“Bovie”); HRS , Heart Rhythm Society; ICD , implanted cardioverter defibrillator; PM , pacemaker; RFA , radio frequency ablation.

This chapter provides an overview of CIEDs and their perioperative care. It begins by discussing the basic function of CIEDs, their indications for use, and modes of operation. It then reviews recommendations for the optimal perioperative management of these patients.

Cardiac Implantable Electronic Device Function

Transvenous (i.e., conventional) CIEDs include PMs, ICDs, and CRT devices (CRT-P [pacemaker], CRT-D [defibrillator]) ( Fig. 3.1A –D). These systems all consist of a pulse generator that is most often implanted underneath the left clavicle in a subcutaneous pectoral pocket, and one to three leads that are implanted into the right atrium (RA), right ventricle (RV), and/or coronary sinus (CS). An atrial lead is used for sinus node dysfunction as well as atrial monitoring. An RV lead is placed for AV block and monitoring RV rhythm. Patients with sinoatrial node disease, but without AV block at the time of implant, often still receive an RV lead because AV block might occur later. A CS lead is used to pace the left ventricle for CRT; the position of the CS lead is best determined by lateral (rather than posteroanterior) chest radiograph ( Fig. 3.1D ). The RV lead of a TV-ICD contains one or two shock coils for antitachycardia therapy (including antitachycardia pacing [ATP] and shocks). On chest x-ray (CXR), the presence or absence of a shock coil can be used to distinguish an ICD from a simple PM.

Figure 3.1, (A) Boston Scientific dual-chamber transvenous pacemaker is shown. This patient presented with coronavirus disease 2019 pneumonia and new complete heart block. (B) Medtronic dual-chamber transvenous implantable cardioverter defibrillator (ICD) is shown. This patient had an out of hospital cardiac arrest secondary to monomorphic ventricular tachycardia, and subsequently had this ICD placed for secondary prevention of sudden cardiac death. (C) Medtronic cardiac resynchronization therapy pacemaker (CRT-P) is shown. This patient had atrioventricular node dysfunction and a high right ventricular pacing burden. The lead in a branch of the coronary sinus vein (ie middle cardiac vein) is used to pace the left ventricle. The absence of a shock coil identifies this device as a CRT-P as opposed to cardiac resynchronization therapy defibrillator (CRT-D). (D) Lateral view of the same Medtronic cardiac resynchronization therapy pacemaker (CRT-P) is shown.

As previously noted, in addition to delivering antitachycardia therapy, all modern TV-ICDs perform all the functions of a conventional PM (i.e., also have antibradycardia capability). With respect to the detection and delivery of antitachycardia therapy, ICDs essentially measure each cardiac R-R interval and categorize the rate as normal, too fast (short R-R interval), or too slow (long R-R interval). An antitachycardia event is initiated when a prescribed number of short R-R intervals within a time period are detected. Most TV-ICDs will then determine whether ATP (less energy use, better tolerated by the patient) or shock is indicated, depending on the presentation and device programming. If the criteria for shock are met, then an internal capacitor is charged. Most ICDs are then programmed to reconfirm ventricular tachycardia (VT) or ventricular fibrillation (VF) after charging to prevent inappropriate shock delivery. Some TV-ICDs will deliver immediate ATP while charging the capacitor in preparation for a shock. Typically, ICDs have six to eight therapies available for each type of event (VT, fast VT, VF), and some of these therapies can be repeated before moving to the next higher energy sequence. Thus, ICDs sometimes deliver many shocks per event. Once an ICD delivers any shock therapy, no further ATP will be administered.

Inappropriate antitachycardia therapy, (ie when ATP or shocks are delivered for a rhythm other than VT or VF), occurs in 8% to 40% of ICD patients. AF with rapid ventricular response and supraventricular tachycardia (SVT) are the most common causes of inappropriate therapy. , ICDs have programmable features to differentiate VT from SVT, which are given in Table 3.2 . Another important cause of inappropriate therapy is in-hospital-induced electromagnetic interference (EMI). This problem appears to be implicated in about 4% of these cases and is usually preventable. Whether inappropriate shocks cause patient injury remains a subject of considerable debate, but a significant number of patients who receive inappropriate antitachycardia therapy demonstrate elevated troponin levels in the absence of an ischemic event, and a death has been reported. Additionally, in a number of trials, both appropriate and inappropriate antitachycardia therapy have been associated with increased mortality, whether ATP , or shock. , , ,

TABLE 3.2
VT vs SVT Discriminators
Feature Description Major Weaknesses
Heart rate and duration Minimum heart rate and duration required to classify the event as a tachyarrhythmia. Very simple, often not accurate without the use of additional features.
Suddenness of onset Measures the abruptness of rhythm onset (in general, the onset of VT is abrupt while the onset of SVT has sequentially shortening R-R intervals). Only discriminates sinus rhythm, cannot discriminate SVT from VT.
Interval stability/regularity Measures the minimum amount of irregularity needed to classify the rhythm as atrial fibrillation (in general, the R-R interval of VT is relatively constant while the R-R interval of AF is variable). Some VTs are irregular, especially at initiation.
At very rapid rates, AF can regularize.
AV relationship Compares the atrial and ventricular rhythms to determine whether there is AV association or dissociation (in general, a hallmark of VT is AV dissociation). VT can have retrograde P waves with 1:1 V:A relationship.
Undersensing in SVT or atrial flutter can mimic 1:multiple V:A relationship.
Electrogram morphology Measures whether the QRS morphology during the tachyarrhythmia matches or differs from the patient’s intrinsic QRS morphology (in general, the morphology of VT should be different from the morphology of the patient’s intrinsic rhythm). Sinus rhythm template can change over time or with different physiologic conditions.
SVT with aberrancy does not match sinus rhythm template.
Mispositioned onset of sense electrogram can cause mismatch of template that would otherwise match.
This table shows a variety of criteria that modern ICDs use to differentiate VT from SVT.
A , Atrial; AF , atrial fibrillation; AV , atrioventricular; SVT , supraventricular tachycardia; V , ventricular; VT , ventricular tachycardia.

The newest CIED systems include the S-ICD ( Fig. 3.2 ) and leadless PM ( Fig. 3.3 ). The S-ICD, which gained US FDA approval in 2012, has two main components, a pulse generator and subcutaneously tunneled single-coil electrode that allows the device to sense tachyarrhythmias and deliver a shock when indicted. Because the electrode is implanted subcutaneously rather than transvenously, the potential for most acute (e.g., pneumothorax, lead dislodgement, perforation) and longer-term (e.g., lead failure, infection) complications appear to be reduced. , In fact, the largest prospective trial to date comparing TV-ICD to S-ICD outcomes over a 4-year period found a higher cumulative incidence of device-related complications in the TV-ICD group but a higher cumulative incidence of inappropriate shocks in the S-ICD group. In addition to a higher risk of inappropriate shocks, the major downside of the S-ICD is its limited functionality; high-voltage output is fixed at 80 J (ie nonprogrammable), and the system does not provide antitachycardia or antibradycardia pacing (aside from brief postshock pacing), nor can it provide biventricular pacing for heart failure (ie CRT). It may also not be optimal for patients with recurrent monomorphic VT because this rhythm can often be terminated with ATP, a feature that is also not available in current S-ICDs.

Figure 3.2, Boston Scientific subcutaneous implantable cardioverter defibrillator (S-ICD) is shown. This patient initially had a transvenous ICD placed for secondary prevention. The transvenous ICD was then extracted because of a lead malfunction and replaced with this S-ICD. The S-ICD cannot deliver antitachycardia pacing (ATP), and has very limited antibradycardia pacing (ie it paces for approximately 30 seconds after delivering a shock).

Figure 3.3, Medtronic leadless pacemaker is shown. This patient had sick sinus syndrome and second-degree heart block for which a transvenous pacemaker was initially placed. The transvenous pacemaker then became infected; thus, it was extracted and this leadless pacemaker was ultimately placed. This leadless pacemaker cannot provide atrial pacing and has no magnet response.

The first leadless PM (Medtronic Micra VR; Medtronic Inc., Minneapolis, MN), which received FDA approval in 2016, is about one-tenth the size of a conventional PM and is implanted through a catheter to provide single-chamber RV pacing. The Medtronic Micra AV was subsequently developed, and FDA approved in 2020. In addition to RV pacing, this device utilizes an accelerometer to sense mechanical atrial activity and maintain AV synchrony (i.e., it can be programmed to the VDD pacing mode). In the MARVEL 2 (Micra Atrial tRacking using a Ventricular accELerometer 2) trial, AV synchrony in Micra AV patients was achieved 89.2% of the time in the VDD mode, compared with 26.8% of the time in the VVI mode. Leadless PMs from two other manufacturers (Nanostim; St. Jude Medical Inc., Sylmar, CA and EMPOWER; Boston Scientific, Marlborough, MA]) have been developed. Nanostim was subsequently discontinued and EMPOWER is not yet FDA approved. Of particular note, the magnet behaviors of S-ICD and leadless PMs are different from their traditional transvenous counterparts.

Cardiac Implantable Electronic Device Indications

The American College of Cardiology (ACC), American Heart Association (AHA), and HRS have issued guidelines on indications for CIED placement. , An in-depth review of the indications for implanting CIEDs is beyond the scope of this chapter, however, a general overview of the most common indications follows and is summarized in Box 3.1 .

BOX 3.1
Common Indications for CIED Implantation
AV , atrioventricular; VT , ventricular tachycardia; VF , ventricular fibrillation; LVEF : left ventricular ejection fraction.

Pacemaker

  • Symptomatic sinus node dysfunction without a reversible cause

  • Symptomatic Mobitz 1 second-degree AV block without reversible cause or vagal etiology

  • Mobitz 2 second-degree AV block, high-grade AV block or third-degree AV block without reversible cause or vagal etiology

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