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Information

  1. CIEDs
    1. Increasing numbers of patients with permanent pacemaker (PPM) and ICD devices are undergoing noncardiac surgery. Familiarity with the indications, functions, and perioperative management of these devices is essential.
    2. PPMs are utilized in a variety of conditions where the patient’s native conduction is compromised or inadequate, including from structural or ischemic heart disease, infiltrative diseases, and postprocedural alterations in conduction pathways, among many others.
    3. ICDs have significantly improved the mortality of patients at high risk for sudden cardiac death. The four key ICD functions are antitachycardia pacing (ATP), cardioversion, defibrillation, and backup pacing. The conventional ICD is implanted in the upper chest and is connected to one or two defibrillating transvenous leads that also have sensing and pacing capabilities.
    4. Current PPM and ICD devices include traditional subcutaneous generators with transvenous leads that have single or dual chamber sensing and pacing and possibly antitachycardia therapies (ie, cardioversion-defibrillation, antitachycardia pacing), as well as newer technologies including leadless pacemakers and subcutaneous ICDs (see below).
    5. Indications for PPM
      1. Symptomatic bradycardia.
      2. Third-degree (complete) AV block.
      3. Type II, second-degree AV block.
      4. Cardiac resynchronization therapy. Biventricular pacing to synchronize RV and LV depolarization in patients with symptomatic HFrEF (left ventricular ejection fraction [LVEF] ≤ 35%) with sinus rhythm and interventricular conduction abnormality (left bundle branch block [LBBB], QRS ≥ 150 ms).
    6. Indications for ICD
      1. Primary prevention in patients at high risk for sudden cardiac death (LVEF ≤ 35%, at risk for ventricular tachyarrhythmias).
      2. Secondary prevention in patients with prior sudden cardiac death or unstable ventricular arrhythmias.
  2. Pacemaker nomenclature
    1. A standard five-letter code is used to describe pacemaker settings and function. The first letter designates the chamber paced (O, none; A, atrium; V, ventricle; D, dual [both atrium and ventricle]).
    2. The second letter describes the chamber sensed (O, none; A, atrium; V, ventricle; D, dual).
    3. The third letter describes the pacemaker’s response to sensed events (O, none; I, inhibition of pacemaker output; T, triggering of pacemaker output; D, dual response: spontaneous atrial and ventricular activity inhibit atrial and ventricular pacing and atrial activity triggers a ventricular response).
    4. The fourth letter indicates the presence or absence of rate modulation (O, no rate modulation; R, rate modulation present).
    5. The fifth letter specifies the presence and type of multisite pacing (O, none; A, more than one stimulation site in either atrium, stimulation sites in each atrium, or a combination of the two; V, more than one stimulation site in either ventricle, stimulation sites in each ventricle, or a combination of the two; D, any combination of A and V).
    6. For example, a VVI pacemaker will sense and pace the ventricle yet will be inhibited and will not fire if an R wave is detected. A DDD pacemaker senses and paces both the atrium and ventricle. A VVIRV pacemaker has ventricular inhibitory pacing with rate modulation and multisite ventricular pacing. This mode is often used in patients with heart failure, chronic atrial fibrillation, or intraventricular conduction delay. A DDDRD pacemaker has dual-chamber pacing with rate modulation and multisite pacing in both the atrium (or atria) and ventricle(s).
  3. Considerations for magnet application to CIEDs
    1. Applying a magnet to most pacemakers (excluding leadless pacemakers) will cause them to function in an asynchronous mode (eg, VOO), which may be desirable in the pacing-dependent patient undergoing a procedure with possible electromagnetic interference (EMI). However, the magnet response of a pacemaker is most reliably determined by device interrogation. Typically, normal pacemaker function is restored upon removal of the magnet. Use of a magnet during surgical procedures is necessary only if a patient that has not undergone preoperative interrogation and reprogramming is pacing dependent and inhibition of pacemaker output is noted coincident with EMI. If used, the magnet should be placed directly over the pacemaker. It is best to tape the magnet in place to avoid inadvertent dislodgment. Magnet application should be used with caution, as asynchronous pacing has the potential to cause unstable arrhythmias through the R-on-T phenomenon if ventricular pacing output occurs during the relative refractory period of cardiomyocyte repolarization.
    2. All ICDs are exquisitely sensitive to EMI associated with electrocautery above the level of the umbilicus. EMI can be interpreted by an ICD as ventricular fibrillation leading to inappropriate shocks. Inappropriate shocks can be difficult to detect in an anesthetized and paralyzed patient and can lead to battery depletion.
    3. Most ICDs are designed to suspend antitachycardia therapies in response to a magnet application and resume function upon removal of the magnet. Some models of St. Jude and Boston Scientific ICDs can be programmed to ignore magnet application. Furthermore, some older models of Boston Scientific ICDs may be programmed to suspend function with magnet application but require magnet removal and reapplication to resume function. It is best to have ICD function interrogated preoperatively to determine its settings and response to magnet application.
    4. Indiscriminate use of magnets for ICDs is best avoided. It is preferable to reprogram and disable antitachycardia therapies while taking steps to prepare for prompt treatment of any unstable arrhythmia as described below. Also, magnet application to ICDs does not change pacing to an asynchronous mode, and pacing-dependent patients should have the device reprogrammed to an asynchronous mode if indicated.
  4. Leadless pacemakers
    1. CIED technology is rapidly evolving, and there is currently only one leadless pacemaker system available (Medtronic Micra). It comprises of a small generator with contained sensing and pacing electrodes, which is implanted (and removed) directly into the RV via a femoral transcatheter approach. The battery life is approximately 8-12 years.
    2. This system eliminates the need for transvenous leads and subcutaneous pockets, reducing risks of infection and lead-related problems, which can lead to perforation, venous occlusion, tricuspid regurgitation, oversensing, and infection. Major risks of the device itself include perforation, dislodgement and embolization, and tamponade.
    3. The leadless system is designed predominantly for bradyarrhythmias with functional pacing modes of VVI-R, VVI, and VOO. It has a baseline/reset mode of VVI at 65 bpm and is MRI conditional when set in “SureScan” mode (VOO/OVO setting).
    4. There are currently no consensus societal guidelines on the perioperative management of such devices, but the same general principles for other CIEDs described below should apply, with the following unique considerations:
      1. The Medtronic Micra leadless system does not have a Hall sensor; thus, it cannot detect the presence of a magnet and will not switch to an asynchronous mode if a magnet is applied. It requires the use of the leadless programmer to change the settings of the device.
      2. Therefore, consultation with a specialist with the knowledge, equipment, and ability to interrogate the device and reprogram to an appropriate setting for the given clinical circumstance is necessary. There is some evidence to suggest that given its location and sensitivity, electrocautery may not be detected by the Micra device and thus would not need perioperative reprograming.
    5. Wireless ultrasound endocardial pacing, a system which involves a subcutaneous generator and endocardial receiver used with a traditional CIED, is another system which may be seen more in noncardiac surgery patients.
  5. Subcutaneous ICDs (S-ICDs)
    1. New devices that include a subcutaneous generator implanted in the left lateral chest with a tunneled subcutaneous parasternal lead are available for patients with indications for an ICD who have inadequate vascular access, very high risk of infection, or for very young people with a long life-expectancy. These devices avoid the complications associated with transvenous leads. S-ICDs have a battery life of approximately 7 years, can withstand external cardiopulmonary resuscitation (CPR), and can be implanted under monitored anesthesia care.
    2. Limitations include the absence of bradycardia pacing, antitachycardia pacing, or cardiac resynchronization therapies. Unlike traditional ICDs, the S-ICD does not contain any permanent pacemaker functions except a 30-second backup pacing function immediately following a shock (VVI at 50 bpm). The generator is larger than traditional ICDs and delivers a higher energy shock of 80 J. It is susceptible to the same oversensing problems from EMI as traditional ICDs, which could lead to inappropriate shocks.
    3. Currently available S-ICDs respond to external magnet application by temporarily suspending shock therapy while the magnet is applied, with resumption of the permanent settings on removal of the magnet. However, the lateral location of the device and off-centered placement of the magnet may make magnet application more challenging than traditional anteriorly located ICD generators.
  6. Preoperative evaluation and preparation
    1. Determine if a CIED is present by conducting a focused history and physical examination and reviewing any available imaging or cardiology reports.
    2. Determine the type, manufacturer, primary indication, and if the patient is pacing dependent (eg, prior AV nodal ablation, no spontaneous ventricular activity noted on prior interrogation, or concerning history such as syncope related to symptomatic bradycardia).
    3. Determine the current device settings and status (ie, properly functioning generator, leads if present, and battery life) by patient history, electrophysiology records, and ECG. Device interrogation is the only reliable method for determining the settings and battery function of the device.
    4. If the information is not readily available, the manufacturer and model number may be obtained from a radiograph of the generator. The manufacturer of the device must be identified in order to be able to program the pacemaker, as each manufacturer has a unique programming device. Determine whether rate modulation is active. Also, determine the response of the device to a magnet.
    5. Determine if EMI is likely (sources include monopolar electrosurgery or radiofrequency ablation superior to the umbilicus, transcutaneous electrical nerve stimulation, lithotripsy, magnetic resonance, radiofrequency identification devices, and electroconvulsive therapy).
      1. If EMI is likely, reprogram to asynchronous pacing in patients who are pacing dependent, and suspend any antitachycardia therapies if an ICD is present. Rate-responsive mode should also be disabled to prevent inappropriate tachycardia.
      2. Continuously monitor patient and ensure that temporary backup pacing and/or defibrillating methods are immediately available
  7. Intraoperative management
    1. Modern pacemakers are extremely resistant to EMI. If interference does occur, the pacemaker output may be inappropriately inhibited or the pacemaker may be reset to a committed pacing mode (ie, DOO or VOO).
    2. Resetting of pacemakers by EMI will produce asynchronous pacing that can be noted on the ECG.
    3. Intraoperative exposure of the device to EMI can be reduced by placing the current return pad (“grounding pad”) in a location on the patient such that the current path from the electrocautery or radiofrequency ablation catheter does not pass near the pulse generator or leads. Other measures include the use of short, intermittent, irregular bursts at the lowest possible energy level and the use of a bipolar electrocautery system or an ultrasonic (harmonic) scalpel. During lithotripsy, the beam should not be focused near the generator.
    4. Monitor heart rate during EMI with a pulse oximeter, arterial line, precordial or esophageal stethoscope, or a finger on the pulse.
    5. For procedures or diagnostic tests involving MRI, it is essential to follow institutional protocols, and in the event that an external defibrillator, device programmer, or any other MRI unsafe equipment is necessary, the patient should be removed from the MRI area prior to use of these devices.
    6. Prior to any MRI scan in patients with MRI conditional devices, the device should be interrogated as described above, antitachycardia therapies should be suspended, and asynchronous pacing should be activated in pacing-dependent patients.
    7. Avoid using radiofrequency identification devices in close proximity to CIEDs, and ensure continuous monitoring for signs of EMI to allow for prompt discontinuation if interference is noted.
    8. For electroconvulsive therapy (ECT), take the same considerations as above including suspending antitachycardia therapies and switching to an asynchronous mode in pacing-dependent patients, while being prepared to promptly manage any sinus tachycardia or ventricular arrhythmias that can be associated with ECT.
    9. Postoperative evaluation of pacemaker function is recommended by most manufacturers if electrocautery is used or if settings are changed perioperatively.
  8. Temporary perioperative pacing and cardioversion-defibrillation options
    1. Transcutaneous. External pacing and cardioversion-defibrillation can be performed via large pads placed on the anterior and posterior thorax. This is an easy and inexpensive method of ventricular pacing and antitachycardia therapy. Avoid placing pads directly over subcutaneous generators.
    2. Transvenous
      1. A temporary pacing electrode can be inserted via a central vein into the heart.
      2. Various pulmonary artery catheters that have pacing options exist (see Chapter 15).
    3. Transesophageal. The LA can be paced with a pacing probe placed in the esophagus. Transesophageal pacing requires intact AV nodal conduction.
  9. Emergency external cardioversion or defibrillation
    1. If unstable arrhythmias occur and a magnet is being used to disable antitachycardia therapies of an ICD, immediate steps should be to terminate the source of EMI and remove the magnet from the ICD, which should resume antitachycardia therapies usually within 10 seconds.
    2. If after removal of the magnet there is not prompt restoration of antitachycardia therapies with appropriate response to any arrhythmia, or if the antitachycardia therapies were suspended by device interrogation preoperatively, advanced cardiac life support (ACLS) guidelines including external defibrillation should be followed.
      1. If possible, avoid placing pads directly over the generator to minimize current flow through the generator and the leads.
      2. Use the clinically appropriate energy level regardless of the presence of a CIED.
      3. Any device should be immediately interrogated after external cardioversion/ defibrillation, as device reset or malfunction is possible after external electrical therapy.
  10. Postoperative management
    1. Ongoing monitoring of rate and rhythm with electrocardiogram and pulse oximetry should continue in the immediate postoperative period.
    2. If the device was reprogrammed periprocedurally, ensure that backup pacing and cardioversion-defibrillation methods are readily available if indicated until permanent settings are restored.
    3. Have the device interrogated immediately if there is any concern for inappropriate or unreliable device settings or function (eg, emergency surgery without thorough preoperative evaluation, concern for disabled rather than suspended antitachycardia therapy from magnet application in an older device, observed or suspected shocks from device intraoperatively, or any concern for malfunction from EMI, physical disruption, or large fluid shifts).