Perioperative management of pacemakers and implantable cardioverter defibrillators (ICDs) is neither trivial nor easy. These devices, known as cardiovascular implantable electronic devices, are complicated, and there are too many exceptions to allow formulation of simple rules for straightforward management. A prime example of complexity as it applies to the operating room is that of magnet placement. On a pacemaker, a magnet is expected to yield asynchronous pacing, but this response to a magnet can be disabled. With ICDs, a magnet is expected to prevent the device from delivering therapy to tachycardic arrhythmias, but this response can be disabled in the devices manufactured by at least 2 companies (Boston Scientific, St. Jude). Emergency surgery may require the use of a magnet, even if a magnet would not be preferred under ideal circumstances. Therefore, understanding the utility and limitations of using a magnet is valuable.
The report of 3 cases by Schulman and Rozner1 in this issue of the journal present dramatic examples of magnet placement that either had unexpected results (inadequate pacemaker capture) or failed to provide the expected disabling of tachyarrhythmia therapy. Curiously, all 3 reports involve Boston Scientific devices, but the reader is cautioned that the problems observed in the case reports could occur with devices from other companies.
One could write off these cases as being rare, but that would be missing the point. The authors are correct: the blithe assumption that a magnet is the magic cure-all in the perioperative management of these devices is a fallacy, and a more systematic, structured approach is required. Because devices have so much programmable flexibility of function, it is not enough to have a device checked preoperatively to see that the battery is good and that the device is functioning properly. In addition, it is important to determine exactly how the device should be managed during surgery.2,3
The decision to use a magnet versus reprogramming the device at the time of surgery involves many considerations, including whether the surgery is elective or emergent and whether electromagnetic interference (EMI) is likely to be detected by the device. If significant EMI is likely, and the device is an ICD, then clearly activation of tachyarrhythmia therapy must be prevented. In that case, will a magnet suffice? Magnet application to an ICD is only tenable if it is known ahead of time that the device is programmed to respond to the magnet. Moreover, a magnet may not be the best method for disabling tachyarrhythmia therapy since magnets can move and lose contact with the ICD. Loss of magnet contact with the ICD may not be apparent to the clinician, since proper magnet application may not cause tones to be emitted by the device, and will not alter the pacing function of the device. If the patient has an ICD and is also pacer dependent, and extensive EMI is likely, then reprogramming is mandatory, since placement of a magnet on an ICD will not cause an ICD to switch to asynchronous pacing.
If the device is only a pacemaker, asynchronous pacing can usually be achieved with a magnet. The effect of a magnet on the pacemaker can and should be tested by the anesthesia team before surgery. However, magnet-induced asynchronous pacing rates vary among manufacturers (Biotronik: 90, Boston Scientific: 100, Ela/Sorin: 96, Medtronic: 85, St. Jude: 98.6 or 100). A high heart rate may not be appropriate for all patients, especially those with coronary disease, valvular heart disease, or some forms of cardiomyopathy. Even if the patient is not pacing dependent, in which case EMI is less of a concern, consideration has to be given as to whether other features of the device should be disabled, such as rate responsiveness or noise reversion (conversion to asynchronous pacing if the device detects EMI). The preceding considerations beg for participation by the anesthesia team in the decision making about perioperative device management, particularly when close control of the heart rate is important.
A common problem with the perioperative decision-making process about device management is a lack of clear ownership of the process. The device manufacturers have generally reduced the involvement of their representatives in perioperative device management. Furthermore, the use of company representatives to reprogram the devices in the absence of a prescription by a competent hospital practitioner may raise legal issues because the company representatives typically do not have hospital privileges.2 Cardiologists and cardiology midlevel practitioners rarely have the time and often have little interest in rushing to the operating room to interrogate and manage a device. Anesthesiologists only rarely have adequate knowledge and training to reprogram the devices independently.
In short, we believe that an organized, structured approach to perioperative device management is the exception, not the rule. For the past 2 years at the University of Washington, a team of specially trained anesthesiologists has been interrogating devices just before surgery, reprogramming the devices when necessary, and providing education and recommendations to the anesthesia team (e.g., magnet use, what to expect from the device).4 If reprogramming is performed, the same team restores the original settings after surgery. This service started as a response to perceived delays in surgery due to the variable availability of cardiology personnel, but has led, in our opinion, to improved patient care and better understanding of these devices by the anesthesia providers.
The involvement of specially trained anesthesiologists to manage devices is not practical in most hospitals, but other options exist. Patients can be sent to a device clinic or the managing cardiologist with the specific goal of developing a plan for perioperative device management. This process can be enhanced if we as anesthesiologists can provide the cardiologist with the important details of the case, such as the location and extent of expected cautery use, and how stressful the surgery is likely to be to the patient. Should there be a need for reprogramming as determined by a specially trained provider, then there is at least the opportunity to make arrangements in advance. We are aware of hospitals where an organized, structured process for perioperative device management by device clinics and midlevel providers is the norm.
Lastly, we believe that anesthesiologists can and should become more knowledgeable about the perioperative management of devices. By this we do not necessarily mean that anesthesiologists should be trained on a widespread basis to program devices. Anesthesiologists should strive to understand the basic features of the devices and be able to perform basic clinical evaluation, especially in the setting of an emergent surgery.5 The ICD can be distinguished from a pacemaker via the patient or medical record, or by a chest x-ray because the ICD coils are much bigger and more radiopaque than the rest of the lead. A magnet can be placed on the device as a test before surgery. A pacemaker programmed to respond to magnet placement will usually produce asynchronous pacing beats that confirm the device is a pacemaker, allow confirmation of capture, and permit evaluation of the status of the battery (for all pacemakers, the magnet-associated pacing rate decreases as the battery becomes depleted, but the details are manufacturer specific). If the device is an ICD, then magnet placement often results in at least a short period of time when tones are emitted from the device; the implication of these tones varies depending on the ICD brand, model and programming.a If no tones are heard, the ICD has either failed to respond to the magnet or it is an ICD that does not emit tones (e.g., St. Jude, Biotronik). Unfortunately, the magnet response by pacemakers and ICDs varies considerably among the manufacturers, so if the expected result is not observed (e.g., asynchronous pacing at the healthy battery rate in the case of a pacemaker or tones in the case of an ICD), it is best to contact the company for more information about how that particular device responds to a magnet. All companies have 24/7 telephone technical support and respond very quickly, if not immediately. In addition, there is considerable device-specific information contained in the Heart Rhythm Society guidelines.2
In summary, a cardiovascular implantable electronic device should be evaluated before surgery and a plan devised for its perioperative management (Table 1). The plan should take into account pertinent issues related to the surgery and the patient, which is where input from anesthesiologists is particularly important. The anesthesiologist should be knowledgeable enough about these devices to be able to interact intelligently with the expert. When necessary, as in an emergency when the expert may not be available, the anesthesiologist should be able to perform basic device assessment. The anesthesiologist should enter the surgery with as clear an understanding as possible of the status and function of the device, including how the device will respond to a magnet.
Name: G. Alec Rooke, MD, PhD.
Contribution: This author helped write the manuscript.
Attestation: G. Alec Rooke approved the final manuscript.
Conflicts of Interest: G. Alec Rooke is an investigator on a study of EMI and cardiovascular implantable electronic devices that is funded by Medtronic.
Name: T. Andrew Bowdle, MD, PhD.
Contribution: This author helped write the manuscript.
Attestation: T. Andrew Bowdle approved the final manuscript.
Conflicts of Interest: The author has no conflicts of interest to declare.
This manuscript was handled by: Sorin J. Brull, MD, FCARCSI (Hon).
a There are a few ICDs (Boston Scientific Prizm series) still in use, in which magnet placement turns off antitachycardia functions as expected, but the magnet can be removed and the antitachycardia functions will remain disabled indefinitely until the magnet is again placed on the device. Whenever magnet placement on an ICD is contemplated, continuous electrocardiographic monitoring and provision for external cardioversion/defibrillation should be available. Cited Here...
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