Is it Time to Embrace the Humble Magnet?

Introduction

In this article, we summarize our experience with perioperative manual reprogramming of ICDs, with a brief review of the latest literature on this topic. There have been some comprehensive review articles in the last several years regarding magnet application for perioperative device management, but in the light of the very recently published first and only randomized controlled trial that evaluated the two approaches to perioperative ICD management and the persistent controversies surrounding this everyday topic, a brief update is warranted.

Approaches to Perioperative ICD Management

Although perioperative management of the implantable cardioverter defibrillator (ICD) is a routine necessity, there is much controversy about the best way to manage this. There is no evidence-based guideline regarding the appropriateness of the two approaches to perioperative ICD management, i.e., magnet application vs. reprogramming. Professional society statements are mostly derived from case reports and case series, and rely heavily on expert opinion. The American Society of Anesthesiologists (ASA) has cautioned against the routine use of the magnet over an ICD. However, most of the data on management, which has been based on individual experiences and standard local hospital policies, often vary between institutions and practitioners. The 2011 Expert Consensus Statement from the Heart Rhythm Society (HRS) and ASA¹ attempted to consolidate the available evidence. Until recently, there was no randomized controlled trial (RCT) to systemically evaluate the two approaches to perioperative ICD management. 

Gifford et al conducted the first RCT comparing the twin approaches of magnetic ICD deactivation versus manual reprogramming prior to electrocautery usage during surgery, and investigated the frequency and safety of electromagnetic interference (EMI) based on surgical location.² The study primarily looked at ICD “off time” between the two groups, during which these patients are conceivably left vulnerable to malignant ventricular arrhythmias, and found that on average, those in the reprogramming group had “excess” ICD off time (defined as total ICD off time minus total duration of electrocautery) compared to those who had their devices deactivated by a magnet (115 minutes vs 28 minutes, P<.001). This is quite intuitive and easily understandable, as manual reactivation of tachytherapy (reprogramming) would in most hospitals need a member of the cardiovascular implantable electronic device (CIED) team to be available postoperatively. EMI incidence, assessed as one of the secondary endpoints in this RCT, was not statistically different between the two strategies. Interestingly, however, it is not clear when, how, and by whom the incidence of EMI during surgery (specifically electrocautery) was recorded in the magnet group, since these patients were only interrogated at their next ICD clinic visit or by remote transmission; this introduces an element of doubt regarding the validity of their protocol, although, if anything, a delayed interrogation might have overestimated, not underestimated, the actual incidence of EMI in the magnet group.

While the above RCT² and several smaller studies have analyzed surrogate markers of harm during perioperative management of CIEDs, there is little data on “hard outcomes” with either of these two strategies. We analyzed 98 consecutive perioperative patients with ICDs (53 Medtronic, 45 Boston Scientific) in a tertiary care urban teaching hospital who had routine preoperative manual reprogramming per institutional protocol. There were 17 colonoscopies, 13 abdominal surgeries, 10 upper GI endoscopies, 10 head and neck surgeries, 10 upper extremity surgeries, 9 lower extremity surgeries, 6 transurethral resection of the prostate, 5 hip surgeries, 3 spinal surgeries, one video-assisted thoracic surgery, and one ocular (cataract) surgery, with the remaining 20 being miscellaneous/unclassified. Of these, only one patient who had endoscopy/colonoscopy with polyp removal had significant EMI, but didn’t otherwise lead to device malfunction (COGNIS N119 CRT-D, Boston Scientific). One patient with a Medtronic CRT-D (7299 InSync Sentry) had ventricular fibrillation immediately post cataract surgery in the operating room; there was a ~2 minute delay in delivery of the first appropriate external defibrillation in this patient due to prior deactivation of ICD tachytherapy by preoperative reprogramming. This case series illustrates that EMI of ICD is infrequent during routine electrosurgery; however, in spite of the various publications advocating for either of the two approaches to ICD deactivation, there still appears to be lingering doubts regarding the best way to manage this situation.³ This dilemma is perpetuated by different ICD models having different magnet responses in terms of sensing function and tachytherapy. Occasionally, in some (Boston Scientific) models, these functions do not recover completely when the magnet is removed, although in most ICD models, a magnet will lead to deferral of tachyarrhythmia recognition and therefore, inhibition of tachytherapies without affecting the pacing mode. Specifically, in the Medtronic 7299 InSync Sentry ICD that was used in our patient, the magnet response is not programmable and it is designed to promptly reinstate tachyarrhythmia detection upon removal of magnet. The primary disadvantage of magnet application is maintaining its correct position on the chest wall. 

On the other hand, manual reprogramming risks the possibility of communication errors during postoperative handoff, which could either lead to wrongly reinstating parameters or inadvertently keeping tachytherapy disabled. In the RAPID-RF trial,⁴ there were 3 occurrences of the “red alert” for tachytherapy turned off (863 patients monitored for an average of 9 months) using the LATITUDE system (Boston Scientific). Of these, 2 were hospice patients in whom the tachytherapy was voluntarily turned off, and the third patient had its device programmed to ‘monitor only’ prior to lead revision for high pacing lead impedance. BIOTRONIK Home Monitoring^® data from 6548 ICD and 445 CRT-D recipients worldwide showed 63 alerts from 38 of these devices for inadvertent inactivation of the device.⁵ 

Our patient had a perioperative ventricular fibrillation arrest during an ocular procedure, which ultimately led to the death of the patient, that could have been swiftly terminated by quickly removing the magnet if the patient had in fact had magnetic deactivation preoperatively instead of reprogramming. This tragic scenario offers the best example of the potential advantage of perioperative ICD deactivation using a magnet when compared to reprogramming. 

Summary

Although both schools of thought have contended their respective approach (i.e., magnet application vs reprogramming for perioperative ICD deactivation), and rare case reports have been described in which a magnet application led to intraoperative inhibition of pacing or permanently disabling an ICD, we conclude, based on the recent RCT as well as the large contemporary device registries of remote monitoring systems, that: (1) ICD deactivation can usually be safely done by magnet application, and (2) the benefits of instant resumption of ICD tachytherapy on swift removal of the magnet in an emergency outweighs the very rare potential risk of inhibiting bradycardia pacing (Table 1). We also submit that all CIEDs should be evaluated by the CIED team preoperatively to interrogate if a patient is pacing dependent and to check if the magnet response is turned on (Boston Scientific). In general, all proceduralists, particularly anesthesiologists, are expected to know the very basics of perioperative CIED management using a magnet, and given its excellent safety profile, it makes rational medical-economic sense to utilize a magnet intraoperatively. 

References 

1. Crossley GH, Poole JE, Rozner MA, al. The Heart Rhythm Society (HRS)/American Society of Anesthesiologists (ASA) Expert Consensus Statement on the perioperative management of patients with implantable defibrillators, pacemakers and arrhythmia monitors: facilities and patient management. Heart Rhythm. 2011;8:1114-1154.
2. Gifford J, Larimer K, Thomas C, May P, Stanhope S, Gami A. Randomized controlled trial of perioperative ICD management: magnet application versus reprogramming. Pacing Clin Electrophysiol. 2014;37:1219-1224.
3. Porres JM, Laviñeta E, Reviejo C, Brugada J. Application of a clinical magnet over implantable cardioverter defibrillators: is it safe and useful? Pacing Clin Electrophysiol. 2008;31(12):1641-1644; discussion 1645.
4. Boehmer J, Saxon L, Lobban J, et al. Clinician Response to Remote Active Monitoring in Patients with Heart Failure: Results of the RAPID-RF Trial. The Journal of Innovations in Cardiac Rhythm Management. 2014;5:1551-1560. 
5. Lazarus A. Remote, wireless, ambulatory monitoring of implantable pacemakers, cardioverter defibrillators, and cardiac resynchronization therapy systems: analysis of a worldwide database. Pacing Clin Electrophysiol. 2007;30(Suppl 1):S2-S12. Erratum in: Pacing Clin Electrophysiol. 2007;30(11):1424.

Disclosures: The authors have no conflicts of interest to report regarding the content herein.   

Editor’s Note: This article underwent peer review by one or more members of EP Lab Digest’s editorial board.