Heart Rhythm New Zealand consensus statement on the practical management of cardiac implanted electronic devices in the peri-operative environment

Heart Rhythm New Zealand (HRNZ) is an integral part of the Cardiac Society of Australia and New Zealand (CSANZ). It is composed of members of CSANZ who have expertise in the field of electrophysiology and cardiac rhythm devices. The consensus statement was generated using a combination of current international guidelines and publications, adapted to be relevant to the New Zealand medical system. The writing committee was comprised of stakeholders from the specialities who frequently manage cardiac implanted electronic devices (CIED) patients during electrosurgical procedures. Consultation within each specialty was sought, and feedback was discussed as a group and adopted where appropriate.

CIEDs can be prone to electromagnetic interference (EMI) during surgical/medical procedures using electrocautery. The factors determining the potential for EMI to affect normal device function are: the distance between source and site of CIED (less risk if >15cm from device), the intensity and duration of field or source, the frequency and waveform of signal and the path of current and its relation to the orientation of CIED leads. EMI usually only disrupts normal device function transiently, and when the interference ceases, the device typically returns to normal function.

Common adverse effects due to the CIED sensing EMI can include: inhibition of pacing—leading to haemodynamically significant bradycardia or asystole in the pacemaker (PPM) dependent patient, inappropriate tachyarrhythmia therapy with anti-tachycardia pacing and/or shocks in the implantable cardiac defibrillator (ICD) patient, inappropriate tracking of electrical noise causing pacing at upper rate and/or mode switching due to over-sensing of EMI on atrial lead, activation of asynchronous noise reversion mode and changes in pacing behaviour such as the activation of rate response algorithms. Rare adverse effects can include: thermal injury at the lead/myocardial interface, increased pacing thresholds, electrical reset of the device causing change in settings, and permanent damage to device (legacy devices are more prone to this).

Recommendations for peri-operative management of CIED patients have significantly altered in recent years, with advancements in device technology establishing a higher degree of tolerance to routine electrosurgical procedures. However, concurrently, newer electrosurgical technologies and CIED technologies are also occurring; this represents a challenge to the manufacturers of the CIEDs and CIED professionals.

Manufacturer-specific information should be used for magnet placement. Implantable defibrillators are generally implanted at the left prepectoral position, but some may be right prepectoral, abdominal implants or subcutaneously implanted in the left axilla. PPM generators are generally implanted left or right prepectoral, but some are implanted in the abdomen, particularly in children. Leadless devices are implanted directly in the heart.

General principles

Centres performing electrosurgery on patients with CIEDs are recommended to have an institutional protocol. Protocols may vary between centres depending on the availability of specialist device physiologists in each centre. The patient’s CIED service should be contacted for specialist device physiologist advice. For elective procedures, advice should be requested well in advance of surgery.^1–4 The peri-operative management of CIEDs must be individualised to the patient, the type of CIED and the type of procedure being performed.^1–4 A single recommendation for all CIED patients is not appropriate.¹

The decision to reprogram a device vs magnet use will depend on staff availability, urgency of surgery and surgical site. The most effective advice for the peri-operative care of a patient with a CIED will be obtained from the team that monitors that patient and device, combined with an understanding of the procedure to be performed and risk for EMI.^1–4

All patients with PPM undergoing elective surgery should have had a device interrogation as part of routine care within the past 12 months. All patients with ICDs or any cardiac resynchronisation therapy (CRT) device (cardiac resynchronisation therapy defibrillator [CRT-D], cardiac resynchronisation therapy pacemaker [CRT-P]) undergoing elective surgery should have had a device interrogation as a part of routine care within the past 6 months; this may be in person or via remote monitoring.^1–4 Implantable loop recorders (ILRs) should be interrogated prior to surgery if the surgery is near the device, as EMI from electrosurgery may overwrite data. Interrogation can be done via remote monitoring or in person.²

Electrosurgery and CIEDs

Electrosurgery may be either monopolar or bipolar. Bipolar electrosurgery or the use of an ultrasonic scalpel is preferred to monopolar electrosurgery as these result in less EMI; however, these technologies are not appropriate for all electrosurgery operations.² Bipolar electrosurgery does not use a return pad and is unlikely to cause EMI unless applied directly to the device, but precautions need to be taken for some legacy devices.⁵ Monopolar electrosurgery has the current flow through the patient’s body to a patient return electrode, casting a wider electrical field. Device interference is unlikely if surgery is below the iliac crest and the return pad is on the thigh ipsilateral to the surgical site.² Newer capacitive return electrodes (mattress type) may disperse the current throughout the body depending on mattress placement regardless of the anatomical site of surgery, so devices are at higher risk of EMI, especially if the mattress is under the patient’s chest.^6,7 PPM implanted in the abdomen will be more exposed to EMI during abdominal or pelvic surgery. Monopolar electrosurgery above the iliac crest and/or <15cm from the device has a higher risk of EMI.^1–4

Recommendations for use of electrosurgery to avoid EMI interference with CIEDs:

• Follow electrosurgery unit manufacturer’s guidelines for patient return electrode orientation.
• Use a harmonic (ultrasonic) scalpel or bipolar electrosurgery where possible.
• Place the patient return electrode on clean, dry, hair-free skin over a large, well-perfused muscle mass as close as possible to the surgical site, but >15cm from CIED.
• Ensure the heart and CIED are not between the site of surgery and the return electrode, e.g., patients undergoing head/neck surgery should have the grounding pad placed on the shoulder contralateral to the device (not the thigh), whereas those undergoing breast and axillary surgery should have the pad placed on the upper arm.^8–10
• Capacitive full body return electrodes (mattress type) are designed to remove the risk of pad-site burns associated with the adhesive return electrodes. The return current is distributed over the whole area of the mattress, which may cause inhibition of pacing or ICD therapy even if the surgical site is below the iliac crest.^6,11
• In PPM-dependent patients, the use of an adhesive return electrode pad is preferred to a mattress type electrode as there is potential for pacemaker inhibition due to EMI regardless of surgery site, unless the device is appropriately programmed prior to the procedure.^2,6,11,12
• Use monopolar electrosurgery in short bursts (<5 secs), intersected by pauses. Pure unblended cut is less likely to cause interference than the blended or coagulation settings of the electrosurgery unit. Use the lowest feasible energy.^1–4,10
• Monitor patients with electrocardiogram (ECG) and pulse oximetry (and/or arterial line). Interference may saturate the ECG signal during electrosurgery, making it impossible to see inhibition of pacing.
• Ensure an external defibrillator capable of transcutaneous pacing is readily available for PPM-dependent patients or operations with high risk of EMI identified by the specialist device physiologist. Place transcutaneous pacing/defibrillator pads, including ECG, prior to draping if there are any concerns or barriers to placement during a case.
• If a specialist physiologist has recommended the use of a magnet, the magnet should only be applied for the duration of the electrosurgery.

Pre-operative device reprogramming and/or magnet use

All patients undergoing electrosurgery who have a CIED should be discussed with a specialist device physiologist prior and have a peri-operative CIED management plan established. This may include a recommendation for device reprogramming and/or magnet use.

Magnet use, placement and CIED response must be fully understood before use.^1–4,13,14 Magnet use may be recommended to inhibit ICD therapy or force asynchronous pacing. The use of a magnet and the response of the device to a magnet should be guided by a specialist device physiologist, as this varies depending on device type and manufacturer.^1,2,4,13,14 When a magnet has been recommended, the magnet response should be verified as expected prior to being required in PPM-dependent patients (Table 1 and 2).

If device reprogramming is recommended, it should be performed by a specialist device physiologist. Programming should be performed as close as possible to the time of surgery in case of delay or cancellation of surgery. ICDs should be reprogrammed to therapy off/or a magnet used to inhibit therapy only once the patient is in a monitored environment with ECG/pulse oximetry monitoring; defibrillator pads should be placed prior to programming the ICD off.^1–4 PPM that are programmed asynchronous (DOO/VOO/AOO) for the duration of surgery should also be monitored as above.^1,2 Rate response functions may increase heart rate during surgery in response to external stimulus or intra-operative events and may cause PPM-driven tachycardia. Minute ventilation sensors may emit a current to measure changes in thoracic impedance that can be detected by monitoring equipment and appear to be rapid pacing without capture. The rate response sensor may need to be programmed off prior to surgery if recommended by a specialist device physiologist.^1–4,15 Any changes to the CIED settings should be documented in the patient record (Figure 1).

When to consider CIED reprogramming for surgery rather than magnet application

• Where the device is not easily accessible to allow placement of the magnet during surgery, due to site of surgery or patient positioning.^1–4
• Unipolar leads or where a CIED is programmed to unipolar sensing, due to a greater risk of oversensing EMI.^1–4
• Biotronik PPM where asynchronous mode is likely to be required, i.e., pacing-dependent patient—magnet mode should be reprogrammed from “auto” to “async” or device programmed to asynchronous.¹³
• Pacing-dependent ICD patients as magnet use will not provide asynchronous pacing.^1–4
• For ICD patients where correct magnet placement is difficult to assess (no tones) and monopolar electrosurgery is being used above the iliac crest or a capacitive return mattress is used.⁸
• If surgery is less than 15cm from the CIED generator for PPM-dependent patients and all ICD patients.
• Where a higher or lower base rate is desirable due to patient haemodynamics as requested by the medical team, surgeon or anaesthetist.
• Leadless PPM, which are implanted directly into the ventricle (Micra/Nanostim/Aveir) and subcutaneous ICDs (S-ICD Emblem/EV-ICD), need specific advice from a device physiologist as the advice, response to magnets and magnet placement may differ.^1–4

View Figure 1–3, Table 1–2.

Intra-operative CIED management

Patients should be monitored with ECG and pulse oximetry/or arterial line during the procedure, as the ECG tracing will be obscured during electrosurgery.^1–4 An external defibrillator with pacing capabilities should be readily available for all CIED patients, along with staff trained in its use.^1–4

A magnet should be immediately available for all CIED patients who are undergoing a procedure that may involve EMI even if reprogrammed, along with staff familiar with the use of magnets ^1–4 Caution should be exercised when using magnetic drapes to hold surgical equipment; placement of these on the thorax should be avoided. The use of bottom-isolated magnetic drapes may reduce the risk of interaction.¹⁶

Post-operative indications for CIED interrogation

• Patients with CIEDs reprogrammed prior to the procedure.^1–4 If ICD therapies are deactivated for surgery/procedure or a PPM is programmed to asynchronous mode, the team requesting reprogramming are responsible to ensure the device is returned to normal operation as soon as practicable and should have a clear plan for this.^3,4
• Patients with CIEDs who underwent hemodynamically challenging surgeries such as cardiac surgery or significant vascular surgery (e.g., abdominal aortic aneurysmal repair), which likely have higher probability of significant EMI.^1–4
• Patients with CIEDs who experienced significant intra-operative events including cardiac arrest requiring temporary pacing or cardiopulmonary resuscitation and those who required external electrical cardioversion.^1–4
• Patients with CIEDs who underwent monopolar electrosurgery with a capacitive return mattress and there is a greater probability of EMI affecting device function, as determined by a specialist device physiologist.^2,6
• Patients with CIEDs who underwent monopolar electrosurgery above the iliac crest and there is a greater probability of EMI affecting device function, as determined by a specialist device physiologist.^1–4
• Patients with signs of device dysfunction observed intra-operatively, e.g., heart rates below or above programmed or expected rates, pectoral or diaphragmatic twitching, erroneous pacing spikes (such as pacing spikes that vary considerably in size) and alarms, beeping or vibrating from device.^1–4
• Post-magnet use where the specialist device physiologist has identified the CIED is nearing elective replacement. In this situation, magnet movement, EMI and battery status may cause unintended device programming due to tripping elective replacement. Changes in programming may not always be noticeable, e.g., increase in pacing rate, change in pacing mode, deactivation of rate response sensors for PPM, device alarms, beeping or vibration for ICDs due to battery status alert.³
• Where a specialist cardiac device physiologist has recommended post-operative interrogation.
• Where a specialist cardiac device physiologist has identified the CIED is a legacy Abbott/St Jude Medical device subject to safety alert (Affinity, Entity, Integrity, Identity, Verity, Frontier, Victory, Zephyr) see Special considerations.⁵

When emergency surgery is required

In situations where CIED patients present for urgent surgery, contact the patient’s CIED centre or nearest tertiary hospital for advice. The availability of staff at local follow-up centres will vary during work hours and after hours. All tertiary cardiology centres in New Zealand have staff on call after hours.

Prior to making contact, it is helpful to the on-call team if the type of device/model can be identified—access hospital notes, question patient/attending support people and enquire if patient has a device ID card. Review the chest X-ray and 12-lead ECG.^1–4 If PPM spikes are present it should be presumed the patient is potentially PPM-dependent. Newer devices will have bipolar pacing spikes, which are very small (1mm) and may be difficult to see on the ECG. Unipolar pacing spikes are large spikes and obvious on the ECG; the presence of these may indicate older device/leads that may be more susceptible to interference.^1–4 A remote monitoring transmission can be considered as a substitute for in-person interrogation if no available specialist device physiology staff are on site.^1–3

Defibrillator/pacing pads should be readily available in the event defibrillation or transcutaneous pacing is required. A defibrillator capable of transcutaneous pacing and a magnet with instructions for use (Table 1 and 2) should be readily available along with staff trained in its use.^1–4 In individual circumstances, pads may need to be placed prophylactically, which would be advised by a specialist device physiologist. If magnet use is likely to be required, identify the expected magnet response prior to surgery (Table 2).^1–4

If surgery is above the iliac crest or a capacitive return electrode mattress is used, have a magnet available for PPM patients to provide asynchronous pacing should significant periods of inhibition occur during electrosurgery resulting in asystole or haemodynamically compromising bradycardia. Transient inhibition of pacing should be expected during the delivery of electrosurgery, but normal pacing is expected to return immediately upon termination of this. Asynchronous pacing will only occur while the magnet is in situ.^1–3,6 Please note the magnet response for Biotronik devices is only asynchronous for 10 beats unless the magnet response is specifically programmed to “async”.^1–4

For ICD patients there is the potential for inappropriate ICD shock therapy during electrosurgery due to sensing of EMI (Table 1). ICD tachyarrhythmia therapy can be temporarily disabled by placing a magnet over the device during electrosurgery. Therapies will resume on removal of magnet. When access to the device for magnet placement is not possible (e.g., due to patient position), programming by a specialist device physiologist may be required prior to surgery to disable tachyarrhythmia therapies. The correct positioning of a magnet is manufacturer specific; advice should be sought from a specialist device physiologist where possible (Table 1). In pacing-dependent ICD patients, electrosurgery should be in short bursts of <5 seconds to prevent long periods of inhibition—a magnet will only inhibit tachyarrhythmia therapy and will not provide asynchronous pacing.^1–4 In pacing-dependent ICD patients, the CIED may need to be reprogrammed to provide asynchronous pacing if the operative field is above the iliac crest and EMI is likely to cause significant periods of inhibition, or if a capacitive return mattress is being used.^1,2 Where the positioning of the patient limits access to the device for magnet placement, a specialist physiologist may be required prior to surgery to disable tachyarrhythmia therapies.

The post-operative device follow-up after surgery should be guided by a specialist device physiologist and should generally only be required for patients where CIED malfunction is suspected, significant exposure to EMI has occurred or if the device was reprogrammed prior to surgery.^1–4

Special considerations

Cardioversion, defibrillation and transcutaneous pacing of adult CIED patients

High-voltage cardiac defibrillation can introduce a large amount of current to CIEDs. Adverse events during cardioversion, defibrillation and transcutaneous pacing are rare, though can include: elevated pacing thresholds/failure to capture, damage to the device and reversion to backup safety mode. Ideally, patients who have the potential requirement for defibrillation or transcutaneous pacing during a procedure will have pads placed in advance.

In pacing-dependent patients undergoing cardioversion, consider reprogramming the device to fixed outputs. This is to ensure 2x threshold safety margins, which may not always be the case when automatic threshold testing is enabled. The need to have a physiologist present during cardioversion is at the discretion of the specialist device physiologist.

In patients with an ICD or a permanent PPM, the placement of paddles/pads should not delay defibrillation.²⁰ A defibrillator capable of transcutaneous pacing should be utilised. The recommended positioning of the defibrillation pads should be in an anterior–posterior configuration (Figure 2) where possible, with the anterior pad placed at least 15cm from the generator.^1–4,21 For patients with large breasts, the anterior pad should be placed under the breast.²² Alternative positioning with anterior–anterolateral (Figure 3) pad placement can be used if anterior–posterior placement is within the surgical field, or preferred for cardioversion of atrial fibrillation (AF).^1–4,23 Alternative anterior–anterolateral pad placement may also be required in an emergency where it is not possible to attach a posterior pad easily.

Following the procedure, the device should be interrogated and fully evaluated by a specialist device physiologist to ensure normal function.^1–4 When operating the defibrillator in automated external defibrillator (AED) mode, be aware that PPM pulses may prevent advisement of an appropriate shock, regardless of the patient’s underlying rhythm.^20,24

St Jude legacy devices

Abbott Medical (formerly St Jude Medical) legacy devices that are subject to a safety alert are more susceptible to transient anomalous device function during electrosurgery. This refers to a specific subset of legacy generation PPM, specifically: SJM Affinity, Entity, Integrity, Identity, Verity, Frontier, Victory and Zephyr. These devices may exhibit a temporary change in function that can persist for 30 seconds or longer, the most clinically significant observation being transient loss of capture due to reduction in pacing output voltage. This may occur regardless of program mode or magnet use.⁵