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Pacing and Defibrillation Interface: ECG Monitoring in the OR [ Medical Education ](https://mdster.com/blog?category=medical-education) Pacing and Defibrillation Interface: ECG Monitoring in the OR =============================================================== How to recognize electrosurgical interference, confirm external pacing capture, and manage implanted cardiac devices safely [ MDster Editorial Team ](https://mdster.com/about) · Aug 09, 2026 · 5 min read · 30 [ Reviewed by Dr. Ali Ragab, MBBCH, MSc, MCAI ](https://mdster.com/medical-reviewers/dr-ali-ragab) [Editorial Policy](https://mdster.com/editorial-policy) | [Corrections Policy](https://mdster.com/corrections) [ Anesthesiology ](https://mdster.com/blog?tag=anesthesiology) [ Anesthesia Equipment ](https://mdster.com/blog?tag=anesthesia-equipment) [ ECG Monitoring ](https://mdster.com/blog?tag=ecg-monitoring) [ Pacing ](https://mdster.com/blog?tag=pacing) [ Defibrillation ](https://mdster.com/blog?tag=defibrillation) [ Cardiac Devices ](https://mdster.com/blog?tag=cardiac-devices) ![Pacing and Defibrillation Interface: ECG Monitoring in the OR](https://mdster.com/storage/blog/images/pacing-and-defibrillation-interface-ecg-monitoring-in-the-or.jpg) Share this article Share this post On this page 1. [ Electrosurgery Interference: When the ECG Lies ](#electrosurgery-interference-when-the-ecg-lies) 2. [ External Pacing: Capture Is a Two-Part Diagnosis ](#external-pacing-capture-is-a-two-part-diagnosis) 3. [ Establish pacing methodically ](#establish-pacing-methodically) 4. [ Defibrillation Through the Same Interface ](#defibrillation-through-the-same-interface) 5. [ Implanted Device Considerations ](#implanted-device-considerations) 6. [ Clinical Correlations: A Rapid Troubleshooting Sequence ](#clinical-correlations-a-rapid-troubleshooting-sequence) 7. [ Key Takeaways ](#key-takeaways) 8. [ Conclusion ](#conclusion) 9. [ Frequently Asked Questions ](#blog-faqs) 10. [ References ](#references-heading) On this page 1. [ Electrosurgery Interference: When the ECG Lies ](#electrosurgery-interference-when-the-ecg-lies) 2. [ External Pacing: Capture Is a Two-Part Diagnosis ](#external-pacing-capture-is-a-two-part-diagnosis) 3. [ Establish pacing methodically ](#establish-pacing-methodically) 4. [ Defibrillation Through the Same Interface ](#defibrillation-through-the-same-interface) 5. [ Implanted Device Considerations ](#implanted-device-considerations) 6. [ Clinical Correlations: A Rapid Troubleshooting Sequence ](#clinical-correlations-a-rapid-troubleshooting-sequence) 7. [ Key Takeaways ](#key-takeaways) 8. [ Conclusion ](#conclusion) 9. [ Frequently Asked Questions ](#blog-faqs) 10. [ References ](#references-heading) A pacing spike appears before every QRS, yet the arterial pressure is collapsing. Is the patient paced—or are you watching false capture? At the pacing-defibrillation interface, ECG appearance alone is never enough. Anesthesiologists must integrate electrical activity with actual perfusion. Electrosurgery Interference: When the ECG Lies ---------------------------------------------- Monopolar electrosurgery produces electromagnetic interference (EMI) that may saturate the ECG, mimic ventricular arrhythmia, or hide genuine bradycardia. More dangerously, a pacemaker may oversense EMI and inhibit pacing, while an ICD may misclassify it as VT or VF and deliver inappropriate therapy. [\[1\]](#cite-1 "Reference [1]") When cautery obscures the tracing, do not diagnose asystole or VF from the ECG alone. Ask the surgeon to stop electrosurgery and immediately examine the arterial waveform, pulse oximeter plethysmograph, pulse, and capnography. Reduce EMI systematically: - Prefer bipolar electrosurgery or an ultrasonic device. - Use monopolar energy in short, intermittent bursts at the lowest effective power. - Position the return electrode so current travels away from the generator and leads. - Avoid full-body return electrodes unless the CIED plan specifically accounts for them. - Keep ECG electrodes separated from multifunction therapy pads. Bipolar electrosurgery rarely causes clinically important EMI. Procedures below the iliac crest are also lower risk when the return electrode is placed on the thigh and the current path remains distant from the CIED. [\[1\]](#cite-1 "Reference [1]") > **Clinical Pearl:** During electrosurgery, trust a pulsatile arterial or plethysmographic waveform more than a chaotic ECG. Electrical noise cannot create genuine forward blood flow. External Pacing: Capture Is a Two-Part Diagnosis ------------------------------------------------ Transcutaneous pacing is a rapid bridge for hemodynamically unstable bradycardia when medication is ineffective or while preparing for transvenous pacing. It is not recommended as routine treatment for established asystolic cardiac arrest. [\[2\]](#cite-2 "Reference [2]") ### Establish pacing methodically 1. Apply multifunction pads in an anterior-posterior or anterior-lateral configuration according to the device instructions. 2. Monitor through separate ECG electrodes and confirm that the pacer senses intrinsic QRS complexes correctly. 3. Select an appropriate pacing rate and increase current until electrical capture occurs. 4. Look for a broad paced QRS and repolarization wave after each pacing marker. 5. Confirm mechanical capture using an arterial waveform, blood pressure, plethysmographic pulse, or a reliably palpable pulse. 6. Maintain output above the capture threshold according to the device and local protocol. A pacing marker followed by a distorted complex may represent artifact rather than depolarization. Even true electrical capture does not prove adequate cardiac output. The definitive bedside question is: **Did the pacing stimulus produce perfusion?** [\[3\]](#cite-3 "Reference [3]") Transcutaneous pacing is painful because it stimulates skeletal muscle. Provide analgesia and sedation when consciousness and hemodynamics permit, but do not delay stabilization of profound shock. Defibrillation Through the Same Interface ----------------------------------------- Multifunction pads often support monitoring, pacing, cardioversion, and defibrillation. Know your machine before the emergency; switching modes should not become the rate-limiting step in treating VF. If a patient deteriorates from paced bradycardia into VF or pulseless VT: - Stop or pause pacing according to the defibrillator controls. - Select unsynchronized defibrillation and use manufacturer-recommended energy. - Resume CPR immediately after shock delivery. - Do not continue assessing pacing capture during cardiac arrest. Implanted Device Considerations ------------------------------- Before anesthesia, identify the device type, indication, pacing dependence, battery status, programmed functions, magnet response, and expected proximity of electrosurgery. Coordinate with the CIED team when EMI is likely or the response is uncertain. [\[4\]](#cite-4 "Reference [4]") DeviceTypical magnet effectMajor exam trapPacemaker or CRT-PUsually asynchronous pacingResponse is manufacturer- and programming-dependentICD or CRT-DSuspends tachyarrhythmia detection or therapyIt usually does **not** make bradycardia pacing asynchronousLeadless pacemakerModel-specific; response may be absentDo not assume a chest magnet will work A pacing-dependent patient with an ICD may therefore require reprogramming if substantial EMI is expected. Simply applying a magnet may disable shocks while leaving pacing vulnerable to inhibition. When ICD therapies are suspended, maintain continuous ECG and perfusion monitoring, apply external defibrillation/pacing pads, and keep immediate shock capability available. Restore and verify prescribed device function before the patient leaves a monitored environment. For external cardioversion or defibrillation, do not delay a lifesaving shock. When feasible, use an anterior-posterior vector and keep the anterior pad at least 15 cm from the generator. Arrange interrogation afterward when malfunction is suspected or high-risk pad positioning was unavoidable. [\[1\]](#cite-1 "Reference [1]") Clinical Correlations: A Rapid Troubleshooting Sequence ------------------------------------------------------- If the ECG becomes unreliable or pacing appears ineffective: 1. Stop electrosurgery or other suspected EMI. 2. Check the patient and a mechanical perfusion signal. 3. Inspect cables, pad adhesion, sensing markers, and selected mode. 4. Reconfirm electrical and mechanical capture. 5. Use the magnet or reprogramming plan only after confirming the device type. 6. Escalate to external pacing, defibrillation, or ACLS when clinically indicated. Key Takeaways ------------- - Never equate a pacing spike with myocardial capture. - Confirm both electrical capture and mechanical perfusion. - Use peripheral pulse monitoring whenever electrosurgery may corrupt the ECG. - Remember: a magnet affects pacemakers and ICDs differently. - Do not delay defibrillation because an implanted device is present. Conclusion ---------- Treat the ECG as one data stream, not the patient. At this interface, safe anesthesia depends on understanding the equipment, anticipating EMI, and confirming that electrical therapy produces circulation. Frequently Asked Questions ---------------------------- ### How should I confirm transcutaneous pacing capture? Confirm a paced QRS after each stimulus, then demonstrate mechanical perfusion using an arterial waveform, blood pressure, plethysmography, or a reliable pulse. ### Does a magnet make an ICD pace asynchronously? Usually not. An ICD magnet generally suspends tachyarrhythmia therapy without changing bradycardia pacing, so pacing-dependent patients may require reprogramming. ### What should I do when electrosurgery obscures the ECG? Stop electrosurgery briefly and assess an arterial waveform, plethysmograph, pulse, and capnography before diagnosing an arrhythmia. ### Can a patient with a pacemaker receive external defibrillation? Yes. Never delay a necessary shock. Place pads away from the generator when feasible and arrange device assessment if malfunction is suspected. References (6) ------------------ 1. 1. [ EHRA Consensus on Interference Due to Medical Procedures in CIED Patients, 2022 ](https://academic.oup.com/europace/article/24/9/1512/6562768) [↩](#cite-ref-1-1 "Back to text") 2. 2. [ 2025 American Heart Association Guidelines: Adult Advanced Life Support ](https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/adult-advanced-life-support) [↩](#cite-ref-2-1 "Back to text") 3. 3. [ www.stryker.com/content/dam/stryker/ems/resources/operating-instructions/lifepak\_15\_operating\_instructions\_en.pdf ](https://www.stryker.com/content/dam/stryker/ems/resources/operating-instructions/lifepak_15_operating_instructions_en.pdf) [↩](#cite-ref-3-1 "Back to text") 4. 4. [ www.ahajournals.org/doi/epdf/10.1161/CIR.0000000000001264 ](https://www.ahajournals.org/doi/epdf/10.1161/CIR.0000000000001264) [↩](#cite-ref-4-1 "Back to text") 5. 5. [ AHA Scientific Statement: Periprocedural Management of Cardiac Implantable Electronic Devices, 2024 ](https://pubmed.ncbi.nlm.nih.gov/38984417/) 6. 6. 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