Pacemaker Mode for Pacemaker-Dependent Patients Undergoing Total Knee Replacement
For pacemaker-dependent patients undergoing total knee replacement, reprogram the pacemaker to an asynchronous mode (VOO for single-chamber or DOO for dual-chamber) before surgery to prevent life-threatening pacing inhibition from electromagnetic interference. 1, 2
Rationale for Asynchronous Mode Programming
Total knee replacement requires monopolar electrocautery above the umbilicus, which creates significant electromagnetic interference (EMI) risk that can inhibit pacing in dependent patients. 1, 2
Asynchronous pacing (VOO/DOO) eliminates intrinsic sensing and delivers stimuli at a fixed rate regardless of EMI, making it the only proven method to ensure continuous pacing when significant EMI is expected. 2
The American College of Cardiology and American Society of Anesthesiologists both provide Class I recommendations (highest level) for asynchronous mode programming in pacemaker-dependent patients undergoing surgery with anticipated EMI. 1, 2
Specific Programming Steps
Perform device interrogation 3-6 months before surgery to verify battery status, programmed mode, lead impedances, and capture thresholds. 2
Use a dedicated programmer for formal reprogramming rather than relying on magnet placement, as magnet responses are inconsistent across manufacturers and some devices have the magnet function disabled entirely. 1, 2
Disable rate-responsive features (DDDR → DOO or VVIR → VOO) even in asynchronous mode, because motion sensors can be falsely triggered by surgical activity and electrocautery. 1, 2
Set the asynchronous pacing rate to 60-80 bpm for hemodynamic stability during the procedure. 2
Critical Intraoperative Precautions
Maintain continuous ECG monitoring together with continuous pulse monitoring (pulse oximetry or arterial line), because electrocautery obscures the ECG trace and pulse oximetry becomes the reliable indicator of cardiac activity. 1, 2, 3
Request bipolar electrocautery whenever technically feasible, as it virtually eliminates EMI and is the single most effective strategy to protect pacing function. 1, 2
If monopolar cautery is unavoidable, apply it in short, intermittent, irregular bursts at the lowest effective power setting, and place the ground pad to minimize current flow through the pacemaker generator. 1, 2
Keep external pacing and defibrillation equipment immediately available, as rare catastrophic pacemaker failure from EMI can still occur despite asynchronous programming. 1, 2
Postoperative Device Restoration
After surgery and before hospital discharge, reprogram the pacemaker back to its original mode (typically DDD or DDDR) using formal interrogation with a programmer to verify restoration of normal sensing and pacing thresholds. 1, 2, 3
Do not discontinue cardiac monitoring until device function is confirmed restored, as failure to reactivate devices has resulted in documented deaths. 2
Common Pitfalls to Avoid
Never assume magnet placement provides adequate management, as the magnet-induced pacing rate may be too high or otherwise unsuitable, and there is no reliable way to confirm appropriate function without pre-operative testing. 1, 2
Do not forget that rare modern pacemaker models can experience output failure or inappropriate low pacing rates below 30 bpm during electrosurgery despite being programmed in asynchronous mode—this has been documented in 2.8% of certain St. Jude Medical models. 4
Remember that for patients with both pacemaker dependency and an ICD, the pacing function must be set to asynchronous mode AND the shock therapy must be disabled as separate steps. 2