Percutaneous radiofrequency ablation (RFA) is now a frequently used treatment for trigeminal neuralgia (1). Radiofrequency is a potential source of electromagnetic interference (EMI) to implanted cardiac pacemakers, and interference from intracardiac ablation has been well documented (2–5). No previous cases of percutaneous radiofrequency of the trigeminal nerve in patients with an implanted cardiac pulse generator have been reported.
An 80-yr-old man presented with a 30-yr history of right-sided trigeminal neuralgia not responding to medical therapy. The patient had a history of mitral and aortic valve replacements 9 yr before, after which a permanent pacemaker (Intermedics 284–09 c/o Guidant, St Paul, MN) was implanted in the immediate postoperative period for sinus arrest. It was in the left infraclavicular position. He had no recent history of angina or dyspnea at rest and reasonable exercise tolerance. The electrocardiogram (ECG) showed a ventricular paced rhythm at a rate of 77 bpm. His electrolytes were normal. His most recent echocardiogram demonstrated a left ventricular ejection fraction of 20%. His medications included carbamazepine, candesartan, digoxin, bisoprolol, furosemide, spironolactone, and warfarin (temporarily replaced with tinzaparin immediately before surgery).
Upon presentation, the pacemaker was programmed to VVIR mode in a unipolar sensing configuration with a rate responsive mode of 65–130 bpm. His background rhythm was atrial fibrillation with a rate of 38 bpm on the day of surgery. For the procedure, the rate responsive mode had been switched off, and the pacemaker remained in VVI mode at a rate of 80 bpm. A temporary transcutaneous pacemaker and isoproterenol were available in the operating room if required.
The patient was monitored with pulse oximetry, noninvasive arterial blood pressure, 5 lead ECG, and capnography. He was sedated with IV remifentanil and propofol for insertion of the rhizotomy electrode into the foramen ovale and the radiofrequency lesioning. He remained conscious for the remainder of the procedure. The RFA-receiving plate was placed under the right buttock. The radiofrequency equipment used was a Radionics RFG-3CF generator (Radionics, Burlington, MA). Stimulation at 50 Hz, 1 ms, and 0–0.3 volts was applied. The lesion was made at 68°C–70°C for 60 s at 102 mA, 25 V, and 2.7 W. During the stimulation and the RFA, the usual radiofrequency artifact in the ECG (Fig. 1) was noted, but the pacemaker output remained continuous, as evidenced by the peripheral pulse waveform on the pulse oximeter plethysmograph; the procedure was completed uneventfully. The patient remained stable throughout. Postoperatively, the pacemaker was interrogated, showing no change in its variables and reprogrammed to its original settings.
Percutaneous radiofrequency trigeminal rhizotomy is a well-recognized treatment for trigeminal neuralgia (1). There are no reported cases of percutaneous radiofrequency trigeminal rhizotomy in patients with an implanted pacemaker. There are a number of reports of pacemaker interference with intracardiac radiofrequency (2–5). Theoretically, radiofrequency current can cause generator damage and complete inhibition caused by oversensing or pacing-rate increase (2). We report this case as an example of potential pacemaker interference from another source of EMI.
Despite technological advances, an implanted cardiac pacemaker can still be susceptible to interference from EMI. The EM spectrum that interferes with pacemakers includes the 0–109-Hz range, which includes radiofrequency and microwave energy (2,6). In this case of percutaneous trigeminal RFA, 50 Hz was used. Modern pacemakers are shielded against EMI, however EMI signals between 5 and 100 Hz are not filtered because they overlap the frequency range of intracardiac signals (2,5,7). Unipolar configured pacemakers, which our patient had, are more susceptible to interference. When available, bipolar sensing configuration of the pacemaker leads minimizes the risk of the leads acting as antennae for EMI (2,5,6).
Several reviews on pacemakers describe different responses of pacemakers to various EMI sources, including inappropriate pacing inhibition or triggering, reversion to asynchronous pacing, unintentional reprogramming, or damage to electrical components (5–7).
General principles of management for patients with pacemakers have been published (8,9) and were followed in this case. Rate responsive modes should be turned off and consideration given to reprogramming the pacemaker to an asynchronous mode before surgery, particularly if the patient is pacemaker-dependent. Our patient was not put into asynchronous mode because the pacemaker clinic assumed this mode was not available on this older generation pacemaker. (This was erroneous information, and he probably would be placed in VOO mode if he presented again). An alternative means of pacing should be available. The use of magnets is no longer recommended to protect the pulse generator from EMI because the magnet response will vary depending on the pacemaker design, programming, and battery voltage (7,8,10). Other measures include placing the rhizotomy current receiving plate away from the pacemaker. This reduces the opportunity for current to be conducted through the pacemaker and lead system as it flows from the needle electrode to the RFA receiving plate.
The potential problems associated with intracardiac RFA have been reported (2–5). A case report involving hepatic RFA has been published in which no complications were encountered (11). Recommendations cannot be made based on a single case report regarding the use of RFA for trigeminal rhizotomy and pacemakers. As with all EMI exposure, the pacemaker should be checked before and after the procedure and the peripheral pulse monitored in the same way during the case, because EMI generators often produce artifacts on the electrocardiac display. Based on our experience, we suggest that the management of similar cases proceed with the same precautions for potential pacemaker interference.
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