To the Editor:—
The recent case report, “Electrocautery-induced Tachycardia in a Rate-responsive Pacemaker,” by Drs. Wong and Middleton 1indicates that widespread understanding of certain aspects of pacemaker function and management is not optimum. In their report, Wong and Middleton state that during the use of monopolar electrosurgery, they noted the “gradual” onset of pacemaker-driven tachycardia. Their patient possessed a Telectronics Meta VVIR device (Englewood, CO), which is one of the earliest devices to incorporate a bioimpedance, minute ventilation activity sensor. Our concerns go beyond the specific experience cited by the authors, and it is appropriate to discuss again a number of issues relevant to this topic.
Issue 1: Pacing at the upper activity rate (UAR) in response to electromagnetic interference by devices that incorporate minute ventilation sensors should be well-known. Van Hemel et al. 2first described such behavior in 1989. Smith et al. 3reported two cases of inappropriate UAR pacing to diathermy (the British term for electrosurgical unit) in 1993. Vangelder et al. 4reported UAR pacing during a radiofrequency ablation in 1994. In 1997, Chew et al. 5reported inappropriate UAR pacing owing to connection to a Marquette 7010 monitor (Marquette Medical Systems, Milwaukee, WI), Spacelabs Alpha PC-1 monitor (Spacelabs Medical, Redmond, WA), or a Hewlett Packard Sonos 2500 Cardiac Doppler Ultrasound echocardiograph machine (Phillips Medical, Andover, MA). Subsequently, Troughear 6reported UAR in a patient connected to an IVY Biomedical Systems Model 101 ECG monitor (Ivy Biomedical Systems, Branford, CT). He showed that any device applying a small amount of electrical current to a patient's chest (for respiratory rate monitoring, electrocardiographic lead-off detection, or from allowable leakage) could cause a pacemaker using a bioimpedance sensor to believe that a patient has begun to exercise. In addition, this inappropriate response is not gradual. The device changes to UAR pacing abruptly after the electromagnetic interference begins.
In July 1998, after Wallden et al. 7published their report of inappropriate UAR pacing owing to connection to a Datex monitor (Datex- Ohmeda, Madison, WI), Rozner and Nishman petitioned the Center for Devices and Radiologic Health at the US Food and Drug Administration to issue an alert about this problem. The Food and Drug Administration quickly reviewed the data, and they placed an alert in October 1998 on the Food and Drug Administration Web site. *The alert was sent to numerous medical groups; the American Society of Anesthesiology included the alert in their January 1999 newsletter. 8
These alerts, along with other primers about the perioperative care of the patient with an implantable generator, 9–11make clear that failure to disable rate-responsive minute ventilation sensors can lead to inappropriate tachycardia with misinterpretation and possible poor patient outcome. In fact, nearly any kind of activity sensor can be fooled during an anesthetic procedure, and pacemaker manufacturers routinely suggest suspending such behavior. 12
Issue 2: The strips shown in the report have poorly visible electrocardiographic pacemaker artifacts (i.e. , “spikes”). Thus, one could easily misinterpret the second tracing as a sinus tachycardia with aberrant conduction or, even worse, as ventricular tachycardia resulting in the administration of intravenous antiarrhythmic medications or initiation of external cardioversion. These tracings likely were obtained from a Datex or Marquette intraoperative monitor. Both of these devices collect digitized electrocardiographic information and, when appropriately programmed, will “paint” pacemaker artifacts onto the record. The default mode for these devices, however, is to treat the sensed pacemaker artifacts as noise with subsequent filtering. When caring for a patient with an implantable pulse generator, it is imperative to remove this filtering. 10On the Datex machine, the setting should be “Show pacing artifacts”; on the Marquette, either “Pace 1” or “Pace 2” under the “Detect Pace” selection should be made. Perhaps the filtering of pacemaker artifacts made the immediate detection of the paced tachycardia more difficult to detect.
Issue 3: The recommendations by the authors are incomplete. More complete recommendations include: checking the device before the procedure to ensure adequate safety margins for pacing and sensing; obtaining current programming information to ensure appropriate behavior for the case; reprogramming to “OFF” features that can mimic pacer dysfunction (such as rate responsiveness, rate hysteresis, sleep mode, circadian rate, AV search hysteresis, and automatic detection of threshold levels); taking appropriate steps in the operating room (or elsewhere) to limit exposure to monopolar electrosurgery; and checking the device after the procedure is complete to ensure appropriate function and correct programming. 13
Issue 4: In the absence of specific knowledge of a device, a call to the manufacturer will provide general guidelines for pacemaker evaluation and reprogramming for any case. Most manufacturers provide toll-free support throughout North America, and toll-free numbers are found on the patient's pacemaker card, on the Internet, 14and in a variety of publications. 10,11,15
The apparent simplicity of the original report belies the multitude of potential problems faced when caring for a patient with an implantable generator. This report, in conjunction with the literature, provides evidence that any physician who must care for a patient with an implantable pulse generator needs to stay abreast of the field, which is constantly changing.