In Reply:—
We thank Drs. Rozner and Nishman for taking the time to increase the amount of issues about our case report that we were unable to address because of word limitations.
In response to issue 1, we believe that anesthesiologists in general do not have in-depth knowledge of pacemakers, especially newer pacemakers with features such as rate responsiveness. Drs. Rozner and Nishman cited a number of references reporting upper activity rate pacing in response to electromagnetic interference. However, the majority of these were case reports in nonanesthesia journals, such as Pacing and Clinical Electrophysiology . One needs only to refer to major anesthesia textbooks to see the lack of details regarding these devices. We practice in an academic center with a large cardiovascular program. Although most anesthesiologists are aware of potential problems with pacemakers, many are not familiar with the details for this type of pacemaker. The patient in our case report was referred to a cardiologist at a pacemaker clinic in another academic center who did not reprogram the pacemaker out of the rate-responsive mode preoperatively. Therefore, we believe that it is worthwhile to draw wider attention to electromagnetic interference in rate-responsive pacemakers with our case report.
Drs. Rozner and Nishman implied that a gradual onset of pacemaker-driven tachycardia is not possible. A company representative from St. Jude Medical in California stated that a gradual onset of pacemaker driven tachycardia is the usual response to cautery interference in the Telectronics META II pacemaker (Englewood, CO). This pacemaker has two programmable response times: medium (36 s) or fast (18 s). The response time determines the time required to reach 50% of the metabolically indicated rate in response to an instantaneous change in the measured minute ventilation. Therefore, it would typically take four response times to reach greater than 90% of maximum programmed rate with real or perceived step changes in minute ventilation. This abnormal response to electromagnetic interference usually results from erroneous interpretation of the mixture of bioimpedance signals rather than a direct effect on the pulse generator itself; thus, a gradual rather than a sudden response is expected.
In response to issue 2, the pacemaker spikes were clearly visible on the monitor screen and to a lesser extent on the printout tracing. Therefore, recognition of pacemaker tachycardia is not the central issue—prevention and management are.
In response to issue 3, we intentionally kept our recommendations brief because of word limitations and at the request of the editor. Detailed recommendations could be obtained from the Web page *cited in the case report reference.
In response to issue 4, we agree with the recommendations of Drs. Nishman and Rosner.
We believe that practicing anesthesiologists need to maintain knowledge of and be familiar with the potential complications of rate-responsive pacemakers, and we hope the case report and its correspondence will heighten awareness of this subject.
