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Behavior of a respiratory rate-responsive pacemaker during and after cardiac surgery
Behavior of a Respiratory D. Newman,
Rate-Responsive Pacemaker Cardiac Surgery
During and After
MD, FACC, C.D. Mazer, MD, D.K. Rose, MD, J. Yao, MD, P. Dorian, MD, D. Darling, BSc, and S. Wilkie, BSc
A
DVANCES IN pacemaker technology now allow devices to increase their paced rates in response to information from biologic sensors.’ Previous case reports have described unexpected adverse device behavior related to sensor activation during surgery in the presence of these “rate-responsive” devices. 2-5In this report, a patient with a minute ventilation-sensing device who underwent coronary artery bypass surgery had sensor and device function assessed during the operation. The device estimates minute ventilation by calculating thoracic impedance from measurements of voltage obtained during a low energy current application (1 mA, 7.6 usec, 18 Hz) delivered between the extrathoracic pulse generator and the proximal pole of the intrathoracic bipolar pacemaker electrode. It was hypothesized that the marked changes in thoracic impedance consequent to chest opening would affect sensor behavior. In addition, the effects of cautery and mechanical ventilation settings on device sensor function were observed in a prospective manner. CASE REPORT
A 65year-old woman was admitted for urgent coronary revascularization because of unstable angina. Three months previously, she received a Telectronics Meta II VU-R 1204H minute volume monitoring rate-responsive pacemaker (Denver, CO) for episodes of symptomatic bradycardia with fatigue. Her predominant rhythm was sinus with normal atrioventricular conduction. Her baseline 12-lead electrocardiogram showed evidence of old inferior infarction. Device telemetry preoperatively revealed that all beats were sensed with no evidence of paced beats. In order to maintain a stable baseline for the sensor, the device was in a “WI + adapt” mode for the 2 hour period before the operation. In this mode, the device obtains sensor data but does not adjust the paced rate. The sensitivity of the sensor or “rate-response factor” was 18 with an upper rate of 120 beats/min and a minimum rate of 60 beats/min. The patient was anesthetized using a moderate-dose fentanyl and benzodiazepine technique. With the sternum open, the pacemaker was interrogated. This showed sensing only with no paced beats. During electrocautery, high frequency (> 10 Hz) continuous interference was detected and appropriately led to no more than two to three beats of temporary asynchronous (noise reversion mode) pacing. WI-R pacing was then instituted at the preoperative rateresponse settings. The device immediately showed sensing only. There was no evidence of a change in paced rate consequent to sensor activation with the chest open (Fig 1 A). Post-cautety, occasional asynchronous noise reversion mode output pulses were seen followed by upper rate pacing at the sensor-driven maximal rate (Fig 1 B). Interestingly, the upper rate, sensor-driven behavior seen after cautery was intermittent and not observed on all occasions (Fig 1 C). Where it occurred, cauteryrelated upper rate, sensor-driven pacing lasted up to 30 seconds. The device was then reprogrammed to WI + adapt mode following which coronary artery bypass surgery was performed without complication. One day postoperatively, while the patient was still intubated, the rate-responsive mode was enabled and the
effect of changing ventilation was assessed (Table 1). When this was done, the pacemaker responded appropriately by augmenting the standby rate in response to increased minute ventilation. Pacing occurred when the rate-response factor was increased, resulting in a more aggressive rate modulation. The pacemaker was programmed to Wl. There were no changes in sensing or pacing thresholds from preoperative to postoperative values. The patient had an uneventful recovery and was discharged from the hospital after a lo-day admission. DISCUSSION
The goal in this study was to determine if interventions during and after cardiac surgery would affect the behavior of a thoracic impedance monitoring WI-R pacemaker. Although it was hypothesized that the measurement of thoracic impedance might be different with the chest open, pacemaker sensor malfunction did not occur after sternotomy. As seen with sensor tracking of mechanical hyperventilation, it is possible that a more sensitive sensor would perhaps have led to an increased paced rate consequent to the thoracotomy. Electrocautery may interfere with pacemaker function in many ways. Alternating high voltage signals, which mimic the characteristics of an endocardial electrogram, could be interpreted as cardiac signals and inhibit pacing output in the VVI pacemaker. Application of a magnet in this situation causes asynchronous pacing by the device and may be required if inhibition of device function occurs in a pacemaker-dependent patient. Newer devices have noise reversion mode circuits designed to identify the high frequency used by electrocautery. This then leads to asynchronous device pacing. In older units, however, electrocautery in combination with the precordial magnet application have been reported to reprogram a demand pacemaker.6,7 One other case similar to the one in this report of sensor-driven upper rate pacing induced by electrocautery has been recorded.5 In that case, unexpected pacemakermediated tachycardia caused sufficient hemodynamic compromise to necessitate cardiopulmonary resuscitation. In this prospective investigation, programming was available to immediately disable sensor function in the operating room. The location of the electrocautery grounding pad may be relevant to sensor activation in some devices. In this case, the grounding pad of the electrocautery unit was
From the Division of Cardiology, St. Michael’s Hospital, Toronto, Ontario, Canada. Address reprint requests to D. Newman, MD, FACC, St. Michael’s Hospital, Division of Cardioloo, 30 Bond St, Rm 7198, Toronto, Ontario, M5B 1 W8, Canada. Copyright o 1994 by WB. Saunders Company 1053-0770194/0806-0014$03.00/0 Key words: surgery, pacemakers, respiratory sensors
Journalof Cardiothoracic and VascularAnesthesia, Vol8. No 6 (December), 1994: pp 675677
675
NEWMAN
676
Speed
25
ET
At
I
mm/s
VVIR
Speed
12.5
vents Pace Sense Noise
Speed
mm/s
VVIR
12.5
mm/s
L
Fig 1. Illustrated in the three panels are the main timing event recordings telemetered from the device during cardiac surgery with the chest opened. The open circle represent beats that are sensed, the stars represent beats that are paced, and the circles with the slash represent events considered noise. The upper tracing shows the timing markers and the lower tracing in panels B and C the telemetered intracardiac electrogram. Applications of cautery are indicated by the arrows. The paper speed in A is 25 mm/s and 12.5 mm/s in Band C. (A) The rate-responsive sensor is off. During cautery, noise events are documented with one asynchronous, interference reversion output pulse seen after the second application. (B and C) The rate-responsive sensor is activated. Before cautery and with the chest open, appropriate sensing is seen. After the application of cautery, upper rate pacing at 120 beats/min ensues in panel B. Panel C demonstrates further applications of cautery with occasional noise reversion mode asynchronous pacing but no evidence of upper rate pacing, despite the fact that programming settings are unchanged. See text for discussion.
placed over the patient’s right thigh. Electrocautery produces voltages in the range of 5,000 to 7,000 volts, whereas the sensor measures voltages in the 1 to 10 volt range. Accordingly, it is doubtful that any other positioning of the cautery pad would significantly attenuate the magnitude of the voltage signal that prompts sensor activation. The phenomenon of cautery-induced sensor-driven upper rate pacing is likely due to the noise signal interfering with the electronic acquisition and processing of the minute ventilation measures. In this case such interference occurred in a random fashion with effects that lasted up to 30 Table 1. Postoperative Ventilation and Pacemaker Function Minute Ventilation (mL/min)
Respiratory Rate (breathslmin)
Rate-
SfXl%X
Responsive
Predicted
Factor*
Actual Rate
(beats/min)t
Heart
Rate
lbeats/min)
10.6
13
18
60
85
16.9
20
18
68
83
(sensed)
10
12
30
81
81
(paced)
15.5
18
30
90
90 (paced)
NOTE. All respiratory settings on IMV
(sensed)
mode, day 1 postoperative, and
heavily sedated. In all settings, tidal volume was 800 mL. *Rate-responsive
Factor (arbitrary units) defines sensor sensitivity to
measured changes in minute volume. Maximum RRF = 43, nominal = 15. Maximal sensor driven paced rate programmed to 90 beats/min. Sensor
predicted rate is the rate the sensor would have chosen had
the patient been pacemaker dependent. heart rate, the patient is not being paced.
When lower than the actual
seconds. The variable duration of cautery-related sensordriven upper rate pacing is likely due to the degree of interference with the sensor as well as the rate of decay algorithm used for the cessation of sensor-driven pacing. Sensor-related inappropriate pacing could potentially be diagnosed with magnet application, which causes the device to pace asynchronously at a rate dependent on battery status (100 pulses/min at start, and 80 pulsesimin at end-of-life). Current manufacturer recommendations state that the sensor not be activated during electrocautery,* and as a corollary that pacemaker identification and programming be performed before any surgery. Nonetheless, exigencies may prevent identification and reprogramming of device functions preoperatively, and sensor-based pacing may occur. This should be suspected whenever a paced output or unexplained (paced) wide complex rhythm occurs in a patient with a rate-responsive pacemaker. In such situations, marked changes in paced rate may occur in response to electrocautery or to hyperventilation. Magnet application would be an important diagnostic and therapeutic maneuver for this phenomenon. In summary, it was found that with a respiratory rateresponsive pacemaker and a moderate rate responsive factor, the opening of the chest did not significantly affect sensor behavior of a thoracic impedance sensing device.
RESPIRATORY
SENSOR PACEMAKER
BEHAVIOR
677
Intraoperatively, electrocautery led to transient and intermittent episodes of sensor-based upper-rate pacing. Finally, postoperatively, clinical hyperventilation was able to initiate sensor-driven pacing, which in turn was dependent
on the programmed sensitivity of the device. These findings are limited to one model of device and sensor system. Further study would be needed to generalize these results to other devices or sensors.
REFERENCES
1. Andersen C, Madsen GM: Rate-responsive pacemakers and anesthesia. Anesthesia 45:472-476, 1990 2. Andersen C, Oxhoj H, Arnsbo P, Lybecker H: Pregnancy and cesarean section in a patient with a rate-responsive pacemaker. PACE 12:386-391, 1989 3. Lau CP, Lee CP, Wong CK, et al: Rate responsive pacing with a minute ventilation sensing pacemaker during pregnancy and delivery. PACE 13:158-163, 1990 4. Madsen GM, Andersen C: Pacemaker-induced tachycardia during general anesthesia: A case report. Br J Anesth 63:360-361, 1989
5. Van Hemel NM, Hamerlijnck RPHM, Pronk KJ, Van Der Veen EDP: Upper limit ventricular stimulation in respiratory rate responsive pacing due to electrocautery. PACE 12:1720-1723, 1989 6. Belott PH, Sands S, Warren .I: Resetting of DDD pacemakers due to EMI. PACE 7:169-172, 1984 7. Domino KB, Smith TC: Electrocautery-induced reprogramming of a pacemaker using a precordial magnet. Anesth Analg 62:609-612, 1983 8. Telectronics Pacing Systems Inc. Meta II Model 1204H: Physicians Manual. Denver, CO, 1991.
Rate-Responsive Pacemaker Cardiac Surgery
During and After
MD, FACC, C.D. Mazer, MD, D.K. Rose, MD, J. Yao, MD, P. Dorian, MD, D. Darling, BSc, and S. Wilkie, BSc
A
DVANCES IN pacemaker technology now allow devices to increase their paced rates in response to information from biologic sensors.’ Previous case reports have described unexpected adverse device behavior related to sensor activation during surgery in the presence of these “rate-responsive” devices. 2-5In this report, a patient with a minute ventilation-sensing device who underwent coronary artery bypass surgery had sensor and device function assessed during the operation. The device estimates minute ventilation by calculating thoracic impedance from measurements of voltage obtained during a low energy current application (1 mA, 7.6 usec, 18 Hz) delivered between the extrathoracic pulse generator and the proximal pole of the intrathoracic bipolar pacemaker electrode. It was hypothesized that the marked changes in thoracic impedance consequent to chest opening would affect sensor behavior. In addition, the effects of cautery and mechanical ventilation settings on device sensor function were observed in a prospective manner. CASE REPORT
A 65year-old woman was admitted for urgent coronary revascularization because of unstable angina. Three months previously, she received a Telectronics Meta II VU-R 1204H minute volume monitoring rate-responsive pacemaker (Denver, CO) for episodes of symptomatic bradycardia with fatigue. Her predominant rhythm was sinus with normal atrioventricular conduction. Her baseline 12-lead electrocardiogram showed evidence of old inferior infarction. Device telemetry preoperatively revealed that all beats were sensed with no evidence of paced beats. In order to maintain a stable baseline for the sensor, the device was in a “WI + adapt” mode for the 2 hour period before the operation. In this mode, the device obtains sensor data but does not adjust the paced rate. The sensitivity of the sensor or “rate-response factor” was 18 with an upper rate of 120 beats/min and a minimum rate of 60 beats/min. The patient was anesthetized using a moderate-dose fentanyl and benzodiazepine technique. With the sternum open, the pacemaker was interrogated. This showed sensing only with no paced beats. During electrocautery, high frequency (> 10 Hz) continuous interference was detected and appropriately led to no more than two to three beats of temporary asynchronous (noise reversion mode) pacing. WI-R pacing was then instituted at the preoperative rateresponse settings. The device immediately showed sensing only. There was no evidence of a change in paced rate consequent to sensor activation with the chest open (Fig 1 A). Post-cautety, occasional asynchronous noise reversion mode output pulses were seen followed by upper rate pacing at the sensor-driven maximal rate (Fig 1 B). Interestingly, the upper rate, sensor-driven behavior seen after cautery was intermittent and not observed on all occasions (Fig 1 C). Where it occurred, cauteryrelated upper rate, sensor-driven pacing lasted up to 30 seconds. The device was then reprogrammed to WI + adapt mode following which coronary artery bypass surgery was performed without complication. One day postoperatively, while the patient was still intubated, the rate-responsive mode was enabled and the
effect of changing ventilation was assessed (Table 1). When this was done, the pacemaker responded appropriately by augmenting the standby rate in response to increased minute ventilation. Pacing occurred when the rate-response factor was increased, resulting in a more aggressive rate modulation. The pacemaker was programmed to Wl. There were no changes in sensing or pacing thresholds from preoperative to postoperative values. The patient had an uneventful recovery and was discharged from the hospital after a lo-day admission. DISCUSSION
The goal in this study was to determine if interventions during and after cardiac surgery would affect the behavior of a thoracic impedance monitoring WI-R pacemaker. Although it was hypothesized that the measurement of thoracic impedance might be different with the chest open, pacemaker sensor malfunction did not occur after sternotomy. As seen with sensor tracking of mechanical hyperventilation, it is possible that a more sensitive sensor would perhaps have led to an increased paced rate consequent to the thoracotomy. Electrocautery may interfere with pacemaker function in many ways. Alternating high voltage signals, which mimic the characteristics of an endocardial electrogram, could be interpreted as cardiac signals and inhibit pacing output in the VVI pacemaker. Application of a magnet in this situation causes asynchronous pacing by the device and may be required if inhibition of device function occurs in a pacemaker-dependent patient. Newer devices have noise reversion mode circuits designed to identify the high frequency used by electrocautery. This then leads to asynchronous device pacing. In older units, however, electrocautery in combination with the precordial magnet application have been reported to reprogram a demand pacemaker.6,7 One other case similar to the one in this report of sensor-driven upper rate pacing induced by electrocautery has been recorded.5 In that case, unexpected pacemakermediated tachycardia caused sufficient hemodynamic compromise to necessitate cardiopulmonary resuscitation. In this prospective investigation, programming was available to immediately disable sensor function in the operating room. The location of the electrocautery grounding pad may be relevant to sensor activation in some devices. In this case, the grounding pad of the electrocautery unit was
From the Division of Cardiology, St. Michael’s Hospital, Toronto, Ontario, Canada. Address reprint requests to D. Newman, MD, FACC, St. Michael’s Hospital, Division of Cardioloo, 30 Bond St, Rm 7198, Toronto, Ontario, M5B 1 W8, Canada. Copyright o 1994 by WB. Saunders Company 1053-0770194/0806-0014$03.00/0 Key words: surgery, pacemakers, respiratory sensors
Journalof Cardiothoracic and VascularAnesthesia, Vol8. No 6 (December), 1994: pp 675677
675
NEWMAN
676
Speed
25
ET
At
I
mm/s
VVIR
Speed
12.5
vents Pace Sense Noise
Speed
mm/s
VVIR
12.5
mm/s
L
Fig 1. Illustrated in the three panels are the main timing event recordings telemetered from the device during cardiac surgery with the chest opened. The open circle represent beats that are sensed, the stars represent beats that are paced, and the circles with the slash represent events considered noise. The upper tracing shows the timing markers and the lower tracing in panels B and C the telemetered intracardiac electrogram. Applications of cautery are indicated by the arrows. The paper speed in A is 25 mm/s and 12.5 mm/s in Band C. (A) The rate-responsive sensor is off. During cautery, noise events are documented with one asynchronous, interference reversion output pulse seen after the second application. (B and C) The rate-responsive sensor is activated. Before cautery and with the chest open, appropriate sensing is seen. After the application of cautery, upper rate pacing at 120 beats/min ensues in panel B. Panel C demonstrates further applications of cautery with occasional noise reversion mode asynchronous pacing but no evidence of upper rate pacing, despite the fact that programming settings are unchanged. See text for discussion.
placed over the patient’s right thigh. Electrocautery produces voltages in the range of 5,000 to 7,000 volts, whereas the sensor measures voltages in the 1 to 10 volt range. Accordingly, it is doubtful that any other positioning of the cautery pad would significantly attenuate the magnitude of the voltage signal that prompts sensor activation. The phenomenon of cautery-induced sensor-driven upper rate pacing is likely due to the noise signal interfering with the electronic acquisition and processing of the minute ventilation measures. In this case such interference occurred in a random fashion with effects that lasted up to 30 Table 1. Postoperative Ventilation and Pacemaker Function Minute Ventilation (mL/min)
Respiratory Rate (breathslmin)
Rate-
SfXl%X
Responsive
Predicted
Factor*
Actual Rate
(beats/min)t
Heart
Rate
lbeats/min)
10.6
13
18
60
85
16.9
20
18
68
83
(sensed)
10
12
30
81
81
(paced)
15.5
18
30
90
90 (paced)
NOTE. All respiratory settings on IMV
(sensed)
mode, day 1 postoperative, and
heavily sedated. In all settings, tidal volume was 800 mL. *Rate-responsive
Factor (arbitrary units) defines sensor sensitivity to
measured changes in minute volume. Maximum RRF = 43, nominal = 15. Maximal sensor driven paced rate programmed to 90 beats/min. Sensor
predicted rate is the rate the sensor would have chosen had
the patient been pacemaker dependent. heart rate, the patient is not being paced.
When lower than the actual
seconds. The variable duration of cautery-related sensordriven upper rate pacing is likely due to the degree of interference with the sensor as well as the rate of decay algorithm used for the cessation of sensor-driven pacing. Sensor-related inappropriate pacing could potentially be diagnosed with magnet application, which causes the device to pace asynchronously at a rate dependent on battery status (100 pulses/min at start, and 80 pulsesimin at end-of-life). Current manufacturer recommendations state that the sensor not be activated during electrocautery,* and as a corollary that pacemaker identification and programming be performed before any surgery. Nonetheless, exigencies may prevent identification and reprogramming of device functions preoperatively, and sensor-based pacing may occur. This should be suspected whenever a paced output or unexplained (paced) wide complex rhythm occurs in a patient with a rate-responsive pacemaker. In such situations, marked changes in paced rate may occur in response to electrocautery or to hyperventilation. Magnet application would be an important diagnostic and therapeutic maneuver for this phenomenon. In summary, it was found that with a respiratory rateresponsive pacemaker and a moderate rate responsive factor, the opening of the chest did not significantly affect sensor behavior of a thoracic impedance sensing device.
RESPIRATORY
SENSOR PACEMAKER
BEHAVIOR
677
Intraoperatively, electrocautery led to transient and intermittent episodes of sensor-based upper-rate pacing. Finally, postoperatively, clinical hyperventilation was able to initiate sensor-driven pacing, which in turn was dependent
on the programmed sensitivity of the device. These findings are limited to one model of device and sensor system. Further study would be needed to generalize these results to other devices or sensors.
REFERENCES
1. Andersen C, Madsen GM: Rate-responsive pacemakers and anesthesia. Anesthesia 45:472-476, 1990 2. Andersen C, Oxhoj H, Arnsbo P, Lybecker H: Pregnancy and cesarean section in a patient with a rate-responsive pacemaker. PACE 12:386-391, 1989 3. Lau CP, Lee CP, Wong CK, et al: Rate responsive pacing with a minute ventilation sensing pacemaker during pregnancy and delivery. PACE 13:158-163, 1990 4. Madsen GM, Andersen C: Pacemaker-induced tachycardia during general anesthesia: A case report. Br J Anesth 63:360-361, 1989
5. Van Hemel NM, Hamerlijnck RPHM, Pronk KJ, Van Der Veen EDP: Upper limit ventricular stimulation in respiratory rate responsive pacing due to electrocautery. PACE 12:1720-1723, 1989 6. Belott PH, Sands S, Warren .I: Resetting of DDD pacemakers due to EMI. PACE 7:169-172, 1984 7. Domino KB, Smith TC: Electrocautery-induced reprogramming of a pacemaker using a precordial magnet. Anesth Analg 62:609-612, 1983 8. Telectronics Pacing Systems Inc. Meta II Model 1204H: Physicians Manual. Denver, CO, 1991.