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Correspondence  |   October 2003
Interference Masquerading as Atrial Extrasystole
Author Affiliations & Notes
  • Graham T Bell, F.R.C.A.
    *
  • *Royal Hospital for Sick Children, Glasgow, United Kingdom.
Article Information
Correspondence
Correspondence   |   October 2003
Interference Masquerading as Atrial Extrasystole
Anesthesiology 10 2003, Vol.99, 1032-1033. doi:
Anesthesiology 10 2003, Vol.99, 1032-1033. doi:
To the Editor:—
We would like to report a source of potential electrocardiograph interference that may occur under anesthesia for laser treatment of capillary vascular malformation in children. During pulsed dye laser therapy (Scleroplus SPT-1 day; Candela, Wayland, MA) to a capillary vascular malformation that extended onto the chest, the electrocardiograph trace shown in Figure 1was recorded. The initial diagnosis was atrial extrasystole, but there was no disturbance in the patients’ radial pulse or pulse-oximetry waveform. It became apparent that each of the extra pulses on the electrocardiograph coincided with the laser being fired. The electrocardiograph was a modern Datex AS3 (Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland).
Fig. 1. Vertical black lines  along baseline of electrocardiograph strip indicate when the laser and dynamic cooling device were fired.
Fig. 1. Vertical black lines 
	along baseline of electrocardiograph strip indicate when the laser and dynamic cooling device were fired.
Fig. 1. Vertical black lines  along baseline of electrocardiograph strip indicate when the laser and dynamic cooling device were fired.
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A relatively new development in medical laser technology is the inclusion of a dynamic cooling device as part of the laser handpiece. The cooling device is activated by the same trigger as the laser and fires a jet of cryogen gas onto the skin before each laser pulse. This minimizes thermal injury to the epidermis and enables the patient to receive higher therapeutic laser exposure per theater session, reducing the total number of visits required. The cooling device has an actuator, which emits an electromagnetic pulse each time the laser is fired. The actuator is activated by the firing trigger either in the handset or the foot pedal.
Because it is possible to fire the laser and the cooling piece separately from each other, we have been able to prove that the cooling device alone is responsible for the electrocardiograph interference. We have also reduced the level of interference experimentally by shielding the handset in a μ-metal box, although this is practically cumbersome. The amplitude of electrocardiograph interference is inversely proportional to the distance between an electrocardiograph electrode and the dynamic cooling device. Candela indicates that all handpieces in their manufactured lasers that use the dynamic cooling device could exhibit this characteristic to varying degrees (personal written communication between author (G.T.B.) and C. Johnson, Director of Engineering, Candela Corporation, Wayland, MA, March 2003). Our advice is to be aware of the possibility of electrocardiograph interference, perhaps with appropriate “caution” labels on the handset. Positioning electrocardiograph electrodes further away from the area requiring laser therapy will minimize interference; however, this must be bal-anced against the potential of reduced electrocardiograph signs of ischemia, and clinicians must consider these relative risks in any individual patient.
Fig. 1. Vertical black lines  along baseline of electrocardiograph strip indicate when the laser and dynamic cooling device were fired.
Fig. 1. Vertical black lines 
	along baseline of electrocardiograph strip indicate when the laser and dynamic cooling device were fired.
Fig. 1. Vertical black lines  along baseline of electrocardiograph strip indicate when the laser and dynamic cooling device were fired.
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