Figure 35-5 Disabling the pacemaker artifact filter on a digitally processed electrocardiographic (ECG) monitor results in the "painting" of environmental interference (EMI) as pacemaker artifacts. A, The patient's underlying rate exceeded the pacemaker's programmed lower rate limit, and no pacing took place. However, activation of the monopolar electrosurgical unit (ESU) in the "cut" mode produced sufficient electromagnetic noise that the monitor began painting pacemaker artifacts at a rate of about 20 Hz. The top tracing is ECG lead II, the middle tracing is ECG lead V5, and the bottom tracing is the invasive arterial pressure waveform. B, "Coagulation" ESU produced ventricular oversensing with pacemaker inhibition and left this patient with a compromised cardiac output. There is also evidence of inappropriate monitor painting of pacemaker artifacts from the EMI. The top tracing is ECG lead II, the middle tracing is the pulse oximeter plethysmogram, and the bottom tracing is the invasive arterial pressure waveform. (Adapted from Rozner MA: [untitled letter]. Pacing Clin Electrophysiol 26:923–925, 2003.)