<p>The Nociception Level (NOL) index of the PMD-200™ monitor measures intraoperative nociception–antinociception balance. Because it relies on photoplethysmography, it may be affected by pacemaker interference. We evaluated its response to pacemaker stimulation in the absence of nociceptive input. Mechanically ventilated adults after elective cardiac surgery were studied. NOL index, bispectral index, mean arterial pressure, and heart rate were recorded every minute for 35&#xa0;min across seven five-minute periods: baseline (pacemaker off), pacing at 90 beats.min^− 1, pacing at 110 beats min^− 1, pacemaker off (washout), pacing at 110 beats min^− 1 (rechallenge), after PMD-200™ recalibration at 110 beats min^− 1, and continued monitoring at 110 beats min^− 1. Data were analysed with mixed-model repeated measures (random intercept for patient, time fixed; bispectral index covariate for NOL). Results are least-square adjusted means ± (standard error), comparing the last minute of each period. Twenty patients were analysed. Pacemaker-induced heart rate changes significantly affected NOL over time (F = 28.420, <i>p</i> &lt; 0.001). Compared with baseline 2.1 ± (1.74), pacing at 90 beats min^− 1 increased NOL to 8.4 ± (1.73) (<i>p</i> = 1.000) and at 110 beats min^− 1 to 18.4 ± (1.73) (<i>p</i> &lt; 0.001). Stopping pacing returned NOL to 1.1 ± (1.73) (<i>p</i> = 1.000), which rose again at 110 beats.min^− 1 rechallenge to 18.0 ± (1.73) (<i>p</i> &lt; 0.001). Recalibration restored baseline values 1.1 ± (1.73) (<i>p</i> = 1.000), with stability maintained during continued monitoring 1.5 ± (1.73) (<i>p</i> = 1.000). The NOL index captured the studied nociception–antinociception balance during pacemaker stimulation when recalibrated to the paced rate<b>.</b> <i>ClinicalTrials.gov:</i> NCT06696781 on 17.11.2024.</p>