Variations of peak and baseline heart rates

The heart rate (HR) rises rapidly with ECT seizure onset and falls with seizure termination. The peak HR is a potential reflection of the intensity of the seizure. Because it varies greatly among patients, comparison with a benchmark HR for each patient should be useful. By comparing variations in the peak and baseline HRs, this study aims to determine if the peak HR should be compared with the baseline. HRs were measured on all treatments for 24 subjects receiving asymmetric bilateral ECT, excluding treatments with motoric seizure duration under 18s or no EEG postictal suppression. The resulting mean variations within subjects were significantly larger for the baseline (7.7 bpm, 8.1%, SD 4.6 bpm, p = 0.004 2-tail, p = 3.2 than the peak HR (4.6 bpm, 3.0%, SD 2.4 bpm). This indicates that comparison of the peak HR with the baseline substantially increases random variations. There was a general absence of correlation between peak and baseline HRs; this reveals no rationale for subtraction of the baseline from the peak. An expression of the peak HR that allows comparisons between patients but avoids the baseline HR is the difference between the seizure peak HR and the highest peak HR seen during that patient's ECT course.