Slew Rates for Electrocardiographic Signals

Frank lead electrocardiograms from 100 adults and 61 infants were recorded on magnetic tape and digitized at 2 ms intervals after bandwidth limiting fmst at 200 Hz and then at 100 Hz. Slew rates based on voltage differences between successive sampled values during QRS were computed for one cardiac cycle for each lead. Considered as a group, 200 μV/ms rates occur about 1% of the time in adult records, and 400 μV/ms rates occur about 1% of the time in infants' records. In extreme individual records, 300 μV/ms rates were exceeded 2% of the time in an adult record, and 400 μV/ms rates were exceeded 6.5% of the time in an infant's record. No significant differences in slew rates were observed to be caused by variation in bandwidth from 100 Hz to 200 Hz. It is recommended that ECG instruments be designed to be capable of faithfully reproducing at least 400 μV/ms slew rates.