The continuing problem of incorrect heart rate estimation in psychophysiological studies: an off-line solution for...

A wide variety of procedures are commonly used to record and estimate heart rate in psychophysiological studies. We analyze biases inherent in some estimates of mean heart rate based on cardiotachometers. Two types of errors are described, the time lag error and the incorrect weighted averaging error. These lead to an overestimation of the true heart rate, even when the analysis is based on digitized samples. Digitized samples provide a series of heart rate values per beat which correspond to the prior interbeat interval but during a time which does not correspond to the prior interval, but to the current one. A simple and practical solution, which eliminates both types of errors, is presented: an algorithm that corrects off-line the cardiotachometer data, reproducing the heart rate value with a length of time equal to the length of its own R R interval. Several comparisons between the corrected and uncorrected data are made to illustrate the magnitude of the error.