Extracellular electrograms can be sampled at rates as low as 250 Hz without significantly impairing the accuracy of activation mapping in localizing ventricular tachycardia.
The Precision of Electrophysiological Mapping: Localizing Depolarization Wave Fronts from Digitized Extracellular Electrograms and the Role of Data Sampling Rate. Electrophysiological mapping uses extracellular electrograms to estimate the timing of local cellular depolarization. To measure the precision of localizing propagating wave fronts with this technique and determine its dependence on data sampling rate, extracellular electrograms were recorded with a laboratory computer from 61 bipolar epicardial and endocardial electrodes during 10 morphologically distinct episodes of ventricular tachycardia (VT) in 10 chronically infarcted dogs. Four investigators assigned local activation times to 610 computer displayed local electrograms (61 from each of 10 VTs) sampled at 1,000 Hz (trial 1). With the investigators blinded to the result of the first trial, activation mapping was again repeated in serial independent trials using identical eleetrograms displayed at the data acquisition rate (1,000 Hz), in addition to sampling rates of 500 Hz, 250 Hz, and 125 Hz. The temporal precision of activation mapping (± 10 msec, 95% confidence) was derived from the reproducibility of measuring local activation time from maximally sampled (1,000 Hz) extracellular electrograms. Multivariate analysis revealed decreased precision at epicardial (P <0,02) and infarcted sites, which was attributed to fractionated eleetrograms observed in these regions. Nonetheless, map guided localization of the anatomic breakthrough site of each tachycardia varied by only 1.0 ± 1.2 cm between trials. This value was consistent with the spatial resolution (± 0.5 to + 1.0 cm) that was predicted from the measured temporal precision. Extracellular electrograms contained minimal frequency content above 150 Hz resulting in negligible distortion of waveform morphology at sampling rates as low as 250 Hz. Moreover, the accuracy of activation mapping was not significantly impaired until sampling rate was slowed to 125 Hz.
Rosenbaum et al. (Thu,) studied this question.