Aortic-finger pulse transit time vs. R-derived Pulse Arrival Time: A beat-to-beat assessment

Due to the difficult identification of the Aortic valve Opening (AO), Pulse Transit Time (PTT) is often surrogated by the Pulse Arrival Time (PAT) in which AO is approximated by the R peak in the ECG signal. This procedure introduces a fraction of the Pre Ejection Period variability into the PAT dynamics and makes the PAT variability partially different from the PTT variability. In this pilot study we aim to quantify the possible discrepancies between PTT and PAT dynamics on a beat-to-beat basis. In 5 sitting healthy subject we simultaneously recorded ECG, continuous finger blood pressure and the chest micro-accelerations produced by the heart contraction (the seismocardiogram) before and after a 100W exercise at the cycloergometer. When compared to PTT, PAT is characterized not only by the expected greater mean value but also by a larger beat-to-beat variability, The spectral analysis and a subsequent averaging of the data indicates that the correlation between PTT and PAT dramatically increases when the high frequency components of their variability are removed.