Small intra-individual variability of the pre-ejection period justifies the use of pulse transit time as approximation of the vascular transit

Abstract

BackgroundVascular transit time (VTT) is the propagation time of a pulse wave through an artery; it is a measure for arterial stiffness. Because reliable non-invasive VTT measurements are difficult, as an alternative we measure pulse transit time (PTT). PTT is defined as the time between the R-wave on electrocardiogram and arrival of the resulting pulse wave in a distal location measured with photoplethysmography (PPG). The time between electrical activation of the ventricles and the resulting pulse wave after opening of the aortic valve is called the pre-ejection period (PEP), a component of PTT. The aim of this study was to estimate the variability of PEP at rest, to establish how accurate PTT is as approximation of VTT.MethodsPTT was measured and PEP was assessed with echocardiography (gold standard) in three groups of 20 volunteers: 1) a control group without cardiovascular disease aged <50 years and 2) aged >50 years, and 3) a group with cardiovascular risk factors, defined as arterial hypertension, dyslipidemia, kidney failure and diabetes mellitus.ResultsPer group, the mean PEP was: 1) 58.5 ± 13.0 ms, 2) 52.4 ± 11.9 ms, and 3) 57.6 ± 11.6 ms. However, per individual the standard deviation was much smaller, i.e. 1) 2.0–5.9 ms, 2) 2.8–5.1 ms, and 3) 1.6–12.0 ms, respectively. There was no significant difference in the mean PEP of the 3 groups (p = 0.236).ConclusionIn conclusion, the intra-individual variability of PEP is small. A change in PTT in a person at rest is most probably the result of a change in VTT rather than of PEP. Thus, PTT at rest is an easy, non-invasive and accurate approximation of VTT for monitoring arterial stiffness.

Pulse transit time estimation of aortic pulse wave velocity and blood pressure using machine learning and simulated training data

“…As mentioned above, in practice, the R-peak location in ECG signal is often used as a surrogate to aortic valve opening due to simpler measurement. However, using PATs gives only mediocre accuracy compared to PTT due to the physiological variations in PEP [7,8]. Our finding are similar, see for example, Fig.…”

“…To overcome this difficulty, PTT is often approximated using pulse arrival time (PAT) which uses the R-wave of electrocardiogram (ECG) as a reference timing [6]. However, there exists controversy in the clinical accuracy of using PAT in the predictions due to variations in pre-ejection period (PEP) from the R-wave to aortic valve opening [7,8]. An alternative approach is to approximate the reference with a measurement from another distal site near aorta.…”

Contactless seismocardiography via deep learning radars

“…These numbers are in line with the nominal values from the literature on inter-subject variability[26].…”

Deep learning for prediction of cardiac indices from photoplethysmographic waveform: A virtual database approach

“…In such case, the time difference is referred to as pulse arrival time (PAT). Clinical accuracy is, however, questionable due to physiological variations in pre‐ejection period (from the R‐wave to aortic valve opening) . PTT and PAT have also been suggested to be used for the cuff‐less blood pressure monitoring (see, for example, previous studies), even though clinical reliability of such measurement is also questionable …”

“…Clinical accuracy is, however, questionable due to physiological variations in pre-ejection period (from the R-wave to aortic valve opening). 8,9 PTT and PAT have also been suggested to be used for the cuff-less blood pressure monitoring (see, for example, previous studies 7, 10,11 ), even though clinical reliability of such measurement is also questionable. 12 There are also many studies suggesting to use machine learning (ML) for predicting factors related to cardiac health.…”