Utility of estimated pulse wave velocity for assessing vascular stiffness: comparison of methods
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Evaluation Summary:
The authors of this paper have attempted to evaluate shortcomings of an algorithm for estimation of aortic pulse wave velocity, which is base on a single-point (brachial artery) measurement. The paper will potentially be of interest to other researchers working in the field of arterial hemodynamics, those interested in examining the health benefits of regular exercise and, possibly, health professionals looking for further tools to improve risk stratification. The authors test the single-point, pulse wave velocity algorithm using a number of approaches, including an interesting study of Masters athletes and sedentary controls, where they identify a strong dependency of the algorithm on age, which has been documented previously. The paper adds to the continuing debate over the ideal methods for non-invasive estimation of aortic stiffness and highlights the need for further studies in this area.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #2 agreed to share their name with the authors.)
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Abstract
Pulse wave velocity (PWV) independently predicts cardiovascular risk. Easy to use single-cuff oscillometric methods are utilized in clinical practice to estimate PWV. We applied the approach in master athletes to assess possible beneficial effects of lifelong exercise on vascular health. Furthermore, we compared single-cuff measurements with a two-cuff method in another cohort.
Methods:
We obtained single-cuff upper arm oscillometric measurements thrice in 129 master athletes aged 35–86 years and estimated PWV using the ArcSolver algorithm. We applied the same method in 24 healthy persons aged 24–55 years participating in a head down tilt bedrest study. In the latter group, we also obtained direct PWV measurements using a thigh cuff.
Results:
Estimated pulse velocity very highly correlated with age (R 2 = 0.90) in master athletes. Estimated PWV values were located on the same regression line like values obtained in participants of the head down tilt bed rest study. The modest correlation between estimated and measured PWV (R² 0.40; p<0.05) was attenuated after adjusting for age; the mean difference between PWV measurements was 1 m/s.
Conclusions:
Estimated PWV mainly reflects the entered age rather than true vascular properties and, therefore, failed detecting beneficial effects of lifelong exercise.
Funding:
The AGBRESA-Study was funded by the German Aerospace Center (DLR), the European Space Agency (ESA, contract number 4000113871/15/NL/PG), and the National Aeronautics and Space Administration (NASA, contract number 80JSC018P0078). FH received funding by the DLR and the German Federal Ministry of Economy and Technology, BMWi (50WB1816). SM, JT and JJ were supported by the Austrian Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation, and Technology, BMK (SPACE4ALL Project, FFG No. 866761).
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Evaluation Summary:
The authors of this paper have attempted to evaluate shortcomings of an algorithm for estimation of aortic pulse wave velocity, which is base on a single-point (brachial artery) measurement. The paper will potentially be of interest to other researchers working in the field of arterial hemodynamics, those interested in examining the health benefits of regular exercise and, possibly, health professionals looking for further tools to improve risk stratification. The authors test the single-point, pulse wave velocity algorithm using a number of approaches, including an interesting study of Masters athletes and sedentary controls, where they identify a strong dependency of the algorithm on age, which has been documented previously. The paper adds to the continuing debate over the ideal methods for non-invasive estimation …
Evaluation Summary:
The authors of this paper have attempted to evaluate shortcomings of an algorithm for estimation of aortic pulse wave velocity, which is base on a single-point (brachial artery) measurement. The paper will potentially be of interest to other researchers working in the field of arterial hemodynamics, those interested in examining the health benefits of regular exercise and, possibly, health professionals looking for further tools to improve risk stratification. The authors test the single-point, pulse wave velocity algorithm using a number of approaches, including an interesting study of Masters athletes and sedentary controls, where they identify a strong dependency of the algorithm on age, which has been documented previously. The paper adds to the continuing debate over the ideal methods for non-invasive estimation of aortic stiffness and highlights the need for further studies in this area.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #2 agreed to share their name with the authors.)
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Reviewer #1 (Public Review):
Single point measurements of pulse wave velocity may be a way to bring the measurement of arterial stiffness into daily clinical practice. However, the advantages and drawbacks of such a method need to be carefully investigated. This short communication aims to identify shortcomings of the so-called "ARCSolver" algorithm for pulse wave velocity estimation. Unfortunately, this manuscript does not bring many additional insights to the existing knowledge. We will assess their arguments in the following discussion:
The authors argue that the PWV measurements did not meet the expectations by master athletes, i.e. were higher than athletes and study personal expected. However, no other assessment of vascular properties in these subjects is presented, which could back up the argument. Thus, no scientifically solid …
Reviewer #1 (Public Review):
Single point measurements of pulse wave velocity may be a way to bring the measurement of arterial stiffness into daily clinical practice. However, the advantages and drawbacks of such a method need to be carefully investigated. This short communication aims to identify shortcomings of the so-called "ARCSolver" algorithm for pulse wave velocity estimation. Unfortunately, this manuscript does not bring many additional insights to the existing knowledge. We will assess their arguments in the following discussion:
The authors argue that the PWV measurements did not meet the expectations by master athletes, i.e. were higher than athletes and study personal expected. However, no other assessment of vascular properties in these subjects is presented, which could back up the argument. Thus, no scientifically solid conclusion can be drawn from this data. The expectation that older athletes will have a lower PWV compared to sedentary subjects is based on a paper from Vaitkevicius et al. In that study, only 14 senior athletes were included, and PWV measurements were a mixture of two methods. More recent studies in marathon runners show that athletes had a significant higher PWV than controls (Vlachopoulos et al, doi: 10.1038/ajh.2010.99), had increased coronary artery plaque volume compared to controls (Schwartz et al, PMID: 30323509) and that conventional cardiovascular risk stratification using the Framingham Risk score underestimates the CAC burden in presumably healthy marathon runners (Möhlenkamp et al, doi: 10.1093/eurheartj/ehn163).
The authors also argue that it unexpected that PWV values from master athletes lie on the same regression line as PWV values from participants of a head down tilt bed rest study called AGBRESA. When we understand correctly, the authors would expect that the PWV values from the master athletes should be comparably lower when trajected to the age of the bed rest study participants. However, when looking at the inclusion criteria for the AGBRESA study, only very healthy subjects were included. Furthermore, study participants were rather young, where no manifest arterial changes can be expected. Thus, when assuming that master athletes are also relatively healthy, it would actually be fully logical that they lie on the same regression line as the bed rest study participants.
Within the subjects of the bed rest study, a comparison to a PWV estimated from the pulse arrival time at the thigh (corrected by isovolumic contraction time) was performed. It was found that the difference between this PWV and the ARCSolver PWV correlates with the age of the subjects. This is an interesting finding. However, this does not show that the one or the other method is not reliable. It is already well known from literature, that aortic (invasive) PWV and carotid-femoral PWV have different trajectories over age, thus values are not directly comparable. While the ARCSolver PWV was developed to estimate aortic PWV, the PAT-based PWV in this study rather mimics a carotid-femoral PWV. In consequence, a diverging prolongation over age is expected.
In another experiment, the authors measured ARCSolver PWV repeatedly in the same subject, but changed the age of the subject in the software. Then they concluded that the changes in the resulting PWV almost exclusively depend on the entered age. However, this is not at all surprising but is exactly what should be the result of this experiment. It is known from previous publications that ARCSolver PWV is estimated from age, systolic blood pressure and waveform information. Since only age has been altered as an input in this experiment, the change in output can only depend on age as well.
In conclusion, the role of different methods for PWV estimation still needs to be found. While some studies have found a prognostic value of estimated PWV, other studies criticise estimation methods to be too simplistic and not capable of assessing vascular aging as detailed as needed. Thus, further studies are needed to bring more clarification.
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Reviewer #2 (Public Review):
This short report reveals a profoundly important issue relating to at least one device that claims to estimate pulse wave velocity (PWV) from a single arm cuff recording. The authors reveal a near-perfect correlation between age and estimated PWV, strongly implying that the device makes use of a statistical model that is almost entirely dependent on entered age. This finding is not surprising, given similar high (and unbelievable) correlations with age reported in prior work. The authors also showed that a factor other than age (long term exercise) that is expected to have an impact on actual PWV, had no impact on estimated PWV. Such a device could therefore lead to false conclusions in scientific studies. The authors rightly conclude that PWV estimated by such a device is no substitute for directly measured …
Reviewer #2 (Public Review):
This short report reveals a profoundly important issue relating to at least one device that claims to estimate pulse wave velocity (PWV) from a single arm cuff recording. The authors reveal a near-perfect correlation between age and estimated PWV, strongly implying that the device makes use of a statistical model that is almost entirely dependent on entered age. This finding is not surprising, given similar high (and unbelievable) correlations with age reported in prior work. The authors also showed that a factor other than age (long term exercise) that is expected to have an impact on actual PWV, had no impact on estimated PWV. Such a device could therefore lead to false conclusions in scientific studies. The authors rightly conclude that PWV estimated by such a device is no substitute for directly measured PWV via, e.g. the carotid-femoral technique.
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