Assessment of arterial stiffness via measurement of pulse wave velocity a study for the normotensive population

• Main Author: Chang, Serene Wei Nee.
• Other Authors: Yeo Joon Hock
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Bioengineering
• Online Access: http://hdl.handle.net/10356/17087
• Institution: Nanyang Technological University

Cardiovascular diseases are the number one killer in the world which represents 30% of all global deaths and it is predicted by World Health Organisation to remain the single leading cause of death globally. Cardiovascular deterioration is usually unassuming and difficult to detect. Stiffening of arteries in the form of atherosclerosis is one of the major causes of cardiovascular diseases. Hence, arterial stiffness is an important area of interest for researchers and doctors striving to counter the threat of cardiovascular diseases. Stiffness of a blood vessel is quantified by E, the Young’s Modulus of the arterial wall. Measurement of pulse wave velocity (PWV) is a method to identify arterial stiffening. The objectives of this Final Year Project, is to study the relationship of pulse wave velocity with age, and hence, the relationship between arterial stiffness and age, in the normotensive population. The equipment used in this project is PulseTrace PWV PT4000. It measures PWV between two sites of the arterial tree by using a 5MHz Doppler transducer to identify the arrival of the arterial pulse to calculate the PWV. The foot to foot technique is used here, and Doppler pulses are recorded sequentially in the brachial site and the dorsalis pedis site. Brachial-ankle pulse wave velocity (baPWV) is measured in 291 subjects of whom 158 are male and 133 females). The youngest and oldest subjects are 11 and 88 years old respectively. The lowest and highest measured baPWV are 5.6m/s and 20.2m/s respectively. The data obtained are analysed with Regression Analysis and Analysis of Variance (ANOVA). Using the method of sum of least squares, the proposed regression model is baPWV = 0.093*age + 5.464, with Pearson factor r of 0.791, R2 of 0.624, and significant value < 0.001. A good correlation was shown and statistical significance was proven. Based on the proposed relationship that baPWV = 0.093*age + 5.464, 91.8% of the subjects are within a 95% confidence interval, while 86.6% are within a 90% confidence interval. The measured waveform and published literature comes into agreement with the obtained readings and further improve the confidence of the results. i The elastic modulus of the artery is then derived from the Moens-Korteweg equation, C₀= /2 from the baPWV values. The plot of this derived elastic modulus against age gave a polynomial upward trend. It can be seen that a steeper rate of increase of arterial stiffness in the elderly as compared to that of the young subjects was attributed to various factors such as vascular remodelling, vascular functional changes and reduction in physical activity, all of which are more prevalent in the old than the young. Comparison made between the derived elastic modulus of men and women showed that women up till approximately the age of 50, where their arterial stiffness start to increase very rapidly, have a lower arterial stiffness than men. Such an observation was attributed to the change in hormones during menopause especially in estrogen which serves as protection against atherosclerosis. As a result, PWV is without doubt a strong indicator of arterial stiffness and thus a very useful parameter for the prediction of cardiovascular risk. In addition, the ease of measuring reproducible baPWV non-invasively and taking reading in the absence of any psychological stress on the subject make it very favourable. As such, assessment of arterial stiffness via measurement of baPWV can be very useful in both the detection and treatment of cardiovascular disorders. Hence, further development and in depth study of such a method will be very valuable in detecting and fighting against the top global cardiovascular disease threat.