Measuring arterial stiffness in clinical practice: Moving one step forward

Arterial stiffness or arteriosclerosis is the degeneration of the arterial beds, which may be the earliest detectable manifestations of adverse functional and structural changes in the arterial wall. ¹ It should be differentiated from atherosclerosis, defined as an occlusive arterial disease characterized by lipid oxidation, inflammation, and plaque formation in the arterial wall. ² With cumulating evidence, arterial stiffness has been established as an important parameter for the assessment of cardiovascular (CV) risk.

1. THE APPLICATION OF ARTERIAL STIFFNESS MEASUREMENTS IN CLINICAL PRACTICE

There have been multiple biomarkers proposed for primary and secondary prevention of CV disease. However, their prognostic significance has to be demonstrated beyond the established risk factors such as blood pressure (BP), cholesterol levels, diabetes mellitus, smoking, as well as age and sex. ³ It has been shown that increased arterial stiffness may predict cardiovascular events in asymptomatic individuals with ⁴ or without overt CV disease. ⁵ As such, arterial stiffness has been recommended as a useful prognostic biomarker. ⁶ Besides, in addition to a mechanical biomarker for risk stratification of long‐term CV risks, arterial stiffness has also been suggested as a potential modifiable risk factor. Randomized controlled trials with a variety of interventions designed to investigate the effects on arterial stiffness and hopefully to improve the CV disease outcomes have been summarized in several systematic reviews, such as antihypertensive treatment, ⁷ body weight reduction, ⁸ statin, ⁹ and anti‐diabetic drugs. ¹⁰ Therefore, measuring arterial stiffness may not only identify patients at risk at an early stage, but also serve as a surrogate index for treatment monitoring for the effectiveness of therapeutic interventions of interest. ² , ¹¹ , ¹²

2. TRANSLATING THE CONCEPT OF ARTERIAL STIFFNESS INTO ROUTINE CLINICAL PRACTICE

Several methods exist that can determine parameters related to arterial stiffness, both local and in specific artery beds such as the aorta. Carotid‐to‐femoral pulse wave velocity (cfPWV), because of its perceived reliability, ¹³ and more importantly the large body of evidence demonstrating its association with incident CV disease independently of traditional risk factors and in various populations, ⁵ has long been regarded as the gold standard of all methods used to measure arterial stiffness. ¹³

Despite the cumulating supporting evidence, arterial stiffness has mostly been used in research protocols, and it is still not a commonly used prognostic indicator in clinical practice. The main reason behind this wide gap between research evidence, and clinical practice is that translating research evidence into clinical practice is not an easy step. ¹⁴ Actually, in the complex social system such as health care, it can be even more complex than our previous understanding about translational science especially. ¹⁵ Bettering individual and public health is the fundamental goal of biomedical research by discovering new effective strategies for the prevention and treatment of disease. To achieve this goal, the Institute of Medicine Clinical Research Roundtable identified two “translational gaps.” The first gap, or T1, is “the transfer of new understandings of disease mechanisms gained in the laboratory into the development of new methods for diagnosis, therapy, and prevention and their testing in humans.” The second gap, or T2, is “the translation of results from clinical studies into everyday clinical practice and health decision making.” Some experts further dissected T2 into 2 parts: T2 mainly refers to guideline development, meta‐analyses, and systematic reviews, whereas T3 includes dissemination and implementation research (or knowledge translation). ¹⁴

To apply the concept of arterial stiffness in daily health care, one of the main causes contributing to the evidence‐to‐practice gap is the need of trained personnel to conduct the arterial stiffness measurements (T3 gap). ¹⁴ To obtain the cfPWV, experienced personnel should utilize applanation tonometry to acquire stable carotid and femoral pressure waveforms and measure the traveling distance. Reimbursement issue by health insurance and required knowledge of healthcare providers about the application of arterial stiffness concept is other common barriers to facilitate its routine clinical use.

3. NOVEL METHODS USED TO SIMPLIFY THE ARTERIAL STIFFNESS MEASUREMENTS

Several novel methods have been proposed to close the research‐to‐practice gap. ¹⁶ , ¹⁷ Of these novel methods, cuff‐based pulse wave velocity measurements such as brachial‐ankle pulse wave velocity (baPWV) ¹⁸ and Cardio‐Ankle Vascular Index ¹⁹ are user‐friendly and more reproducible methods to evaluate arterial stiffness and may increase its utility as a risk factor of CV disease in clinical practice.

The basic calculating principle of baPWV, calculated as the ratio of the distance between the brachial and the tibial artery divided by the transit time between these 2 arteries, is simple, and the measurements could be easily implemented by using a professional oscillometric office blood pressure monitor. However, before it can be used in health care, ¹⁴ its agreement with the gold standard has to be demonstrated (T1 gap). In this issue, Kollias et al. investigated the agreement between automated baPWV taken by a professional oscillometric blood pressure monitor (Microlife WatchBP Office Vascular) versus the reference cfPWV (Complior device). ²⁰ The study concluded that the automated baPWV measurement by a professional oscillometric blood pressure monitor is feasible and observer‐independent. The baPWV values were higher than cfPWV by 4.0 ± 1.4 m/s (P < .01), yet they were closely correlated (r = .70, P < .01), and had reasonable agreement in detecting increased arterial stiffness and carotid plaques. ²⁰ Automatic and easy measurement of arterial stiffness with reasonably good accuracy could therefore be realized and help bridge the T2 gap.

4. THE MEASUREMENTS OF baPWV AND ITS AGREEMENT WITH cfPWV

Because of the complexity of the anatomic course of the brachial‐ankle arterial system, it is argued that whether baPWV is appropriate to define any particular segmental stiffness or whether it is just the ratio of a virtual brachial‐ankle distance and the measurement of the brachial‐ankle transit time. ¹⁸ It should be emphasized that cfPWV and baPWV are two different stiffness indices. With a modest correlation coefficient (r = .7) presented in the study, ²⁰ they represent the extent of stiffness over two different arterial trees but may be associated with the same ongoing systematic pathophysiology, such as aging, high BP, and diabetes. Nevertheless, both baPWV and cfPWV were associated with cardiovascular risk factors and indices of carotid stiffness and atherosclerosis and presented similar predictive value for the detection of carotid plaques, which demonstrates the clinical relevance of baPWV measurement in risk stratification. ²⁰

5. CONCLUSION

Bringing the concept of arterial stiffness into clinical practice is a vital but challenging task. The study conducted by Kollias et al ²⁰ represents an imperative step further by investigating the agreement between baPWV and cf PWV and their relationships with target organ indices. With a more convenient, reliable, and accurate measurement of arterial stiffness, the widespread clinical application of arterial stiffness concept can be expected consequently.

CONFLICT OF INTEREST

None.

Cheng H‐M, Chen C‐H. Measuring arterial stiffness in clinical practice: Moving one step forward. J Clin Hypertens. 2020;22:1824–1826. 10.1111/jch.13965