A lesson in vigilance: pressure dependency of a presumed pressure-independent index of arterial stiffness

Five years of cardio-ankle vascular index (CAVI) and CAVI0: how close are we to a pressure-independent index of arterial stiffness?

Pulse wave velocity, a common metric of arterial stiffness, is an established predictor for cardiovascular events and mortality. However, its intrinsic pressure-dependency complicates the discrimination of acute and chronic impacts of increased blood pressure on arterial stiffness. Cardio-ankle vascular index (CAVI) represented a significant step towards the development of a pressure-independent arterial stiffness metric. However, some potential limitations of CAVI might render this arterial stiffness metric less pressure-independent than originally thought. For this reason, we later introduced CAVI0. Nevertheless, advantages of one approach over the other are left debated. This review aims to shed light on the pressure (in)dependency of both CAVI and CAVI0. By critically reviewing results from studies reporting both CAVI and CAVI0 and using simple analytical methods, we show that CAVI0 may enhance the pressure-independent assessment of arterial stiffness, especially in the presence of large inter-individual differences in blood pressure.

Pulmonary Arterial Remodeling Is Related to the Risk Stratification and Right Ventricular-Pulmonary Arterial Coupling in Patients With Pulmonary Arterial Hypertension

Background

Pulmonary arterial (PA) stiffness has an essential contribution to the right ventricular (RV) failure pathogenesis. A comprehensive and multiparameter risk assessment allows predicting mortality and guiding treatment decisions in PA hypertension (PAH). We characterize PA remodeling with intravascular ultrasound (IVUS) in prevalent and stable patients with PAH according to the ESC/ERS risk table and analyze the RV-PA coupling consequences.

Methods

Ten control subjects and 20 prevalent PAH adult patients underwent right heart catheterization (RHC) with simultaneous IVUS study. We estimated cardiac index (CI), pulmonary vascular resistance, and compliance (PVR, PAC) by standard formulas. From IVUS and RHC data, PA diameter, wall thickness/luminal diameter ratio, and indexes of stiffness (pulsatility, compliance, distensibility, incremental elastic modulus - Einc-, and the stiffness index β) were measured. We evaluated RV-PA coupling by the ratio of tricuspid annular plane systolic excursion to systolic pulmonary arterial pressure (TAPSE/sPAP). The individual average risk was calculated by assigning a score of 1 (low-risk -LR-), 2 (intermediate-risk -IR-), and 3 (high-risk -HR-) for each of seven variables (functional class, six-minute walking test, brain natriuretic peptide, right atrial area and pressure, CI, and PA oxygen saturation) and rounding the average value to the nearest integer.

Results

All PA segments interrogated showed increased vessel diameter, wall cross-sectional area (WCSA), and stiffness in patients with PAH compared to control subjects. 45% corresponded to LR, and 55% corresponded to IR PAH patients. The different measurements of PA stiffness showed significant correlations with TAPSE/sPAP (r = 0.6 to 0.76) in PAH patients. The IR group had higher PA stiffness and lower relative WCSA than LR patients (P < 0.05), and it is associated with a lower PAC and TAPSE/sPAP (P < 0.05).

Conclusion

In prevalent PAH patients, the severity of proximal PA remodeling is related to the risk stratification and associated with PAC and RV-PA coupling impairment beyond the indirect effect of the mean PA pressure. The concomitant assessment of IVUS and hemodynamic parameters at diagnosis and follow-up of PAH patients could be a feasible and safe tool for risk stratification and treatment response of the PA vasculopathy during serial hemodynamic measurements.

Evaluation of the calculation formulas of the cardio-ankle vascular index used in the Japanese apparatus

Background

Recently, coefficients in the equation of cardio-ankle vascular index (CAVI) used in VaSera^® device were disclosed. This study aimed to simulate the influence of adjusting the coefficients in the equation of CAVI and also aimed to validate the equation.

Methods

The CAVI displayed by VaSera (CAVIvs) and the CAVI estimated (CAVIes) with fixing the coefficients of the middle range of the heart-ankle stiffness parameter β (haβ) in the equation were compared. Moreover, the heart-ankle pulse wave velocity (haPWV) which corresponds to the low cutoff haβ of 7.348 was estimated in various blood pressure patterns to validate the formula.

Results

The CAVIvs was clearly lower than CAVIes in the low and the high range of CAVIvs. Moreover, it was virtually impossible to obtain the low cutoff haβ of 7.348 by using typical values of haPWV.

Conclusion

The CAVIvs in the high-range of VaSera underestimates the original property of stiffness parameter β. Moreover, there will be also a missing information in the equations introduced in the corresponding article, especially in the calculation formula of CAVIvs from haβ. Therefore, in order to make the best use of the nature of the stiffness parameter β to be used in VaSera, fixing the coefficients or termination of its use should be considered.

Novel Biomarkers of Early Atherosclerotic Changes for Personalised Prevention of Cardiovascular Disease in Cervical Cancer and Human Papillomavirus Infection

Cervical cancer is associated with a causative role of human papillomavirus (HPV), which is a highly prevalent infection. Recently, women with a genital HPV infection were found to have increased incidence of cardiovascular diseases (CVD), including severe cardiovascular events such as myocardial infarction and stroke. The pathomechanisms of this relation are not yet fully understood, and may significantly affect the health of a large part of the population. Accelerated atherosclerosis is assumed to play a key role in the pathophysiology of this relationship. To identify high-risk groups of the population, it is necessary to stratify the CVD risk. Current algorithms, as widely used for the estimation of CVD risk, seem to be limited by the individual misclassification of high-risk subjects. However, personalised prediction of cardiovascular events is missing. Regarding HPV-related CVD, identification of novel sensitive biomarkers reflecting early atherosclerotic changes could be of major importance for such personalised cardiovascular risk prediction. Therefore, this review focuses on the pathomechanisms leading to HPV-related cardiovascular diseases with respect to atherosclerosis, and the description of potential novel biomarkers to detect the earliest atherosclerotic changes important for the prevention of CVD in HPV infection and cervical cancer.

Brachial-ankle pulse wave velocity, cardio-ankle vascular index, and prognosis

Background

Brachial–ankle pulse wave velocity (baPWV) and cardio-ankle vascular index (CAVI) are indices of arterial stiffness, and several studies have used these indices. However, there is no comprehensive review of these parameters in the prognostic significance.

Methods

The aim of this study was to review the articles exploring the prognostic significance of these parameters. Articles demonstrating independent significance after multivariate analysis on the Cox proportional hazards model were defined as “successful.” The success rate was compared using Fisher’s exact test. In addition, multivariate logistic regression analysis was performed to explore the independent determinants of the success of prognostic prediction.

Results

The success rate of the baPWV articles (65.7% [46/70]) tended to be higher than that of the CAVI articles (40.0% [6/15]; P=0.083). Multivariate analysis demonstrated that log (number of patients) (OR 11.20, 95% CI 2.45–51.70, P=0.002) and dialysis population (OR 0.28, 95% CI 0.08–0.94, P=0.039) were positive and negative independent determinants of the success of prognostic prediction, respectively. In addition, after redefining two studies as the absence of arteriosclerosis obliterans (ASO) exclusion, baPWV (OR 3.36, 95% CI 0.86–13.20, P=0.083) and the existence of exclusion criteria of ASO (OR 3.08, 95% CI 0.96–9.93, P=0.060) exhibited statistical tendency in the multivariate analysis.

Conclusion

This study demonstrated that the number of study participants and dialysis population were the independent determinants of the success of prognostic prediction. This study also showed the importance of exclusion criteria of ASO when using these indices. In addition, a prospective large-scale study to confirm the superiority in the prognostic prediction of these indices is warranted.

Direct means of obtaining CAVI0-a corrected cardio-ankle vascular stiffness index (CAVI)-from conventional CAVI measurements or their underlying variables

OBJECTIVE

Cardio-ankle vascular index (CAVI) as measured using the VaSera device (CAVI_VS, Fukuda Denshi), has been proposed as a stiffness index that does not depend on blood pressure. We have recently shown theoretically that CAVI_VS still exhibits blood pressure dependence, and proposed the corrected index CAVI₀. The present study aims to establish a method of calculating [Formula: see text] either (i) from VaSera-reported values of cardiac-brachial and brachial-ankle pulse transit times (tb and tba, respectively) and blood pressure, or (ii) directly from CAVI_VS. To derive this method, the relationship among CAVI_VS and its scale constants a and b, tb, tba, and blood pressure has to be established.

APPROACH

From data of 497 subjects, eight candidate CAVI parameters were defined and calculated, containing all combinations of left or right tb/tba/blood pressure. Candidates were evaluated through correlation with measured left and right CAVI_VS. Correlations were compared statistically. Once the correct candidates were determined, two constants (a and b) required for converting CAVI_VS to CAVI₀ were estimated through linear regression.

MAIN RESULTS

Left and right CAVI_VS are calculated using left and right tba; however, both left and right CAVI_VS are calculated using right brachial blood pressures and right tb. Constants a and b for conversion of CAVI_VS to CAVI₀ were estimated to be 0.842 [0.836 0.848] and 0.753 [0.721 0.786] (mean [95%CI]), respectively. Equations to estimate CAVI₀ from CAVI_VS, and to directly calculate CAVI₀ from the VaSera output are provided in this paper, as well as in a directly usable spreadsheet supplement.

SIGNIFICANCE

Our results permit straightforward calculation of [Formula: see text] during a study, as well as retrospective estimation of [Formula: see text] from CAVI_VS in already published studies or where the original transit time values are not available, paving the way for thorough comparison of CAVI₀ to CAVI_VS in clinical and research settings. Novelty and significance Cardio-ankle vascular index (CAVI) as measured using the VaSera device (CAVI_VS, Fukuda Denshi), has been proposed as a blood pressure-independent arterial stiffness index. We have recently shown theoretically that CAVI_VS still exhibits pressure dependence, and proposed a corrected index, CAVI₀. In the present study, we derived equations to directly obtain CAVI₀ using data from the VaSera device. Our results permit straightforward calculation of [Formula: see text] during a study, as well as retrospective estimation of [Formula: see text] from CAVI_VS in already published studies, paving the way for thorough comparison of CAVI₀ to CAVI_VS in clinical and research settings.

Options for Dealing with Pressure Dependence of Pulse Wave Velocity as a Measure of Arterial Stiffness: An Update of Cardio-Ankle Vascular Index (CAVI) and CAVI0

Pulse wave velocity (PWV), a marker of arterial stiffness, is known to change instantaneously with changes in blood pressure. In this mini-review, we discuss two main approaches for handling the blood pressure dependence of PWV: (1) converting PWV into a pressure-independent index, and (2) correcting PWV per se for the pressure dependence. Under option 1, we focus on cardio-ankle vascular index (CAVI). CAVI is essentially a form of stiffness index β - CAVI is estimated for a (heart-to-ankle) trajectory, whereas β is estimated for a single artery from pressure and diameter measurements. Stiffness index β, and therefore also CAVI, have been shown to theoretically exhibit a slight residual blood pressure dependence due to the use of diastolic blood pressure instead of a fixed reference blood pressure. Additionally, CAVI exhibits pressure dependence due to the use of an estimated derivative of the pressure-diameter relationship. In this mini-review, we will address CAVI's blood pressure dependence theoretically, but also statistically. Furthermore, we review corrected indices (CAVI₀ and β₀) that theoretically do not show a residual blood pressure dependence. Under option 2, three ways of correcting PWV are reviewed: (1) using an exponential relationship between pressure and cross-sectional area, (2) by statistical model adjustment, and (3) through reference values or rule of thumb. Method 2 requires a population to be studied to characterise the statistical model, and method 3 requires a representative reference study. Given these limitations, method 1 seems preferable for correcting PWV per se for its blood pressure dependence. In summary, several options are available to handle the blood pressure dependence of PWV. If a blood pressure-independent index is sought, CAVI₀ is theoretically preferable over CAVI. If correcting PWV per se is required, using an exponential pressure-area relationship provides the user with a method to correct PWV on an individual basis.