Diameter and compliance of the greater saphenous vein - effect of age and nitroglycerine

Optimal Conduit Diameter Selection in Coronary Bypass Grafting Using Saphenous Vein

BACKGROUND

Predictors of long-term saphenous vein graft (SVG) patency following coronary artery bypass grafting (CABG) include harvesting technique, degree of proximal coronary stenosis, and target vessel diameter and runoff. The objective of this study was to evaluate the association between vein graft diameter and long-term survival.

METHODS

Patients undergoing primary CABG (2000-2017) at Flinders Medical Centre, Adelaide, Australia, were categorised into three groups according to average SVG diameter (<3.5 mm [small], 3.5-4 mm [medium], >4 mm [large]). Survival data was obtained from the Australian Institute of Health and Welfare National Death Index. To determine the association of SVG diameter with long-term survival we used Kaplan-Meier survival analysis and Cox proportional hazard models adjusted for preoperative variables associated with survival.

RESULTS

Vein graft diameter was collected in 3,797 patients. Median follow-up time was 7.6 years (interquartile range, 3.9-11.8) with 1,377 deaths. SVG size >4 mm was associated with lower rates of adjusted survival up to 4 years postoperatively (hazard ratio 1.48; 95% confidence interval 1.05-2.1; p=0.026).

CONCLUSIONS

Vein graft diameter >4mm was found to be associated with lower rates of survival following CABG.

Prevalence, clinical presentation, and risk factors of chronic venous disease in Cameroon: A general population-based study

INTRODUCTION

Chronic venous disease is a global public health problem, with high morbidity and economic distress. There is scarcity of data on this disease in sub-Saharan Africa.

METHODS

We conducted the first population-based study over a period of 20 months from 1st February 2020 to 30th September 2021 in the 10 regions of Cameroon. A stratify sampling method was chose to select study site. Socio-demographic data, personal and family history, anthropometric parameters, clinical signs, illustrative images, CEAP (Clinical-Etiological-Anatomical-Pathophysiological) classification revised in 2004, VCSS (venous Clinical Severity Score) and risk factor assessment score were used to construct the survey form. Chi-squared test and Fischer exact test were used to compare the prevalence of chronic venous disease across different potential risk factors (sex, age category, previous history of deep vein thrombosis, hypertension, diabetes, smoking status, obesity). Simple and multiple logistic regression models were used to obtain crude and adjusted odds ratio for risk factors associated with chronic venous insufficiency. Statistical analyses were done with R version 4.2 for Linux and the threshold for statistical significance was 0.05.

RESULTS

A total of 6578 participants were included in the study, with a mean age of 41.09 ± 16.02 years with female predominance (54.3%). The prevalence of chronic venous disease was 21.8% (95% CI: 20.8-22.9) and the prevalence of chronic venous insufficiency (C3-C6) was 7.02% (n = 462). Night cramps (43.2%), oedema (21.7%), lower limbs pain (20.4%) mostly worsens by walking and heavy legs (16.2%) were more common symptoms. The mean total venous clinical severity score was 0.69 ± 1.76 and this score had a significant positive correlation with C classification (p < .001). In the multivariate analysis, the following factors were independently associated with CVD: Male gender (aOR: 1.27; 95%CI: 1.04-1.56; p = .021), retired people (aOR: 46.9; 95% CI: 12.6-174.5; p < .001), hypertension (aOR: 289.5; 95%CI: 169.69-493.1; p < .001), diabetes (aOR: 2.19; 95% CI: 1.21-3.96; p = .009), obesity (aOR: 10.22; 95%CI: 7.67-13.62; p < .001). Smoking appears as a protective factor (aOR: 0.18; 95%CI: 0.10-0.30; p < .001).

CONCLUSION

Chronic venous disease is frequent in Cameroon and main traditional cardiovascular risk factors are associated to this condition. Systematic screening of the CVD in these specific groups could reduce the burden of the disease and its economic impact.

Preserved endothelium-independent vascular function with aging in men and women: evidence from the peripheral and cerebral vasculature

In the peripheral and cerebral vasculature, the impact of aging and sex on the endothelial-independent functional capacity of vascular smooth muscle cells (VSMCs) is not well understood, nor is it known whether such VSMC functions in these vascular beds reflect one another. Therefore, endothelium-independent dilation, at both the conduit (Δ diameter) and microvascular (Δ vascular conductance, VC) level, elicited by sublingual nitroglycerin (NTG, 0.8 mg of Nitrostat), compared with sham-delivery (control), was assessed using Doppler ultrasound in the popliteal (PA) and middle cerebral (MCA) artery of 20 young [23 ± 4 yr, 10 males (YM)/10 females (YF)] and 21 old [69 ± 5 yr, 11 males (OM)/10 females (OF)] relatively healthy adults. In the PA, compared with zero, NTG significantly increased diameter in all groups (YM: 0.29 ± 0.13, YF: 0.35 ± 0.26, OM: 0.30 ± 0.18, OF: 0.31 ± 0.14 mm), while control did not. The increase in VC only achieved significance in the OF (0.22 ± 0.31 mL/min/mmHg). In the MCA, compared with zero, NTG significantly increased diameter and VC in all groups (YM: 0.89 ± 0.30, 1.06 ± 1.28; YF: 0.97 ± 0.31, 1.84 ± 1.07; OM: 0.90 ± 0.42, 0.72 ± 0.99; OF: 0.74 ± 0.32, 1.19 ± 1.18, mm and mL/min/mmHg, respectively), while control did not. There were no age or sex differences or age-by-sex interactions for both the NTG-induced PA and MCA dilation and VC. In addition, PA and MCA dilation and VC responses to NTG were not related when grouped by age, sex, or as all subjects (r = 0.04-0.44, P > 0.05). Thus, peripheral and cerebral endothelial-independent VSMC function appears to be unaffected by age or sex, and variations in such VSMC function in one of these vascular beds are not reflected in the other.NEW & NOTEWORTHY To confidently explain peripheral and cerebral vascular dysfunction, it is essential to have a clear understanding of the endothelial-independent function of VSMCs across age and sex. By assessing endothelium-independent dilation using sublingual nitroglycerin, endothelial-independent VSMC function in the periphery (popliteal artery), and in the cerebral circulation (middle cerebral artery), was not different due to age or sex. In addition, endothelial-independent VSMC function in one of these vascular beds is not reflected in the other.

Determinants of orthostatic cerebral oxygenation assessed using near-infrared spectroscopy

BACKGROUND

To understand the relationship between blood pressure changes during standing up and clinical outcome, cerebral oxygenation needs to be measured, which may be performed using near-infrared spectroscopy (NIRS). However, the role of potential determinants of NIRS-derived orthostatic cerebral oxygenation, i.e., age, sex, type of postural change (i.e., standing up from sitting versus supine position), blood pressure (BP) and baroreflex sensitivity (BRS) is still unknown and needed to better interpret findings from studies using orthostatic NIRS measurements.

METHODS

34 younger (median age 25 years, inter quartile range (IQR) 22-45) and 31 older adults (median age 77 years, IQR 72-81) underwent BP, BRS and NIRS measurements during standing up from sitting and supine position. Linear regression models were used to assess the potential determinant role of age, sex, type of postural change, BP and BRS in orthostatic cerebral oxygenation drop and recovery. Orthostatic cerebral oxygenation test-retest reliability was assessed using intra class correlations.

RESULTS

Younger age, male sex and standing up from supine compared to sitting position were positively associated with cerebral oxygenation drop; older age and standing up from sitting compared to supine position were associated with higher cerebral oxygenation recovery. Test-retest reliability was highest (ICC > 0.83) during standing up from supine position.

CONCLUSION

Based on the findings of this study, age, sex and type of postural change are significant determinants of NIRS-derived orthostatic cerebral oxygenation and should be taken into account in the interpretation of NIRS measurements. In the design of new studies, standing up from supine position is preferable (higher reliability) over standing up from sitting position.

The aging venous system: from varicosities to vascular cognitive impairment

Aging-induced pathological alterations of the circulatory system play a critical role in morbidity and mortality of older adults. While the importance of cellular and molecular mechanisms of arterial aging for increased cardiovascular risk in older adults is increasingly appreciated, aging processes of veins are much less studied and understood than those of arteries. In this review, age-related cellular and morphological alterations in the venous system are presented. Similarities and dissimilarities between arterial and venous aging are highlighted, and shared molecular mechanisms of arterial and venous aging are considered. The pathogenesis of venous diseases affecting older adults, including varicose veins, chronic venous insufficiency, and deep vein thrombosis, is discussed, and the potential contribution of venous pathologies to the onset of vascular cognitive impairment and neurodegenerative diseases is emphasized. It is our hope that a greater appreciation of the cellular and molecular processes of vascular aging will stimulate further investigation into strategies aimed at preventing or retarding age-related venous pathologies.

A review of methodologies evaluating superficial vein properties in viv: focus on compliance and reactivity

The saphenous vein (SV) is a hindlimb superficial vein which has aroused a considerable interest because of its implication in chronic venous disease and its use in coronary artery or lower limb bypass grafts. The morphology and patency of the SV are commonly assessed for diagnosis and management, but the dynamic properties of the vein - compliance, elasticity and reactivity, less widely studied, are also fundamental issues. The subject of this review is neither to review the pathologies, nor the treatments or surgical procedures. The goal is to gather together all existing types of investigation on the superficial vein and to focus on the dynamic venous properties in vivo. The data collected indicate that plethysmography (PG) and ultrasound (US) are extensively used to evaluate SV patency, reflux and morphology. Their use to evaluate superficial vein compliance is less widespread but highly necessary. The protocols used via venous occlusion are described and the various parameters used to accurately measure compliance and distensibility versus elasticity are presented and discussed. The advantage of US diameter measurement is shown, including additional pulsatile compliance evaluation. The overview of venous reactivity greatly differs, being poorly studied in vivo, mainly by optical methods in humans or US echotracking in animals. Existing methodologies are potent but could be certainly developed and improved further for better characterization of the SV in human and for investigations of new devices, surgical techniques and pharmacological treatment in preclinical animal studies.

Acute effects of graduated and progressive compression stockings on leg vein cross-sectional area and viscoelasticity in patients with chronic venous disease

OBJECTIVE

To determine the effects of graduated and progressive elastic compression stockings (ECS) on postural diameter changes and viscoelasticity of leg veins in healthy controls and in limbs with chronic venous disease (CVD).

METHODS

In 57 patients whose legs presented with C_1S, C₃, or C₅ CEAP classes of CVD and treated primarily with compression, and 54 healthy controls matched for age and body mass index, we recorded interface pressures at 9 reference leg levels. Cross-sectional areas of the small saphenous vein (SSV) and a deep calf vein (DCV) were measured with B-mode ultrasound with subjects supine and standing, recording the force (PF) applied on the ultrasound probe to collapse each vein with progressive ECS, and with and without graduated 15‒20 mmHg and 20‒36 mmHg elastic stockings. We chose these veins because they were free of detectable lesion and could be investigated at the same level (mid-height of the calf), while their compression by the ultrasound probe was not hampered by bone structures.

RESULTS

Interface pressures decreased from ankle to knee with graduated 15‒20 and 20‒36 mmHg, but increased with progressive ECS, and were 8.4‒13.8 mmHg lower for C_1s than for control or C₃ and C₅ limbs. Without ECS, SSV median [lower‒upper quartile] cross-sectional area was 4.9[3.6‒7.1] and 7.1[3.0‒9.9]mm² in C₃ and C₅ limbs vs. 2.9[1.8‒5.2] and 3.8[2.1‒5.4]mm² in controls (p<.01), respectively while supine and standing. It remained greater in C₃ and C₅ than in C_1S and control limbs wearing any ESC. Wearing compression, especially with progressive ECS, decreased SSV and DCV cross-sectional area only with subjects supine, thus lowering postural changes which remained highly diverse between individuals. The SSV cross-sectional area vs. PF function traced a hysteresis loop of which the area, related to viscosity, was greater in C₃ and C₅ limbs than controls, even with graduated 15‒20 or 20‒36 mmHg ECS. Progressive ECS lowered vein viscosity in the supine position whereas 20‒36 mm Hg and progressive ECS increased distensibility in the standing position.

CONCLUSION

Elastic compression stockings reduce cross-sectional area of superficial and deep calf veins with patients supine but not upright. C_1s limbs show distinctive features, especially regarding interface pressures. Graduated 20‒36 mm Hg and progressive stockings lower viscosity and increase distensibility of the small saphenous vein.

Mechanical Assessment and Hyperelastic Modeling of Polyurethanes for the Early Stages of Vascular Graft Design

The material design of vascular grafts is required for their application in the health sector. The use of polyurethanes (PUs) in vascular grafts intended for application in the body appears to be adequate due to the fact that native tissues have similar properties as PUs. However, the influence of chemical structure on the biomechanics of PUs remains poorly described. The use of constitutive models, together with numerical studies, is a powerful tool for evaluating the mechanical behavior of materials under specific physiological conditions. Therefore, the aim of this study was to assess the mechanical properties of different PU mixtures formed by polycaprolactone diol, polyethylene glycol, and pentaerythritol using uniaxial tensile, strain sweep, and multistep creep-recovery tests. Evaluations of the properties were also recorded after samples had been soaked in phosphate-buffer saline (PBS) to simulate physiological conditions. A hyperelastic model based on the Mooney–Rivlin strain density function was employed to model the performance of PUs under physiological pressure and geometry conditions. The results show that the inclusion of polyethylene glycol enhanced viscous flow, while polycaprolactone diol increased the elastic behavior. Furthermore, tensile tests revealed that hydration had an important effect on the softening phenomenon. Additionally, after the hydration of PUs, the ultimate strength was similar to those reported for other vascular conduits. Lastly, hyperelastic models revealed that the compliance of the PUs showed a cyclic behavior within the tested time and pressure conditions and is affected by the material composition. However, the compliance was not affected by the geometry of the materials. These tests demonstrate that the materials whose compositions are 5–90–5 and 46.3–46.3–7.5 could be employed in the designs of vascular grafts for medical applications since they present the largest value of compliance, ultimate strength, and elongation at break in the range of reported blood vessels, thus indicating their suitability. Moreover, the polyurethanes were revealed to undergo softening after hydration, which could reduce the risk of vascular trauma.

Gluteal Vein Anatomy: Location, Caliber, Impact of Patient Positioning, and Implications for Fat Grafting

BACKGROUND

Deaths in gluteal autografting occur due to gluteal vein injuries, but data are lacking on the precise location and caliber of these veins.

OBJECTIVES

The authors sought to present the first in vivo study of gluteal vein anatomy utilizing magnetic resonance imaging.

METHODS

Magnetic resonance imaging venography of 16 volunteer hemi-sections was conducted in the supine, prone, prone with a bump (jack-knife), and left and right decubitus positions in 1 session after a single contrast administration. Caliber and course of the superior and inferior gluteal veins (SGV/IGV) were analyzed vs bony landmarks and position changes.

RESULTS

The SGV has a very short submuscular course before splitting into 2 smaller branches superolaterally. The IGV runs immediately deep to the gluteus maximus in the center of the buttock as a single large trunk, on average 56 mm deep (mean 27 mm of muscle belly and 30 mm subcutaneous fat). No intramuscular or subcutaneous branches greater than 2 mm were found. In the prone position, the IGV and SGV have an average caliber of 5.96 mm and 5.63 mm. Vessel caliber decreased by 21% and 27%, respectively, in the jack-knife position and by 14% and 15% in lateral decubitus.

CONCLUSIONS

The SGV and IGV are immediately deep to gluteus maximus approximately 6 cm deep with a caliber on the order of 6 mm in the prone position. The distribution of these vessels suggests there is no "safe zone" in the intramuscular or submuscular planes. The jackknife or lateral decubitus positions can decrease vein caliber by up to 27%, possibly reducing the risk of injury due to either traction or direct cannula impact.

Compliance in the deep and superficial conduit veins of the nonexercising arm is unaffected by short-term exercise

The effects of short-term dynamic and static exercise on compliance (CPL) in a single conduit vein in the nonexercising limb are not fully understood, although prolonged cycling exercise was found to produce a significant reduction of CPL in the veins. In this study, we investigated the cross-sectional area (CSA) and CPL in the brachial (deep) and basilic (superficial) veins of the nonexercising arm in 14 participants who performed a 5-min cycling exercise at 35% and 70% of peak oxygen uptake (study 1) and in 11 participants who performed a 2-min static handgrip exercise at 30% of maximal voluntary contraction (study 2). The CSA in the deep and superficial veins at rest and during the final minute of exercise was measured by high-resolution ultrasonography during a short-duration cuff deflation protocol. The CPL in each vein was calculated as the numerical derivative of the cuff pressure and CSA curve. During short-term dynamic and static exercise, there was no change in CPL in either vein, but there was a decrease in CSA in both veins. The simultaneous findings of unchanged CPL and decreased CSA suggest that CPL during short-term exercise are independently controlled by the mechanisms responsible for exercise-induced sympathoexcitation in both single veins. Thus, short-term exercise does not alter CPL in both conduit superficial and deep veins in nonexercising upper arm.

Decreased compliance in the deep and superficial conduit veins of the upper arm during prolonged cycling exercise

We examined whether there is a difference in compliance between the deep and superficial conduit veins of the upper arm in response to prolonged exercise. Eight young men performed cycling exercise at 60% of peak oxygen uptake until rectal temperature had been increased by 1.1°C for 38–48 min. The cross‐sectional area (CSA) of the brachial (deep) and basilic (superficial) veins was assessed by ultrasound during a cuff deflation protocol. Compliance (CPL) was calculated as the numerical derivative of the cuff pressure and CSA curve. During prolonged exercise, CPL in both conduit veins was similarly decreased when compared with pre‐exercise values; however, the CSA decreased in the deep vein but increased in the superficial vein. In addition, passive heating caused an analogous change in CSA and CPL of superficial vein when compared with prolonged exercise, but did not change CSA and CPL of deep vein. Cold pressor test induced the decreased CSA of deep and superficial veins without the alteration of CPL of both veins. These results suggest that CPL in the deep and superficial conduit veins adjusts to prolonged exercise via different mechanisms.

The influence of age and gender on venous symptomatology. An epidemiological survey in Belgium and Luxembourg

Aim

The aim of this study is to measure the incidence of the symptoms in patients with chronic venous disease (CVD) and to look for the influence of age on the severity of symptoms for both genders.

Materials and methods

A survey was carried out in Belgium and Luxembourg between May and September 2013. Patient recruitment was done by 406 general practitioners (GPs). Each GP screened 10–20 consecutive patients older than 18 years. Inquiries were made regarding the presence of symptoms and possible signs of CVD. Patients with diagnosed CVD filled out a questionnaire including a quality of life score (CIVIQ-14). These data were converted into a CIVIQ Global Index Score (GIS). Statistical analysis was performed in order to calculate the effect of age and gender on the number of symptoms and the estimated probabilities of having CVD.

Results

Totally 6009 patients were included in this survey. The mean age was 53.4 years. Of all, 61.3% of the patients have CVD (C1-C6). Of all, 64.7% of patients were symptomatic. Age and female gender were major risk factors for developing CVD. Most common symptoms were ‘heavy legs’ (70.4%), pain (54.0%), and sensation of swelling (52.7%). The number of symptoms increases with age ( p < 0.001). Female patients have significantly more symptoms in comparison with male patients in all age groups. In both females and males, age is negatively correlated with GIS score ( p < 0.001). The estimated probability of having CVD was significantly higher for woman compared to men and increases with age for both gender.

Conclusion

CVD is a very common progressive disease with age as a major risk factor. Increasing age results in a higher C-classification, more symptoms, and a lower GIS score (quality of life). Female gender interacts significantly with age and results in a more advanced stage of CVD.

Calf venous compliance measured by venous occlusion plethysmography: methodological aspects

PURPOSE

Calf venous compliance (C calf) is commonly evaluated with venous occlusion plethysmography (VOP) during a standard cuff deflation protocol. However, the technique relies on two not previously validated assumptions concerning thigh cuff pressure (P cuff) transmission and the impact of net fluid filtration (F filt) on C calf. The aim was to validate VOP in the lower limb and to develop a model to correct for F filt during VOP.

METHODS

Strain-gauge technique was used to study calf volume changes in 15 women and 10 age-matched men. A thigh cuff was inflated to 60 mmHg for 4 and 8 min with a subsequent decrease of 1 mmHg s(-1). Intravenous pressure (P iv) was measured simultaneously. C calf was determined with the commonly used equation [Compliance = β 1 + 2β 2 × P cuff] describing the pressure-compliance relationship. A model was developed to identify and correct for F filt.

RESULTS

Transmission of P cuff to P iv was 100 %. The decrease in P cuff correlated well with P iv reduction (r = 0.99, P < 0.001). Overall, our model showed that C calf was underestimated when F filt was not accounted for (all P < 0.01). F filt was higher in women (P < 0.01) and showed a more pronounced effect on C calf compared to men (P < 0.05). The impact of F filt was similar during 4- and 8-min VOP.

CONCLUSIONS

P cuff is an adequate substitute for P iv in the lower limb. F filt is associated with an underestimation of C calf and differences in the effect of F filt during VOP can be accounted for with the correction model. Thus, our model seems to be a valuable tool in future studies of venous wall function.

A global multiscale mathematical model for the human circulation with emphasis on the venous system

We present a global, closed-loop, multiscale mathematical model for the human circulation including the arterial system, the venous system, the heart, the pulmonary circulation and the microcirculation. A distinctive feature of our model is the detailed description of the venous system, particularly for intracranial and extracranial veins. Medium to large vessels are described by one-dimensional hyperbolic systems while the rest of the components are described by zero-dimensional models represented by differential-algebraic equations. Robust, high-order accurate numerical methodology is implemented for solving the hyperbolic equations, which are adopted from a recent reformulation that includes variable material properties. Because of the large intersubject variability of the venous system, we perform a patient-specific characterization of major veins of the head and neck using MRI data. Computational results are carefully validated using published data for the arterial system and most regions of the venous system. For head and neck veins, validation is carried out through a detailed comparison of simulation results against patient-specific phase-contrast MRI flow quantification data. A merit of our model is its global, closed-loop character; the imposition of highly artificial boundary conditions is avoided. Applications in mind include a vast range of medical conditions. Of particular interest is the study of some neurodegenerative diseases, whose venous haemodynamic connection has recently been identified by medical researchers.

Late effects of radial artery versus saphenous vein grafting in patients aged 70 years or older

BACKGROUND

We aimed to determine whether the reported late survival benefit of radial artery (RA) versus saphenous vein (SV) grafting in the general coronary artery bypass graft surgery (CABG) population is maintained in elderly patients aged 70 years or older.

METHODS

We reviewed our 1996 to 2007 experience in 2,120 elderly patients (RA, n = 607; SV, n = 1,513) who underwent primary, nonsalvage CABG with multiple completed grafts including at least one internal thoracic artery (ITA) graft. Patients were excluded in case of single-vessel disease, bilateral ITA, ITA-only grafts, or concomitant valve/aortic surgery. Kaplan-Meier 12-year survival estimates were compared for 1-to-1 matched ITA/RA and ITA/SV cohorts based on a nonparsimonious RA use propensity model (48 variables).

RESULTS

The ITA/RA and ITA/SV cohorts (both, aged 75 ± 4yrs and 3.5 ± 0.8 grafts) were well matched and had identical operative mortality (2.3%; 11 of 480 each). Late survival was superior ITA/RA versus ITA/SV (p < 0.001), estimated at 85.1% versus 70.6% and 70.9% versus 50.5% for 5 and 10 years, respectively. Late survival risk ratios (95% confidence interval) for RA versus SV grafting was 0.47 (0.36 to 0.61), and the relative SV to RA death hazard was greater than 1 between 1 and 144 months.

CONCLUSIONS

The late survival results suggest that elderly (≥70 years) primary multivessel CABG patients benefit substantially when RA is used as the second conduit in combination with ITA. Indeed, compared with previously published comparisons including all age groups, the derived risk ratio indicates that the benefit for the elderly may exceed that for younger patients in the initial decade after CABG. Use of RA should not be avoided in the elderly.

The effects of aging on the intimal region of the human saphenous vein: insights from multimodal microscopy and quantitative image analysis

We hypothesized that structural remodeling associated with advancing age occurs in human saphenous veins. To address this hypothesis, we have identified structural remodeling in human saphenous veins by applying histochemistry, fluorescence staining and quantitative image analysis to specifically assess intimal area, intimal cellularity and intimal collagen content and organization. Saphenous veins were collected from patients undergoing coronary artery bypass graft surgery. Area measurements and cellularity were quantified using the image analysis software Stereo Investigator, employing planimetry and counting frames, respectively. Collagen content and organization were quantified in MetaMorph image analysis software based on measurements of color (hue, saturation, and intensity) from polarized light images. Intimal area and cellularity showed no statistically significant increases with age; in contrast, total collagen content showed a significant decrease with advancing age. Furthermore, collagen fiber types also demonstrated a statistically significant alteration with age; increases in age resulted in decreases in larger collagen fibers. No significant changes in small collagen fibers were identified. These results raise the possibility that age-associated structural alterations in total collagen content, specifically collagen fiber size, could be a factor in the etiology of age-associated venous diseases.

Effect of ageing on the murine venous circulation

The effect of ageing on the morphology of veins, venous valves and arteries was investigated in male wild-type mice using an adapted procedure with injection of a silicone polymer Microfil(®) that preserves morphology of the vasculature. Throughout the hind limb the arterial, but not the venous, lumen area and wall thickness were significantly greater in 24-month as compared to 10-week-old C57BL/6 mice. Venous valves were most frequently located at the sapheno-femoral vein junction in the lower extremities, and appeared thicker at the base supported by structurally intact collagen fibers, and thinner towards the proximal end of the valve leaflet, with less organized collagen. Overall, valves were less supported by structurally intact collagen at 24 months as compared to 10 weeks. Endothelial expression of CD31, endothelial protein C receptor or von Willebrand factor (VWF) was not affected by age, while thrombomodulin expression was lower in aged versus young arteries. At both ages, expression of VWF was lower at venous valves versus veins. Evaluation of the blood coagulation profile revealed that aged mice had shortened prothrombin time, elevated plasma levels of factor (F)VII, FVIII and VWF and increased neutrophil and platelet counts. Thus, our data indicate that in mice with ageing, venous valves become more fragile, in association with a procoagulant and inflammatory blood phenotype. Taken together, we found that the procoagulant state in ageing, is accompanied by mild vascular changes.