Factors predicting the diameter of the popliteal artery in healthy humans

Sex disparities in popliteal artery aneurysms

OBJECTIVE

Only 5% of patients with popliteal artery aneurysms (PAAs) are female. Evidence on PAA treatment and outcomes in women is therefore scarce. The POPART Registry provides one of Europe's largest data collections regarding PAA treatment. Data on clinical presentation, aneurysm morphology, and perioperative outcomes after open surgical PAA repair in women will be presented.

METHODS

POPART is a multicenter, noninterventional registry for open and endovascular PAA repair, with 42 participating centers in Germany and Luxembourg. All patients aged >18 years who have been treated for PAA since 2010 are eligible for study inclusion. Data collection is based on an online electronic case report form.

RESULTS

Of the 1236 PAAs, 58 (4.8%) were in women. There were no significant differences in age or cardiopulmonary comorbidities. However, female patients had a lower prevalence of contralateral PAAs and abdominal aortic aneurysms (P < .05). PAAs in women were more likely to be symptomatic before surgery (65.5% vs 49.4%; P = .017), with 19% of women presenting with acute limb ischemia (vs 11%; P = .067). Women had smaller aneurysm diameters than men (22.5 mm vs 27 mm; P = .004) and became symptomatic at smaller diameters (20 mm vs 26 mm; P = .002). Only 8.6% of women and 11.6% of men underwent endovascular aneurysm repair (P > .05); therefore, the perioperative outcome analysis focused on open surgical repair. In total, 23.5% of women and 16.9% of men developed perioperative complications (P > .05). There were no differences in major cardiovascular events (P > .05), but women showed a higher incidence of impaired wound healing (15.7% vs 7.2%; P = .05) and major amputation (5.9% vs 1.1%; P = .027). Female sex was significantly associated with the need for nonvascular reinterventions within 30 days after surgery (odds ratio: 2.48, 95% confidence interval: 1.26-4.88), whereas no significant differences in the odds for vascular reinterventions were observed (odds ratio: 1.98, 95% confidence interval: 0.68-5.77). In the multiple logistic regression model, female sex, symptomatic PAAs, poor quality of outflow vessels, and graft material other than vein graft were independently associated with perioperative reinterventions.

CONCLUSIONS

Women have smaller PAAs, are more likely to be symptomatic before treatment, and are more often affected by nonvascular reinterventions in the perioperative course. As our understanding of aneurysmatic diseases in women continues to expand, sex-specific treatment strategies and screening options for women in well-selected cohorts with modified screening protocols should be continuously re-evaluated.

Body surface area is positively associated with ankle-brachial index

BACKGROUND

Ankle-brachial index (ABI) measurement is a widely used diagnostic test for lower extremity artery disease. Previously, a larger body surface area (BSA) has been associated with lower blood pressure and lower 2-h post-load glucose concentrations in the oral glucose tolerance test. Our aim was to evaluate whether BSA has an impact on ABI and the prevalence of lower ABI values.

METHODS

ABI measurements were performed on 972 subjects aged 45 to 70 years at high cardiovascular disease (CVD) risk. Subjects with previously diagnosed kidney disease, CVD, and diabetes were excluded. Their BSA was calculated by the Mosteller formula. Study subjects were divided into five BSA levels corresponding to 12.5th, 25th, 25th, 25th, and 12.5th percentiles of the total distribution. Effect modification by BSA in ABI between sexes was derived from a four-knot restricted cubic splines regression model.

RESULTS

After adjustments for age, sex, pulse pressure, glucose regulation, waist circumference, alcohol intake, smoking status, leisure-time physical activity and medication, BSA level had a positive linear relationship with ABI (p for linearity <0.001). When BSA was less than 2.0 m2, there was no difference between the sexes, but when BSA was higher than 2.0 m2, men had higher ABI.

CONCLUSION

BSA shows a positive linear relationship with ABI in CVD risk subjects without manifested CVD. The difference in ABI between men and women is modified by BSA and is appreciable when BSA is larger than 2.0 m2.

Vascular Aging: Assessment and Intervention

Vascular aging represents a collection of structural and functional changes in a blood vessel with advancing age, including increased stiffness, vascular wall remodeling, loss of angiogenic ability, and endothelium-dependent vasodilation dysfunction. These age-related alterations may occur earlier in those who are at risk for or have cardiovascular diseases, therefore, are defined as early or premature vascular aging. Vascular aging contributes independently to cardio-cerebral vascular diseases (CCVDs). Thus, early diagnosis and interventions targeting vascular aging are of paramount importance in the delay or prevention of CCVDs. Here, we review the direct assessment of vascular aging by examining parameters that reflect changes in structure, function, or their compliance with age including arterial wall thickness and lumen diameter, endothelium-dependent vasodilation, arterial stiffness as well as indirect assessment through pathological studies of biomarkers including endothelial progenitor cell, lymphocytic telomeres, advanced glycation end-products, and C-reactive protein. Further, we evaluate how different types of interventions including lifestyle mediation, such as caloric restriction and salt intake, and treatments for hypertension, diabetes, and hyperlipidemia affect age-related vascular changes. As a single parameter or intervention targets only a certain vascular physiological change, it is recommended to use multiple parameters to evaluate and design intervention approaches accordingly to prevent systemic vascular aging in clinical practices or population-based studies.

Intraoperative angiography via popliteal artery access for spinal neurovascular lesions: an institutional experience and systematic review

BACKGROUND

Intraoperative DSA is used to confirm complete obliteration of neurovascular pathologies. For spinal neurovascular lesions, femoral access can be challenging given the need to flip the patient after sheath placement. Similarly, radial access can be complicated by arch navigation difficulties. Vascular access via the popliteal artery represents an appealing alternative option; however, data regarding its utility and efficacy in these cases are limited.

METHODS

A retrospective series of four consecutive patients between July 2016 and August 2022 who underwent intraoperative spinal DSA via the popliteal artery was analyzed. Additionally, a systematic review was conducted to collect previously reported such cases. Collective patient demographics and operative details are presented to consolidate the available evidence supporting popliteal access.

RESULTS

Four patients met the inclusion criteria from our institution. The systematic review yielded six previously published studies reporting 16 additional transpopliteal access cases. Of the 20 total cases (mean±SD age 60.8±17.2 years), 60% were men. Most treated lesions were dural arteriovenous fistulas (80%) located in the thoracic spine (55%) or cervical spine (25%). The left popliteal artery was most accessed and the highest visualized level was the craniocervical junction. All outcomes were either stable or improving after surgery, and no complications were observed.

CONCLUSIONS

We report the safety and feasibility of transpopliteal access for intraoperative DSA in the prone position in four cases in addition to 16 previously reported cases in the literature. Our case series highlights popliteal artery access as an alternative to transfemoral or transradial access in this setting.

Assessment of Intraoperative Spinal Angiography via the Popliteal Artery for Spinal Vascular Diseases

OBJECTIVE

Intraoperative spinal angiography via the popliteal artery for patients in the prone position has been reported only twice in 4 patients. This study aimed to clarify the safety precautions to be taken with this technique in a larger patient cohort.

METHODS

Seven patients with spinal vascular disorders underwent intraoperative spinal angiography in the prone position via the popliteal artery. Ultrasound was used to evaluate the neurovascular anatomy in the popliteal fossa and guide the arterial puncture. Patient characteristics, features of angiography devices, puncture attempts, and angiography-related complications, such as hematoma formation and injury to the neurovascular bundle, were analyzed.

RESULTS

The average number of arterial puncture attempts was 1.3 times (range: 1-2). Sheaths (4 and 4.5 Fr) with different ineffective lengths were used. In 1 case, a 4.5-Fr sheath was replaced with a 4-Fr sheath with a shorter noneffective length as the length of the catheter limited access to the target. Catheters with Type-JB2 tip shapes were used for craniocervical junction lesions, and those with Type-KAGAWA tip shapes were used for thoracic and lumbar spinal lesions. No puncture site complications were observed in any patient.

CONCLUSIONS

Intraoperative spinal angiography via the popliteal artery was an effective tool in surgeries for spinal vascular diseases. The introduction of the ultrasound enabled atraumatic puncture of the popliteal artery. Spinal targets above T5 to T6 may be inaccessible from the popliteal fossa when using a 100-cm-long catheter.

Wave propagation through a viscous fluid-filled elastic tube under initial pressure: theoretical and biophysical model

The velocity of propagation of pulse waves through the arteries is one of the indicators of the health of the cardiovascular system. By measuring the pulse wave velocity, cardiologists estimate the elasticity of the blood vessel walls and the changes that occur with aging. When the Moens-Korteweg equation is used in analysis, it leads to an erroneous assessment. This paper presents the solution of Navier-Stokes equations for propagation of pulse waves through an elastic tube filled with viscous fluid under initial pressure. The equation for pulse wave velocity depending on viscosity, density and initial fluid pressure, density and elasticity of the wall and geometry of the tube is derived. The results of the equation were compared with experimental results measured using a biophysical model of the cardiovascular system.

Post-surgical wireless monitoring of arterial health progression

Early detection of limb ischemia, strokes, and heart attacks may be enabled via long-term monitoring of arterial health. Early stenosis, decreased blood flow, and clots are common after surgical vascular bypass or plaque removal from a diseased vessel and can lead to the above diseases. Continuous arterial monitoring for the early diagnosis of such complications is possible by implanting a sensor during surgery that is wirelessly monitored by patients after surgery. Here, we report the design of a wireless capacitive sensor wrapped around the artery during surgery for continuous post-operative monitoring of arterial health. The sensor responds to diverse artery sizes and extents of occlusion in vitro to at least 20 cm upstream and downstream of the sensor. It demonstrated strong capability to monitor progression of arterial occlusion in human cadaver and small animal models. This technology is promising for wireless monitoring of arterial health for pre-symptomatic disease detection and prevention.

The Society for Vascular Surgery clinical practice guidelines on popliteal artery aneurysms

The Society for Vascular Surgery clinical practice guidelines on popliteal artery aneurysms (PAAs) leverage the work of a panel of experts chosen by the Society for Vascular Surgery to review the current world literature as it applies to PAAs to extract the most salient, evidence-based recommendations for the treatment of these patients. These guidelines focus on PAA screening, indications for intervention, choice of repair strategy, management of asymptomatic and symptomatic PAAs (including those presenting with acute limb ischemia), and follow-up of both untreated and treated PAAs. They offer long-awaited evidence-based recommendations for physicians taking care of these patients.

Comparison of morphometric, structural, mechanical, and physiologic characteristics of human superficial femoral and popliteal arteries

Peripheral arterial disease differentially affects the superficial femoral (SFA) and the popliteal (PA) arteries, but their morphometric, structural, mechanical, and physiologic differences are poorly understood. SFAs and PAs from 125 human subjects (age 13-92, average 52±17 years) were compared in terms of radii, wall thickness, and opening angles. Structure and vascular disease were quantified using histology, mechanical properties were determined with planar biaxial extension, and constitutive modeling was used to calculate the physiologic stress-stretch state, elastic energy, and the circumferential physiologic stiffness. SFAs had larger radii than PAs, and both segments widened with age. Young SFAs were 5% thicker, but in old subjects the PAs were thicker. Circumferential (SFA: 96→193°, PA: 105→139°) and longitudinal (SFA: 139→306°, PA: 133→320°) opening angles increased with age in both segments. PAs were more diseased than SFAs and had 11% thicker intima. With age, intimal thickness increased 8.5-fold, but medial thickness remained unchanged (620μm) in both arteries. SFAs had 30% more elastin than the PAs, and its density decreased ~50% with age. SFAs were more compliant than PAs circumferentially, but there was no difference longitudinally. Physiologic circumferential stress and stiffness were 21% and 11% higher in the SFA than in the PA across all ages. The stored elastic energy decreased with age (SFA: 1.4→0.4kPa, PA: 2.5→0.3kPa). While the SFA and PA demonstrate appreciable differences, most of them are due to vascular disease. When pathology is the same, so are the mechanical properties, but not the physiologic characteristics that remain distinct due to geometrical differences.

Simulation of blood flow into the popliteal artery to explain the effect of peripheral arterial disease: Investigation the conditions and effects of different foot states during the daily activity of the patient

BACKGROUND AND OBJECTIVE

Peripheral artery disease, one type of atherosclerosis, is a common medical condition in the world that results from plaque build-up in the peripheral blood vessels. The symptoms of this disease are the senses of pain and weakness in outer muscles.

METHODS

The artery under consideration is called the popliteal artery. In this model, the blood flow is considered as pulsating. Therefore the inlet boundary condition is taken as unsteady velocity, and the outlet boundary condition is taken the outflow. The inlet boundary condition represents the increasing systole flow and the decreasing diastole flow, which occur naturally in blood flow. Systolic flow occurs when the heart contracts and pumps blood into the arteries. The inlet blood flow is in the form of a sine-cosine parabolic profile.

RESULTS

The artery bends from the middle at an angle of 45°. As the bending of the artery begins, the flow field also takes a bent form. At this point, the flow bends from the outside of the top wall and enfolds the bottom wall in its bending. For different periods, the popliteal flow is closer to the lower bend when the inlet velocity is more significant. While the top wall experiences a low-intensity region along the bend, the bottom wall experiences the same effect just before and after the bend. As the blood flows along the bend, the flow path becomes significantly curved near the bend, similar to the model. The clotted artery exhibits a large increase in flow due to a reduction in the cross-section as a result of the clotting in half of the artery. The flow before the clotting is not considerably different from the main model of the straight artery.

CONCLUSIONS

Like shear stress, the pressure drop has a linear relationship with the blood HCT and, hence, the viscosity. The pressure drop decreases with the inlet velocity reaching its maximum value and then increases with the start of the acceleration reduction in the second and third-time steps. This indicates that the pressure drop has a stronger relationship with the acceleration than the inlet velocity.

Greater Height Is Associated with a Larger Carotid Lumen Diameter

Background: Previous studies link tall stature with a reduced ischemic stroke risk. One theory posits that tall people have larger cerebral artery lumens and therefore have a lower plaque occlusion risk than those who are short. Previous studies have not critically evaluated the associations between height and cerebral artery structure independent of confounding factors. Methods: The hypothesis linking stature with cerebral artery lumen size was tested in 231 adults by measuring the associations between height and common carotid artery diameter (CCAD) and intima-media thickness (IMT) after controlling for recognized vascular influencing factors (e.g., adiposity, blood pressure, plasma lipids, etc.). Results: Height remained a significant CCAD predictor across all developed multiple regression models. These models predict a ~0.03 mm increase in CCAD for each 1-cm increase in height in this sample. This magnitude of CCAD increase with height represents over a 60% enlargement of the artery's lumen area across adults varying in stature from short (150 cm) to tall (200 cm). By contrast, IMT was non-significantly correlated with height across all developed regression models. Conclusions: People who are tall have a larger absolute CCAD than people who are short, while IMT is independent of stature. These observations potentially add to the growing cardiovascular literature aimed at explaining the lower risk of ischemic strokes in tall people.

Prevalence of Synchronous and Metachronous Aneurysms in Women With Abdominal Aortic Aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) is three to five times more common among men compared with women, yet up to 38% of all aneurysm related deaths affect women. The aim of this study was to estimate the prevalence of synchronous or metachronous aneurysms among women with AAA, as diagnosis and treatment could improve survival.

PATIENTS AND METHODS

This is a retrospective study of prospectively registered patients. All women operated on, or under surveillance for, AAA were identified at two Swedish hospitals. Aneurysms in different locations were identified using available imaging studies. Aneurysms were defined according to location: thoracic ascending aorta ≥42 mm, descending ≥33 mm, abdominal aorta ≥30 mm, common iliac artery ≥20 mm or 50% wider than the contralateral artery, common femoral artery ≥12 mm, popliteal artery ≥10 mm.

RESULTS

A total of 339 women with an AAA were included. The median follow up was 2.8 (range 0-15.7) years. Thirty-one per cent had an aneurysm in the thoracic aorta (67 of 217 investigated, 84% were located in the descending aorta), 13 (19%) underwent repair. Twelve per cent had a common iliac artery aneurysm (24/259, 76% were investigated). Common femoral artery aneurysms were identified in 4.3% (8/184, 54% investigated). Popliteal artery aneurysms were identified in 4.0% (6/149, 44% investigated). The prevalence of infrainguinal aneurysms was higher among patients with synchronous iliac aneurysms (40% vs. 1.6%, OR 42, 95% CI 6.4-279, p < .001).

CONCLUSIONS

Thoracic aortic aneurysms are common among women with AAA, most commonly affecting the descending aorta, and detection frequently results in repair. Popliteal and femoral aneurysms are not rare among women with AAA, and even common if there is a synchronous iliac aneurysm.

Reference values of vessel diameters, stenosis prevalence, and arterial variations of the lower limb arteries in a male population sample using contrast-enhanced MR angiography

Introduction

Morphological characterization of leg arteries is of significant importance to detect vascular remodeling triggered by atherosclerotic changes. We determined reference values of vessel diameters and assessed prevalence of stenosis and arterial variations of the lower limb arteries in a healthy male population sample.

Methods

Gadolinium-enhanced magnetic resonance angiography at 1.5 Tesla was performed in 756 male participants (median age = 52 years, range = 21–82 years) of the population-based Study of Health in Pomerania. Vessel diameters were measured in 9 predefined segments of the pelvic and leg arteries and 95th percentiles were used for upper reference values of means of left and right side arteries.

Results

Reference values of vascular diameters decreased from proximal to distal arteries: common iliac = 1.18cm; internal iliac = 0.75cm; external iliac = 1.03cm; proximal femoral = 1.02cm; distal femoral = 0.77cm; popliteal = 0.69cm; anterior tibial = 0.42cm; posterior tibial = 0.38cm; fibular = 0.40cm. Body-surface area indexed reference values increased with age in all segments. A number of 53 subjects (7.0%) had at least one stenosis, mainly in the lower leg arteries anterior tibial (n = 28, 3.7%), posterior tibial (n = 18, 2.4%) and fibular (n = 20, 2.6%). The risk of stenosis increased considerably with age (odds ratio = 1.08; p<0.001). The most common arterial variant was type I-A in both legs (n = 620, 82%).

Conclusion

We present reference values for different pelvic and leg artery segment diameters in men that decrease from proximal to distal and increase with age. Stenoses were most prevalent in lower leg arteries and type I-A was the most common variant in the lower leg.

Popliteal Artery Aneurysm in Women

OBJECTIVES

Ninety-five per cent of those operated on for popliteal artery aneurysm (PA) are men. Thus, PAs in women are difficult to investigate. The aim was to study the disease in women.

METHODS

Women treated for PA in 1987-2012, prospectively registered in the Swedish vascular registry, Swedvasc, supplemented by case records, were compared with the larger male cohort. Survival was determined through cross linkage with the National Population Registry.

RESULTS

1509 patients (men and women), 1872 legs, were identified; of these 74 patients (4.9%) were women, 81 legs (4.3%). The median age was 70 years in women versus 69 in men. Twenty-nine centres operated on women (range 1-7 women/centre). There were no time trends in the proportion of women operated on (p=.5). Bilateral PA occurred in 9.5% of women and 27.0% of men (p=.002). For symptomatic aneurysms, there was a larger proportion of small aneurysms (<2 cm) among women than men (24% vs. 8%, p=.005), there was no such difference in asymptomatic aneurysms. Distribution between asymptomatic and symptomatic PA was 31% versus 69%, similar to men. The prevalence of concomitant aneurysms in the aorto-iliac and femoral arteries, and the frequency of presenting symptoms were similar compared with men. Three PA were ruptured (3.7%). Thrombolysis was used in 23 of 45 legs treated for acute ischaemia (51%). Eight legs were treated with endovascular stent grafts (9.8%), compared with 7.9% in men (p=.5). Seven legs were amputated (8.6%). Crude survival was similar to men.

CONCLUSIONS

PA is similar in women and men, but bilateral disease was less common in women and symptomatic PA were more often <2 cm in diameter. Women had the same survival as men, despite women generally having better life expectancy. Although the largest series ever published on women with PA, the sample size is small, making it prone to type II statistical error.

Analysis of the Velocity Profile of the Popliteal Artery and Its Relevance During Blood Flow Studies

The mean blood velocity is required to calculate blood flow and to determine the associated shear rate. The maximal blood flow velocity is assumed to have a parabolic velocity profile; therefore, the mean velocity is half of the maximal value. Previous studies have been carried out on vessels such as the brachial and femoral artery, but none have been reported for the popliteal artery. To assess the velocity profile of the popliteal artery, a spectral Doppler analysis was performed on ten healthy patients during varied flow states (resting, distal occlusion, hyperemia). The results were then averaged over the entire cardiac cycle. The flow described in these patients’ popliteal artery had a blunted parabolic flow profile with a TAVmean:TAVmax ratio of 0.68 ± 0.07 at baseline. The baseline measures were compared to a TAVmean:TAV max ratio of 0.68 ± 0.12 during distal occlusion and 0.67 ± 0.16 during reactive hyperemia. These descriptive results may suggest that adjustments may be needed for a blunted parabolic profile, especially when calculating the mean velocity of the popliteal artery.

Arterial structure and function in vascular ageing: are you as old as your arteries?

Advancing age may be the most potent independent predictor of future cardiovascular events, a relationship that is not fully explained by time-related changes in traditional cardiovascular risk factors. Since some arteries exhibit differential susceptibility to atherosclerosis, generalisations regarding the impact of ageing in humans may be overly simplistic, whereas in vivo assessment of arterial function and health provide direct insight. Coronary and peripheral (conduit, resistance and skin) arteries demonstrate a gradual, age-related impairment in vascular function that is likely to be related to a reduction in endothelium-derived nitric oxide bioavailability and/or increased production of vasoconstrictors (e.g. endothelin-1). Increased exposure and impaired ability for defence mechanisms to resist oxidative stress and inflammation, but also cellular senescence processes, may contribute to age-related changes in vascular function and health. Arteries also undergo structural changes as they age. Gradual thickening of the arterial wall, changes in wall content (i.e. less elastin, advanced glycation end-products) and increase in conduit artery diameter are observed with older age and occur similarly in central and peripheral arteries. These changes in structure have important interactive effects on artery function, with increases in small and large arterial stiffness representing a characteristic change with older age. Importantly, direct measures of arterial function and structure predict future cardiovascular events, independent of age or other cardiovascular risk factors. Taken together, and given the differential susceptibility of arteries to atherosclerosis in humans, direct measurement of arterial function and health may help to distinguish between biological and chronological age-related change in arterial health in humans.

Increased cardiovascular risk without generalized arterial dilating diathesis in persons who do not have abdominal aortic aneurysm but who are first-degree relatives of abdominal aortic aneurysm patients

There is a strong genetic predisposition towards abdominal aortic aneurysm (AAA), but it is unknown whether persons without AAA but with first-degree relatives who are AAA patients have a generalized dilating diathesis, defect arterial wall mechanics, or increased cardiovascular risk. The aim of the study was to investigate arterial diameters and wall mechanics at multiple arterial sites in these subjects and compare them with controls without a family history of AAA. This study included 118 first-degree relatives of patients with AAA and 66 controls (age: 40-80 years). The abdominal aorta, common carotid artery, common femoral artery, and popliteal artery were investigated by echo-tracking ultrasound. The relatives had no arterial dilatation, but they did tend to have smaller diameters than controls. Relatives had a higher heart rate, diastolic blood pressure, and mean arterial pressure than controls. The distensibility coefficient and the compliance coefficient were decreased in all arteries in male relatives, adjusted for age and smoking; these coefficients were normalized after adjustment for mean arterial pressure and heart rate. Female relatives had a lower compliance coefficient in the abdominal aorta, adjusted for age and smoking. After adjustment for mean arterial pressure and heart rate, the difference disappeared. No general arterial dilatation in relatives without AAA was found, supporting the hypothesis that the dilating diathesis is linked to the aneurysmal manifestation in the abdominal aorta. Although the threat of aneurysmal dilatation and rupture seems to be lacking in these subjects, heart rate, blood pressure, and arterial wall stiffness were all increased, which may indicate a higher risk of developing cardiovascular morbidity and mortality.

Tailoring the flow sensitivity of fast spin-echo sequences for noncontrast peripheral MR angiography

There has recently been renewed interest in noncontrast techniques for peripheral MR angiography following the discovery of an association between gadolinium-based contrast agents and nephrogenic systemic fibrosis in patients with renal insufficiency. The "fresh blood imaging" technique proposed by Miyazaki et al. involves the subtraction of two three-dimensional fast spin-echo image sets, one acquired in systole, when the arteries appear dark due to flow-related dephasing, and the other obtained in diastole, when the arteries are brighter. Our goal was to investigate how parameters of the fast spin-echo sequence influence its flow sensitivity, and how that in turn impacts the depiction of large and small arteries. Results from phantom experiments and human studies in the calf suggest that the flow sensitivity is governed largely by the flip angle of the radiofrequency refocusing pulses. The area of the spoiler gradients has a lesser effect, and at low flip angles the echo time plays a role. These parameters can be optimized to obtain good depiction of the calf arteries in healthy subjects. It remains to be seen whether they provide sufficient control over flow sensitivity to achieve diagnostic-quality images in other vascular beds and in the presence of pathology.

Growth and risk factors for expansion of dilated popliteal arteries

OBJECTIVES

The aims of this study were to investigate the change in maximum diameter of ectatic popliteal arteries during ultrasound surveillance and assess clinical predictors of their expansion.

METHODS

Over a ten year period 67 patients with ectasia affecting one (n = 1) or both (n = 66) popliteal arteries entered this surveillance study. Patients were followed for a median of 3.1 years, at a median scan interval of 7.6 months.

RESULTS

Growth of ectatic popliteal arteries was typically slow (<1 mm/yr). Initial artery diameter at entry to the study was not found to be predictive of subsequent growth. Seven patients followed for a median of 2 years had an expansion in popliteal artery diameter to >or=20 mm during follow-up. All of these patients had undergone aneurysm repairs at other arterial sites and none of them had diabetes. These participants also had a significantly higher rate of previous intervention of the contralateral popliteal artery in comparison to those that did not reach the 20 mm threshold (p < 0.001). Growth profiles of arteries that underwent significant expansion during surveillance were frequently characterised by a staccato pattern.

CONCLUSIONS

Expansion of ectatic popliteal arteries is typically slow but difficult to predict. Trends observed in this study suggest that patients with extra-popliteal aneurysms, patients with previously treated contralateral popliteal artery ectasia and those who are not diabetics may be more prone to significant expansion. Further studies are required to validate these potential growth predictors.

Lower extremity CT angiography (CTA): initial evaluation of a knowledge-based centerline estimation algorithm for femoro-popliteal artery (FPA) occlusions

RATIONALE AND OBJECTIVES

Existing density- and gradient-based automated centerline-extraction algorithms fail in severely diseased or occluded arterial segments for the generation of curved planar reformations (CPRs). We aimed to quantitatively and qualitatively assess the precision of a knowledge-based centerline-extraction algorithm in patients with occluded femoro-popliteal artery (FPA).

MATERIAL AND METHODS

Computed tomography angiograms of 38 FPA occlusions (mean length 120 mm) were retrospectively identified. Reference centerlines were determined as the mean of eight manual expert readings. Each occlusion was also interpolated using a new knowledge-based algorithm (partial vector space projection [PVSP]), which uses shape information extracted from a separate database of 30 nondiseased FPAs. Precision of PVSP was quantified as the maximum departure error (MDE) from the standard of reference and the proportion of the interpolated centerlines remaining within an assumed vessel radius of 3 mm. Multiple regression method was used to determine the factors predicting the precision of the algorithm. CPR quality was independently assigned by two readers.

RESULTS

The mean MDE (in mm) for occlusion lengths of <50 mm, 50-100 mm, 100-200 mm, and >200 mm was 0.95, 1.19, 1.40, and 2.25, for manual readings and 1.68, 2.90, 9.43, and 19.95 for PVSP, respectively. MDEs of the algorithm were completely contained within 3 mm of the assumed vessel radius in 20 of 38 occlusions. CPR quality was rated diagnostic by both readers in 23 of 38 occlusions.

CONCLUSION

Shape-based centerline extraction of FPA occlusions in lower extremity CTA is feasible, and independent from local density and gradient information. PVSP centerline extraction allows interpolation of occlusions up to 100 mm within the variability of manually derived centerlines.

An improved algorithm for femoropopliteal artery centerline restoration using prior knowledge of shapes and image space data

Accurate arterial centerline extraction is essential for comprehensive visualization in CT Angiography. Time consuming manual tracking is needed when automated methods fail to track centerlines through severely diseased and occluded vessels. A previously described algorithm, Partial Vector Space Projection (PVSP), which uses vessel shape information from a database to bridge occlusions of the femoropopliteal artery, has a limited accuracy in long (>100 mm) occlusions. In this article we introduce a new algorithm, Intermediate Point Detection (IPD), which uses calcifications in the occluded artery to provide additional information about the location of the centerline to facilitate improvement in PVSP performance. It identifies calcified plaque in image space to find the most useful point within the occlusion to improve the estimate from PVSP. In this algorithm candidates for calcified plaque are automatically identified on axial CT slices in a restricted region around the estimate obtained from PVSP. A modified Canny edge detector identifies the edge of the calcified plaque and a convex polygon fit is used to find the edge of the calcification bordering the wall of the vessel. The Hough transform for circles estimates the center of the vessel on the slice, which serves as a candidate intermediate point. Each candidate is characterized by two scores based on radius and relative position within the occluded segment, and a polynomial function is constructed to define a net score representing the potential benefit of using this candidate for improving the centerline. We tested our approach in 44 femoropopliteal artery occlusions of lengths up to 398 mm in 30 patients with peripheral arterial occlusive disease. Centerlines were tracked manually by four-experts, twice each, with their mean serving as the reference standard. All occlusions were first interpolated with PVSP using a database of femoropopliteal arterial shapes obtained from a total of 60 subjects. Occlusions longer than 80 mm (N = 20) were then processed with the IPD algorithm, provided calcifications were found (N = 14). We used the maximum point-wise distance of an interpolated curve from the reference standard as our error metric. The IPD algorithm significantly reduced the average error of the initial PVSP from 2.76 to 1.86 mm (p < 0.01). The error was less than the clinically desirable 3 mm (smallest radius of the femoropopliteal artery) in 13 of 14 occlusions. The IPD algorithm achieved results within the range of the human readers in 11 of 14 cases. We conclude that the additional use of sparse but specific image space information, such as calcified atherosclerotic plaque, can be used to substantially improve the performance of a previously described knowledge-based method to restore the centerlines of femoropopliteal arterial occlusions.

Endovascular treatment of popliteal artery aneurysms

Popliteal artery aneurysms are relatively uncommon but potentially limb-threatening lesions that can thrombose or cause distal embolization. Identification of these aneurysms, especially in patients with abdominal aortic aneurysms, is imperative, and prophylactic treatment with either surgical exclusion and bypass or endoluminal stent grafting is critical to prevent these poor outcomes. Endovascular approaches currently using the Viabahn stent graft offer several advantages, including a minimally invasive approach, fewer perioperative complications, and a faster recovery. This must be balanced with a potentially higher failure rate or requirement for reintervention, although contemporary series report comparable short-term outcomes. We present our approach to the evaluation and diagnosis of popliteal aneurysms, the technical aspects of endovascular popliteal aneurysm repair, and a representative case study.

Screening for popliteal aneurysms should not be a routine part of a community-based aneurysm screening program

Introduction

Several studies have found an increased incidence of peripheral aneurysms in patients with an abdominal aortic aneurysm (AAA). The aim of this study was to determine whether screening for popliteal aneurysms should be part of an AAA screening programme.

Setting

A community-based AAA screening programme

Methods

The diameters of the internal abdominal aorta and both popliteal arteries were assessed by B-Mode ultrasound in a subgroup of the screened population. An AAA was defined as an infrarenal aortic diameter >29 mm. A popliteal aneurysm was defined as a popliteal diameter >19 mm.

Results

Information was available for 283 subjects, 112 subjects with a small AAA, and 171 subjects with a normal aorta. No popliteal aneurysms were found in the subjects with a normal aorta. Three popliteal aneurysms were found in patients with a small AAA. Scanning both popliteal arteries took an experienced sonographer on average three times as long as scanning for an AAA (5 vs 15 minutes).

Conclusion

Popliteal artery aneurysms are seen in less than 3% of men with a small AAA and not at all in men with a normal aortic diameter. It is therefore not cost effective to include screening for popliteal aneurysms in population screening for AAA.

Doppler ultrasound assessment of posterior tibial artery size in humans

PURPOSE

The difference between structural remodeling and changes in tone of peripheral arteries in the lower extremities has not been evaluated. The purpose of this study was to (1) evaluate the day-to-day reproducibility and interobserver reliability (IOR) of posterior tibial artery (PTA) diameter measurements and (2) evaluate the effect of posture on PTA diameter at rest (Drest), during 10 minutes of proximal cuff occlusion (Dmin), and after the release of cuff occlusion (Dmax), as well as range (Dmax - Dmin) and constriction [(Dmax - Drest)/(Dmax - Dmin) x 100] in vivo.

METHODS

We used B-mode sonography to image the PTA during each condition.

RESULTS

Day-to-day reliability was good for Drest (intraclass correlation coefficient [ICC] 0.95; mean difference 4.2%), Dmin (ICC 0.93; mean difference 5.4%), and Dmax (ICC 0.99; mean difference 2.2%). The coefficient of repeatability for IOR was 70.5 microm, with a mean interobserver error of 4.7 microm. The seated position decreased Drest (2.6 +/- 0.2 to 2.4 +/- 0.3 mm; p = 0.002), increased Dmin (2.1 +/- 0.2 to 2.4 +/- 0.2 mm; p = 0.001), and decreased Dmax (3.1 +/- 0.4 to 2.8 +/- 0.3 mm; p < 0.001) compared with the supine position. The seated position also decreased arterial range (Dmax - Dmin) from 0.9 +/- 0.2 to 0.5 +/- 0.1 mm (p = 0.003) and increased basal arterial constriction from 57 +/- 19% to 105 +/- 27% (p = 0.007).

CONCLUSIONS

The system employed for measuring PTA diameter yields unbiased and consistent estimates. Furthermore, lower extremity arterial constriction and range change with posture in a manner consistent with known changes in autonomic activity.

Size of normal and aneurysmal popliteal arteries: A duplex ultrasound study

OBJECTIVE

To define diameter at three levels along the popliteal artery and its relation to the inflow arteries in the normal state and in popliteal aneurysms.

METHODS

The external diameter of the arteries was determined by duplex ultrasound scanning at the common femoral (CFA), superficial femoral artery (SFA), proximal popliteal artery (PPOP), mid-popliteal artery (MPOP), and distal popliteal artery (DPOP). Examinations were performed in 104 healthy men and 100 women. In addition, patients were screened for the presence of popliteal aneurysms (diameter >10 mm). Findings in healthy male subjects were compared with those with popliteal aneurysms.

RESULTS

Mean arterial diameters in normal men were larger than in women, but the SFA/CFA ratio was smaller in women (0.74 +/- 0.08 vs 0.78 +/- 0.09; P < .001) and the MPOP/SFA ratio was larger (0.98 +/- 0.11 vs 0.94 +/- 0.12; P = .001). In both genders, normal popliteal artery diameter was not uniform throughout its length, with PPOP and MPOP being nearly identical, and DPOP was smaller. MPOP diameter correlated most closely with SFA diameter (r = 0.51; P < .001) and less with height, weight and body surface area (r = 0.2 to 0.3) and was not associated with age or the presence of hypertension. In 27 men with 45 patent, fusiform popliteal aneurysms (10 to 44 mm) the site of maximal dilatation was in the region of the MPOP in 39 cases and near the PPOP in only 6 cases. The DPOP was never the largest segment and only in one case was it >10 mm. Arterial diameter in aneurysm patients was larger than normal at all levels but was greatest near the MPOP level (15.7 +/- 6.9). Popliteal-to-SFA diameter ratios were increased in the aneurysm group at all three levels but were greatest at the MPOP level (1.85 vs 0.94, P < .001). Comparing 15 popliteal aneurysms >20 mm with smaller ones, distal popliteal artery changed to the least extent but did increase in diameter (6.1 +/- 1.2 vs 7.0 +/- 1.4, P < .04). In larger aneurysms the MPOP/SFA ratio increased from 1.54 to 2.5 (P < .001).

CONCLUSION

The diameter of the normal popliteal artery is not uniform throughout its length. In popliteal aneurysms, the region of the MPOP is most commonly the largest diameter. The MPOP/SFA ratio is greater than normal in popliteal aneurysms and increases in larger aneurysms. DPOP does dilate but to a lesser extent then PPOP and MPOP, making endovascular repair anatomically feasible in most popliteal aneurysms.

Is Assessment of Popliteal Artery Diameter in Patients Undergoing Screening for Abdominal Aortic Aneurysms a Worthwhile Procedure

PURPOSE

The aim of this study was to assess whether screening of popliteal arteries in patients undergoing ultrasound screening of their abdominal aortas was worthwhile.

METHODS

All male patients undergoing ultrasound screening for abdominal aortic aneurysm (AAA) during the period February 2000 to June 2002 were offered scanning of their popliteal arteries. All scans were performed by a single, trained operator using a Sonosite 180.

RESULTS

Four hundred and forty-nine patients underwent screening and thus 898 popliteal arteries were assessed. The mean aortic diameter was 2.1 standard deviations (SD) 0.5 cm and the upper limit of normal (2 SD) was 2.7 cm. The mean diameter of the popliteal arteries was 0.74 SD 0.11 and the upper limit of normal was 0.96 cm. Thirty patients had aortic diameters greater than 2.5 cm (ectatic or aneurysmal aortas) but based on a popliteal diameter of 2 cm, no popliteal aneurysms were detected. However, 39 (4.3%) popliteal arteries measured > or = 1 cm (> mean+2 SD); 3/60 (5%) in the ectatic/AAA subgroup and 36/838 (4.3%) in the non-AAA subgroup.

CONCLUSIONS

This study has shown that, using conventional definitions, the imaging of popliteal arteries during screening for AAAs does not detect any popliteal aneurysms and is thus of limited value. However, if a definition of popliteal aneurysm of > or = 1 cm (based on mean+2 SD) is used then 39/898 (4.3%) of arteries would be regarded as having abnormal diameters and may require surveillance.

Type I aneurysmosis: complementary index for diagnosis

The aim of this study was to investigate the diameters of the superficial femoral artery (SFA) and the popliteal artery (PA) in patients with type I aneurysmosis (diffuse aneurysm in the aortoiliac-common femoral segments combined with arteriomegaly of the femoropopliteal segments). The ratio between these diameters (SFA/PA index) was calculated. A retrospective study was carried out on 76 limbs of 38 patients with type I aneurysmosis. The SFA/PA index calculated on these patients was compared with the index of a control group: 76 limbs of 38 patients with abdominal aortic aneurysm. The SFA/PA index proved to be <1.00 in the limbs of patients with type I aneurysmosis, whereas it was > or =1.00 in all patients with an abdominal aortic aneurysm. There was a statistically significant difference between the type I aneurysmosis group and the control group (p < .001). This finding can be considered a complementary sign in the diagnosis of type I aneurysmosis.

The popliteal artery, an unusual muscular artery with wall properties similar to the aorta: implications for susceptibility to aneurysm formation?

OBJECTIVE

The popliteal artery is, after the aorta, the most common site for aneurysm formation. Why the popliteal artery is more susceptible than other peripheral muscular arteries is unknown. An important factor may be differences in arterial wall composition as compared with other peripheral muscular arteries, which in turn affect wall properties. These are however unknown. We studied the mechanical wall properties of the popliteal artery in healthy subjects.

MATERIAL AND METHODS

An ultrasound echo-tracking system was used to measure pulsatile changes in popliteal diameter in 108 healthy subjects (56 female, 52 male; age range, 9-82 years). In combination with blood pressure, stiffness (beta), strain, cross-sectional artery wall compliance coefficient (CC), and distensibility coefficient (DC) were calculated. Intima-media thickness (IMT) was registered with a Philips P700 ultrasound scanner.

RESULTS

The popliteal diameter increased with age, and was larger in male subjects than in female subjects (P<.001). Fractional diameter change (strain) decreased with age (P<.001), and strain values were lower in male subjects than in female subjects (P<.01). Accordingly, stiffness increased with age (P<.001), with higher stiffness values in male subjects (P<.01). DC decreased with age (P<.001), with lower DC values in male subjects (P<.01). CC decreased with age, with no difference between genders (P<.001). IMT increased with age (P<.001), with higher IMT values in male subjects (P<.001). The increase in IMT did not affect distensibility.

CONCLUSION

The wall properties of the popliteal artery are affected by age and gender, not only with an increase in diameter, but also with an age-related decrease in distensibility, with male subjects having lower distensibility than in female subjects. This seems not to be the behavior of a true muscular artery, but of a central elastic artery, such as the aorta, and might have implications for susceptibility to arterial dilatation, as well as the association of aneurysm formation between the aorta and the popliteal artery.

CLINICAL RELEVANCE

The popliteal artery is, after the abdominal aorta, the most common location for aneurysm formation in the arterial system. Why it is more susceptible than other arteries is unknown. This study shows that the wall function of the popliteal artery differs from other peripheral arteries, and instead show striking similarities to the abdominal aorta, indicating that the functional arrangement of arterial wall components are similar in the two arteries. This may have implications for the susceptibility to aneurysm formation, as well as the association of dilating disease between the popliteal artery and the abdominal aorta.

Morphometric analysis of the popliteal artery for endovascular treatment

This study intended to determine the precise diameter of the popliteal artery in patients at risk for popliteal aneurysms. Accurate sizing is necessary to develop devices for endovascular treatment of popliteal aneurysms. Fifty-four patients with abdominal aortic aneurysms (AAAs) had computed tomography (CT) scans of the popliteal arteries. Age- and gender-matched control subjects were measured by ultrasound. NIH Image was used to measure the minor diameter at the adductor hiatus (proximal) and femoral condyles (midpopliteal artery). There were 4 unsuspected popliteal aneurysms (7.4%). The proximal popliteal artery was ectatic in these patients: 13.4 +/- 5.2 mm. Proximal and midpopliteal arteries were significantly larger in the other patients with AAAs compared with controls: 9.6 +/- 1.8 mm vs 7.9 +/- 1.1 mm at the hiatus (p<0.001) and 10.2 +/- 2 mm vs 7.9 +/- 0.9 mm at the condyles (p<0.001). The popliteal artery was focally larger in patients with AAAs without popliteal aneurysms. The popliteal artery was larger in men compared with women; 9.8 +/- 1.8 mm vs 8.8 +/- 1.9 mm at the hiatus (p=0.024) and 10.5 +/- 1.9 mm vs 9.0 +/- 2.4 mm at the condyles (p=0.005). The proximal popliteal artery was 2 mm larger in patients at risk for popliteal aneurysms and 5 mm larger in patients with popliteal aneurysms compared to controls. Focal ectasia of the midpopliteal artery was common. Planning for endovascular treatment of popliteal aneurysms must incorporate this striking enlargement.

Arterial dimensions in the lower extremities of patients with abdominal aortic aneurysms--no indications of a generalized dilating diathesis

PURPOSE

This study assessed whether there is a dilating diathesis in peripheral arteries of patients with abdominal aortic aneurysms (AAAs).

METHODS

The anteroposterior diameters of the common femoral artery (CFA) and popliteal artery (PA) were measured in 183 consecutive patients with an AAA (158 men, 25 women; age range, 57-78 years) before elective surgery on the AAA and compared with that of healthy age-matched control subjects. The diameter registrations were performed on the right leg by using a noninvasive echo-tracking ultrasound scanning technique.

RESULTS

Eight CFA aneurysms and four PA aneurysms were found in the male patients with AAAs. Of the patients with AAAs in the CFA and in the PA who were investigated, 46% and 49%, respectively, were affected by peripheral vascular occlusive disease (PVOD). The CFA diameters in the patients with AAAs were 97.8% of those in healthy control subjects (P = not significant [NS]). After exclusion of the CFA aneurysms, the diameters were 92.7% of those in healthy control subjects (P = .0003). If patients with PVOD were also excluded, the CFA diameters were 95.2% of those in healthy control subjects (P = .022). The PA diameters in the patients with AAAs were 97.8% of those in healthy control subjects (P = NS). If PA aneurysms were excluded, the diameters were 94.4% of those in healthy control subjects (P = .0003). If patients with PVOD were also excluded, the PA diameters were 96.1% of those in healthy control subjects (P = NS).

CONCLUSION

After excluding the few patients with AAAs who had peripheral aneurysmal disease and the patients with PVOD, no dilating diathesis in CFAs and PAs was found. This supports the hypothesis that specific genetic, or other factors, not present in most AAAs are responsible for the occurrence of concomitant peripheral aneurysms. Furthermore, the generalized vascular dilating diathesis seen in some patients seems to be a specific entity that was not necessarily affiliated with AAA disease.

The diameter of the common femoral artery in healthy human: influence of sex, age, and body size

PURPOSE

To determine the relevance of dilatations of the common femoral artery (CFA), knowledge of the normal CFA diameter is essential. The diameter of the CFA in healthy male and female subjects of different ages was investigated.

METHODS

The diameter of the CFA was measured in 122 healthy volunteers (59 male, 63 female; 8 to 81 years of age) with echo-tracking B-mode ultrasound scan. The influence of age, sex, height, weight, body surface area (BSA), and systolic blood pressure was analyzed by means of a multiple regression model.

RESULTS

The CFA increased steadily in diameter throughout life. From 25 years onwards, the diameter was larger in men than in women. Significant correlations were found between the CFA diameter and weight (r = 0.58 and r = 0.57 in male and female subjects, respectively; P <.0001), height (r = 0.49 and r = 0.54 in male and female subjects, respectively; P <.0001), and BSA (r = 0.60 and r = 0.62 in male and female subjects, respectively; P <.0001). Age and BSA were used to create a model for prediction of the CFA diameter (r = 0.71 and r = 0.77 in male and female subjects, respectively; P <.0001).

CONCLUSION

The diameter of the CFA increases with age, initially during growth but also in adults. This is related to age, body size, and sex male subjects have larger arteries than female subjects. It is now possible to predict the normal CFA diameter, and nomograms that may be used in the study of aneurysmal disease are presented.