Accurate Noninvasive Arterial Assessment of the Wounded Lower Limb: A Clinical Challenge for Wound Practitioners.

Arterial investigations are an essential part of lower extremity wound assessment. The results of these investigations assist the wound clinician to determine the etiology of the wound, predict healing capacity, and inform further management. There are a number of noninvasive testing methods available to practitioners, all with varying levels of reliability and accuracy. Clinical wound assessment guidelines give varied recommendations when it comes to lower limb vascular assessment in the presence of a wound. This leaves clinicians with little guidance on how to choose the most appropriate test, and uncertainty remains about which tests provide the most accurate information in different patient-specific contexts. Conditions such as advanced age, diabetes, and renal disease are known to affect the accuracy of some commonly used lower limb arterial assessment methods, and alternate testing methods should be considered in these cases. This seminal review discusses the reliability and accuracy of lower limb vascular assessment methods used to guide lower limb arterial assessment in the presence of wounds.

Computational study on phase lag of arterial-wall motion for assessment of plaque vulnerability.

The wall motion of atherosclerotic plaque was analyzed using a computational method, and the effects of tissue viscoelasticity, fibrosis thickness, and lipid-core stiffness on wall displacement waveforms were examined. The viscoelasticity of plaque tissues was modeled using a time Prony series with four Maxwell elements. Computational simulation of tissue indentation tests showed the validity of the proposed viscoelastic constitutive models. Decreasing the relative moduli of the viscoelastic model reduced their viscous characteristics while enhancing the stiffness of the wall, which corresponded with the effects of decreased smooth muscle cells content. A finite-element analysis was conducted for atherosclerotic wall models and wall displacement waveforms were computed. The phase difference between the first harmonics of pressure and displacement waves was selected to represent the time delay of the wall motion. As the relative modulus decreased, the wall displacement and phase lag decreased. A thinner wall and softer lipid core corresponded to a greater wall displacement and smaller phase lag. Because the phase lag of the arterial-wall motion was smaller for the plaque with a thinner cap, lower smooth muscle cells content, and softer lipid core (all features of plaques with high rupture risk), first harmonics of pressure and displacement waves can be used as an index to assess plaque vulnerability.

Post-exercise Response of Arterial Parameters for Arterial Health Assessment Using a Microfluidic Tactile Sensor and Vibration-Model-Based Analysis: A Proof-of-Concept Study.

OBJECTIVE: Arterial stiffness and endothelial function are two established surrogate markers of subclinical atherosclerosis and are quantified by three arterial parameters: elasticity, viscosity and radius of the arterial wall. Yet, the current methods for their assessment are unsuitable for routine use. Post-exercise response of the cardiovascular (CV) system serves as a more sensitive detection of subclinical arterial abnormalities that are not apparent at-rest. The objective of this study is to propose a novel method that can measure post-exercise response of arterial parameters and is also suitable for routine use. APPROACH: A microfluidic tactile sensor with a location-insensitive configuration was used for arterial pulse signal measurements on six asymptomatic male subjects, offering measurement reliability, ease use by a layperson, and affordability. By treating the arterial pulse signal as a vibration signal of the arterial wall, vibration-model-based analysis of only one measured pulse signal with no calibration was conducted for simultaneous estimation of three arterial parameters. Exercise-intensity-normalized percent changes in arterial parameters were utilized to remove the influence of variation in exercise intensity on post-exercise response, and then their measured values were compared for difference in post-exercise response between the subjects. MAIN RESULTS: One subject who was obese, on subject who had insomnia, and the oldest subject in the study demonstrated differences in post-exercise response at the radial artery (RA), as compared with the three subjects free of those three factors. Despite a lack of statistical significance, the observed difference at the RA between subjects was supported by (i) their consistency with the related findings in the literature, and (ii) their consistency with the measured values at the carotid artery (CA) and superficial temporal artery (STA) and the anatomical difference between the three arteries. SIGNIFICANCE: The proposed method has the potential of offering an affordable and convenient diagnosis tool for routine arterial health assessment.

Non-invasive assessment of arterial pulsatility in patients with continuous-flow left ventricular assist devices.

INTRODUCTION: Long-term use of continuous-flow left ventricular assist devices may have negative consequences for autonomic, cardiovascular and gastrointestinal function. It has thus been suggested that non-invasive monitoring of arterial pulsatility in patients with a left ventricular assist device is highly important for ensuring patient safety and longevity. We have developed a novel, semi-automated frequency-domain-based index of arterial pulsatility that is obtained during suprasystolic occlusions of the upper arm: the 'cuff pulsatility index'. PURPOSE: The purpose of this study was to evaluate the relationship between the cuff pulsatility index and invasively determined arterial pulsatility in patients with a left ventricular assist device. METHODS: Twenty-three patients with a left ventricular assist device with end-stage heart failure (six females: age = 65 ± 9 years; body mass index = 30.5 ± 3.7 kg m-2) were recruited for this study. Suprasystolic occlusions were performed on the upper arm of the patient's dominant side, from which the cuff pressure waveform was obtained. Arterial blood pressure was obtained from the radial artery on the contralateral arm. Measurements were obtained in triplicate. The relationship between the cuff pressure and arterial blood pressure waveforms was assessed in the frequency-domain using coherence analysis. A mixed-effects approach was used to assess the relationship between cuff pulsatility index and invasively determined arterial pulsatility (i.e. pulse pressure). RESULTS: The cuff pressure and arterial blood pressure waveforms demonstrated a high coherence up to the fifth harmonic of the cardiac frequency (heart rate). The cuff pulsatility index accurately tracked changes in arterial pulse pressure within a given patient across repeated measurements. CONCLUSIONS: The cuff pulsatility index shows promise as a non-invasive index for monitoring residual arterial pulsatility in patients with a left ventricular assist device across time.

New insights into arterial stiffening: does sex matter?

This review discusses sexual dimorphism in arterial stiffening, disease pathology interactions, and the influence of sex on mechanisms and pathways. Arterial stiffness predicts cardiovascular mortality independent of blood pressure. Patients with increased arterial stiffness have a 48% higher risk for developing cardiovascular disease. Like other cardiovascular pathologies, arterial stiffness is sexually dimorphic. Young women have lower stiffness than aged-matched men, but this sex difference reverses during normal aging. Estrogen therapy does not attenuate progressive stiffening in postmenopausal women, indicating that currently prescribed drugs do not confer protection. Although remodeling of large arteries is a protective adaptation to higher wall stress, arterial stiffening increases afterload to the left ventricle and transmits higher pulsatile pressure to smaller arteries and target organs. Moreover, an increase in aortic stiffness may precede or exacerbate hypertension, particularly during aging. Additional studies are needed to elucidate the mechanisms by which females are protected from arterial stiffness to provide insight into its mechanisms and, ultimately, therapeutic targets for treating this pathology.

Arterial Wall Properties in Men and Women: Hemodynamic Analysis and Clinical Implications.

The properties of arterial walls are dictated by their underlying structure, which is responsible for the adequate perfusion of conduit branching arteries and their vascular beds. Beginning with the mechanobiology of arteries in terms of their composition and individual contributions to overall viscoelastic behavior in men and women, pressure-flow relations are analyzed and noted in terms of sex differences. Hemodynamic function in terms of indices of vascular stiffness-such as pressure-strain elastic modulus, pulse wave velocity, augmentation index, and cardio-ankle vascular index-are evaluated. They all showed differences between the sexes, and these differences also were shown among people of different cultures. Recent studies also showed, in heart failure patients, a comparatively greater increase in peripheral resistance and a greater decreased arterial compliance in women. Wave separation into forward and reflected waves allows elucidation of mechanical and drug-treated similarities and differences in induced hypertension. This may provide insight into treatment strategy in terms of improving mechanobiology and designing drug therapy for the sexes. Finally, modeling studies are useful in identifying how arterial compliance and its pressure dependence can be better used in differentiating aging- and hypertension-induced changes that differentially affect the sexes.

Serial assessment of endothelial function 1, 6, and 12 months after ST-elevation myocardial infarction.

Knowledge about the changes in endothelial function after ST-elevation myocardial infarction (STEMI) is of substantial interest, but serial data are scarce. The aim of the present study was to noninvasively evaluate whether endothelial function, as assessed shortly after primary percutaneous coronary intervention (PPCI) for STEMI, may improve until 12-month follow-up. This prospective observational cohort study was performed in patients in the RESPONSE randomized trial who participated in a substudy and underwent noninvasive assessment of endothelial function at 1 (baseline), 6, and 12-month follow-up after treatment of a STEMI by PPCI. The reactive hyperemia peripheral artery tonometry (RH-PAT) method was used to assess endothelial function (higher RH-PAT index signifies better function). Of the 70 study participants, who were 57.4 ± 9.7 years of age, 55 (78.6%) were male and 9 (13%) had diabetes. The endothelial function deteriorated significantly during follow-up: the RH-PAT index at baseline, 6, and 12-month follow-up was 1.90 ± 0.58, 1.81 ± 0.57, and 1.69 ± 0.49, respectively (p = 0.04). Although patients were carefully treated in outpatient clinics and adequate pharmacological therapy was prescribed, we noted an increase in total cholesterol (p = 0.001), LDL cholesterol (p = 0.002), HbA1C (p = 0.054), and diastolic blood pressure (p = 0.047) However, multivariate analysis revealed that this increase in cardiovascular risk factors could not explain the observed deterioration in endothelial function. In patients with STEMI, we observed a significant deterioration in endothelial function during 12 months after PPCI that could not be explained by changes in the traditional cardiovascular risk profile.

Simplifying Arterial Coupling in Microsurgery-A Preclinical Assessment of an Everter Device to Aid with Arterial Anastomosis.

BACKGROUND: A novel arterial everter device was engineered to simplify microvascular coupling of arteries by reliably securing the stiff, muscular wall of arteries over coupler pins. We compare microvascular coupling with the everter device to manual suturing for arterial anastomoses in a live large animal model. MATERIALS AND METHODS: In this preliminary study, bilateral external femoral arteries of five male swine were exposed and sharply divided. Arteries were anastomosed using either interrupted sutures (n = 5) or the everter device and Synovis Coupler (n = 5). The efficiency in engaging coupler pins, the time taken to perform the anastomosis, and vessel patency immediately post-op and at 1-week postanastomosis were evaluated. Vessel wall injury and luminal stenosis were compared between groups using histomorphometric analyses. RESULTS: On an average, 80% of coupler pins engaged the vessel walls after a single pass of the everter. The average time to perform the anastomosis was significantly less when using the everter/coupler compared with manual suturing (6:35 minutes versus 25:09 minutes, p < 0.001). Immediately post-op, 100% patency was observed in both groups. At 1 week post-op, four of five (80%) of coupled arteries and all five (100%) of hand-sewn arteries were patent. The degree of arterial wall injury, neointimal formation, and luminal stenosis for patent arteries were similar between groups. CONCLUSIONS: Successful arterial anastomoses using the everter device with the Synovis Coupler was easier and significantly more efficient when compared with a standard hand-sewn technique. Both techniques had acceptable patency rates and similar effects on the vessel wall and intima.

Utility of arterial stiffness assessment in children.

Atherosclerotic cardiovascular disease is a leading cause of death and disability worldwide, and the atherosclerotic process begins in childhood. Prevention or containment of risk factors that accelerate atherosclerosis can delay the development of atherosclerotic cardiovascular disease. Although current recommendations are to periodically screen for commonly prevailing risk factors for atherosclerosis in children, a single test that could quantify the cumulative effect of all risk factors on the vasculature, thus assessing arterial health, would be helpful in further stratifying risk. Measurement of pulse wave velocity and assessment of augmentation index - measures of arterial stiffness - are easy-to-use, non-invasive methods of examining arterial health. Various studies have assessed pulse wave velocity and augmentation index in children with commonly occurring conditions including obesity, hypertension, insulin resistance, diabetes mellitus, dyslipidaemia, physical inactivity, chronic kidney disease, CHD and acquired heart diseases, and in children who were born premature or small for gestational age. This article summarises pulse wave velocity and augmentation index assessments and the effects of commonly prevailing chronic conditions on arterial health in children. In addition, currently available reference values for pulse wave velocity and augmentation index in healthy children are included. Further research to establish widely applicable normative values and the effect of lifestyle and pharmacological interventions on arterial health in children is needed.

Evaluation of different metrics as an index for the assessment of arterial stiffness.

Elevated intravascular pressure is a contributing factor to increased arterial stiffness, and is a risk factor for cardiovascular morbidity and mortality. Assessment of arterial stiffness is of importance in evaluating cardiovascular risk. Pulse wave velocity (PWV) has been broadly used in the assessment of arterial stiffness. We compared three different metrics of arterial stiffness to PWV. Hemodynamic recordings were carried out in anesthetized hypertensive and normotensive rats (n = 25; 13-14 weeks old). Four parameters were calculated (PWV, elastic modulus (Einc), stiffness index (ß), and pressure-strain modulus (Ep)) as metrics of arterial stiffness. Hypertensive in comparison to normotensive rats had significantly higher systolic and diastolic blood pressures. Metric for arterial stiffness were significantly (p < 0.002) higher in hypertensive animals: PWV (8.46 ± 2.01 vs. 6.39 ± 1.28 m/s), Ep (0.246 ± 0.019 vs. 0.137 ± 0.010 dyn/cm2 × 10-6), Einc (17.5 ± 1.8 vs. 10.1 ± 0.9 dyn/cm2 × 10-6), and ß (2.43 ± 0.11 vs. 1.98 ± 0.08) (mean±SE). Bland-Altman analysis revealed ß as the only metric aligned with PWV in hypertensive state. We find in state of reduced arterial compliance associated with high systemic pressure, ß but not Einc or Ep is an index of arterial stiffness showing agreement with PWV.

[Assessment of endothelial dysfunction for prevention of complications in patients with lesions of peripheral arteries]. / Otsenka éndotelial'noi disfunktsii v profilaktike oslozhnenii u bol'nykh s porazheniem perifericheskikh arterii.

BACKGROUND: Severity of endothelial dysfunction and impairments of the vasomotor function of arteries correlate with the degree of the development of atherosclerosis and the risk of cardiovascular complications. To date, poorly studied still remains the problem concerning alteration of the regulatory function of the endothelium in patients diagnosed with pronounced atherosclerotic lesions of peripheral arteries, as well as the impact of a surgical intervention on indices of endothelial dysfunction. PATIENTS AND METHODS: Presented in the article are the results of preoperative study of the endothelial function by means of peripheral arterial tonometry (PAT) using the Endo PATTM 2000 device (Itamar Medical Ltd.) in a total of 74 patients undergoing surgical treatment at the Institute of Surgery named after A.V. Vishnevsky. The male-to-female ratio in the studied group was 1:2.52, with the patients' average age amounting to 67Ѓ}8 years. Of the 74 patients, 21 were subjected to a repeat examination performed at terms varying from 2 to 23 months postoperatively. Of these, 17 (80.95%) patients took statins. Fourteen (66.7%) patients had endured an operative intervention on carotid arteries and seven (33.3%) had been operated on for lesions of lower-limb arteries. RESULTS: The statistical analysis of the obtained findings revealed no significant differences of the indices of the endothelial function in the studied group between the genders, depending on age, smoking or taking statins. Neither were there statistically significant differences in the reactive hyperaemia index (RHI) amongst the patients with the involvement of one or several arterial basins. We did not reveal a direct relationship or regularity of the effect of a surgical intervention on the RHI values in the operated patients. This might be explained by the fact that the method of PAT to a greater degree assesses the state of the microvascular bed rather than that of large arteries.

Assessment of arterial stiffness from pedal artery Korotkoff sound recordings: feasibility and potential utility.

Brachial artery (BA) Korotkoff sound (KS) timing reflects arterial stiffness. We recorded pedal artery (PA) KS in 68 healthy subjects using an electronic stethoscope and electrocardiography. Intervals between QRS complex of the electrocardiogram and KS waveform peaks (termed the QKD interval) were measured for 60 seconds, averaged, and QKD velocity (v) calculated. Carotid-BA and carotid-PA pulse wave velocities (PWVs) were measured by applanation tonometry. Analyzable KS recordings were obtained from BA and PA in 100% and 92% subjects. PA QKDv decreased less than BA QKDv with progressive cuff inflation. At diastolic blood pressure + 20 mm Hg (maximal yield), BA QKDv was independently associated with weight and pulse pressure, whereas PA QKDv was related to weight and age. PA QKDv correlated with its corresponding PWV stronger than BA QKDv. In conclusion, PA KS is optimally recorded at diastolic blood pressure + 20 mm Hg; PA QKDv is correlated with age and better correlates with PWV than does BA QKDv. This technique may provide a simple arterial stiffness measure.

Assessment of systemic and pulmonary arterial remodelling in women with systemic sclerosis.

OBJECTIVES: Systemic sclerosis (SSc) leads to pulmonary circulation dysfunctionand there are some indications of systemic circulation impairment. We evaluated the influence of SSc on the elastic properties of large systemic arterial walls and potential correlations between systemic and pulmonary circulation involvement. METHOD: We examined 75 consecutive women (mean age 53.13±10.1 years) with confirmed SSc [mean disease duration (DD) 7.1±9.1 years] and 21 age-matched female volunteers (mean age 52.6±8.3 years, ns). Pulse wave velocity (PWV) and transthoracic echocardiography were performed. SSc patients were divided into two groups according to the median of DD: ≤3 years (39 patients) and >3 years (36 patients). RESULTS: Patients with DD>3 years had higher PWV than those with DD≤3 years and controls (log PWV: 2.23±0.23 vs. 2.13±0.16 and vs. 2.11±0.16 m/s; p=0.028 and 0.029, respectively). In addition, echocardiographic indices showed impaired right ventricular (RV) function in the patients with DD>3 years. Also in these SSc patients, PWV correlated with clinical and echocardiographic parameters of pulmonary circulation: age (r=0.64, p<0.0001), acceleration time of pulmonary ejection (AcT; r=-0.38, p=0.021), and tricuspid regurgitation peak gradient (TRPG; r=0.34, p=0.04). Multiple linear regression analysis showed that PWV was independently associated with DD (ß=0.22, p==0.02), AcT (ß=-0.215, p=0.03), and age (ß=0.44, p<0.001). CONCLUSIONS: In patients with SSc lasting more than 3 years, the disease is characterized by increased stiffness of the large systemic arteries. Longer duration of SSc leads simultaneously to the increased stiffness of the large systemic arteries and to the progressive impairment of RV function and its coupling to the pulmonary arterial bed.

Assessment and prognosis of peripheral artery measures of vascular function.

The endothelium plays a crucial role in the regulation of vascular homeostasis. Our understanding of its role in health and disease has increased dramatically since the pivotal discovery of nitric oxide more than 30 years ago. Clinical researchers utilized emerging technologies to study the vasodilator properties of the endothelium in both the coronary and peripheral circulation. Early studies established the methodologies and were able to demonstrate attenuated endothelium-dependent vasodilation in response to atherosclerosis and its risk factors. A variety of interventions can modulate endothelial function. More recent studies have established that some of these measures are independent predictors of cardiovascular outcomes. As such, peripheral measures of endothelial function are now established surrogate markers of vascular risk and have become important markers for clinical research. In this review, we will discuss a variety of measures of peripheral artery function to assess both conduit and resistance vessel function in humans.

Defining uremic arterial functional abnormalities in patients recently started on haemodialysis: combined in vivo and ex vivo assessment.

Endothelial dysfunction is a key initiating event in vascular disease in chronic kidney disease (CKD) patients and haemodialysis (HD) patients exhibit significant vascular abnormalities. To understand this further, we examined how ex vivo intrinsic function in isolated arteries correlates with in vivo assessments of cardiovascular status in HD patients. Abdominal fat biopsies were obtained from 11 HD patients and 26 non-uremic controls. Subcutaneous arteries were dissected and mounted on a wire myograph, and cumulative concentration-response curves to noradrenalin, endothelin-1, a thromboxane A2 agonist (U46619), angiotensin II, vasopressin, bradykinin (BK), acetylcholine (ACh) and sodium nitroprusside (SNP) were constructed. Pulse wave velocity and blood pressure were measured in HD patients. Enhanced (P<0.05-0.0001) maximal contractile responses (Rmax) to all spasmogens (particularly vasopressin) were observed in arteries from HD patients compared to controls, and this effect was more pronounced in arteries with an internal diameter>600 µm. The potency (pEC50) of U46619 (P<0.01) and vasopressin (P<0.001) was also increased in arteries>600 µm of HD patients. The maximal relaxant response to the endothelium-dependent dilators ACh and BK were lower in HD patients (P<0.01-P<0.0001) (worse for ACh than BK); however the endothelium-independent dilator SNP was similar in both groups. PWV was significantly correlated with the vasoconstrictor response to vasopressin (P = 0.042) in HD patients. HD patients are primed for hypertension and end organ demand ischaemia by a highly sensitised pressor response. The failure of arterial relaxation is mediated by endothelial dysfunction. Intrinsic vascular abnormalities may be important in sensitising HD patients to recurrent cumulative ischaemic end organ injury.

Daily assessment of arterial distensibility in a pediatric population before and after smoking cessation.

OBJECTIVES: Cigarette smoking is an important modifiable cardiovascular risk factor associated with increased stiffness of the large arteries in adulthood. This study aimed to 1) evaluate arterial distensibility and echocardiographic measures in adolescent smokers before and after participation in a successful smoking cessation program and to 2) compare the findings obtained with data from a control population of healthy non-smokers. METHODS: A total of 31 young smoking subjects (58.1% male; range: 11-18 years old; mean: 16.5±1.4 years old; mean tobacco consumption: 2.6±0.6 years) were examined before commencing and after taking part for at least 1 year in a smoking cessation program (mean: 1.4±0.3 years). Arterial stiffness was measured using the previously validated QKd100-60 method. Twenty-four-hour ambulatory blood pressure monitoring and transthoracic echocardiography were also performed. RESULTS: (Smokers before abuse cessation vs. smokers after abuse cessation) systolic blood pressure: p<0.004; diastolic blood pressure: p<0.02; mean blood pressure: p<0.01; QKd100-60 value: 183±5 vs. 196±3 msec, p<0.009; p = ns for all echocardiographic parameters. (Smokers after abuse cessation vs. controls) systolic blood pressure: p<0.01; diastolic blood pressure: p<0.03; mean blood pressure: p<0.02; QKd100-60 value: 196±3 vs. 203±2 msec, p<0.04; p<0.02, p<0.01, and p<0.05 for the interventricular septum, posterior wall, and left ventricular mass, respectively. CONCLUSIONS: Despite successful participation in a smoking cessation program, arterial distensibility improved but did not normalize. This finding underlines the presence of the harmful effect of arterial rigidity in these individuals, despite their having quit smoking and their young ages, thus resulting in the subsequent need for a lengthy follow-up period.

Daily assessment of arterial distensibility in a pediatric population before and after smoking cessation

OBJECTIVES: Cigarette smoking is an important modifiable cardiovascular risk factor associated with increased stiffness of the large arteries in adulthood. This study aimed to 1) evaluate arterial distensibility and echocardiographic measures in adolescent smokers before and after participation in a successful smoking cessation program and to 2) compare the findings obtained with data from a control population of healthy non-smokers. METHODS: A total of 31 young smoking subjects (58.1% male; range: 11-18 years old; mean: 16.5±1.4 years old; mean tobacco consumption: 2.6±0.6 years) were examined before commencing and after taking part for at least 1 year in a smoking cessation program (mean: 1.4±0.3 years). Arterial stiffness was measured using the previously validated QKd100-60 method. Twenty-four-hour ambulatory blood pressure monitoring and transthoracic echocardiography were also performed. RESULTS: (Smokers before abuse cessation vs. smokers after abuse cessation) systolic blood pressure: p<0.004; diastolic blood pressure: p<0.02; mean blood pressure: p<0.01; QKd100-60 value: 183±5 vs. 196±3 msec, p<0.009; p = ns for all echocardiographic parameters. (Smokers after abuse cessation vs. controls) systolic blood pressure: p<0.01; diastolic blood pressure: p<0.03; mean blood pressure: p<0.02; QKd100-60 value: 196±3 vs. 203±2 msec, p<0.04; p<0.02, p<0.01, and p<0.05 for the interventricular septum, posterior wall, and left ventricular mass, respectively. CONCLUSIONS: Despite successful participation in a smoking cessation program, arterial distensibility improved but did not normalize. This finding underlines the presence of the harmful effect of arterial rigidity in these individuals, despite their having quit smoking and their young ages, thus resulting in the subsequent need for a lengthy follow-up period. .

Multimodality imaging approach for serial assessment of regional changes in lower extremity arteriogenesis and tissue perfusion in a porcine model of peripheral arterial disease.

BACKGROUND: A standard quantitative imaging approach to evaluate peripheral arterial disease does not exist. Quantitative tools for evaluating arteriogenesis in vivo are not readily available, and the feasibility of monitoring serial regional changes in lower extremity perfusion has not been examined. METHODS AND RESULTS: Serial changes in lower extremity arteriogenesis and muscle perfusion were evaluated after femoral artery occlusion in a porcine model using single photon emission tomography (SPECT)/CT imaging with postmortem validation of in vivo findings using gamma counting, postmortem imaging, and histological analysis. Hybrid 201Tl SPECT/CT imaging was performed in pigs (n=8) at baseline, immediately postocclusion, and at 1 and 4 weeks postocclusion. CT imaging was used to identify muscle regions of interest in the ischemic and nonischemic hindlimbs for quantification of regional changes in CT-defined arteriogenesis and quantification of 201Tl perfusion. Four weeks postocclusion, postmortem tissue 201Tl activity was measured by gamma counting, and immunohistochemistry was performed to assess capillary density. Relative 201Tl retention (ischemic/nonischemic) was reduced immediately postocclusion in distal and proximal muscles and remained lower in calf and gluteus muscles 4 weeks later. Analysis of CT angiography revealed collateralization at 4 weeks within proximal muscles (P<0.05). SPECT perfusion correlated with tissue gamma counting at 4 weeks (P=0.01). Increased capillary density was seen within the ischemic calf at 4 weeks (P=0.004). CONCLUSIONS: 201Tl SPECT/CT imaging permits serial, regional quantification of arteriogenesis and resting tissue perfusion after limb ischemia. This approach may be effective for detection of disease and monitoring therapy in peripheral arterial disease.

Assessment of arterial stiffness for clinical and epidemiological studies: methodological considerations for validation and entry into the European Renal and Cardiovascular Medicine registry.

Epidemiological studies have highlighted the role of arterial stiffness as a risk factor for development of cardiovascular (CV) diseases. Moreover, aortic stiffness has been shown to be a significant predictive factor of all-cause and CV mortality in different populations including patients with end-stage renal disease. Pulse-wave velocity (PWV) is the most widely used technique to assess arterial stiffness. Although PWV can be measured on any artery or between any arterial sites, only carotid-to-femoral PWV, representing stiffness of the aorta and iliofemoral axes, has been shown to have predictive value for morbidity and mortality. The several available commercial devices differ according to the type of signal (pressure, distension, flow) or by recording both sites simultaneously or using ECG synchronization. It is also possible to directly measure arterial diameter changes during the cardiac cycle and link them to local pulse-pressure changes, which provides the pressure-diameter relationship and stress-strain relationship if arterial wall thickness is also measured. These techniques are based on high-precision vascular echo tracking or magnetic resonance imaging and applanation tonometry. This paper summarizes the basic principles of arterial haemodynamics and various methodologies to assess stiffness and the latest consensus recommendations for clinical applications.