Prevention and treatment of venous thromboembolism--International Consensus Statement

The aim of this document is to provide a clear and concise account of the evidence regarding efficacy or harm for various methods available to prevent and manage venous thromboembolism (VTE).

Asian venous thromboembolism guidelines: prevention of venous thromboembolism

Venous thromboembolism (VTE) prophylaxis is under-utilized in Asia because of the misconception that its incidence is lower in Asians as compared to the Caucasians. The available data on VTE in Asia is limited due to the lack of well-designed multicenter randomized controlled trials as well as non-standardized research designs, making data comparison difficult. Emerging data indicates that the VTE incidence is not low in Asia, and is comparable to that reported in the Western literature in some instances. There is also a trend towards increasing incidence of VTE, as demonstrated by a number of hospital-based studies in Asia. This could be attributed to lifestyle changes, ageing population, increasing awareness of VTE and wider availability of Duplex ultrasound. The risk of VTE in hospitalized patients remain the same in Asians and Caucasians, even though there may be factors that are inherent to patients in Asia that influence the slight variation in incidence. The utilization rate of VTE prophylaxis remains suboptimal in Asia. The Asian Venous Thrombosis Forum (AVTF) comprises participants from various countries such as China, Hong Kong, India, Indonesia, Korea, Malaysia, Philippines, Singapore, Taiwan, Thailand and experts from Australia and Europe. The forum evaluated the available data on VTE from the Asian region and formulated guidelines tailored to meet the needs of the region. We recommend that serious considerations are given to VTE prophylaxis especially in the at-risk group and a formal hospital policy be established to facilitate the implementation. On admission to the hospital, we recommend assessing the patients for both VTE and bleeding risk. We recommend mechanical prophylaxis for patients at increased risk of bleeding and utilizing it as an adjunctive measure in combination with pharmacological prophylaxis in patients with high risk of VTE. For patients undergoing general or gynecological surgery and with moderate risk for VTE, we recommend prophylaxis with one of the following: low dose unfractionated heparin (LDUH), low molecular weight heparin (LMWH), fondaparinux or intermittent pneumatic compression (IPC). For the same group of patients at high risk of VTE, we recommend pharmacological or combination of pharmacological and mechanical prophylaxis. For patients undergoing major orthopedic surgeries like total hip replacement, total knee replacement and proximal hip fracture surgery, we recommend using one of the following: LMWH, fondaparinux, rivaroxaban, apixaban, edoxaban, dabigatran, warfarin or aspirin with IPC. For patients admitted to the hospital with acute medical illness and has moderate risk of VTE, we recommend prophylaxis with LDUH, LMWH or Fondaparinux. For the same group at high risk of VTE, we recommend combination of pharmacological and mechanical prophylaxis.

Combined (mechanical and pharmacological) modalities for the prevention of venous thromboembolism in joint replacement surgery

We performed a systematic review and meta-analysis to compare the efficacy of intermittent mechanical compression combined with pharmacological thromboprophylaxis, against either mechanical compression or pharmacological prophylaxis in preventing deep-vein thrombosis (DVT) and pulmonary embolism in patients undergoing hip or knee replacement. A total of six randomised controlled trials, evaluating a total of 1399 patients, were identified. In knee arthroplasty, the rate of DVT was reduced from 18.7% with anticoagulation alone to 3.7% with combined modalities (risk ratio (RR) 0.27, p = 0.03; number needed to treat: seven). There was moderate, albeit non-significant, heterogeneity (I2 = 42%). In hip replacement, there was a non-significant reduction in DVT from 8.7% with mechanical compression alone to 7.2% with additional pharmacological prophylaxis (RR 0.84) and a significant reduction in DVT from 9.7% with anticoagulation alone to 0.9% with additional mechanical compression (RR 0.17, p < 0.001; number needed to treat: 12), with no heterogeneity (I2 = 0%). The included studies had insufficient power to demonstrate an effect on pulmonary embolism.

We conclude that the addition of intermittent mechanical leg compression augments the efficacy of anticoagulation in preventing DVT in patients undergoing both knee and hip replacement. Further research on the role of combined modalities in thromboprophylaxis in joint replacement and in other high-risk situations, such as fracture of the hip, is warranted.

Screening for chronic cerebrospinal venous insufficiency (CCSVI) using ultrasound--recommendations for a protocol

Chronic cerebrospinal venous insufficiency (CCSVI) is a syndrome characterized by stenoses or obstructions of the internal jugular and/or azygos veins with disturbed flow and formation of collateral venous channels. Studies using ultrasound in patients with multiple sclerosis (MS) have demonstrated a high prevalence of CCSVI (mean 70%; range 0-100%; N.=1496), whereas, in normal controls and patients without MS the prevalence was much lower (mean 10%; range 0-36%; N.=635). Ultrasound uses a combination of physiological measurements as well as anatomical imaging and has been used for the detection of CCSVI by different centers with variable results. A high prevalence ranging from 62% to 100% of obstructive lesions has been found by some teams in patients with MS compared with a lower prevalence of 0-25% in controls. However, absence of such lesions or a lower prevalence (16-52%) has been reported by others. This variability could be the result of differences in technique, training, experience or criteria used. The current lack of a methodology shared among experts is a confounding element in epidemiologic studies, and does not permit further Bayesan or other kind of analysis. In order to ensure a high reproducibility of Duplex scanning with comparable accuracy between centers, a detailed protocol with standard methodology and criteria is proposed. This is also necessary for training. It has been shown that inter-rater variability increases post-training (from k=0.47 to k=0.80), while within-rater reproducibility in trained operators was k=0.75. Finally, the consensus document proposes a reporting standard of Duplex measurements, and future research to answer areas of uncertainty.

Can combined (mechanical and pharmacological) modalities prevent fatal VTE?

AIM

The aim of this paper was to perform a systemic review and meta-analysis of the efficacy of combined modalities (intermittent pneumatic leg compression and pharmacological prophylaxis, treatment group) against single modalities alone (control group) in preventing pulmonary embolism (PE), including fatal PE and deep-vein thrombosis (DVT) in high-risk patients.

METHODS

Databases searched included the Cochrane Central Register of Controlled Trials, the Specialized Register of the Peripheral Vascular Diseases Group, MEDLINE and EMBASE.

RESULTS

Seventeen studies, six of them randomized controlled trials (RCTs), which enrolled a total of 9998 patients in a variety of specialties were identified. Sixteen of the included studies evaluated the role of combined modalities on the incidence of symptomatic PE. These showed a reduction in symptomatic PE from 2.83% (122/4313) in the control group to 0.86% (33/3838) in the treatment group. Odds ratio was 0.34, 95% Confidence interval (CI) 0.23 to 0.50. Fatal PE was reduced from 0.56% (11/1972) in the control group to 0.07% (1/1377) in the treatment group (results were available in 10 studies). Odds ratio was 0.37 (95% CI; 0.09 to 1.48). Fourteen studies investigated the role of combined modalities on the incidence of DVT. These showed a reduction in DVT from 6.18% (200/3238) in the control group to 2.05% (63/3074) in the treatment group. Odds ratio was 0.31, 95% CI 0.23 to 0.43.

CONCLUSION

Combined prophylactic modalities decrease significantly the incidence of PE and DVT, compared to single modalities, but the reduction seen in fatal PE did not reach statistical significance. Further research on the role of combined modalities in reducing DVT and PE is necessary.

Introduction to the biomechanics of carotid plaque pathogenesis and rupture: review of the clinical evidence

The management of patients with asymptomatic carotid disease is currently under debate and new methods are warranted for better risk stratification. The role of the biomechanical properties of the atherosclerotic arterial wall together with the effect of different stress types in plaque destabilisation has only been recently investigated. PubMed and Scopus databases were reviewed. There is preliminary clinical evidence demonstrating that the analysis of the combined effect of the various types of biomechanical stress acting on the carotid plaque may help us to identify the vulnerable plaque. At present, MRI and two-dimensional ultrasound are combined with fluid-structure interaction techniques to produce maps of the stress variation within the carotid wall, with increased cost and complexity. Stress wall analysis can be a useful tool for carotid plaque evaluation; however, further research and a multidisciplinary approach are deemed as necessary for further development in this direction.

The efficacy of a new stimulation technology to increase venous flow and prevent venous stasis

OBJECTIVES

Electrical stimulation of calf muscles has been shown to be effective in prevention of DVT. The aim was to determine: (a) dependence of venous blood velocity and ejected volume on the rates of stimulated calf contractions: (b) clinical factors affecting efficacy in healthy individuals.

METHODS

The maximum intensity stimulus tolerated was applied to calves of 24 volunteers. In popliteal veins, peak systolic velocities (PSV), ejected volume per individual stimulus (stroke volume SV) and ejected total volume flow per minute (TVF) of expelled blood were determined using ultrasound. Stimulation rates from 2 to 120 beats per minute (bpm) were applied.

RESULTS

Mean baseline popliteal PSV was 10 cm/s. For stimulation rates between 2 and 8 bpm, the PSV was 10 times higher and reached 96-105 cm/s. Stroke volume (SV) per individual stimulus decreased in a similar fashion. With increasing rates of stimulation the TVF increased by a factor of 12 times (from 20 ml/min to 240 ml/min).

CONCLUSION

Electrical stimulation is an effective method of activating the calf muscle pump. Enhancements of popliteal blood velocity and volume flow are key factors in the prevention of venous stasis and DVT. Further studies are justified to determine the stimulation rates in those with a compromised venous system.

Association of plaque echostructure and cardiovascular risk factors with symptomatic carotid artery disease

AIM

Severity of stenosis remains the main factor for assessing risk of stroke in patients with internal carotid artery (ICA) disease. This study was conducted to investigate the association of plaque echostructure and other established and emerging cardiovascular risk factors with symptomatic ICA disease.

METHODS

Cross-sectional study of consecutive patients with significant (>50%) ICA stenosis. Carotid plaque echostructure, smoking, hypertension, diabetes mellitus, serum lipoprotein (a), homocysteine, vitamin B12, folate, cholesterol to high-density lipoprotein ratio, triglycerides, C-reactive protein, and the Framingham risk score were assessed in 124 consecutive patients (70 asymptomatic; 54 symptomatic) with significant (>50%) ICA stenosis.

RESULTS

The asymptomatic and symptomatic groups did not differ in terms of gender distribution (P=0.76) and severity of stenosis (P=0.62). Echolucent plaques (type 1 and 2) were more predominant in patients with symptomatic disease (P=0.004, OR=2.13, 95% CI=1.26-3.6). Patients with plaques type 1 were relatively younger than those with type 4 (P=0.02). None of the other factors assessed had any significant association with symptomatic disease and any type of carotid plaque.

CONCLUSION

Besides the severity of carotid stenosis, the presence of an echolucent plaque appears as an important factor associated with symptomatic ICA disease. Also young patients are more likely to have an echolucent plaque suggesting an age-related association with plaque maturation.

Association of plaque echostructure and cardiovascular risk factors with symptomatic carotid artery disease

BACKGROUND

Severity of stenosis remains the main factor for assessing risk of stroke in patients with internal carotid artery (ICA) disease. This study was conducted to investigate the association of plaque echostructure and other established and emerging cardiovascular risk factors with symptomatic ICA disease.

DESIGN

Cross-sectional study of consecutive patients with significant (> 50%) ICA stenosis.

PATIENTS AND METHODS

Carotid plaque echostructure, smoking, hypertension, diabetes mellitus, serum lipoprotein (a), homocysteine, vitamin B12, folate, cholesterol to high-density lipoprotein ratio, triglycerides, C-reactive protein, and the Framingham risk score were assessed in 124 consecutive patients (70 asymptomatic; 54 symptomatic) with significant (> 50%) ICA stenosis.

RESULTS

The asymptomatic and symptomatic groups did not differ in terms of gender distribution (p = 0.76) and severity of stenosis (p = 0.62). Echolucent plaques (type 1 and 2) were more predominant in patients with symptomatic disease (p = 0.004, OR = 2.13, 95% CI = 1.26-3.6). Patients with plaques type 1 were relatively younger than those with type 4 (p = 0.02). None of the other factors assessed had any significant association with symptomatic disease and any type of carotid plaque.

CONCLUSIONS

Besides the severity of carotid stenosis, the presence of an echolucent plaque appears as an important factor associated with symptomatic ICA disease. Also, young patients are more likely to have an echolucent plaque suggesting an age-related association with plaque maturation.

Leukocyte telomere length is associated with measures of subclinical atherosclerosis

AIMS

Our aim was to test the association of mean leukocyte telomere length (LTL) with ultrasonic measures of subclinical atherosclerosis such as intima-media thickness in the common carotid (IMTcc) and sum of plaque areas (SPA) and with serological markers.

METHODS AND RESULTS

Carotid and femoral bifurcations were scanned in 762 general population volunteers (46% men) over 40. Four features were considered: (a) IMTcc, (b) sum plaque areas of carotid plaques (SPAcar), (c) sum plaque area of common femoral plaques (SPAfem) and (d) sum plaque area (SPA--sum of the plaque areas of the largest plaques present in each of both carotid and femoral bifurcations). Mean LTL was determined with a quantitative real-time PCR-based method. IMTcc was strongly associated with mean LTL both before and after correction for traditional risk factors (B=-0.002; 95% CI=-0.004 to -0.00; p=0.014). In sex-specific analysis, the association was stronger in men (p for sex interaction<0.001). SPAfem was associated with LTL in women before and after correction (B=-0.195; 95% CI=-0.38 to -0.01; p=0.037) (p for sex interaction<0.001). LTL was also associated with age and sex-adjusted levels of hsCRP (p=0.012), sCD40L (p=0.042), homocysteine (p=0.006), creatinine (p=0.02), ApoA1 (p=0.01), Lp(a) (p=0.04) and HOMA-IR (p=0.008).

CONCLUSIONS

Our results support the telomere hypothesis and highlight potential differences in the biological mechanisms leading to intima-media thickening and/or plaque formation between vascular beds. They may provide insights into a novel treatment of antisenescence to prevent atherosclerosis.

Common femoral artery intima-media thickness as marker for cardiovascular disease in asymptomatic adults

BACKGROUND

The common carotid intima-media thickness (IMT) is considered as a marker of cardiovascular disease, while the value of the common femoral IMT is not well defined. The aim of the present study was to investigate the value of common femoral IMT alone or in combination with the common carotid IMT as a marker of cardiovascular disease in asymptomatic adults.

PATIENTS AND METHODS

Eighty-three individuals with no history of cardiovascular disease were subjected to IMT measurement of both common carotid and common femoral arteries with high-resolution ultrasonography. The Framingham Heart Study (FHS) risk score was calculated for each subject (according to gender) and was correlated with the carotid IMT, femoral IMT, and the combined IMT measured at both arterial sites.

RESULTS

The carotid and femoral IMT separately and in combination were found to be correlated with the FHS risk score, calculated based on either the total cholesterol or low density lipoprotein plasma levels (carotid IMT: r = 0.28, p = 0.035, and r = 0.35, p = 0.007, respectively, femoral IMT: r = 0.38, p = 0.003, and r = 0.43, p = 0.001, respectively, carotid-femoral IMT: r = 0.37, p = 0.005, and r = 0.46, p = 0.0001, respectively). In addition, femoral IMT was found to be correlated with the carotid IMT (r = 0.41, p = 0.001).

CONCLUSIONS

Common carotid and common femoral IMT showed similar correlation with the FHS risk score. Additionally, the combination of IMT from both arterial sites was found to have similar correlation with the FHS risk score to carotid IMT alone.

Combined intermittent pneumatic leg compression and pharmacological prophylaxis for prevention of venous thrombo-embolism in high-risk patients

BACKGROUND

It has been suggested that combined modalities (methods of treatment) are more effective than single modalities in preventing venous thrombo-embolism (defined as deep vein thrombosis and pulmonary embolism, or both) in high-risk patients.

OBJECTIVES

To assess the efficacy of intermittent pneumatic leg compression combined with pharmacological prophylaxis versus single modalities in preventing venous thrombo-embolism in high-risk patients.

SEARCH STRATEGY

The Cochrane Peripheral Vascular Diseases (PVD) Group searched the reference lists of their Specialised Register (last searched 17 July 2007) and the Cochrane Central Register of Controlled Trials (CENTRAL) (last searched The Cochrane Library 2008, issue 3) for relevant articles to identify additional trials.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or controlled clinical trials (CCTs) of combined intermittent pneumatic leg compression and pharmacological interventions used to prevent venous thrombo-embolism in high-risk patients.

DATA COLLECTION AND ANALYSIS

Data extraction was undertaken independently by two review authors using data extraction sheets.

Comparison of three intermittent pneumatic compression systems in patients with varicose veins: a hemodynamic study

AIM

Previous studies have demonstrated the hemodynamic impact of sequential leg compression, compared to uniform compression. The aim of this study was to compare the hemodynamic effectiveness of three compression devices: 1) circumferential sequential gradient compression (CSG); 2) a posterior uniform compression device (PU) and a posterior sequential rapid gradient inflation device (PSR).

METHODS

DESIGN OF THE STUDY

open, controlled trial. Thigh length sleeves were tested in 12 patients with primary bilateral varicose veins.

INTERVENTIONS

the three devices were tested in the semirecumbent position.

MAIN OUTCOME MEASURES

augmented flow velocity and volume flow, including the total and peak volume of blood expelled per hour during compression, were measured using duplex scanning. Refilling time was determined from velocity recordings of the common femoral vein. All values were expressed as median and interquartile range with P values obtained using the Mann-Whitney U-test.

RESULTS

Compared to the median baseline flow, all three devices increased flow during compression by 2.5-3 times (P<0.0001). The cycles per hour for the three devices CSG, PSR and PU were 78 (70-88), 60 and 60, respectively; the duplex effective compression time was 11, 12 and 6 s, respectively; single cycle volume expelled during compression was 105, 85 and 45 mL (P<0.005), respectively; the total volume expelled per hour was 7 800, 5 200 (P<0.028) and 3 300 (P<0.005) mL/hr, respectively; peak velocity increased (P<0.001) from baseline of 12 cm/s to 38 cm/s for the CSG, 33 cm/s for the PU and to 68 cm/s for the PSR.

CONCLUSION

The highest volume expelled per hour during compression was observed with the CSG and the lowest with the PSR. This was due to increased volume per cycle and more compression cycles over time, because of the CSG device's sensing of refill time. Although the peak velocity with the PSR was high, it was associated with reduced expelled volume, because of its short compression period. The PU occupied an intermediate position. The relative effectiveness of the three devices in deep vein thrombosis prevention should be tested in future studies.

Texture Analysis of Ultrasonic Images of Symptomatic Carotid Plaques can Identify Those Plaques Associated with Ipsilateral Embolic Brain Infarction

OBJECTIVES

The aim of our study was to determine the association between objective, computerised texture analysis of carotid plaque ultrasonic images and embolic CT-brain infarction in patients presenting with hemispheric neurological symptoms.

DESIGN

Cross-sectional study in patients with 50%-99% (ECST) carotid stenosis.

PATIENTS AND METHODS

Carotid plaque ultrasonic images (n=54, 26 with TIAs and 28 with stroke) obtained during carotid ultrasound were normalised and standardised for resolution and subsequently assessed visually for the presence of discrete echogenic or juxtaluminal echolucent components and overall echogenicity (plaque type). Using computer software, 51 histogram/textural features of the plaque outlines were calculated. Factor analysis was subsequently applied to eliminate redundant variables. Small cortical, large cortical and discrete subcortical infarcts on CT-brain scan were considered as being embolic.

RESULTS

Twenty-five cases (46%) had embolic infarcts. On logistic regression, grey-scale median (GSM), a measure of echolucency, spatial grey level dependence matrices (SGLDM) correlation and SGLDM information measure of correlation-1, measures of homogeneity were significant (p<0.05), but not grey level runlength statistics (RUNL) Run Percentage (RP), stenosis severity, type of symptoms or echolucent juxtaluminal components. Using ROC curves methodology, SGLDM information measure of correlation-1 improved the value of GSM in distinguishing embolic from non-embolic CT-brain infarction.

CONCLUSION

Computerised texture analysis of ultrasonic images of symptomatic carotid plaques can identify those that are associated with brain infarction, improving the results achieved by GSM alone. This methodology could be applied to prospective natural history studies of symptomatic patients not operated on or randomised trials of patients undergoing carotid angioplasty and stenting in order to identify high-risk subgroups for cerebral infarction.

Characterization of carotid atherosclerosis based on motion and texture features and clustering using fuzzy c-means

Analysis of B-mode ultrasound images of the carotid atheromatous plaque includes the estimation of texture from static images and the estimation of motion from image sequences. The combination of these two types of information may be valuable for accurate diagnosis of vascular disease. The purpose of this paper was to study texture and motion patterns of carotid atherosclerosis and select the optimal combination of features that can characterize plaque. B-mode ultrasound images of 10 symptomatic and 9 asymptomatic plaques were interrogated. A total of 99 texture features were estimated using first-order statistics, second-order statistics, Laws texture energy and the fractal dimension. Only five texture features were significantly different between the two groups. In the same subjects, the motion of selected plaque regions was estimated using region tracking and block-matching and expressed through: a/maximal surface velocity (MSV), and b/maximal relative surface velocity (MRSV). MSV and MRSV were significantly lower in asymptomatic plaques suggesting more homogeneous motion patterns. Clustering using fuzzy c-means correctly classified 74% of plaques based on texture features only, and 79% of plaques based on motion features only. Classification performance reached 84% when a combination of motion and texture features was used.

Haemodynamic and Clinical Impact of Superficial, Deep and Perforator Vein Incompetence

OBJECTIVE

The purpose of this study was to assess the effect of venous incompetence of the deep, superficial and perforator veins combined (i.e. multi-system incompetence) on the venous haemodynamics and clinical condition of limbs with chronic venous disease (CVD).

METHODS

One hundred and thirty two limbs (16-C(1); 30-C(2); 20-C(3); 25-C(4); 21-C(5); 20-C(6)) of 121 patients were studied. We excluded those with previous venous surgery/sclerotherapy, peripheral arterial disease, recent deep vein thrombosis (< or =6 months), or inability to comply with the tests. The CEAP clinical class was assessed. Duplex ultrasonography (ultrasound) enabled classification according to: the presence of superficial([S]) (+/- perforator([P])) or deep([D]) (+/-S, +/-P) reflux (>.5s); the number of incompetent venous systems (single-system([S/P/D]), dual-system([S+P/S+D/P+D]), or triple-system([S+P+D])), and the number of incompetent perforators([0/1/2/> or =3]). The amount of reflux (Venous Filling Index([VFI])); calf pump Ejection Fraction([EF]), and Residual Volume Fraction([RVF]) were studied with air-plethysmography.

RESULTS

VFI in limbs with triple-system incompetence (VFI median 6.68 [IQR: 4.7-9.7]ml/s) was higher than in limbs with dual-system incompetence (4.5 [2.1-7.4]ml/s), and VFI in the latter was higher than in limbs with single-system incompetence (1.3 [0.69-2.3]ml/s)(p<0.01 Kruskal-Wallis). Although EF changes were small, RVF in limbs with triple-incompetence (39 [30-51] %) was higher than in single-system incompetence (26 [16-33] %)(p<0.01 Mann-Whitney). Limbs with superficial (+/-P) incompetence had a lower VFI (p<0.01) and RVF (p<0.02) than limbs with deep (+/-S+/-P) incompetence, and limbs with > or =2 incompetent perforator veins had a higher VFI (p<0.04) than those without perforators. All limbs with single-system incompetence were C(1-3,) whereas 78% of those with triple-incompetence were C(4-6) (p<0.01). The number of incompetent systems increased with clinical class (p<0.01).

CONCLUSIONS

The frequency of incompetence of more than one venous system increased with the clinical severity of venous disease and was accompanied by a 5-fold increase in the amount of reflux and a 50% rise in the RVF. The number of incompetent perforators per limb increased with the amount of reflux. The number of incompetent venous systems (superficial, deep, perforator) and perforator veins can be assessed by duplex ultrasound giving an objective indication of the functional severity of venous disease. In this way duplex ultrasound could be used to grade venous function in clinical practice as an alternative to APG measures which are less widely available.

Comparison of two intermittent pneumatic compression systems. A hemodynamic study

AIM

Sequential leg compression has been previously shown to be superior to uniform compression. The aim of our study was to compare the hemodynamic effectiveness of the portable sequential compression device (SCD Express Compression System, Tyco Healthcare Group LP, Mansfield, MA, USA) with a rapid inflation device (VenaFlow, Aircast, Inc, Summit, NJ, USA). The former, by sensing venous refill time, commences compression when the calf veins are refilled.

METHODS

The two devices were tested in 12 normal volunteers in the semirecumbent position using duplex ultrasound. Baseline and augmented flow velocity and volume flow were measured at the level of the common femoral vein, above the saphenofemoral junction. Refilling time was determined from velocity recordings of the common femoral vein. Total and peak volume of blood expelled per hour during compression were calculated using flow data and the individual cycling rate.

RESULTS

Both devices increased venous flow velocity, up to 3.8 times the baseline (all P<0.001). Refill time of the rapid inflation device was shorter in comparison with the sequential compression device (15+/-2.2 vs 25+/-4 s; P<0.001), suggesting incomplete vein evacuation. The sequential compression device, by augmenting flow throughout a significantly longer compression period per cycle (10.9 s vs 6.3 s), expelled significantly more venous blood (121+/-68 vs 81+/-63 mL; P<0.001). Similarly, the total volume of blood expelled per hour with the sequential compression device was 100% higher than the rapid inflation device (9685+/-5426 vs 4853+/-3658 mL; P<0.001). Although peak velocity enhancement was higher with the rapid inflation device, flow augmentation (a product of average blood flow velocity) was comparable (669+/-367 vs 771+/-574 cm/s; P=0.223) with the sequential compression device, mainly because the rapid inflation device failed to maintain flow enhancement beyond the initial flow surge.

CONCLUSIONS

Sequential compression showed hemodynamic superiority compared to a rapid inflation device. This was enhanced further by the sensing of refill time, which resulted in more compression cycles over time. The relative efficacy of the two devices in deep vein thrombosis prevention should be tested in future studies.

Severity of Asymptomatic Carotid Stenosis and Risk of Ipsilateral Hemispheric Ischaemic Events: Results from the ACSRS Study

OBJECTIVES

This study determines the risk of ipsilateral ischaemic neurological events in relation to the degree of asymptomatic carotid stenosis and other risk factors.

METHODS

Patients (n=1115) with asymptomatic internal carotid artery (ICA) stenosis greater than 50% in relation to the bulb diameter were followed up for a period of 6-84 (mean 37.1) months. Stenosis was graded using duplex, and clinical and biochemical risk factors were recorded.

RESULTS

The relationship between ICA stenosis and event rate is linear when stenosis is expressed by the ECST method, but S-shaped if expressed by the NASCET method. In addition to the ECST grade of stenosis (RR 1.6; 95% CI 1.21-2.15), history of contralateral TIAs (RR 3.0; 95% CI 1.90-4.73) and creatinine in excess of 85 micromol/L (RR 2.1; 95% CI 1.23-3.65) were independent risk predictors. The combination of these three risk factors can identify a high-risk group (7.3% annual event rate and 4.3% annual stroke rate) and a low risk group (2.3% annual event rate and 0.7% annual stroke rate).

CONCLUSIONS

Linearity between ECST per cent stenosis and risk makes this method for grading stenosis more amenable to risk prediction without any transformation not only in clinical practice but also when multivariable analysis is to be used. Identification of additional risk factors provides a new approach to risk stratification and should help refine the indications for carotid endarterectomy.

Improvement of the Walking Ability in Intermittent Claudication due to Superficial Femoral Artery Occlusion with Supervised Exercise and Pneumatic Foot and Calf Compression: A Randomised Controlled Trial

OBJECTIVES

To compare the effect of unsupervised exercise, supervised exercise and intermittent pneumatic foot and calf compression (IPC) on the claudication distance, lower limb arterial haemodynamics and quality of life of patients with intermittent claudication.

METHODS

Thirty-four eligible patients with stable intermittent claudication were randomised to IPC (n = 13, 3h/d for 6 months), supervised exercise (n = 12, three hourly sessions/week for 6 months) or unsupervised exercise (n = 9). In each patient, initial claudication distance (ICD), absolute claudication distance (ACD), resting ankle brachial pressure index (ABPI), and resting hyperaemic calf arterial inflow were measured before, 6 weeks, 6 months and 1 year after randomisation. Quality of life was assessed with the short form (SF)-36, walking impairment (WIQ) and intermittent claudication questionnaires (ICQ).

RESULTS

Compared with unsupervised exercise, both IPC and supervised exercise, increased ICD and ACD, up to 2.83 times. IPC increased arterial inflow (p < 0.05 at 6 weeks) and ABPI. Supervised exercise decreased arterial inflow and increased ABPI (p < 0.05 at 6 months). Unsupervised exercise had no effect on arterial inflow or ABPI. IPC improved significantly the ICQ score and the speed score of the WIQ, while supervised exercise improved the WIQ claudication severity score. At 1 year clinical effectiveness of supervised exercise and IPC was largely preserved.

CONCLUSIONS

IPC, by augmenting leg perfusion, achieved improvement in walking distance comparable with supervised exercise. Long-term results in a larger number of patients will provide valuable information on the optimal treatment modality of intermittent claudication.