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Andrew N Nicolaides

Publications and source records attributed to Andrew N Nicolaides.

At least 19 recordsLinked to original sources
PubMed2007

Computer-aided diagnosis of carotid atherosclerosis based on ultrasound image statistics, laws' texture and neural networks.

Quantitative characterisation of carotid atherosclerosis and classification into symptomatic or asymptomatic is crucial in planning optimal treatment of atheromatous plaque. The computer-aided diagnosis (CAD) system described in this paper can analyse ultrasound (US) images of carotid artery and classify them into symptomatic or asymptomatic based on their echogenicity characteristics. The CAD system consists of three modules: a) the feature extraction module, where first-order statistical (FOS) features and Laws' texture energy can be estimated, b) the dimensionality reduction module, where the number of features can be reduced using analysis of variance (ANOVA), and c) the classifier module consisting of a neural network (NN) trained by a novel hybrid method based on genetic algorithms (GAs) along with the back propagation algorithm. The hybrid method is able to select the most robust features, to adjust automatically the NN architecture and to optimise the classification performance. The performance is measured by the accuracy, sensitivity, specificity and the area under the receiver-operating characteristic (ROC) curve. The CAD design and development is based on images from 54 symptomatic and 54 asymptomatic plaques. This study demonstrates the ability of a CAD system based on US image analysis and a hybrid trained NN to identify atheromatous plaques at high risk of stroke.

Algorithms↗
PubMed2006

Effect of zooming on texture features of ultrasonic images.

BACKGROUND: Unstable carotid plaques on subjective, visual, assessment using B-mode ultrasound scanning appear as echolucent and heterogeneous. Although previous studies on computer assisted plaque characterisation have standardised B-mode images for brightness, improving the objective assessment of echolucency, little progress has been made towards standardisation of texture analysis methods, which assess plaque heterogeneity. The aim of the present study was to investigate the influence of image zooming during ultrasound scanning on textural features and to test whether or not resolution standardisation decreases the variability introduced. METHODS: Eighteen still B-mode images of carotid plaques were zoomed during carotid scanning (zoom factor 1.3) and both images were transferred to a PC and normalised. Using bilinear and bicubic interpolation, the original images were interpolated in a process of simulating off-line zoom using the same interpolation factor. With the aid of the colour-coded image, carotid plaques of the original, zoomed and two resampled images for each case were outlined and histogram, first order and second order statistics were subsequently calculated. RESULTS: Most second order statistics (21/25, 84%) were significantly (p < 0.05) sensitive to image zooming during scanning, in contrast to histogram and first order statistics (4/25, 16%, p < 0.001, Fisher's exact test). Median (interquartile range) change of those features sensitive to zooming was 18.14% (4.94-28.43). Image interpolation restored these changes, the bicubic interpolation being superior compared to bilinear interpolation (p = 0.036). CONCLUSION: Texture analysis of ultrasonic plaques should be performed under standardised resolution settings; otherwise a resolution normalisation algorithm should be applied.

Algorithms↗
PubMed2006

Review on the value of graduated elastic compression stockings after deep vein thrombosis.

Graduated elastic compression stockings (GECS) are commonly used in the primary prevention of deep vein thrombosis (DVT); however, their role in preventing recurrent DVT and also post-thrombotic syndrome is less well established. The aim of this review was to investigate the effect of GECS after DVT. A literature search was performed by two independent searchers in order to identify randomised controlled trials on the effect of GECS in preventing recurrent DVT and post-thrombotic syndrome. Four randomised trials, including 537 patients, were identified. Two of the studies demonstrated that below-knee GECS significantly reduced post-thrombotic syndrome during follow-up, while a smaller study showed equivocal results. GECS reduced the incidence of post-thrombotic syndrome from 54% to 25.2% [relative risk (RR) 0.47, 95% confidence interval (CI) 0.36-0.61] with the number needed to treat (NNT) being 4 (95% CI 2.7-5.0). The rate of recurrent asymptomatic DVT was also significantly reduced by GECS (RR 0.20, 95% CI 0.06-0.64; NNT 5); the reduction in symptomatic DVT was not significant (RR 0.79, 95% CI 0.50-1.26; NNT 34). In conclusion, there is level Ia evidence to suggest that GECS can significantly reduce the incidence of post-thrombotic syndrome (PTS) after DVT, and therefore these should be routinely prescribed. The evidence for recurrent DVT is less conclusive. Further research is needed towards standardising PTS diagnostic criteria and evaluating more effective preventive measures after DVT.

Bandages↗
PubMed2005

Breastfeeding and atherosclerosis: intima-media thickness and plaques at 65-year follow-up of the Boyd Orr cohort.

OBJECTIVES: The impact of breastfeeding in infancy on cardiovascular disease risk is uncertain. We related breastfeeding in infancy to atherosclerosis in adulthood. METHODS AND RESULTS: A historic cohort study based on a 65-year follow-up of the Carnegie (Boyd Orr) survey of diet and health in prewar Britain, 1937 to 1939. A total of 732 eligible cohort members living in or around Aberdeen, Bristol, Dundee, Wisbech, and London were invited for follow-up examinations in 2002, and 405 (55%) participated. In models controlling for age and sex, breastfeeding was inversely associated with common carotid intima-media thickness (IMT; difference -0.03 mm; 95% CI, -0.07 to 0.01), bifurcation IMT (difference -0.19 mm; 95% CI, -0.37 to -0.01), carotid plaque (odds ratio [OR], 0.52; 95% CI, 0.29 to 0.92), and femoral plaque (OR, 0.54; 95% CI, 0.26 to 1.12), compared with bottle-feeding. Controlling for socioeconomic variables in childhood and adulthood, smoking and alcohol made little difference to effect estimates. Controlling for factors potentially on the causal pathway (blood pressure, adiposity, cholesterol, insulin resistance, and C-reactive protein) made little difference to observed associations. CONCLUSIONS: Breastfeeding may be associated with a reduced risk of atherosclerosis in later life. Measurement error and power considerations limit the extent to which conclusions about the mechanisms underlying this relationship can be made.

Aged↗
PubMed2005

The efficacy of a new portable sequential compression device (SCD Express) in preventing venous stasis.

OBJECTIVE: It has been previously shown that the SCD Response Compression System, by sensing the postcompression refill time of the lower limbs, delivers more compression cycles over time, resulting in as much as a 76% increase in the total volume of blood expelled per hour. Extended indications for pneumatic compression have necessitated the introduction of portable devices. The aim of our study was to test the hemodynamic effectiveness of a new portable sequential compression system (the SCD Express), which has the ability to detect the individual refill time of the two lower limbs separately. METHODS: This was an open, controlled trial with 30 normal volunteers. The new SCD Express was compared with the SCD Response Compression System in the supine and semirecumbent positions. The refilling time sensed by the device was compared with that determined from velocity recordings of the superficial femoral vein using duplex ultrasonography. Baseline and augmented flow velocity and volume flow, including the total volume of blood expelled per hour during compression with the SCD Express, were compared with those produced by the SCD Response compression system in the same volunteers and positions. RESULTS: Both devices significantly increased venous flow velocity as much as 2.26 times baseline in supine position and 2.67 times baseline in semirecumbent position (all P < .001). There was a linear relationship between duplex ultrasonography-derived refill time and the SCD Express-derived refill time in both the supine (r = 0.39, P = .03) and semirecumbent (r = 0.71, P < .001) positions but not with the SCD Response. Refill time measured by the SCD Express device was significantly shorter and the cycle rate higher in comparison with the SCD Response in both positions. The single-cycle flow velocity and volume flow parameters generated by the two devices were similar in both positions. However, median (interquartile range) total volume of blood expelled per hour was slightly higher with the SCD Express device in the supine position (7206 mL/h [range, 5042-8437] vs 6712 mL/h [4941-10,676]; P = .85) and semirecumbent position (4588 mL/h [range, 3721-6252] vs 4262 mL/h [3520-5831]; P = .22). Peak volume of blood expelled per hour by the SCD Express device in the semirecumbent position was significantly increased by 10% in comparison with the SCD Response (P = .03). CONCLUSIONS: Flow velocity and volume flow enhancement by the SCD Response and SCD Express were essentially similar. The latter, a portable device with optional battery power that detects the individual refill time of the lower limbs separately, is anticipated to be associated with improved overall compliance and therefore optimized thromboprophylaxis. Studies testing its potential for improved efficacy in preventing deep vein thrombosis are justified.

Adolescent↗
PubMed2005

Effect of intermittent pneumatic compression of foot and calf on walking distance, hemodynamics, and quality of life in patients with arterial claudication: a prospective randomized controlled study with 1-year follow-up.

SUMMARY BACKGROUND DATA: Perioperative mortality, graft failure, and angioplasty limitations militate against active intervention for claudication. With the exception of exercise programs, conservative treatments yield modest results. Intermittent pneumatic compression [IPC] of the foot used daily for 3 months enhances the walking ability and pressure indices of claudicants. Although IPC applied to the foot and calf together [IPCfoot+calf] is hemodynamically superior to IPC of the foot, its clinical effects in claudicants remain undetermined. OBJECTIVE: This prospective randomized controlled study evaluates the effects of IPCfoot+calf on the walking ability, peripheral hemodynamics, and quality of life [QOL] in patients with arterial claudication. METHODS: Forty-one stable claudicants, meeting stringent inclusion and exclusion criteria, were randomized to receive either IPCfoot+calf and aspirin[75 mg] (Group 1; n = 20), or aspirin[75 mg] alone (Group 2; n = 21), with stratification for diabetes and smoking. Groups matched for age, sex, initial [ICD] and absolute [ACD] claudication distances, pressure indices [ABI], popliteal artery flow, and QOL with the short-form 36 Health Survey Questionnaire (SF-36). IPCfoot+calf (120 mm Hg, inflation 4 seconds x 3 impulses per minute, calf inflate delay 1 second) was used for 5 months, > or =2.5 hours daily. Both groups were advised to exercise unsupervised. Evaluation of patients, after randomization, included the ICD and ACD, ABI, popliteal artery flow with duplex and QOL* at baseline*, 1/12, 2/12, 3/12, 4/12, 5/12* and 17/12. Logbooks allowed compliance control. Wilcoxon and Mann-Whitney corrected[Bonferroni] tests were used. RESULTS: At 5/12 median ICD, ACD, resting and postexercise ABI had increased by 197%, 212%, 17%, and 64%, respectively, in Group 1 (P < 0.001), but had changed little (P > 0.1) in Group 2; Group 1 had better ICD, ACD, and resting and postexercise ABI (P < 0.01) than Group 2. Inter- and intragroup popliteal flow differences at 5/12 were small (P > 0.1). QOL had improved significantly in Group 1 but not in Group 2; QOL in the former was better (P < 0.01) than in Group 2. QOL in Group 1 was better (P < 0.01) than in Group 2 at 5/12. IPC was complication free. IPC compliance (> or =2.5 hours/d) was >82% at 1 month and >85% at 3 and 5 months. ABI and walking benefits in Group 1 were maintained a year after cessation of IPC treatment. CONCLUSIONS: IPCfoot+calf emerged as an effective, high-compliance, complication-free method for improving the walking ability and pressure indices in stable claudication, with a durable outcome. These changes were associated with a significant improvement in all aspects of QOL evaluated with the SF-36. Despite some limited benefit noted in some individuals, unsupervised exercise had a nonsignificant impact overall.

Aged↗
PubMed2004

Carotid plaque echolucency increases the risk of stroke in carotid stenting: the Imaging in Carotid Angioplasty and Risk of Stroke (ICAROS) study.

BACKGROUND: Carotid artery stenting (CAS) has recently emerged as a potential alternative to carotid endarterectomy. Cerebral embolization is the most devastating complication of CAS, and the echogenicity of carotid plaque has been indicated as one of the risk factors involved. This is the first study to analyze the role of a computer-assisted highly reproducible index of echogenicity, namely the gray-scale median (GSM), on the risk of stroke during CAS. METHODS AND RESULTS: The Imaging in Carotid Angioplasty and Risk of Stroke (ICAROS) registry included 418 cases of CAS collected from 11 international centers. An echographic evaluation of carotid plaque with GSM measurement was made preprocedurally. The onset of neurological deficits during the procedure and the postprocedural period was recorded. The overall rate of neurological complications was 3.6%: minor strokes, 2.2%, and major stroke, 1.4%. There were 11 of 155 strokes (7.1%) in patients with GSM < or =25 and 4 of 263 (1.5%) in patients with GSM >25 (P=0.005). Patients with severe stenosis (> or =85%) had a higher rate of stroke (P=0.03). The effectiveness of brain protection devices was confirmed in those with GSM >25 (P=0.01) but not in those with GSM < or =25. Multivariate analysis revealed that GSM (OR, 7.11; P=0.002) and rate of stenosis (OR, 5.76; P=0.010) are independent predictors of stroke. CONCLUSIONS: Carotid plaque echolucency, as measured by GSM < or =25, increases the risk of stroke in CAS. The inclusion of echolucency measured as GSM in the planning of any endovascular procedure of carotid lesions allows stratification of patients at different risks of complications in CAS.

Aged↗
PubMed2004

Sex differences in body fat distribution and carotid intima media thickness: cross sectional survey using data from the British regional heart study.

OBJECTIVE: To determine the role of central adiposity in explaining sex differences in carotid intima media thickness (IMT). DESIGN: Cross sectional survey. SETTING: Two British towns. PARTICIPANTS: 800 men and women aged 56-75 years. MAIN OUTCOME MEASURES: Carotid IMT. RESULTS: There was a continuous linear association between waist-hip ratio and IMT in both men and women. The magnitude of the association between waist to hip ratio and IMT was identical in both sexes. In age adjusted analyses IMT was 14% greater in men compared with women (age adjusted male to female ratio of geometric means 1.14; 95% confidence interval 1.07 to 1.21) with adjustment for waist to hip ratio this attenuated to no difference (1.00; 0.92 to 1.09). Adjustment for body mass index and for lifestyle risk factors had very little effect on the sex difference in mean intima media thickness. CONCLUSIONS: Sex differences in body fat distribution may explain sex differences in arterial atherosclerosis.

Aged↗
PubMed2004

Echogenicity of B-mode sonographic images of the carotid artery: work in progress.

OBJECTIVE: The echogenicity of the carotid atheromatous plaque estimated from B-mode sonographic images may be related to plaque content and has been analyzed with a number of techniques. The purpose of this study was to compare plaque with surrounding muscle tissue echogenicity and to validate the use of first-order mathematical descriptors as determinants of tissue echogenicity. METHODS: We estimated echogenicity descriptors for regions in the following 3 distinct areas of a typical B-mode sonographic image of a diseased carotid artery: plaque, blood, and sternocleidomastoid muscle. Two-dimensional B-mode sonographic images from 19 symptomatic and asymptomatic plaques (17 subjects) were interrogated, in which the following estimators were calculated: minimal, maximal, mean, and median gray levels, SD of gray levels, coefficient of variation, and gray level skewness, kurtosis, entropy, and energy. Plaque echogenicity was estimated at systole and diastole for studying the effect of the phase of the cardiac cycle. To assess the effect of different fascial tissue-muscle fiber composition on the first-order mathematical descriptors, we estimated echogenicity at 3 different sites within the muscle tissue. RESULTS: Compared with the echogenicity of surrounding muscle tissue, plaque echogenicity was characterized by (1) significantly lower (Student t test, P < .05) gray level mean, median, SD, and entropy; (2) significantly higher (Student t test, P < .05) coefficient of variation, gray level skewness, and kurtosis; and (3) similar minimal and maximal gray levels and gray level energy. The phase of the cardiac cycle, systole or diastole, did not affect the estimation of plaque echogenicity. Echogenicity was found to vary within the muscle tissue. The coefficient of variation was significantly higher in the asymptomatic plaques in the small group that was investigated. CONCLUSIONS: First-order statistical descriptors may be used to characterize atheromatous plaques and the surrounding muscle tissue.

Aged↗
PubMed2003

Carotid artery wall motion estimated from B-mode ultrasound using region tracking and block matching.

The motion of the carotid atheromatous plaque relative to the adjacent wall may be related to the risk of cerebral events. A quantitative method for motion estimation was applied to analyse arterial wall movement from sequences of 2-D B-mode ultrasound (US) images. Image speckle patterns were tracked between successive frames using the correlation coefficient as the matching criterion. The size of the selected region-of-interest (ROI) was shown to affect the motion analysis results; an optimal size of 3.2 x 2.5 mm(2) was suggested for tracking a region at the wall-lumen interface and of 6.3 x 2.5 mm(2) for one within the tissue. The results showed expected cyclical motion in the radial direction and some axial movement of the arterial wall. The method can be used to study further the axial motion of the carotid artery wall and plaque and, thus, provide useful insight into the mechanisms of atherosclerosis.

Carotid Arteries↗
PubMed2003

Effect of elastic compression stockings on venous hemodynamics during walking.

PURPOSE: Venous hemodynamics evaluated during walking better reflect changes that occur under active physiologic conditions than do conventional static modes of exercise such as tip-toe exercise, knee bending, or dorsiflexion. We prospectively studied the efficacy of air-plethysmography (APG) in monitoring venous hemodynamics during ambulation, and with this method we determined the hemodynamic effects of graduated elastic compression stockings on the lower limb during walking at various speeds. METHODS: The residual volume fraction (RVF%) during treadmill walking was monitored with APG in 10 limbs with primary chronic venous insufficiency (CVI)(CEAP(2-4)) at four speeds (1.0, 1.5, 2.0 and 2.5 km/h consecutively), with and without elastic compression (21 mm Hg at the ankle). The method was validated in comparison with standard APG, which is based on tip-toe exercise. RVF obtained during treadmill walking at 1.5 km/h was correlated with RVF measured with standard APG in 30 subjects: 12 healthy volunteers, 11 patients with primary CVI, and 7 postthrombotic limbs. Data were analyzed with nonparametric statistics. RESULTS: RVF measurements during walking were reproduced with an intra-day coefficient of variation of 5.1% to 16.5%. RVF during walking correlated well with RVF during standard APG (tip-toe) (r = 0.5, P =.004). At each of the investigated walking speeds, stockings improved venous hemodynamics by decreasing RVF, from a median of 50.5% without stockings to 40.5% with stockings at 1.0 km/h (19.8% decrease), from 49% to 39.5% at 1.5 km/h (19.4% decrease), from 50.5% to 41% at 2.0 km/h (18.8% decrease), and from 53% to 45.5% at 2.5 km/h (14.2% decrease) (all speeds, P <.02). Efficacy of the stockings in decreasing RVF (percent change in RVF) was similar across the spectrum of examined speeds (P =.47). During walking with elastic stockings, nominal RVF values were also similar across the spectrum of walking speeds, except at 2.5 km/h (P =.012). During walking without stockings, RVF did not change with treadmill speed, nor did it differ from that obtained with conventional APG (tip-toe) (P =.46). The percentage decrease in RVF generated with elastic stockings correlated with the venous filling index (r = 0.73, P =.017) at 1.0 km/h. CONCLUSIONS: APG is a reproducible and valid method for monitoring venous hemodynamics during walking. Graduated elastic compression stockings significantly improved venous hemodynamics by reducing RVF in limbs with primary CVI at all examined walking speeds (1.0 to 2.5 km/h). The effect was linearly correlated with the amount of reflux (1.0 km/h). The modified application of APG during walking offers a new noninvasive method for assessment of venous hemodynamics in limbs with CVI, enabling quantification of the actual effect of elastic compression therapy during ambulation.

Adult↗
PubMed2003

The LONFLIT4-Concorde--Sigvaris Traveno Stockings in Long Flights (EcoTraS) Study: a randomized trial.

UNLABELLED: The LONFLIT1/2 studies have established that in high-risk subjects after long ( > 10 hours) flights the incidence of deep venous thrombosis (DVT) may be between 4% and 6%. The LONFLIT4 study was aimed at evaluating the control of edema and DVT prevention in low-medium-risk subjects. In this study prophylaxis of edema with specific travel stockings was evaluated in 2 separate studies involving flights lasting 7 hours and 10-12 hours. Part I. Subjects at low-medium risk for DVT were contacted; 55 subjects were excluded for several nonmedical, travel-related problems or inconvenient evaluation time; the remaining 211 were randomized into 2 groups to evaluate prophylaxis with elastic stockings in 7-8-hour, long-haul flights. The control group had no prophylaxis; the treatment group used below-knee, Sigvaris Traveno elastic stockings (Ganzoni, Switzerland, producing 12-18 mm Hg of pressure at the ankle). Color duplex scanning was used to evaluate the possible presence of DVT; edema/swelling were evaluated with a composite score including the presence of edema (with an edema tester), variations in ankle circumference and leg volumetry, subjective swelling, and discomfort (scale ranging from 0 to 10). RESULTS: Of the 103 included subjects in the stockings group and 108 in the control group (total 211), 195 subjects completed the study. Dropouts (16) were due to low compliance or traveling and connection problems. Age, sex distribution, and risk factors distributions were comparable in the 2 groups. Stockings Group: Of 97 subjects none had DVT or superficial thromboses. CONTROL GROUP: Of 98 subjects none had thrombosis. The level of edema at inclusion was comparable in the 2 groups of subjects. After flights there was an average score of 6.4 (1.3) in the control group, while in the stockings group the score was on average 2.4 (SD 1), 2.6 times lower than in the control group (p < 0.05). In the control group 83% of the subjects had an evident increase in ankle circumference and volume that was visible at inspection and associated with discomfort. The control of edema with stockings was clear, considering both parametric data (circumference and volume) and nonparametric (analogue scale lines) measurements. Part II. In this part of the study 200 subjects at low-medium risk for DVT were contacted; 35 subjects were excluded for several nonmedical, travel-related problems or inconvenient evaluation time; the remaining 165 were randomized into 2 groups to evaluate prevention in flights lasting between 11 and 12 hours. The control group had no prophylaxis; the treatment group used Traveno stockings. Of the 83 included subjects in the stockings group and 82 in the control group (total 165), 146 subjects completed the study. Dropouts were due to low compliance or connection problems. Age/sex distribution were comparable. Of 75 subjects completing the study in the stockings group and 71 in the control group, none had thrombosis. The average level of edema at inclusion was comparable in the 2 groups (1.1). After the flight there was a score of 8.9 (2) in controls; in the stockings group the score was 2.56 (1.3) (p < 0.05). The control of edema and swelling with stockings even after 11 hours of flight was clear, considering both parametric (circumference, volume) and nonparametric (analogue scale lines) measurements. The tolerability of the stockings was very good and there were no complaints or side effects. In conclusion Sigvaris Traveno stockings are very effective in controlling edema in long-haul flights.

Adult↗
PubMed2003

The LONFLIT4-VENORUTON study: a randomized trial prophylaxis of flight-edema in normal subjects.

This study evaluated the protective effects of Venoruton on the development of flight edema in normal subjects travelling in economy in long-haul flights (8-9 hours). Edema is a relevant aspect of long-haul flights affecting both venous patients and normal subjects. Edema and flight microangiopathy were studied in a group of 164 subjects randomized (after informed consent) into two groups to evaluate prophylaxis in 8- to 9-hour flights. The treatment group received Venoruton (hydroxyethyl rutosides) 1 g twice daily for 3 days (2 days before the flight and the day of the flight). The control group received comparable placebo. Edema was evaluated with a composite edema score based on the edema tester, on the measurements of ankle circumference, volume measurements, subjective swelling, and on a discomfort score. Items 1, 4, and 5 are based on an analogue scale line (1 to 10) directly defined by the subjects before and after the flights. Of the included subjects, 151 completed the study. Dropouts were due to poor compliance, travelling, or connection problems. Age and gender distribution were comparable in the two groups as were risk factor distributions. The level of edema at inclusion was comparable in the two groups of subjects. After the flight there was an average score of 6.7 (SD 1.7) in the control group, while in the Venoruton group the score was on average 3 (SD 1.1) (p < 0.05). In the control group 77% of the subjects had an evident increase in ankle circumference and volume, which was clearly visible at inspection and associated with discomfort. In the Venoruton group, edema was clearly present only in 8% of subjects (associated with discomfort rated between 3 and 6 on the analogue scale line) and it was mild, not associated with symptoms. Therefore the control of flight edema with Venoruton was clear both considering parametric data (circumference and volume) and non-parametric (analogue scale lines) measurements. The combined evaluation of the edema score is significantly favorable for subjects under prophylaxis with Venoruton.

Administration, Oral↗
PubMed2002

Enhancing foot skin blood flux in peripheral vascular disease using intermittent pneumatic compression: controlled study on claudicants and grafted arteriopaths.

Intermittent pneumatic leg compression (IPC) increases arterial calf inflow and foot skin blood flux in normal subjects and claudicants. Our hypothesis was that IPC could enhance foot skin blood flux after infrainguinal grafting and thus promote distal perfusion in limbs with tissue loss. The aim of this study was to compare the effects of three IPC modes [applied to the foot (IPCfoot), the calf (IPCcalf), or both (IPCfoot+calf)] on foot skin perfusion in healthy individuals, claudicants, and patients after infrainguinal arterial revascularization performed for critical or subcritical limb ischemia. Altogether, 20 healthy limbs, 22 claudicating limbs, and 36 limbs of arteriopaths with prior successful autologous femoropopliteal and femorodistal (18 each) grafts were examined. Five-minute laser Doppler recordings were obtained from the pulp of the big toe in the sitting position, at rest, and during random applications of IPCfoot, IPCcalf, and IPCfoot+calf delivered at 120 mmHg for 4 seconds three times per minute. Foot skin blood flux increased using all IPC modes (p <0.001), with IPCfoot and IPCfoot+calf generating higher flux levels than IPCcalf (p <0.01) in all groups. Intergroup differences of flux with each of the three IPC modes were not significant. IPCfoot and IPCfoot+calf similarly (p > 0.14) produced a higher percentage flux increase than IPCcalf in all groups (p <0.004). Controls had a higher percentage flux increase with both IPCcalf and IPCfoot than did claudicants (p? 0.016). No differences were documented between normal and grafted limbs (p > 0.05). The percentage flux increase with IPCfoot+calf and IPCcalf was significantly higher in femorodistal grafts than in femoropopliteal ones (p ? 0.026). IPC enhances skin blood flux in limbs with infrainguinal bypass, claudication, and normal arteries, with IPCfoot and IPCfoot+calf being more effective than IPCcalf. Our findings suggest that IPC may be beneficial in limbs with impaired distal perfusion and thus may have clinical implications in the treatment of leg ulcers either prior to or after revascularization.

Aged↗
PubMed2002

Fractal dimension estimation of carotid atherosclerotic plaques from B-mode ultrasound: a pilot study.

In this paper, a pilot study regarding carotid atherosclerotic plaque instability using B-mode ultrasound (US) images was carried out. The fractal dimension of plaques obtained from ten symptomatic subjects (i.e., subjects having experienced neurological symptoms) as well as from nine asymptomatic subjects, was estimated using a novel method, called the kth nearest neighbour (KNN) method. The results indicated a significant difference, as per the fractal dimension, between the two groups, providing a significantly lower value for the asymptomatic group. Moreover, the phase of the cardiac cycle (systole/diastole) during which the fractal dimension was estimated had no systematic effect on the calculations. The fractal dimension of the plaques was also estimated using a well-known method, namely the box-counting (BC) method. No significant differences between the two groups, as per the fractal dimension, were observed using the BC method. The presented pilot study suggests that the fractal dimension, estimated by the proposed method, could be used as a single determinant for the discrimination of symptomatic and asymptomatic subjects.

Aged↗
PubMed2002

Ambulatory venous pressure measurements: new parameters derived from a mathematic hemodynamic model.

PURPOSE: The mechanism of venous pressure decrease during exercise still remains unclear. To explore the components involved with the regulation of ambulatory venous pressure, we reinvestigated the pattern of pressure decrease during tiptoe exercise with a newly developed mathematic model. METHODS: Seventeen healthy limbs of 16 volunteers (normal group) and 35 limbs of 33 patients with signs and symptoms of chronic venous insufficiency were studied. Seventeen limbs had superficial venous incompetence (SVI), and 18 showed deep venous incompetence with or without concomitant superficial venous reflux. All subjects were examined with ambulatory venous pressure measurements. As parameters obtained from serial phasic changes in pressure during tiptoe movements, the pressure reduction fraction per step (decreasing component) and the pressure increase per step (increasing component) were calculated with application of the mathematic hemodynamic model and assessed comparatively in the three groups with different types of reflux (normal, SVI, and deep venous incompetence group). RESULTS: The pressure increase per step was significantly different in each of the three groups (P <.0001, with analysis of variance), whereas no apparent difference was seen in the mean pressure reduction fraction per step among the groups. With addition of the inflation of ankle cuff, the value of pressure increase in limbs with SVI was significantly reduced (P =.0004, with Wilcoxon signed rank test), although no changes were seen in the pressure reduction fraction in each group. CONCLUSION: Our results indicate that the pressure reduction fraction, representing calf muscle pump function, is independent of the existence or site of valve incompetence. On the other hand, the pressure increase, corresponding to the degree of reflux during exercise, correlates strongly with the severity of venous insufficiency. The theoretic model can separate the two components responsible for ambulatory venous pressure changes, calf muscle pump function and venous reflux, and provide better understanding of venous hemodynamics.

Blood Pressure Monitoring, Ambulatory↗