What you did not know about the North American Symptomatic Carotid Endarterectomy Trial.
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Cerebrovascular Disorders↗
Biomedical subjects
D E Strandness
Publications and source records attributed to D E Strandness.
Relationship between changes in the deep venous system and the development of the postthrombotic syndrome after an acute episode of lower limb deep vein thrombosis: a one- to six-year follow-up.
PURPOSE: This study investigated changes in the deep venous system and the development of the postthrombotic syndrome (PTS) after an episode of acute deep vein thrombosis (DVT). METHODS: Seventy-eight patients (41 male patients, 37 female patients) with acute DVT in 83 legs (31 right, 42 left, five bilateral) underwent annual follow-up examinations for 1 to 6 years (median, 3 years) for symptoms and signs of the PTS. A venous duplex scan was performed at each visit to detect obstruction and reflux in the veins, both of which may contribute to the development of the PTS. DVT was primary in 69 limbs and recurrent in 14 limbs. RESULTS: When last examined 49 limbs were free of symptoms, and 34 had the PTS (23 edema only, 11 hyperpigmentation). Only two patients had ulcers during the follow-up period; both patients had the ulcers in areas of hyperpigmentation in limbs with recurrent DVT. The extent of disease was similar in limbs with the PTS (79% multisegment, 18% single segment) and those without the PTS (69% multisegment, 12% single segment). In limbs with the PTS the deep veins were normal in only one (3%), six (18%) showed reflux only, five (15%) obstruction only, and 22 had features of both obstruction and reflux (65%). In limbs without the PTS the deep veins showed no abnormality in nine (18%), reflux only in 17 (35%), obstruction only in six (12%), and reflux with obstruction in 17 (35%). In the 11 limbs with hyperpigmentation nine had obstruction and reflux noted, one had obstruction only, and one had reflux alone. CONCLUSIONS: After an episode of acute DVT 12% of the limbs returned to normal by duplex criteria. Although only 13% developed skin complications, 41% had features of the PTS. Limbs with the PTS had more than three times the odds of having combined reflux and obstruction than did limbs without the PTS (odds ratio = 3.5, 0.95 confidence intervals = 1.4, 8.6). Continued study of these patients will determine the course of those limbs with venous abnormalities that have not yet developed symptoms and signs of the PTS.
Acute Disease↗
A new method for studying plaque morphology.
A histologic method was developed for three-dimensional (3-D) analysis of atherosclerotic plaques removed from the carotid bifurcation during endarterectomy. By sectioning the plaque at frequent intervals (0.5 to 1.0 mm), it is possible to obtain important information on plaque constituents with regard to their volume and distribution within the lesion. These data from each section are combined with those from other sections and displayed in a 3-D format for the entire length of the lesion. The tissues making up each of the 10 carotid plaques were outlined and digitized for each histologic section by position along the lesion. From the areas outlined a 3-D model was created by a computer-aided design program. Quantitative information on tissue distribution within the plaque was measured. Fibrous tissue constituted between 35% and 70% of plaque volume; loose necrosis from 0.5% to 30% of the plaque and thrombus occupied, at a maximum, 10% even though if was present in six of the 10 plaques. To investigate the distribution of constituents about the long axis, measurements were also made from each of the four quadrants of each section. The reproducibility of the measurements of three sets of sections at 10-mm separation showed that estimates of the amount of some constituents were very reproducible whereas others had considerable variation related to the small volume they occupied within the lesion. By generating a complete 3-D reproduction of the contents of atherosclerotic plaques, it may be possible to identify those features of the plaque that are most responsible for the development of ischemic events.
Arteriosclerosis↗
A comparison of the cuff deflation method with Valsalva's maneuver and limb compression in detecting venous valvular reflux.
OBJECTIVE: This study was designed to test the results of Valsalva's maneuver and limb compression against the standing-cuff inflation-deflation method for the detection of venous valvular reflux. DESIGN: The study was conducted in 67 patients (134 extremities) who had an episode of deep vein thrombosis. An ultrasonic duplex scanner was used to evaluate two methods of testing for reflux. The most commonly used methods are Valsalva's maneuver and limb compression, both of which can raise the venous pressure and promote reflux. With the cuff method, the patient is studied in the standing position. The cuffs are segmentally placed (thigh to foot) with reflux encouraged when the inflated cuff is suddenly deflated. SETTING: The patients were a part of a long-term natural history study of acute deep vein thrombosis and its effects on venous valve function. OUTCOME MEASURES: Valvular reflux was documented by the appearance of retrograde flow in the vein when the normal transvalvular pressure gradient was reversed. RESULTS: Both limb compression and Valsalva's maneuver can elicit reflux, but the maneuvers are difficult to standardize and come up with meaningful results. With the cuff inflation-deflation method, the time to valve closure was less than 0.5 seconds in 95% of normal subjects. The results were easier to quantify and worked well for all segments of the venous systems--superficial and deep. CONCLUSIONS: The cuff inflation-deflation method provides more uniform quantifiable results for detecting reflux in the superficial and deep veins of the leg.
Acute Disease↗
Acute effects of sublingual nitroglycerin on hepatic blood flow in healthy volunteers.
Duplex sonography was used to assess the effects on hepatic blood flow after administering 0.6 mg nitroglycerin (NTG) sublingually to ten healthy volunteers. The study was a randomized, placebo-controlled, cross-over study in which subjects were studied on three separate occasions. Each visit involved administering either placebo or NTG followed by estimation of blood flow through a particular branch of the hepatic artery, portal vein, and hepatic vein every minute for 15 minutes after NTG and placebo administration. Two hours later, subjects were crossed over to the other treatment and the same vessel branch was again examined for 15 minutes. Total blood flow increased 7% in the portal vein and 27% in the hepatic vein during NTG treatment, but did not change significantly in the hepatic artery. Vascular resistance was increased in the hepatic artery and decreased in the portal and hepatic veins after NTG. Qualitatively, flow changed dramatically in the hepatic vein after NTG with the disappearance of normal retrograde flow. The results indicate that nitroglycerin effects hepatic blood flow through the portal and hepatic veins with a decrease in vascular resistance in the portal and hepatic veins and an increase in resistance in the hepatic artery.
Administration, Sublingual↗
Ultrasonic three-dimensional reconstruction: in vitro and in vivo volume and area measurement.
This study validates the use of an ultrasound three-dimensional reconstruction system to measure phantom and blood conduit geometry. Independently determined uniform and stenotic phantom dimensions are compared with reconstruction-based measurements. Lower extremity saphenous vein bypass graft reconstructions were performed to demonstrate clinical application. Uniform phantom independent and reconstructed volume correlation was high (r = 0.989), the average volume difference was 4.68 mm3 and the average area difference was 0.4 mm2. An in vitro 28% diameter reduction was detected. Stenotic bypass graft segment volume was 795 mm3; following successful angioplasty the volume increased to 1419 mm3. Advantages of this technique are its accuracy, the luminal information it provides and the absence of mechanical arm or acoustic transmitter limitations. We are exploring the possibility that measurement of luminal change over time may allow stenosis detection prior to hemodynamic disturbance, in an ongoing clinical saphenous vein bypass graft surveillance study.
Humans↗
Pseudocolor B-mode arterial images to quantify-echogenicity of atherosclerotic plaque.
Based on the differences between tissue impedances in atherosclerotic plaques and on the scattering of ultrasound from blood, colors were assigned to the echo strength scale, replacing the usual gray scale in 2-D B-mode ultrasound images. Using a "green tag" indicating -55 dB to mark blood, other echo strength values from atherosclerotic plaque were assigned specific colors, creating a B-mode color ultrasound display that highlights selected echogenicities. The color scale permits the use of a wider dynamic range in the B-mode image, and allows the instrument gains to be set reproducibly.
Arteries↗
Echolucent regions in carotid plaque: preliminary analysis comparing three-dimensional histologic reconstructions to sonographic findings.
This study compares sonographic and histologic findings within defined spatial regions in carotid artery plaque, using computer generated three-dimensional reconstructions. Twenty-four patients (14 asymptomatic, 10 symptomatic) with angiographically documented 70% to 99% carotid artery stenosis were examined with ultrasonic B-mode imaging prior to endarterectomy. Using a standardized protocol for instrument set-up and scanning technique, echolucent regions in the plaque were identified. After endarterectomy, each plaque was sectioned at 0.5 to 1.0 millimeter increments throughout its length. Sites containing intraplaque hemorrhage, cholesterol clefts, foam cells, necrotic cores, dense calcification and speckled calcification were identified. These areas were outlined on a template, digitized and imported into a computer program that created three-dimensional reconstructions of the histologic findings. Each carotid plaque was divided into quadrants for analysis: (1) lateral wall proximal to the common carotid bifurcation (flow divider); (2) medial wall proximal to the flow divider; (3) lateral wall distal to the flow divider; and (4) medial wall distal to the flow divider. The odds of finding intraplaque hemorrhage, foam cells, necrotic cores and speckled calcification were significantly higher in quadrants with an echolucent region identified by ultrasonography (odds ratio (95% confidence interval) for intraplaque hemorrhage = 3.5 (1.4-8.6); foam cells = 4.0 (1.6-9.9); necrotic cores = 3.2 (1.2-8.4); speckled calcification = 4.0 (1.6-9.8). This preliminary analysis demonstrates the potential of these newly developed techniques for comparing ultrasonic imaging to histology.
Aged↗
3D ultrasonic image feature localization based on magnetic scanhead tracking: in vitro calibration and validation.
The basis of a three-dimensional (3D) ultrasound imaging system was constructed from a commercially available magnetometer-based position and orientation measurement (POM) device, a standard B-Mode ultrasound instrument and a personal computer. To evaluate the system's performance, a novel method was devised using an iterative, least-squares technique to simultaneously determine the system's calibration parameters and measure its precision in locating points in three-dimensional space. When tested separately, the POM system located single points with a root mean squared (RMS) uncertainty of from 1.4 mm to 3.2 mm over the 610 mm working radius of the system. When combined with the ultrasound instrument, the RMS uncertainty in locating point targets varied from 2.1 mm to 3.5 mm. These results establish the lower limits of variability to be expected from this system when locating fiducial anatomical landmarks for repeated examinations of the same region of the body, and when making numerical 3D reconstructions from multiple planar images.
Calibration↗
Natural history of renal artery stenosis.
Renal artery stenosis secondary to atherosclerosis is a cause of both hypertension and renal failure. Since ultrasonic duplex scanning can be used to detect the presence of renal artery stenosis, it is possible to use this modality for follow-up purposes. This study was designed to determine the relationship between the degree of renal artery narrowing and its effects on kidney size. Serial measurements of renal length were taken as a part of the prospective duplex ultrasound measurements of renal artery narrowing. Fifty-four patients (22 men and 32 women with a mean age of 65.8 years) were included in the study. There were 101 renal arteries and kidneys available for follow-up (average, 14.4 months; range, 4 to 24 months). The patients had repeat duplex studies every 6 months. There were no kidneys with normal renal arteries or a less than 60% diameter-reducing stenosis that had a decrease in renal length of more than 1 cm during follow-up. In those kidneys with a > or = 60% diameter-reducing stenosis, 26% had a decrease in renal length of greater than 1 cm. The average decrease in length was 1.9 cm (range, 1.2 to 3.4 cm). The estimated risk of a loss of more than 1 cm length was 19% at 1 year. Loss of renal mass is an important consequence of high-grade renal artery stenosis.
Aged↗
Duplex imaging for the detection of renal artery stenosis.
To determine the accuracy of ultrasonic duplex scanning in detecting and classifying renal artery stenosis, we compared the results of duplex scanning with arteriograms in 41 patients with a total of 74 arteries available for comparison. By using a peak systolic velocity of more than 180 cm/s, duplex scanning was able to discriminate between normal and diseased renal arteries with a sensitivity of 95% and a specificity of 90%. Since blood flow velocity across an area of narrowing will increase is roughly proportional to the degree of narrowing, it appeared that the ratio of peak systolic velocity in the area of stenosis to that in the aorta (RAR) of greater than 3.5 predicted the presence of a more than 60% diameter reduction of the renal artery. Using a RAR of 3.5, duplex scanning agreed in 44 renal arteries the sensitivity was 92%. In the 26 renal arteries in which the lesions were less than 60% by arteriography, duplex scanning agreed in 16 arteries and correctly detected an area of focal narrowing in nine of the 10 remaining vessels. Ten of the 11 occluded renal arteries were correctly identified by duplex scanning. Duplex scanning identified the location of the renal artery stenosis with an accuracy of 95%. We believe the data shows that duplex scanning is an accurate method of detecting renal artery stenosis and provides a suitable method of estimating the degree of narrowing.
Angiography↗
Ultrasound determination of total arterial wall thickness.
PURPOSE: Ultrasonic measurement techniques for determining intima-media thickness and total arterial wall thickness have been described. The intima-media thickness measurements are currently in use in large epidemiologic trials. Intima-media thickness does not evaluate extramedial atherosclerotic change and so may not fully reflect pathologic changes in the arterial wall. METHODS: After we performed variability studies of B-mode image acquisition and measurement, we measured total wall thickness and intima-media thickness of the common carotid arteries in 60 adult subjects in three groups: a control group aged 20 to 29 years, a control group aged 60 to 79 years, and a claudication group aged 60 to 79 years. Measurements were made with B-mode ultrasound images. RESULTS: No statistical difference between sexes was noted. A statistically significant (p < or = 0.05) increase in intima-media thickness and wall thickness was found with increasing age, and an additional increase was observed with clinically significant lower extremity arterial occlusive disease (p < or = 0.05). Image quality had an effect on measurement accuracy. CONCLUSIONS: The finding that the wall thickness of common carotid arteries is increased in those patients with clinically significant lower extremity disease supports the theory that atherosclerosis affects the arterial wall in a systemic fashion. Because intima-media thickness also increases across subject groups without change in its proportional contribution to the total arterial wall thickness, extramedial arterial changes also occur with aging and the development of atherosclerosis. We propose that because increases in wall thickness measurements of common carotid arteries follow intima-media thickness increase (but do not necessarily measure the same physiologic change) and the wall thickness method can be used in cases when the intima-media thickness cannot be measured, arterial wall thickness measurement may serve as an alternate or confirmatory test of peripheral artery atherosclerotic severity.
Adult↗
Natural history of atherosclerotic renal artery stenosis: a prospective study with duplex ultrasonography.
PURPOSE: Although the prevalence of renal artery stenosis in patients with peripheral arterial disease is in the range of 30% to 40%, the role of renal revascularization in patients without severe hypertension or kidney failure is controversial. Duplex scanning is a noninvasive technique that is ideally suited for screening and follow-up of renal artery disease. The purpose of this study was to document the natural history of renal artery stenosis in patients who were not candidates for immediate renal revascularization. METHODS: Eighty-four patients with at least one abnormal renal artery detected by duplex scanning were recruited from patients being screened for renal artery stenosis. Of the 168 renal artery/kidney sides, 29 were excluded (15 prior interventions, 6 nondiagnostic duplex scans, 8 presumed nonatherosclerotic lesions), leaving 80 patients with 139 sides for the follow-up protocol. Renal arteries were classified as normal, less than 60% stenosis, 60% or greater stenosis, or occluded by use of previously validated criteria. RESULTS: The study group included 36 men and 44 women with a mean age of 66 years who were monitored for a mean interval of 12.7 months. The initial status of the 139 renal arteries was normal in 36, less than 60% stenosis in 35, 60% or greater stenosis in 63, and occluded in 5. Although none of the initially normal renal arteries showed disease progression, the cumulative incidence of progression from less than 60% to 60% or greater renal artery stenosis was 23% +/- 9% at 1 year and 42% +/- 14% at 2 years. All four renal arteries that progressed to occlusion had 60% or greater stenoses at the initial visit, and for those sides with a 60% or greater stenosis, the cumulative incidence of progression to occlusion was 5% +/- 3% at 1 year and 11% +/- 6% at 2 years. The mean decrease in kidney length associated with progression of renal artery stenosis to occlusion was 1.8 cm. CONCLUSIONS: Progression of renal artery stenosis, as defined in this study, occurs at a rate of approximately 20% per year. Progression to occlusion is associated with a marked decrease in kidney length. Whether this natural history can be improved by earlier intervention for renal artery stenosis remains to be determined.
Aged↗
Prevalence of carotid and lower extremity arterial disease in patients with renal artery stenosis.
Atherosclerosis is the most common cause of renovascular hypertension secondary to hemodynamically significant stenoses (> 60% diameter reduction). To assess the prevalence of atherosclerosis in the peripheral arteries and carotid bifurcation, we prospectively studied 60 patients who had renal artery stenosis documented by ultrasonic duplex scanning. Disease of the peripheral arterial circulation was assessed by the measurement of the ankle/brachial systolic pressure ratio. To evaluate the extracranial carotid artery, ultrasonic duplex scanning was employed. The prevalence of a 50-100% diameter reducing stenosis in the carotid artery was 46% in patients with a > 60% diameter reducing renal artery stenosis. The prevalence of severe peripheral arterial disease was 73% in those patients with a high grade renal artery lesion. The prevalence of severe disease in the peripheral and carotid arteries was less (50% and 25%, respectively) in patients with renal artery lesions that reduced the diameter of the renal artery less than 60%. The high prevalence of associated lesions in the carotid and peripheral circulation in patients with renovascular disease secondary to atherosclerosis should prompt investigation of these major arteries when renal artery disease is detected. Disease of the carotid and peripheral arteries is a common cause of morbidity and should be treated according to accepted guidelines.
Aged↗
Liver blood flow, antipyrine clearance, and antipyrine metabolite formation clearance in patients with chronic active hepatitis and alcoholic cirrhosis.
Duplex scanning was used to measure liver blood flow (hepatic artery and main branches of the portal and hepatic veins) in six healthy subjects, five cirrhotic patients, and six hepatitis patients. Antipyrine clearance and formation clearances to its metabolites were also measured. Compared with healthy control subjects, cirrhotic patients had a lower hepatic vein blood flow (-76%, P < 0.05). This was due primarily to a lower portal vein blood flow (-36%, NS). A statistically significant difference in liver blood flow between patients with hepatitis and normal subjects was not detected. Antipyrine half-life, clearance, and the area under the serum drug concentration vs time curve were significantly different in cirrhotic patients compared with the healthy subjects (mean +/- s.d.-healthy controls: t1/2 = 13.7 +/- 3.0 h, CL = 30.0 +/- 8.6 ml h-1 kg-1, AUC = 549 +/- 139 mg l-1 h; cirrhotic patients: t1/2 = 32.4 +/- 1.7 h, CL = 12.3 +/- 2.1 ml h-1 kg-1, AUC = 1061 +/- 218 mg l-1 h; P < 0.008). Antipyrine half-life, clearance, and the area under the serum drug concentration vs time curve were not significantly different in hepatitis patients compared with the healthy subjects (hepatitis patients: t1/2 = 14.3 +/- 3.7 h, CL = 29.3 +/- 8.5 ml h-1 kg-1, AUC = 498 +/- 142 mg l-1 h). The volume of distribution of antipyrine was similar in all three groups of subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Renal atrophy and arterial stenosis. A prospective study with duplex ultrasound.
Renal artery disease is an important cause of both renal failure and hypertension. Duplex ultrasound is a reliable noninvasive method for classifying the severity of renal artery lesions and can be repeated to follow the course of the disease over time. The purpose of this study was to determine the changes in kidney size associated with various degrees of renal artery disease. Serial kidney lengths were measured as part of a prospective duplex ultrasound study of patients with renal artery narrowing. Fifty-four patients (22 men, 32 women; mean age, 65.8 years) with 101 renal artery and kidney sides eligible for follow-up were evaluated at 6-month intervals for an average of 14.4 months (range, 4 to 24 months). No kidneys with renal arteries classified as normal or less than 60% diameter stenosis by duplex criteria were found to have a decrease in length of greater than 1 cm during follow-up. In kidneys with a high-grade renal artery stenosis (> or = 60% diameter reduction), 26% (13 of 49 sides) were found to have a decrease in length of greater than 1 cm. The average decrease in length was 1.9 cm (range, 1.2 to 3.4 cm). By life table analysis, the estimated risk of a decrease in length of greater than 1 cm for kidneys with 60% stenosis or greater was 19% at 1 year. Loss of renal mass, as documented by ultrasound measurement of kidney length, is an important consequence of high-grade renal artery stenosis.
Adult↗
Venous diameter and compliance after deep venous thrombosis.
Duplex sonography was used to measure diameters of the common femoral, superficial femoral, and popliteal veins in 56 patients followed for more than 6 months after DVT and in 17 normal subjects. Diameter changes with Valsalva's maneuver were also measured as an index of venous compliance. Among patients with unilateral thrombosis, segments with residual disease were 0.07 to 0.28 cm smaller than the contralateral disease-free side (p < 0.05 for CFV and SFV) with a diameter index (ipsilateral/contralateral diameter) significantly less than that of normal subjects. In contrast, completely recanalized segments were not significantly different from the contralateral side and had diameter indices indistinguishable from normal subjects. Distensibility with Valsalva's maneuver was not significantly different from normal in DVT patients with either resolved or residual disease. Venous diameter does decrease following DVT, but returns to normal following complete recanalization and is not associated with chronic venous compliance changes.
Adolescent↗
Incidence and time of occurrence of valvular incompetence following deep vein thrombosis.
Commencing December 1986 and over the course of 4 years, the diagnosis of acute deep vein thrombosis (DVT) was established by duplex scanning in 286 patients referred to the University of Washington Medical Center in order to rule out this problem. From this group 107 patients (123 legs with DVT) were placed in a long-term follow-up program. The documentation of valvular reflux and its site was demonstrated by duplex scanning. The duplex studies were done at intervals of 1 and 7 days, 1 month, every 3 months for the first year and then yearly thereafter. The mean follow-up time was 341 days. The presence of reflux was also determined in 502 patients with a negative duplex study and no previous history of DVT or chronic venous insufficiency. In the patients with acute DVT, valvular incompetence was noted in 17 limbs (14%) at the time of the initial study. Reflux was absent in 106 limbs (86%). In this last group reflux developed in 17% of the limbs by day 7. By the end of the first month, 37% demonstrated reflux. By the end of the first year, more than two-thirds of the involved limbs had developed valvular incompetence. The distribution of reflux at the end of the first year of follow-up was: 1) popliteal vein, 58%; 2) superficial femoral vein, 37%; 3) common femoral vein, 33%; and 4) posterior tibial vein, 18%. Reflux in the greater saphenous vein occurred in 25% of the limbs after 1 year. Reflux developed more frequently in thrombosed venous segments.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗