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Biomedical subjects

D E Strandness

Publications and source records attributed to D E Strandness.

At least 145 records · Page 8Linked to original sources
PubMed1989

Delayed carotid shunt occlusion detected by electroencephalographic monitoring.

Little has been recorded in the anesthesia literature concerning the changes in the electroencephalogram (EEG) that may occur during carotid endarterectomy many minutes after shunt placement and restoration of flow and that may be attributed to "delayed" shunt occlusion or cerebral emboli. We describe a patient in whom EEG changes indicative of cerebral ischemia occurred at the time of carotid clamping. The changes resolved promptly after placement of a carotid shunt but recurred 11 minutes later. Because of the EEG changes, the carotid shunt was evaluated and found to have become occluded. EEG monitoring was crucial to the detection of shunt occlusion in the absence of other systemic changes or surgical difficulties. The rapidity and magnitude of the changes in the EEG suggest that, if the occlusion had not been discovered and the patency of the shunt restored, the patient would have been at increased risk for neurologic injury.

Aged↗
PubMed1989

Should results of ultrasound Doppler studies be reported in units of frequency or velocity?

There is a current tendency to report the results of ultrasound Doppler studies in units of velocity instead of Doppler frequency. This is probably motivated by the intuitive feeling that blood flow studies should naturally be reported in cm/s and the notion that "velocity" is a normalizing factor for Doppler ultrasound studies. In order to determine velocity, the Doppler angle theta or angle formed by the ultrasound beam and flow velocity vector, must be known. It is not possible, using currently available systems, to obtain an accurate estimate of this angle. The physics related to the Doppler equation are reviewed in this paper along with examples to illustrate the origin and magnitude of errors that could arise when reporting in units of velocity. Guidelines are provided for thinking about and reporting results of Doppler studies in units of velocity. An understanding of the Doppler equation and its use in clinical studies are promoted in this paper to enhance the diagnostic usefulness of Doppler ultrasound studies and to reduce serious errors which could lead to faulty information dictating patient management.

Blood Flow Velocity↗
PubMed1989

An ultrasonic measurement of superficial femoral artery wall thickness.

An ultrasonic measurement of the superficial femoral artery wall thickness was performed on 16 volunteers. The measurement included all echogenic tissue between the lumen of the superficial femoral artery and the lumen of the superficial femoral vein. The average arterial wall plus vein wall thickness in volunteers with peripheral arterial disease was 2.13 +/- 0.87 mm, significantly greater than the 1.27 +/- 0.50 mm found in those without detectable peripheral arterial disease.

Aged↗
PubMed1989

Quantitative segmental evaluation of venous valvular reflux with duplex ultrasound scanning.

The duration of deep venous valvular reflux was studied in 192 venous segments of the legs of 32 patients in good health. Three methods were used to elicit reflux in the supine and upright positions--Valsalva's maneuver, proximal limb compression, and release of distal limb compression. Standardized compressions were achieved with pneumatic cuffs. When this approach was used to study valve function, the time to complete closure of the valve and cessation of retrograde flow was found to be shorter than that for conventional methods of closure. The distal cuff deflation method is the only one that permits a quantitative and reproducible method to measure duration of venous reflux at all levels of the lower limb. Normal values obtained with this test are presented for the common femoral, deep femoral, and superficial femoral veins and for the popliteal and posterior tibial veins midway between knee and ankle level and the posterior tibial vein at the ankle. In the popliteal vein, median duration of reflux is 0.19 second; 95% of the values in the popliteal vein are less than 0.66 second. In distal areas, duration of reflux is short and uniform. The advantage of the cuff deflation test over the Valsalva method is that the cuff method is not hindered by the presence of ileofemoral valves. A better understanding of the relative importance of deep valve dysfunction at different levels and the expected benefit of valve repair may be obtained with this test.

Adolescent↗
PubMed1989

Asymptomatic high-grade internal carotid artery stenosis: is stratification according to risk factors or duplex spectral analysis possible?

High-grade (80% to 99% diameter reduction) asymptomatic internal carotid artery stenoses are associated with an increased neurologic event rate (transient ischemic attack, stroke, asymptomatic internal carotid artery occlusion) compared to less severe asymptomatic lesions. However, many do remain free of associated events. To determine which are most dangerous, we compared risk factors and duplex scan results in two groups with asymptomatic high-grade internal carotid artery stenoses. Group A included 31 patients with 33 unoperated high-grade lesions that remained asymptomatic for at least 12 months (mean 30 months). Group B included 25 patients with 26 initially asymptomatic lesions that subsequently were associated with a neurologic event (mean time to event 7.4 months). The groups did not differ significantly in average age, sex, aspirin use, smoking, or prevalence of hypertension, diabetes, or cardiac disease. With respect to the index high-grade lesion, there was no difference in the frequency of a greater than 50% contralateral internal carotid artery stenosis or greater than 50% ipsilateral external carotid stenosis. However, on duplex scanning, high-grade stenoses with greater than 6.5 kHz end-diastolic frequencies were more frequently associated with an event than high-grade lesions with lower end-diastolic frequency (p = 0.0004). Similarly, seven of 23 lesions (30%) with end-diastolic frequency greater than 6.0 kHz were associated with subsequent internal carotid artery occlusion compared to only one of 29 (3.5%) with end-diastolic frequency less than or equal to 6.0 kHz (p = 0.025). Analysis of internal carotid artery end-diastolic frequency may help select a subgroup of patients with asymptomatic high-grade lesions who are at greatest risk for subsequent neurologic symptoms or ICA occlusion or both.

Aged↗
PubMed1989

Neurologic sequelae of unilateral carotid artery occlusion: immediate and late.

Over a 7-year period (1980 to 1987) 24 patients (18 men: mean age 67 years; range, 52 to 78 years, and six women: mean age 67 years; range, 46 to 82 years) undergoing serial carotid artery duplex scans were observed to progress to unilateral carotid artery occlusion. The occlusions were associated with ipsilateral strokes in six (25%), ipsilateral transient ischemic attacks in four (16%), and the onset of nonhemispheric symptoms in one (5%). Thirteen patients had no symptoms. Follow-up ranged from 4 months to 96 months (mean 39.4 months). Late neurologic events comprised two strokes, three transient ischemic attacks and the onset of nonhemispheric symptoms in six, which in some were disabling. Thirteen patients had no symptoms. Three deaths occurred (one was stroke related). For late events by life-table analysis, the average annual rate over the first 2 years for stroke was 10% and for transient ischemic attack 13%. The combined rate for transient ischemic attack and stroke was 20% per annum. For nonhemispheric symptoms the rate for the first year was 31%. It is concluded that unilateral carotid artery occlusion is associated with an unacceptable incidence of immediate neurologic sequelae and that such patients continue to have a high rate of late neurologic deficits at follow-up. Therefore it seems appropriate that patients who are observed to progress to high-grade stenosis and are therefore at risk for immediate occlusion should undergo prophylactic carotid endarterectomy.

Aged↗
PubMed1989

Follow-up of renal artery stenosis by duplex ultrasound.

We have previously shown that duplex ultrasound is an accurate method of diagnosing renal artery stenosis (93% accuracy compared with angiography in the diagnosis of less than 60% stenosis, 60% to 99% stenosis, or occlusion). With this method we have now serially observed 35 renal arteries with 60% to 99% renal artery stenosis in 27 patients. Nineteen stenotic renal arteries in 15 patients were observed without intervention. There was a significant decrease in kidney size (mean difference - 1.0 cm; p less than 0.01; mean follow-up 13 months) but all 19 renal arteries remained patent. Percutaneous transluminal angioplasty (PTA) was performed in five patients (six renal arteries) for renovascular hypertension. Renal duplex scanning documented relief of renal artery stenosis in two patients whose hypertension improved after PTA and confirmed residual 60% to 99% renal artery stenosis in three patients whose hypertension did not improve after PTA (mean follow-up 6.5 months). Aortorenal bypass was performed for 10 stenotic renal arteries in seven patients. At a mean follow-up of 9 months duplex ultrasound documented eight patent and two occluded aortorenal bypass grafts. Duplex ultrasound is useful both for defining the natural history of untreated renal artery stenosis and assessing the results of renal artery angioplasty or bypass.

Angioplasty, Balloon↗
PubMed1989

Diagnosis of deep venous thrombosis. A prospective study comparing duplex scanning to contrast venography.

Duplex scanning has been proposed as a safe alternative to contrast venography for diagnosing deep venous thrombosis, but its accuracy has not been proved. In this prospective, double-blind study of 47 patients, the sensitivity and specificity of duplex scan criteria were determined relative to contrast venography for lower extremity deep venous thrombosis. Criteria considered to show the presence of deep venous thrombosis included visualization of thrombus (T), absence of spontaneous flow by Doppler ultrasonography (F), absence of phasicity of flow with respiration (P), and incompressibility of the vein with probe pressure (VC). When analyzed individually, the variables T and F had low sensitivities (50% and 76%) but high specificities (92% and 100%). VC had low values for both (79% and 67%, respectively). The best single variable was P (sensitivity and specificity = 92%). The best combinations of variables were T+P (sensitivity = 95%, specificity = 83%), T+F+P (sensitivity = 95%, specificity = 83%), F+P (sensitivity and specificity = 92%), and F+T (sensitivity = 92%, specificity = 87%). The low specificity of vein incompressibility was secondary to cases in which normal veins were difficult to compress in the thigh. All false-negative cases were from isolated calf vein thrombi. We conclude that isolated criteria from duplex scanning should not be used to diagnose deep venous thrombosis. In cases of suspected calf vein thrombosis, repeat duplex examination should be obtained in 3-4 days to determine the most appropriate therapy. In equivocal cases of proximal vein thrombosis, a contrast venogram should be obtained.

Adult↗
PubMed1989

Diagnostic significance of flow separation in the carotid bulb.

Pulsatile blood flow within the normal carotid sinus involves at least two distinct components. That near the flow divider is laminar and antegrade, whereas a boundary layer separation zone in the posterolateral aspect exhibits transient blood flow reversal. It is now possible to document these flow velocity components using pulsed Doppler ultrasound methods. When atherosclerosis develops, it preferentially involves the posterolateral bulb region, obliterating the normal configuration of the sinus with consequent loss of the flow separation zone. It was therefore hypothesized that if flow separation could be detected, it should be predictive of a normal angiogram. To assess this, we evaluated 20 symptomatic patients and two with only bruits found by duplex scanning to have flow separation in either one or both carotid bulbs and who also underwent cerebral angiography. Initial diagnoses were stroke in seven, reversible ischemic neurologic deficit in one, transient ischemic attack in 12, and bruit in two. Flow separation was bilateral in 13 patients (59%). There were 15 patients with symptoms in the territory of a carotid bulb exhibiting flow separation. By angiography, of the 35 bulbs with boundary layer separation, 27 (77%) were normal, with the remainder showing lesions that reduced the diameter of the vessel by 20% or less. Final diagnoses of the 15 patients with symptoms ipsilateral to a carotid sinus exhibiting flow separation were fibromuscular disease in two, lacunar stroke in three, dissection in two, subclavian steal in one, cardiogenic embolus in three, migraine in one, hyperventilation syndrome in one, kink of the mid-internal carotid artery in one, and no diagnosis in one.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid Arteries↗
PubMed1989

Immediate and long-term results of carotid endarterectomy.

We review the long-term results of carotid endarterectomy in 200 consecutive patients operated on from 1980 to 1987. The patients were part of an ongoing study using duplex scanning to assess the status of the carotid bifurcation before and after endarterectomy. The average follow-up for the patients was 31 months. The indications for surgery were transient ischemic attacks in 87 (43.5%) and stroke in 36 (18%) patients; 77 patients (38.5%) were asymptomatic. In 176 sides (88%), the degree of stenosis exceeded 50% in terms of diameter reduction. The perioperative stroke rate was 2.3% in patients with transient ischemic attacks, 2.8% in patients with strokes, and 1.3% in asymptomatic patients. There was one perioperative death (0.5%). There were five occlusions of the internal carotid artery, one during the perioperative period and four after discharge; in three patients the occlusion was associated with the development of a stroke. There was a restenosis rate of 19.7% secondary to myointimal hyperplasia; such lesions did not appear to contribute to new ischemic events during or after their development. The mean stroke incidence after the decision was made for carotid endarterectomy was 2.8%/yr in the patients with transient ischemic attacks, 6.2%/yr in the patients with stroke, and 0.65%/yr in the asymptomatic patients. The annual death rate was 6% for the entire group, 5.5%/yr in the patients with transient ischemic attacks, 9.2%/yr in the patients with stroke, and 4.6%/yr in the asymptomatic patients.

Aged↗
PubMed1989

Long-term follow-up and clinical outcome of carotid restenosis.

The efficacy of carotid endarterectomy is dependent on the inherent ability of the operation to prevent stroke as well as the incidence of restenosis and associated symptoms. To examine the long-term effects of restenosis, 301 patients having carotid endarterectomy were followed by serial duplex scanning for an average of 4 years. Carotid restenosis, defined as 50% or greater diameter reduction by duplex scanning, occurred after 78 of the endarterectomies; regression of recurrent stenosis occurred in 20 arteries. By life-table analysis the cumulative incidence of restenosis at 7 years was 31%, and the cumulative incidence of regression was 10%. Thus the prevalence of recurrent stenosis at 7 years was 21%. Restenosis developed in women more frequently than men (p = 0.01). Transient ischemic attack occurred in 12% of patients with restenosis, and stroke occurred in 3%; however, the cumulative incidence of stroke or transient ischemic attack was not statistically different in those patients with and without restenosis. Similarly, cumulative survival at 7 years was no different. Carotid restenosis usually occurs early in the postoperative period and tends to regress or remain stable during long-term follow-up. A conservative approach to treatment appears justified, since transient ischemic attacks and stroke were rarely associated with restenosis.

Carotid Artery Diseases↗
PubMed1989

Spontaneous lysis of deep venous thrombi: rate and outcome.

Ultrasonic duplex scanning was used to study the rates at which lysis of thrombi, valvular incompetence, and symptoms of the postthrombotic syndrome (edema) developed in 21 patients after deep venous thrombosis (DVT). Lysis of thrombi occurred rapidly in most patients. In 11 of 21 patients (53%), recanalization occurred in all segments by 90 days after presentation. In four patients, extension of the initial DVT occurred between 30 and 180 days, despite treatment with warfarin. Valvular incompetence developed in 13 patients during the study period. The number of patent venous segments with incompetent valves increased from the initial presentation to 180 days, at which time 25% of patent segments contained incompetent valves. Valvular incompetence developed in previously thrombosed segments that were initially competent after recanalization and in segments not previously thrombosed. This suggested that although incompetence may occur as a result of a direct effect of the thrombus on the valve, other mechanisms must also be involved. Patients with edema early after DVT (from 7 to 30 days) were more likely to have residual occlusion than valvular incompetence. The late development of edema (from 90 to 270 days) was more closely correlated with valvular incompetence.

Humans↗
PubMed1988

Duplex ultrasound measurement of postprandial intestinal blood flow: effect of meal composition.

Duplex ultrasound was used to evaluate the effects of 350-cal, 300-ml protein, fat, carbohydrate, and mixed (Ensure-Plus) liquid meals on celiac, superior mesenteric, and femoral artery blood flow in 7 healthy volunteers. Ingestion of separate water and mannitol solutions served as controls for volume and osmolarity. Duplex parameters of peak systolic velocity, end-diastolic velocity, mean velocity, and volume flow were determined before, and serially for 90 min after, ingestion of each test meal. Maximal changes were compared with baseline values. There were no significant changes in any of the blood flow parameters derived from the celiac or femoral arteries after any test meal ingested. In contrast, maximal changes in all superior mesenteric artery parameters were increased significantly over baseline (p less than 0.05) after each of the test meals except water, with end-diastolic velocity showing proportionally the greatest increase. The study demonstrates that duplex ultrasound can provide a noninvasive means of studying the reactivity of the splanchnic arterial circulation to different stimuli and documents differing blood flow responses to variation of nutrients.

Adult↗
PubMed1988

Duplex ultrasound assessment of venous diameters, peak velocities, and flow patterns.

Duplex ultrasound was used to study the diameters, flow patterns, and peak blood flow velocities of the common femoral vein (CFV) in 12 normal subjects (mean age 35 years). Each subject was supine and non-weight-bearing on a tilt table and rotated in 10-degree increments from -10 degrees (head down) to +30 degrees (head up). Cross-sectional B-mode image was used to monitor continuously CFV diameter for 5 minutes in each position. Doppler flow patterns were recorded in longitudinal axis; heart rate and respiratory movements were also noted. CFV flow was affected by respiratory and cardiac events. At -10 degrees flow was primarily related to cardiac events, with flow increasing during diastole. At +30 degrees flow varied minimally with the cardiac cycle and was primarily respiration dependent, stopping at peak inspiration. Proceeding from -10 to +30 degrees the mean maximal CFV diameter corrected for body surface area increased 92% (0.47 +/- 0.11 cm/m2 to 0.90 +/- 0.16 cm/m2, p less than 0.001), whereas peak flow velocity decreased from 41 +/- 10 cm/sec to 13 +/- 5 cm/sec, p less than 0.001. There was a linear, inverse relationship between mean peak velocity and mean corrected diameter, r = -0.99. The study confirms the multiple influences on venous flow patterns and establishes a quantitative relationship between venous diameters and flow velocities.

Adult↗
PubMed1988

Progression of lower-extremity arterial occlusive disease in type II diabetes mellitus.

The prevalence of lower-extremity arterial occlusive disease (LEAOD), the progression of LEAOD, and the incidence of new LEAOD were determined by noninvasive method in 410 volunteers between the ages of 50 and 70 yr; 252 individuals had type II (non-insulin-dependent) diabetes, 158 were control subjects. LEAOD was monitored with the ankle/arm systolic blood pressure index in combination with Doppler arterial velocity waveform analysis. LEAOD was much more prevalent in the type II patients (22%, 55 of 252) than in the control subjects (3%, 4 of 158) (P less than .00001). The prevalence of risk factors for LEAOD was much higher in the type II patients, including elevated triglyceride, depressed high-density lipoprotein (HDL) cholesterol, hypertension, smoking, and elevated systolic blood pressure. In type II diabetic patients the incidence of new LEAOD over a 2-yr period (14%, 28 of 197) was lower than the incidence of LEAOD progression (87%, 45 of 52). Type II patients with LEAOD also had a high incidence of mortality (22%, 12 of 55) compared with those without LEAOD (4%, 8 of 197) (P less than .0005). A risk score including smoking history, duration of diabetes, depressed HDL cholesterol, total cholesterol, elevated systolic blood pressure, and low obesity index is related to LEAOD. After accounting for the effect of all of the risk factors, we suggest that type II diabetes contributes additional risk for LEAOD.

Aged↗
PubMed1988

Duplex scanning for diagnosis of peripheral arterial disease.

At the beginning of the 1970's, duplex scanning was developed to delineate arteriosclerotic changes in the region of the carotid bifurcation. Technical improvements subsequently enabled duplex scanning for evaluation of the peripheral arterial system, the mesenteric arteries and lastly, the renal arteries and the deep veins. Ultrasonic frequencies between 2.5 and 10 MHz are necessary for image processing. The B-image alone is not sufficient to assess the severity of stenoses, however, it serves as a guide for positioning the sample volume to analyze the segmental changes in velocity. Based on the flow profile, the degree of stenosis is classified as normal, 1 to 19%, 20 to 49%, 50 to 99% and total occlusion. The blood vessels of each leg are divided into seven segments and the results of duplex scanning and concurrently performed angiography in a total of 50 patients were compared. The duplex sonographic results were superior to those obtained with angiography as determined by two independent observers. Angiography remains the decisive method if surgical or angioplastic methods are considered. The angiographic assessment of stenosis severity in one plane only is however a matter regarded with increasing criticism. Consequently, duplex sonographic measurements of the pressure gradient at rest and after vasodilatation have been carried out and hemodynamic relevance specified by the criteria of a pressure gradient of more than 10 mm Hg at rest and 20 mm Hg after injection of papaverine. As compared with sonographic evaluation of aorto-iliac segments, the angiographic assessment yielded a relatively high rate of false positive and false negative findings. Duplex scanning appears to be a meaningful alternative for assessment of stenosis severity.

Aorta, Abdominal↗