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Biomedical subjects

D E Strandness

Publications and source records attributed to D E Strandness.

At least 127 records · Page 7Linked to original sources
PubMed1991

Status of the valves in the superficial and deep venous system in chronic venous disease.

The relationship between the functional status of the venous valves in the superficial and deep veins and ulceration was evaluated in 42 patients. Twenty-five patients had ulcers, 12 of these patients had a history of previous deep venous thrombosis and 13 of these patients denied such an event. Seventeen patients had normal ankle skin, 10 of these patients had a documented history of deep vein thrombosis and seven of these patients had varicose veins only. An ultrasonic duplex scanner was used to document the presence of reflux in all segments of the superficial and deep system. In the entire group of 25 limbs with ulceration, valvular incompetence was noted in 22 limbs at levels involving segments that communicated with the ulcer-bearing area. Of the 17 limbs with normal ankle skin, in only two instances was a single segment of posterior tibial vein in midcalf found to be incompetent. For those patients with normal ankle skin and a history of varicose veins, the deep veins below the common femoral vein level were always competent.

Age Factors↗
PubMed1990

The mechanism of venous valve closure. Its relationship to the velocity of reverse flow.

Venous valves will close when the reversal of the normal pressure gradient generates a sufficient reverse flow velocity. By testing 20 healthy subjects with ultrasonic duplex scanning and controlled limb compression. It was found that the velocity of reflux is related to the external compression pressure. Valve closure is an abrupt cessation of reverse flow. In this study, with subjects in a supine position, valve closure was achieved only after reverse velocities exceeded 30 cm/s. This velocity was not generated by manual compression of the limb. With a Valsalva maneuver, this velocity is achieved only in the common femoral vein in 90% of the tested individuals. The reflux velocities in response to a Valsalva maneuver are progressively lower in more distal veins--the profunda femoris, the superficial femoral vein, and the popliteal vein. With reverse velocities lower than 30 cm/s, the valves will not close and reflux can persist. Valsalva's maneuver only allows a diagnosis of valvular competence at the most proximal level in the venous tree.

Blood Flow Velocity↗
PubMed1990

Estimation of hepatic blood flow in branches of hepatic vessels utilizing a noninvasive, duplex Doppler method.

The measurement of hepatic blood flow by indirect methods such as indocyanine green clearance has several limitations. The duplex Doppler offers the potential for noninvasive, real-time measurement of blood flow and has been employed in the evaluation of arterial disease in a variety of vascular beds. We evaluated Doppler ultrasound estimation of blood flow in branches of the hepatic artery, hepatic vein, and portal vein in 12 healthy subjects on two separate days. In vitro accuracy of the scanner was assessed using phantom targets of known diameter and velocity. Blood velocity and vessel diameter measurements were obtained five times over a period of 2 hours. No significant differences were seen in velocity or blood flow measurements within or between days. The interday coefficients of variation, which include intrasubject variability, were 10-15% and 14-20% for velocity and blood flow measurements, respectively. This study demonstrates the potential utility of Doppler ultrasound to detect intrinsic, drug, or disease-induced changes in hepatic blood flow.

Adult↗
PubMed1990

Can duplex scanning replace arteriography for lower extremity arterial disease?

This preliminary study was undertaken to determine if surgeons would choose different intervention for lower extremity occlusive disease when given basic clinical information and data from either a duplex scan or arteriogram. Information on degree of stenosis from duplex scans and arteriograms of 29 patients was indicated on an anatomical line drawing along with the ankle blood pressures and a brief clinical description. Based on these data sheets, six vascular surgeons chose a clinical plan in a blinded fashion for each patient. Each plan was placed into one of eight possible categories for comparison using the kappa statistic. Intraobserver agreement between surgeons' decisions based on duplex scanning versus those based on arteriography was very good (mean kappa .70 with exact agreement in 76%). Interobserver agreement between different surgeons' decisions based on the same studies was significantly less (mean kappa 0.56, p less than .05). Significant disparity in clinical approach occurred in 43% of the patients with nearly identical duplex scan and arteriogram reports, suggesting that much of the discrepancy lies in the clinical decision-making process. Clinical decisions made using duplex scans are very similar to those made using arteriograms. This technique can limit the need for arteriography in assessing patients with lower extremity arterial occlusion disease.

Angiography↗
PubMed1990

Pancreaticoduodenectomy and the celiac artery compression syndrome.

Celiac compression is usually a benign condition, but when surgery necessitates division of collaterals from the superior mesenteric artery, it may cause life-threatening gut ischemia. We report a case of cholangiocarcinoma necessitating pancreaticoduodenectomy in a patient with celiac artery compression by the median arcuate ligament. Preoperative duplex scanning confirmed the celiac stenosis and revealed retrograde flow through collaterals from the superior mesenteric artery. Intraoperative continuous wave Doppler examination revealed that gastric blood flow disappeared with compression of the superior mesenteric artery. This maneuver no longer affected gastric flow after transection of the compressing structures at the celiac origin. Preoperative identification of celiac artery stenosis is crucial to prevent small bowel ischemia and possible anastomotic breakdown or liver failure. Duplex scanning can provide important insight about collateral circulation, and intraoperative Doppler testing can assess the adequacy of revascularization.

Adenoma, Bile Duct↗
PubMed1990

Visualization of calf veins by color flow imaging.

Both indirect and direct noninvasive tests have been shown to be useful for the detection of deep venous thrombi involving the proximal veins (popliteal to inferior vena cava). However, thrombi that are confined to the calf veins will not affect venous outflow and cannot be detected by the plethysmographic methods. B-mode imaging, while excellent for the major deep veins, is also limited in the calf region because the veins are small, and imaging resolution is not always adequate to permit visualization of these smaller veins. With the availability of duplex scanning with "slow flow" color capability, these veins lend themselves to study. In 30 normal subjects, we were able to visualize all paired veins from the level of the ankle to the popliteal fossa. The clinical implications of this approach are discussed.

Adolescent↗
PubMed1990

A triangulation method for the quantitative measurement of arterial blood velocity magnitude and direction in humans.

A triangulation method has been applied to a duplex ultrasound scanner to quantify blood flow velocities in two dimensions. A position locating system (PLS) connected to the scanhead locates the sample volume (SV) in 3-D space to a precision of 1 mm. The PLS is used to obtain flow velocity data from two independent lines of sight in the human femoral artery. Data are gathered from anatomic sites of interest along one line of sight. Later the computer directs the SV to interrogate the same points in space from a second line of sight. Water tank studies using both constant velocity and pulsatile string targets were used to validate the method. Velocity magnitudes could be calculated to within 5% error for Doppler angles below 75 degrees for various string depths and speeds; the error in Doppler angle calculation was usually less than 3 degrees. Results from the superficial femoral artery show flow velocity vectors are nearly parallel to the vessel walls. Peak systolic velocity magnitudes range from 63-66 cm/s in three presumed normal individuals. Following the validation studies addressed in this paper, this triangulation approach is intended in future work to document the complex nonaxial character of blood flow that occurs normally at branch points and in regions of intraluminal disease.

Blood Flow Velocity↗
PubMed1990

Duplex scanning in diagnosis of renovascular hypertension.

Ultrasonic duplex scanning can be used as a noninvasive method for the detection and quantification of the degree of renal artery stenosis. The method is useful for screening patients with hypertension that cannot be controlled by medical means. It can also serve as a method of following the results of intervention via surgery or angioplasty.

Constriction, Pathologic↗
PubMed1990

Functional status of the deep venous system after an episode of deep venous thrombosis.

An episode of deep venous thrombosis is often followed by the opening of collaterals, fibrinolysis, recanalization and valvular dysfunction. The effect of these processes on the peak flow velocity in the superficial femoral and popliteal veins after simulated contraction of the calf muscles was tested in a group of normal subjects and three groups of patients who had deep venous thrombosis. There were 12 patients followed less than two years with no skin changes. The second group consisted of 12 patients followed for 8-15 years without ulceration. The third group of 12 patients had active or healed ulcers. The peak flow velocity in the superficial femoral and popliteal veins was assessed by rapidly inflating cuffs about the calf and ankle to 100 mmHg. The velocities generated by cuff compression were lower in patients than in normal subjects. This was particularly true in the superficial femoral vein. This change in velocity may be secondary to incomplete recanalization with resulting stenosis or valvular incompetence in the calf.

Adolescent↗
PubMed1990

Single and multiple doses of oral cimetidine do not change liver blood flow in humans.

Liver blood flow was measured in 10 healthy men for 6 hours after single (300 mg) and multiple (300 mg every 6 hours for 5 days) oral doses of cimetidine. Blood flow measurements were determined in the superior mesenteric and hepatic arteries and in the intrahepatic branches of the portal and hepatic veins by use of a duplex Doppler ultrasound technique. Compared with baseline measurements obtained before drug administration, cimetidine treatment did not change blood flow in any of the four blood vessels. Cimetidine serum concentrations and pharmacokinetic parameters were similar to those reported in other studies conducted in healthy adults. The findings of this study indicate that single and multiple 300 mg doses of oral cimetidine do not change liver blood flow.

Administration, Oral↗
PubMed1990

Fate of the carotid artery contralateral to endarterectomy.

The management of internal carotid artery disease contralateral to endarterectomy is highly controversial. At our institution we have adopted an approach by which patients are followed with serial duplex scanning after unilateral carotid endarterectomy. Surgery on the contralateral carotid artery is recommended for patients who exhibit ischemic neurologic symptoms or develop an 80% to 99% carotid stenosis. This strategy is based on previous reports that have documented an increased incidence of strokes in these two groups of patients. As a result, 40 patients among a study population of 200 underwent carotid endarterectomy on the originally unoperated side. The current study reviews the natural history of the patients who were followed without or before operation of the contralateral carotid artery in an attempt to identify other cohorts at increased risk for stroke. Patients were followed for up to 126 months after unilateral carotid endarterectomy (mean, 54 months). Six patients were lost to follow-up (3.0%). By life-table analysis the estimated mean annual rate of progression to greater than or equal to 50% diameter reduction was 3.9% and 1.2% for progression to greater than or equal to 80% stenosis. Only two patients went on to occlusion during follow-up. Neurologic events referable to the contralateral carotid distribution were infrequent. The estimated mean annual rate was 2.9% for transient ischemic attacks and less than 0.8% for strokes. Case history review of the six patients who had strokes during follow-up suggested that only one patient may have benefited from carotid endarterectomy. Conservative management with serial duplex scanning of the unoperated, contralateral carotid artery appears appropriate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Testing ultrasonic pulsed Doppler instruments with a physiologic string phantom.

The spatial, temporal, and frequency resolution of conventional ultrasonic Doppler instruments and the time/space distortions in two-dimensional color Doppler imaging systems can be measured using a pulsatile moving string target. The diameter of the string is small compared with the Doppler sample volume, the velocity (speed and direction), acceleration and timing of the string motions are precisely known with reference to the R wave timing mark, and the spatial location of the string is known. A loop of surgical thread or monofilament fishline running between pulleys is driven by a motor that provides constant string speeds from 0.05 to 150 cm/s and variable string speeds programmed to mimic arterial velocity waveforms from the carotid, aortic, and femoral arteries. Constant string speeds are used to evaluate the Doppler sensitivity, frequency processing, and sample volume size; pulsatile movement of the string provides a physiologic model to evaluate the temporal performance of conventional Doppler systems and the temporal and spatial performance of two-dimensional color Doppler imaging scanners.

Blood Flow Velocity↗
PubMed1990

Duplex scanning of normal or minimally diseased carotid arteries: correlation with arteriography and clinical outcome.

This study evaluated the role of duplex scanning in the management of patients with normal or minimally diseases carotid arteries. Carotid duplex scans were interpreted according to previously established criteria and considered normal when pulsed Doppler spectral waveforms showed laminar flow or only minor flow disturbances. Normal flow patterns were noted by duplex scanning in 100 carotid bifurcations of 72 patients who also underwent carotid arteriography. Neurologic symptoms (amaurosis fugax, transient ischemic attack, or stroke) were present in relation to 23 arteries and absent in relation to 77 arteries. On the 23 symptomatic sides arteriography was interpreted as normal in eight, 1% to 15% stenosis in 14, and 16% to 40% stenosis in one. For the 77 asymptomatic sides, arteriography showed normal vessels in 15, 1% to 15% stenosis in 43, and 16% to 40% stenosis in 19. One symptomatic patient was treated by carotid endarterectomy for an irregular 1% to 15% stenosis. None of the asymptomatic lesions were in the range of 80% to 99% stenosis, which would justify endarterectomy for asymptomatic disease. Clinical follow-up for a mean interval of 28 months on 20 of the 22 symptomatic patients not undergoing surgery revealed no strokes and transient recurrent symptoms in two patients. Assuming that the single operation in this study was indicated, duplex scanning correctly identified lesions not requiring carotid endarterectomy in 96% (22/23) of the symptomatic patients. A normal duplex scan also predicted a benign clinical outcome without operation. Duplex scanning can reliably exclude surgically treatable carotid bifurcation lesions in asymptomatic patients, and endarterectomy is rarely indicated in symptomatic patients with normal duplex scan results. This study supports a nonoperative therapeutic approach for most patients with neurologic symptoms and a normal carotid duplex scan on the appropriate side.

Angiography↗