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Biomedical subjects

D E Strandness

Publications and source records attributed to D E Strandness.

At least 163 records · Page 9Linked to original sources
PubMed1988

Duplex ultrasound scanning in the diagnosis of renal artery stenosis: a prospective evaluation.

Since ultrasonic energy can be used to interrogate vessels at great depth, it is only natural that it should be applied to deeply placed arteries in the abdomen. Early studies suggested that high-grade stenoses of the renal artery could be detected by this approach as long as the peak systolic velocity in the renal artery was normalized by that measured in the abdominal aorta. A retrospective study comparing the peak velocity in the renal artery to that from the adjacent abdominal aorta (the renal aortic ratio) showed that if this value exceeded 3.5, it is likely to be associated with a greater than 60% diameter-reducing stenosis. To test this hypothesis, we used duplex scanning to prospectively evaluate 58 renal arteries in 29 patients in whom arteriograms were available. There were 39 renal arteries with 0% to 59% stenosis, 14 with 60% to 99% stenosis, and five occlusions by angiography. Renal duplex scanning accurately diagnosed 38 of 39, 11 of 14, and four of five of these, respectively, giving a sensitivity of 84%, a specificity of 97%, and a positive predictive value of 94% for the detection of a greater than 60% diameter-reducing stenosis. The overall agreement with angiography was 93%. These data show that renal duplex scanning can be used to diagnose renal artery stenosis in patients with hypertension or renal dysfunction, thus providing a rational basis for the selection of patients for angiography.

Adolescent↗
PubMed1987

Variability in measurement of specific parameters for carotid duplex examination.

The variability of four carotid artery frequency parameters used for classifying disease with duplex scanning was prospectively studied. Forty-eight patients (94 patent carotid arteries) were each examined by two technologists. Measured parameters were the peak systolic frequency (PSF) and the first zero slope from the common carotid artery, and the PSF and end diastolic frequency (EDF) from the internal carotid artery. Measurements from all the examinations were made twice by each technologist. Interobserver, intraobserver, and interpatient variability in measurement of the first zero slope was so great that we have abandoned its use. Measurement of variability for PSF and EDF was much less (correlation coefficients 0.68 to 0.92). These parameters were measured with sufficient precision to warrant their continued use for important decision steps in classifying carotid artery disease. Interpatient differences in PSF sufficient to cause disagreement regarding the hemodynamic significance of carotid disease occurred in only three instances. In each of these cases the differences were due to examination technique (failure to identify a very distal internal carotid artery stenosis, difficulty distinguishing between a kink and a stenosis, and failure to recognize an improper Doppler angle). We conclude that the variability of PSF and EDF is within clinically acceptable levels and is mainly due to examination technique rather than measurement of waveform parameters or changes in patient hemodynamics.

Arterial Occlusive Diseases↗
PubMed1987

Noninvasive assessment of normal carotid bifurcation hemodynamics with color-flow ultrasound imaging.

The combination of a B-mode imaging system and a single range-gate pulsed Doppler flow velocity detector (duplex scanner) has become the standard noninvasive method for assessing the extracranial carotid artery. However, a significant limitation of this approach is the small area of vessel lumen that can be evaluated at any one time. This report describes a new duplex instrument that displays blood flow as colors superimposed on a real-time B-mode image. Returning echoes from a linear array of transducers are continuously processed for amplitude and phase. Changes in phase are produced by tissue motion and are used to calculate Doppler shift frequency. This results in a color assignment: red and blue indicate direction of flow with respect to the ultrasound beam, and lighter shades represent higher velocities. The carotid bifurcations of 10 normal subjects were studied. Changes in flow velocities across the arterial lumen were clearly visualized as varying shades of red or blue during the cardiac cycle. A region of flow separation was observed in all proximal internal carotids as a blue area located along the outer wall of the bulb. Thus, it is possible to detect the localized flow patterns that characterize normal carotid arteries. Other advantages of color-flow imaging include the ability to rapidly identify the carotid bifurcation branches and any associated anatomic variations.

Adult↗
PubMed1987

Assessment of pressure gradient by Doppler ultrasound: experimental and clinical observations.

Three methods for estimating peripheral artery pressure gradients from ultrasound data were assessed by means of an acute canine aortic coarctation with a variable stenosis and retrospective data from 18 patients with iliac stenoses who had duplex scanning studies and pressure measurements at the time of angiography. The measured pressure difference was correlated with end-diastolic velocity, the presence or absence of reverse flow in diastole, and a pressure difference calculated with the modified Bernoulli equation. Although the calculated pressure gradients correlated well with measured values in animal studies (11 animals, r = 0.78, n = 224, SD = 8.1), they did not in the clinical studies (r = 0.54, n = 33, SD = 28). In both cases, pressure gradients were consistently overestimated for mild stenoses. There was a strong correlation between end-diastolic velocity and pressure gradient (r = 0.71, n = 94, SD = 5.2 for animal studies; r = 0.81, n = 36, SD = 23 for clinical studies), but the data were too variable to provide useful pressure estimates. In clinical studies the absence of reverse flow in diastole at the site of the stenosis was the best indicator of a resting pressure gradient of greater than 15 mm Hg. We conclude that the modified Bernoulli equation and end-diastolic velocity correlate highly with the pressure gradient but are not clinically useful because the variability is too great. The absence of reverse flow in diastole is a more reliable indicator of hemodynamically significant stenosis.

Animals↗
PubMed1987

Duplex scanning for diagnosis of aortoiliac and femoropopliteal disease: a prospective study.

We compared ultrasonic duplex scanning and angiography for the localization and classification of arterial stenoses and occlusions in 32 patients. The criteria for the detection of a greater than 50% diameter reducing stenosis was an increase in peak systolic velocity of greater than 100%, loss of reverse flow, and spectral broadening. Duplex studies and angiograms were evaluated in a blinded fashion. The agreement between duplex scanning and angiography for the 383 arterial segments studied was not significantly different than the previously reported agreement between two different radiologists reading the same angiograms (kappa of 0.55 vs 0.63). For detecting stenoses that were greater than 50% diameter reducing by angiography, duplex scanning had a sensitivity of 82%, a specificity of 92%, a positive predictive value of 80%, and a negative predictive value of 93%. These results are as good as previously reported comparisons between two different radiologists' readings of the same angiograms.

Aged↗
PubMed1986

Ultrasound in the study of atherosclerosis.

Ultrasound has come to play an increasingly important role in investigating atherosclerosis. The simple, continuous wave directional devices may be used to measure limb blood pressure and assess velocity patterns from accessible arteries. The recent combined B-mode and pulsed Doppler systems are being used regularly to study the carotid bifurcation in the neck. With improvements in image resolution, Doppler technology and signal processing methods, it is now feasible to evaluate the morphology of the plaque and accurately predict the degree of stenosis by the recorded velocity changes in the residual lumen. By the development of transducers of low transmitting frequency (less than 5 mHz), it is now possible to evaluate arteries at greater depth such as the renal and mesenteric vessels. Duplex scanning promises to become the definitive, noninvasive method of assessing both the anatomy and flow characteristics of all major arteries outside the thorax and skull that are common sites for the development of atherosclerosis.

Arterial Occlusive Diseases↗
PubMed1986

Diastolic flow as a predictor of arterial stenosis.

With a pulsed Doppler imaging system, it is now possible to interrogate sites from the aorta to the popliteal trifurcation. To determine which velocity parameters could be correlated with the degree of disease as determined by angiography, 34 arterial stenoses identified by scanning were also evaluated by contrast arteriography and classified in 10% increments. The angiographic readings were blinded with respect to the scan results. Four hand-measured parameters from velocity waveforms obtained at the site of stenosis were correlated with the angiogram--peak systolic velocity, systolic rise time, diastolic reverse velocity, and diastolic reverse flow time. When diastolic reverse flow was absent, diastolic forward flow was recorded. To describe diastolic flow along a continuum, diastolic reverse velocity was ascribed a positive value and diastolic forward velocity was ascribed a negative value. A systolic velocity gradient (peak velocity/rise time) was also calculated. The relationship between the angiographic categories and the measured parameters was evaluated with the Jonkheere-Terpstra trend test. A trend was determined with diastolic flow (diastolic reverse flow or diastolic flow velocity) that was significant (p less than 0.01). The linear regression was calculated (y = 40.8 + [-5.6X]), and correlation coefficient was obtained (r = 0.76) that was statistically significant (p less than 0.01). The method enables mapping and calculation of arterial stenoses by noninvasive means. This can be expected to obviate the need for diagnostic angiograms in certain and select cases in which angioplasty can be expected to be beneficial. It also affords a convenient quantitative means of following lesions over time.

Angiography↗
PubMed1986

Use of hemodynamic parameters in the diagnosis of mesenteric insufficiency.

To evaluate the hemodynamic characteristics of the normal mesenteric circulation, five parameters of the velocity waveforms were measured in 15 normal subjects in the celiac and superior mesenteric arteries (SMA) in the pre- and postprandial periods. It was noted that changes in celiac artery flow after eating was minimal, indicating that this vessel's major supply function is not to the gut. SMA parameters showing the most significant and consistent changes after a meal were the diastolic reverse flow and diastolic forward flow (DFF). Four patients referred with symptoms of intestinal angina underwent scanning and subsequent angiography of their mesenteric circulation. All four exhibited loss of reverse flow in the SMA. The change in DFF in the SMA was statistically significant (p = 0.01). Change in peak systolic velocity in the celiac artery was marginally significant (p = 0.05). Angiography revealed that three patients had greater than 90% stenosis of both vessels. The fourth patient had a 90% celiac artery and 65% SMA stenosis. The technique described offers the first noninvasive means of identifying mesenteric insufficiency. It is an effective screening method for a disease entity difficult to verify without selective arteriography. The use of velocity waveform parameters giving good discrimination between normal subjects and those with stenoses of the visceral arteries should reduce both the incidence of missed diagnosis and unnecessary angiography.

Adult↗
PubMed1986

Noninvasive diagnosis of renal artery stenosis by ultrasonic duplex scanning.

We retrospectively studied the results of duplex scanning for evaluation of renal artery disease in 158 patients. Satisfactory examinations were achieved in 144 patients (90%). Arteriograms were available for 43 renal arteries. We used the ratio of the peak velocities in the renal artery and the aorta (RAR) to separate nonstenotic arteries (less than 60% diameter reduction) from stenotic arteries (greater than 60% diameter reduction). With an RAR of greater than 3.5 to indicate stenotic lesions, duplex scanning had a sensitivity of 91% (20 of 22 diseased arteries correctly identified) and specificity of 95% (20 of 21 normal or insignificantly diseased arteries correctly identified). One of four occluded arteries was incorrectly interpreted as patent because of misidentification of a collateral vessel. Prospective studies will be necessary to validate this test and establish other criteria for a more detailed classification of renal artery stenosis. The ratio of the end-diastolic to peak systolic velocities in the renal artery (EDR) tended to decrease with increasing serum creatinine levels, presumably because renal vascular resistance increases with end-stage parenchymal disease. EDR may prove useful in the detection of advanced parenchymal disease before renal artery revascularization is attempted.

Aorta, Abdominal↗
PubMed1986

Carotid artery occlusion: natural history.

During a 5-year period, 212 patients (170 men and 42 women, median age 65 and 64 years, respectively) were diagnosed as having internal carotid artery occlusion. Mean follow-up was 24.9 months. Five-year cumulative survival and stroke-free rates by life-table analysis were 62% and 75%, respectively. Deaths were due to stroke in 7 of 40 patients (17%) and were of cardiac origin in 22 of 40 patients (55%). The strokes were ipsilateral in 20 of 31 patients (65%). No statistically significant difference between the sexes could be demonstrated for either death or stroke, nor was age correlated with stroke during follow-up. Diabetes and hypertension increased the risk of stroke, whereas gender and aspirin consumption had no discernible effect. Endarterectomy of the opposite carotid artery did not significantly affect the natural history but did reduce the stroke rate in the territory of the operated artery. Presenting symptoms were useful for estimating prognosis. Twenty-two of 111 patients referred for stroke (20%) suffered a further stroke and 21 of 111 patients (19%) died (three were stroke-related), whereas of those patients referred for transient ischemic attack (TIA), only 2 of 42 patients (5%) suffered a stroke and none died. TIAs occurred in 23 patients (11%) during follow-up, and these were premonitory for stroke in three cases (13%). The limited value of TIA in predicting stroke and the high mortality rate unrelated to stroke in this group are important considerations when therapy is considered for these patients.

Actuarial Analysis↗
PubMed1985

An objective assessment of the physiologic changes in the postthrombotic syndrome.

To determine what physiologic changes might contribute to the development of the postthrombotic syndrome, venous outflow, venous refilling time, and valvular competence were assessed in 32 patients (39 limbs) with documented deep venous thrombosis. The follow-up ranged from nine to 144 months (mean, 41 months) after the acute deep venous thrombosis. Pain was noted by 49% of the patients, but more objective end points occurred less frequently (edema, 21%; pigmentation, 26%; ulceration, 3%). Venous outflow was lower in the affected limbs but was not a good indicator of those patients with or without symptoms. Venous refilling time after calf compression was markedly reduced in limbs with incompetent valves (mean +/- SD, 8.4 +/- 3.8 s v 25.3 +/- 12.1 s), as well as in those with edema, pigmentation, and ulceration. It appears that most of the sequelae of the postthrombotic syndrome can be attributed to the loss of valvular function.

Adult↗
PubMed1985

Echo-Doppler (duplex) ultrasonic scanning.

The combination of pulsed echo with pulsed Doppler provides a system that is capable of imaging peripheral arteries and veins and evaluating velocity patterns across suspected areas of narrowing. The method has been most widely applied to the evaluation of carotid artery disease for the detection and grading of lesions in the carotid bulb. Recent experience has suggested that the technique may also be applied to the vessels of the limb, the abdominal aorta, visceral arteries, and the deep veins. The use of this method is indicated for screening purposes and long-term follow-up of patients who have or have not had surgery.

Abdomen↗
PubMed1985

Carotid endarterectomy. Relationship of outcome to early restenosis.

The results following carotid endarterectomy were prospectively evaluated in 134 patients (145 sides) by repeat ultrasonic duplex scanning and clinical evaluation extending for a period of 4 years. There were 107 men and 27 women in the study group. The perioperative stroke rate was 1.3% and the mortality rate, 0.7%. There were 9 late deaths, of which two were stroke related (1.4%). Focal symptoms occurred in 12 patients on the ipsilateral side, six of which were strokes (one lacunar). The remaining symptoms developed in the presence of moderate degrees of carotid stenosis (less than 50%). There were seven patients who had transient ischemic attacks (TIAs) referable to the operated side, but only two of these were associated with a recurrent high-grade stenosis. During follow-up 32 (22%) patients had recurrent high-grade stenosis. Restenosis regressed in seven, giving a persistent rate of 17.1%. The incidence of restenosis was significantly higher in women (p less than 0.01). By life-table analysis, restenosis occurred early, the majority within 24 months. There was no consistent association between the development of symptoms and the occurrence of restenosis. Therefore, it is concluded that there is no justification for reoperation based on the degree of narrowing observed to prevent subsequent TIAs and strokes.

Aged↗