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Biomedical subjects

J P Archie

Publications and source records attributed to J P Archie.

At least 55 records · Page 3Linked to original sources
PubMed1990

Pulsatile two-dimensional flow and plaque formation in a carotid artery bifurcation.

Velocity and pressure fields, streamlines and wall shear stress distributions were numerically obtained for two-dimensional, steady and pulsatile flow in a carotid artery segment. Distinct regions of reverse flow near the bifurcation and wavy flow patterns in the branching channels were observed during portions of the pulse. These phenomena disappear at the end of the systolic phase of the cardiac cycle. A previously validated plaque formation model predicts that plaque sites and the local extent of atherosclerotic lesions are similar for those present on human angiograms.

Arteriosclerosis↗
PubMed1990

Some determinants of papaverine-induced femoral artery pressure gradients.

The accuracy and reliability of papaverine-induced central arterial to common femoral artery pressure gradients, frequently used to estimate the hemodynamic significance of aortoiliac stenosis, depend on a reproducible, between patient increase in resting common femoral artery blood flow because of the linear relationship between pressure gradient and flow. Blood flow variability and the effect of proximal and distal occlusive disease on femoral artery pressure gradient and flow were determined by three methods: intraoperative electromagnetic blood flow measurements, hemodynamic model analysis, and flow calculations using intraoperative segmental resistance measurements. The ratios of papaverine-induced hyperemic to resting common femoral artery blood flow were 2.80 +/- 0.781 (mean +/- 1 SD, n = 19) for occluded and 3.07 +/- 0.819 (n = 13, P greater than 0.5) for open superficial femoral arteries, respectively, when the papaverine-induced central arterial to common femoral artery mean pressure gradient was less than 10 mm Hg. The flow ratios were 2.70 +/- 1.093 (n = 16) and 2.93 +/- 1.027 (n = 10, P greater than 0.5) for superficial femoral occlusion and patency, respectively, when the central to femoral mean pressure gradient was greater than or equal to 10 mm Hg. Hemodynamic model analysis predicts that superficial femoral artery occlusion reduces the hyperemic to resting common femoral artery flow ratio from 2 to 1.8 and from 3 to 2.5. The mean values of segmental resistance measured intraoperatively in 17 additional limbs with and in 17 without superficial femoral occlusion predict a reduction in flow ratios from 2 to 1.75 and from 3 to 2.44 when the superficial femoral is occluded.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1990

Carotid patch angioplasty: immediate and long-term results.

To determine the benefit of carotid patch angioplasty, a retrospective study of 1000 consecutive carotid endarterectomies was done. Based on the type of carotid endarterectomy closure, patients were divided into four groups: 250 had primary closure, 250 had expanded polytetrafluoroethylene patch, 250 had Dacron patch, and 250 had saphenous vein patch. On the basis of operative technique or type of carotid artery closure, no statistical difference was found in the incidence of postoperative stroke (p greater than 0.25): primary closure 1.6% (4), expanded polytetrafluoroethylene 2.0% (5), Dacron patch 1.6% (4), and saphenous vein patch (0). Postoperative carotid patency was determined by B-mode ultrasonography, and 717 patients were evaluated in follow-up extending to 6 years (mean 37.8 months). Based on the method of carotid endarterectomy closure, no significant difference (p greater than 0.25) was found in the incidence of significant restenosis (greater than 50% diameter reduction): primary closure 4.0% (7), expanded polytetrafluoroethylene 4.0% (6), Dacron 5.4% (9), and saphenous vein 1.0% (2). Significant restenosis was most frequent in habitual smokers (93%, 25/28) and females (78%, 22/28) despite the method of carotid endarterectomy closure. No statistical difference was found in the incidence of late ipsilateral stroke either (p greater than 0.25): primary closure 2.9% (5), expanded polytetrafluoroethylene 2% (3), Dacron 5% (3), and saphenous vein 0%. These results indicate that the incidence of postoperative stroke, regardless of method of arterial closure, was not statistically different. The method of carotid closure did not appear to affect the occurrence of late ipsilateral stroke or restenosis; however, patch angioplasty with saphenous vein appears appropriate in habitual smokers, and likely in patients with small internal carotid arteries.

Blood Vessel Prosthesis↗
PubMed1990

Saphenous vein rupture pressure, rupture stress, and carotid endarterectomy vein patch reconstruction.

Early postoperative patch rupture is a catastrophic complication of carotid endarterectomy reconstruction with greater saphenous vein. Mechanical determinants of saphenous vein rupture were identified by structural measurements and the results applied to carotid endarterectomy patch geometry. Diameter and rupture pressure was measured in fresh saphenous vein segments from the ankle, knee, or thigh in 157 patients undergoing bypass operations. Circumferential hoop rupture stress was calculated and the results were applied to 157 carotid endarterectomy reconstructions. All vein ruptures were in the cylindric axis. The mean vein diameter was 4.58 mm. The mean vein rupture pressure was 2873 mm Hg (3.78 atm). Vein diameter was larger in the thigh than in the ankle or knee (p less than 0.01), but there was no significant difference in rupture pressure between veins from the three locations. Women had a smaller vein diameter than had men at all locations (p less than 0.01). There was a positive linear correlation between vein diameter and rupture pressure. The mean maximum diameter of curvature of 157 carotid endarterectomy reconstructions with a vein patch was 13.3 mm. Multiple random applications of the 157 veins to 157 carotid diameters predicted a mean patch rupture pressure of 1087 mm Hg (1.43 atm), 1163 mm Hg (1.53 atm) for men, and 866 mm Hg (1.14 atm) for women. Predicted vein patch rupture pressures less than 300 mm Hg were found in 5.7% of cases (8.8% women and 1.2% men). Only 0.6% of patients (1.8% women and 0% men) had a predicted rupture pressure less than 200 mm Hg. No veins with a diameter greater than or equal to 4.0 mm had a predicted patch rupture pressure less than 300 mm Hg. These results suggest that small-diameter saphenous veins have a higher risk of rupture when used as a carotid patch.

Blood Pressure↗
PubMed1989

Linear response of collateral cerebral perfusion pressure during carotid clamping.

Phenylephrine is frequently used to increase systemic arterial pressure during carotid endarterectomy. However, little is known of its effect on collateral cerebral perfusion pressure, particularly in patients with high collateral cerebral vascular resistance who are at increased risk of cerebral ischemia during carotid clamping. We tested the hypothesis that this subset of patients can have collateral perfusion pressure, and hence collateral cerebral blood flow, increased in a predictable way by elevating systemic arterial pressure. We measured mean systemic arterial pressure (Pa), jugular venous pressure (Pv), and mean carotid back pressure (Pc), and calculated collateral cerebral perfusion pressure (P = Pc - Pv) and the ratio of collateral to ipsilateral hemisphere cerebral vascular resistance (Rc/Rh) in 18 patients with low P. Initial measurements were Pa = 84 +/- 8.8 (mm Hg, mean +/- SD), Pv = 7.8 +/- 3.9, Pc = 26 +/- 5.1, P = 18 +/- 4.5 and Rc/Rh = 3.4 +/- 1.15. During phenylephrine infusion, Pa = 108 +/- 11, Pc = 32 +/- 6.5, and P = 24 +/- 7.2, increases of 29, 23, and 33%, respectively (P less than 0.05). Unchanged were Pv = 8.2 +/- 4.1 (5%) and Rc/Rh = 3.5 +/- 1.30 (3%) (P greater than 0.8). The latter two findings indicate that cerebral perfusion pressure and mean systemic arterial pressure are linearly related according to the fluid mechanics equation governing these parameters: Pa = P(Rc/Rh + 1) + Pv. These results support the use of phenylephrine to increase collateral blood flow during carotid endarterectomy in patients with low cerebral perfusion pressure.

Blood Pressure↗
PubMed1989

Fluid flow and plaque formation in an aortic bifurcation.

Considering steady laminar flow in a two-dimensional symmetric branching channel with local occlusions, a finite element model has been developed to study velocity fields including reverse flow regions, pressure profiles and wall shear stress distributions for different Reynolds numbers, bifurcation angles and lumen reductions. The flow analysis has been extended to include a new submodel for the pseudo-transient formation of plaque at sites and deposition rates defined by the physical characteristics of the flow. Specifically, simulating the onset of atherosclerotic lesions, sinusoidal plaque layers have been placed in areas of critically low wall shear stresses, and simulating the growth of particle depositions, plaque layers have been added in a stepwise fashion in regions of critically high and low shear. Thus two somewhat conflicting hypothetical correlations between critical wall shear stress levels and atheroma have been tested and a solution has been postulated. The validated computer simulation model is a predictive tool for analyzing the effects of local changes in wall curvature due to surgical reconstruction and/or atherosclerotic lesions, and for investigating the design of aortic bifurcations which mitigate plaque formation.

Aorta↗
PubMed1989

Doppler ultrasound evaluation for lower extremity deep venous thrombosis in a community hospital.

The accuracy of Doppler examination for lower extremity deep venous thrombosis in a community hospital vascular laboratory was determined by comparing the Doppler results with venograms of 97 limbs in 90 patients. There were 47 limbs with a normal Doppler study, 46 abnormal (consistent with deep venous thrombosis) and 4 with an equivocal study. The overall accuracy was 95%. Both the sensitivity and specificity were 94% when equivocal studies were considered abnormal. Based on these results, we recommend venography or repeat Doppler examination for patients with a normal Doppler study only if the clinical findings are strongly suggestive of deep venous thrombosis. Patients with an abnormal Doppler examination and clinical findings consistent with deep venous thrombosis can be treated for deep venous thrombosis, with a high degree of confidence in the diagnosis, without venography. Patients with equivocal Doppler examinations are advised to have a venogram. While our results are equal to the best reports from research-oriented university vascular laboratories it should not be assumed that they can be readily reproduced in other settings. The technologists performing these studies should be highly skilled, experienced and preferably board certified. Internal quality control of any testing facility is necessary to assure accurate and reliable Doppler ultrasonic results prior to recommending treatment of deep venous thrombosis based on Doppler ultrasound without venography.

Hospitals, Community↗
PubMed1988

The relationship of early hypertension following carotid endarterectomy to intraoperative cerebral ischemia.

The relationship between early hypertension following carotid endarterectomy, and intraoperative cerebral ischemia was investigated. Two measures of the adequacy of collateral cerebral circulation during carotid clamping were used: collateral cerebral perfusion pressure (delta P), and the ratio of collateral to ipsilateral cerebral vascular resistance (R/R). Change in blood pressure was measured by the ratio of mean early post to preendarterectomy pressure (P/P). Nitroprusside or nitroglycerin (NN) was used after endarterectomy to maintain systolic blood pressure less than 160 mmHg. The mean values for NN (n = 26) and no NN (n = 81) groups were: delta P = 30.0 and 40.2 mmHg (p less than 0.001); R/R = 1.93 and 1.24 (p less than 0.005); and P/P = 1.03 and 0.857 (p less than 0.001 p by unpaired t test). Linear regression analysis of the two measures of cerebral perfusion with the ratio of post-to preoperative blood pressure gave correlation coefficients between 0.629 and 0.841 with a probability that the slope of the regression line greater than 0 of less than 0.01. Low delta P and high R/R correlate with early postcarotid endarterectomy hypertension. These results support the hypothesis that one determinant of early post endarterectomy hypertension is inadequate collateral cerebral circulation during carotid clamping.

Aged↗
PubMed1988

Learning curve for carotid endarterectomy.

It is generally accepted that training and experience are necessary to obtain acceptably low perioperative mortality and permanent neurologic morbidity for carotid endarterectomy. To test this hypothesis I analyzed the results of 600 consecutive primary carotid endarterectomies that I performed over a 13-year period beginning with my senior residency. The overall hospital mortality was 9/600 (1.5%), the permanent neurologic morbidity 11/600 (1.8%), and the combined mortality and permanent neurologic morbidity 20/600 (3.3%). The mortality for the first 300 operations was 6/300 (2%) (4/6 from stroke) and for the last 300, 3/300 (1%) (3/3 cardiac). All 11 nonfatal strokes occurred in the first 300 operations. Morbidity and mortality decreased with both cumulative experience and the number of operations done per year. While it is difficult to separate the effect of these two factors, the results suggest that both may be important in obtaining a combined perioperative mortality and permanent neurologic deficit below 3%.

Arteriosclerosis↗
PubMed1988

Early postoperative femoral-distal bypass graft failure due to vascular clamp injury induced common femoral artery thrombosis.

Acute early postoperative femoral-distal bypass graft failure associated with profound lower extremity ischemia is unusual because early graft failure commonly reverts leg circulation to the preoperative status. Two cases are reported where the etiology of profound early postoperative ischemia and graft failure were not due to technical aspects of graft reconstruction itself but rather to vascular clamp injury to a severely atherosclerotic common femoral artery with early postoperative common femoral artery, profunda femoris artery and graft thrombosis. This event requires immediate recognition and common femoral artery reconstruction for limb salvage.

Aged↗
PubMed1987

The geometry and mechanics of saphenous vein patch angioplasty after carotid endarterectomy.

To elucidate some of the mechanisms that may account for the potential advantages and disadvantages of saphenous vein patch angioplasty (VPA) after endarterectomy of the carotid artery, the author evaluated 50 VPAs with respect to geometry, blood-flow velocities, and wall mechanics. The mean internal carotid artery (ICA) diameter cephalad to the vein patch was 4.5 mm, whereas the mean diameter of the patched segment was 7.4 mm. The mean ratio between the cross-sectional area of the patched ICA and the cross-sectional area calculated as if the artery were nonpatched was 2.9. In the presence of restenosis sufficient to occlude the nonpatched artery, this ratio was decreased to 1.9 when the artery alone was stenosed and to 0.49 when both the artery and the vein patch were stenosed. The mean ratio between the peak blood-flow velocity distal to the patch and the blood-flow velocity in the patched segment was 3.4. These area and velocity ratios indicate that the wall shear stress in the patched segment was three to five times lower than that in the distal ICA. The normal stress in the circumferential vein patch wall was two to three times greater than that in veins used as bypass grafts at the same intraluminal pressure. In comparison to primary arteriotomy closure after carotid endarterectomy, VPA provides a partially endothelialized flow surface, a significantly greater cross-sectional area, and a relatively mild wall shear stress; all three of these factors may protect the artery against both hemodynamically significant restenosis and early post-operative thrombosis.

Journal Article↗
PubMed1987

Anterior compartment exposure of the distal peroneal artery for bypass grafting.

Occasionally, the distal peroneal artery is the only graftable below-the-knee vessel available for limb salvage; in such cases, surgical exposure of this artery can pose a major technical difficulty. The following article describes a simple, satisfactory method of exposure via the anterior compartment that does not necessitate the removal or fracture of a bone.

Journal Article↗
PubMed1984

Pancreatic cystadenoma with obstructive jaundice.

A 64-year-old woman with painless obstructive jaundice had a 7 cm mass in the head of the pancreas. At operation and biopsy the mass was found to be benign. It was removed by a Whipple procedure, and the diagnosis of cystadenoma was made. A three-year follow-up has been satisfactory.

Cholestasis↗
PubMed1984

Intraoperative assessment of carotid endarterectomy by electromagnetic blood flow measurements.

Intraoperative electromagnetic flow meter measurements were made after 143 carotid endarterectomies. Six (4.2 per cent) had low or no internal carotid artery blood flow, and four of these had a clear technical cause. After rearteriotomy, five had restoration of blood flow to the normal range. These data support the hypothesis that there is a small but significant instance of technical causes of immediate carotid endarterectomy failure which may not be detectable by observation and palpation. Postendarterectomy intraoperative internal carotid artery blood flow measurement is an acceptable method of detecting hemodynamically significant technical defects.

Blood Flow Velocity↗