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Biomedical subjects

J P Archie

Publications and source records attributed to J P Archie.

At least 37 records · Page 2Linked to original sources
PubMed1996

Carotid endarterectomy saphenous vein patch rupture revisited: selective use on the basis of vein diameter.

PURPOSE: The single major disadvantage of carotid endarterectomy (CEA) patch reconstruction with greater saphenous vein (GSV) is central patch rupture, which has a reported incidence of 0.5% to 4%. This is a prospective evaluation of the selective use of GSV for a CEA patch based on previously established vein diameter criteria. METHODS: Between 1988 and mid-1995, 534 of 671 CEAs (80%) were reconstructed with GSVs that had a distended diameter > or = 3.5 mm. Thigh veins were used in all 252 women who underwent CEA. Of the 282 men who underwent CEA, 265 GSVs (94%) were harvested from below the knee and 17 from the thigh. During this period four thigh and 13 below-knee veins (3.2%) were rejected because the diameter was < 3.5 mm, and a synthetic patch was used instead. In 408 of the CEAs with GSV (76%) the vein rupture pressures and diameters were measured, the CEA geometry was measured, and the predicted CEA vein patch rupture pressures were calculated. RESULTS: No GSV patches ruptured in this series. This compares favorably with three patch ruptures in 239 previous CEAs when no vein diameter criteria was used (p = 0.03). This also compares favorably with a multicenter series of 13 GSV patch ruptures (0.73%) in 1773 CEAs (p = 0.03) and with a single-center series of eight ruptures (0.47%) in 1699 CEAs (p = 0.05). GSV diameters were 4.9 +/- 0.9 mm (mean +/- 1 SD); vein rupture pressures, 3.9 +/- 1.5 atmospheres; carotid bulb major axis diameters, 12.5 +/- 1.6 mm; carotid bulb maximum diameters of curvature, 14.2 +/- 2.2 mm; and CEA patch rupture pressures, 1.3 +/- 0.6 atmospheres (range, 280 mm Hg to 4 atmospheres). CEA vein patch rupture pressure correlates positively with vein diameter (p < 0.001, slope), but there is wide variability (correlation coefficient = 0.39). The 14 CEAs (3.4%) with predicted rupture pressures < 400 mm Hg were performed with veins 3.5 to 5.5 mm in diameter (mean, 4.2 mm), and all had carotid bulb major axis diameters > 12 mm (mean, 15.3 mm). Eight of these CEAs were reconstructed with thigh veins. CONCLUSIONS: Use of GSVs with a distended diameter > or = 3.5 mm for CEA patch reconstruction significantly reduces the probability of central patch rupture; however, a few CEAs reconstructed with veins > 3.5 mm in diameter and large carotid bulbs have predicted patch rupture pressures < 400 mm Hg. Because at times some veins will have rupture pressures lower than desirable, CEA reconstruction should be tailored to keep the carotid bulb major axis diameter < 13 mm.

Aged↗
PubMed1996

Secondary recurrent carotid stenosis.

PURPOSE: Recurrent carotid stenosis after carotid endarterectomy has been extensively reported. The occurrence, however, of another ipsilateral restenosis that requires a third carotid operation is rare. The purpose of this study was to evaluate possible risk factors and the most efficacious management of the patient with "secondary" recurrent carotid stenosis. METHODS: A survey of the Southern Association for Vascular Surgery was performed, and 31 patients who had had surgery for secondary recurrent carotid stenosis were identified. RESULTS: The mean interval between the recurrent stenosis operation and secondary recurrent carotid stenosis was 39.8 months (range, 9 to 83 months). At the third operation, 21 patients underwent carotid patch angioplasty and 10 underwent carotid resection with an interposition saphenous vein graft. No postoperative strokes or deaths occurred; three patients (10%) had a peripheral nerve injury. Nine early (< 24 mo) secondary recurrent carotid stenoses occurred, and these patients underwent patch angioplasty. Twenty-three female, cigarette-smoking patients and 20 patients with elevated lipid levels had early restenosis and were identified as being at high risk for the development of another stenosis. A fourth significant stenosis developed in five of these high-risk patients who had saphenous vein patch angioplasty at their third carotid operation; eight other high-risk patients had carotid resection with an interposition saphenous vein graft, and no other stenosis developed. CONCLUSION: Patients who have secondary recurrent carotid stenoses can safely undergo a third carotid operation. Female habitual smokers with elevated lipid levels and an early restenosis appear to be at high risk of secondary recurrent carotid stenoses. When surgery is necessary, carotid resection with an interposition saphenous vein graft appears more durable than patch angioplasty.

Adult↗
PubMed1996

The endarterectomy-produced common carotid artery step: a harbinger of early emboli and late restenosis.

PURPOSE: This study analyzes the role of the carotid endarterectomy (CEA)-produced common carotid step or shelf on early and late CEA outcome. A simple method of reconstruction that covers the exposed media and intima of the step and smooths out the flow channel is presented. METHODS: Since 1984 intraoperative geometric measurements were made on 1019 CEA. Duplex scans were made after surgery on 968 (95%); 234 (23%) were monitored for at least 5 years. Of the first 920 CEA, 261 (28%) had a step > or = 2 mm. Of the last 99 operations, the 27 (27%) with a step > or = 2 mm had inversion plication reconstruction of the step. RESULTS: Three patients had early post-CEA neurologic events attributed to a common carotid step, two had transient ischemic attacks, and one had a mild stroke. All three had a CEA-produced step > or = 2 mm (1.2% of 261, p = 0.03 when compared with no unexplained early neurologic events in the 659 without a step). Duplex scans were normal in all three except for a common carotid artery step. Six patients had seven reoperations for common carotid artery restenosis at 23 to 104 months (mean 73 months) after CEA. All had a step > or = 2 mm at the origin CEA (2.7% of 261, p = 0.001 when compared with no reoperations for common carotid artery stenosis in the 659 CEA without a step). All but one patient had > 75% restenosis. Four were asymptomatic. All seven with restenosis were within 2 mm of the original common carotid end point step. Four restenoses were concentric, two eccentric, and one ulcerated. Six of the seven arteries were originally reconstructed with a greater saphenous vein patch that extended 3 to 6 mm proximal to the step. Early postoperative duplex scans of the 27 recent CEA with step reconstruction demonstrated a tortuous but smooth common carotid artery flow channel. CONCLUSION: The CEA-produced common carotid artery step is a potential source of both early postoperative emboli and late restenosis. The incidence is approximately 4% in patients with a CEA step > or = 2 mm. CEA vein patch reconstruction does not prevent restenosis in the region of the step but may lower the incidence. Although not proven, reconstruction techniques directed at covering the exposed step media and intima and smoothing the flow channel may favorably alter outcome.

Carotid Artery, Common↗
PubMed1996

The value of donor iliac artery pressure gradients in predicting the outcome of femorofemoral bypass.

PURPOSE: This study tests the clinical value of femoral artery pressure measurements by analysis of the relationship between iliac artery pressure gradients (PGs) and both femorofemoral bypass graft patency and the hemodynamic changes produced in the donor and recipient limbs. METHODS: Systemic and donor femoral artery systolic and mean pressures were measured during surgery at rest and during papaverine-induced hyperemia before 94 femorofemoral bypasses. Ankle/brachial (A/B) pressure ratios and pulse volume recordings (PVRs) were measured before and early after surgery. Donor iliac artery stenosis was 25% +/- 23% (mean +/- 1 SD). Follow-up was 23+/- 20 months. RESULTS: Eight bypasses failed at 21 +/- 20 months. Patients with failed bypasses had a resting systolic and mean PG of 23 +/- 22 mm Hg and 5 +/- 7 mm Hg, respectively, compared with 10 +/- 11 mm Hg (p = 0.007) and 1 +/- 2 mm Hg (p = 0.001) for the 86 patent bypasses. Donor limb A/B ratios and PVRs decreased 9% +/- 5% and 15% +/- 14%, respectively, had a linear regression slope less than 0 (p < 0.05) with resting and hyperemic PGs, and correlated best with resting PGs (p < 0.05). Recipient limb A/B ratios and PVRs increased 86% +/- 48% and 191% +/- 111%, respectively, had a linear regression slope greater than 0 (p < 0.05) with all resting and hyperemic PGs, and correlated best with hyperemic systolic PGs (p < 0.05). However, all regressions had a large SD, wide 95% confidence limit, and a low correlation coefficient. Sensitivity-specificity receiver-operating characteristic curves for optimal PG criteria for both graft failure and donor limb hemodynamic impairment are weak, with an accuracy of 50% to 75%. Recommended criteria for not performing a femorofemoral bypass are a resting systolic PG of 28 mm Hg or greater or a resting mean PG of 6 mm Hg or greater. CONCLUSIONS: Although iliac artery PGs correlate with graft failure and both the degree of donor limb hemodynamic impairment and recipient limb improvement, the large variability in PGs between patients with similar outcomes and the low accuracy of optimal PG criteria indicate that they have limited clinical value in decision making.

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PubMed1996

Effect of carotid artery geometry on the magnitude and distribution of wall shear stress gradients.

PURPOSE: Recent information indicates that large, sustained wall shear stress gradients are a dominant hemodynamic parameter associated with the location and severity of atherosclerosis and myointimal hyperplasia. This study computes the spatial values of wall shear stresses and their gradients for three carotid artery bifurcation geometries. METHODS: A computational fluid dynamics program was used to solve the transient two-dimensional partial differential equations that describe fluid flow. Blood was treated as both a Newtonian and a non-Newtonian incompressible fluid. Solutions for the velocities, wall shear stresses, and wall shear-stress gradients were obtained for three carotid bifurcation geometries: a normal carotid bifurcation (similar to a primarily reconstructed carotid endarterectomy), a patch-reconstructed carotid endarterectomy, and a gradually tapered, low-angle carotid bifurcation (no carotid bulb). RESULTS: Computed velocity profiles closely match published experimental ones. Disturbed flow velocities are largest in the bulb segment of the normal carotid bifurcation. Peak and minimum wall shear stresses and peak shear stress gradients occurred in the lateral internal carotid artery wall. These were binodal in the normal or primarily reconstructed carotid artery, localized at the distal end of the patch-reconstructed carotid bifurcation, and minimal in the smooth, tapered carotid bifurcation. Wall shear stresses and their gradients were slightly higher for non-Newtonian than Newtonian fluids in the normal carotid artery but were similar in the other two geometric configurations. CONCLUSION: These results indicate that flow disturbances in general and wall shear stress gradients in particular are markedly reduced in carotid artery bifurcations that are smooth and gradually tapered and do not have a bulb. Abrupt geometric wall changes such as those occurring in the normal carotid bulb and at the distal end of a patch-reconstruction after carotid endarterectomy are harbingers of disturbed flow and high wall shear stress gradients. These results suggest that carotid endarterectomy reconstruction geometry characterized by a gradually tapered internal carotid artery may minimize the hemodynamically induced component of early myointimal hyperplasia and thrombosis and late atherosclerotic restenosis.

Arteriosclerosis↗
PubMed1996

Flow input waveform effects on the temporal and spatial wall shear stress gradients in a femoral graft-artery connector.

Employing a validated finite volume code, a computer-aided design of the distal end of a femoral graft-artery junction has been considered to simulate transient three-dimensional blood flow for various flow input waveforms. The study relies on the hypothesis that large sustained wall shear stress gradients play a major role in the rapid recurrence of intimal hyperplasia plus atheroma after bypass surgery, leading to early graft failure. Two new dimensionless parameters have been introduced to correlate flow waveform characteristics with the severity of nonuniform hemodynamics and hence the potential risk for restenosis. The transient and, more importantly, the time-averaged wall shear stress gradient distributions shown, map out the junction areas which are still susceptible to restenosis, especially the toe region. Future geometric modifications will further reduce disturbed flow patterns and hence the probability of graft failure.

Anastomosis, Surgical↗
PubMed1996

Geometric design improvements for femoral graft-artery junctions mitigating restenosis.

The present study is based on the hypothesis that nonuniform hemodynamics, represented by large time-averaged wall shear stress gradients, trigger abnormal biological processes leading to rapid restenosis, i.e. excessive tissue overgrowth and renewed plaque formation, and hence early graft failure. It implies that this problem may be significantly mitigated by finding graft-artery bypass configurations for which the wall shear stress gradient is approximately zero and hence nearly uniform hemodynamics is achieved. These fluid flow and geometric design considerations are applied to four different end-to-side anastomoses for the distal end of a femoral artery bypass with an appropriate test input pulse and a typical 20-80 flow division. A validated finite-volume code has been used to compute the transient three-dimensional velocity vector fields, wall shear stress distributions and surface contours of the wall shear stress gradients. It is shown that large anastomotic flow areas, small continuously changing bifurcation angles, and smooth junction wall curvatures reduce local time-averaged wall shear stress gradients significantly and hence should mitigate restenosis.

Algorithms↗
PubMed1994

Analysis and comparison of pressure gradients and ratios for predicting iliac stenosis.

Over the past 35 years five different pressure variables and their numeric criteria have been recommended to determine the hemodynamic significance of iliac artery stenosis. To analyze and compare the five variables, systolic and mean radial and femoral artery pressures were measured intraoperatively in 144 legs at rest and in 119 (83%) of these during hyperemic flow augmentation with papaverine. Iliac artery diameter stenosis measured from preoperative two-view arteriograms was 48 +/- 37% (mean +/- 1 SD). Resting systolic and resting mean pressure gradients (radial minus femoral artery pressure), hyperemic mean pressure gradients, hyperemic systolic pressure ratios (femoral/radial), and the percentage change from rest to hyperemia of the systolic pressure ratios were measured. For completeness a sixth variable, the hyperemic systolic pressure gradient, was also measured. High-grade (75%) stenosis is predicted with 95% confidence by resting pressure gradients > or = 52 mm Hg systolic and > or = 16 mm Hg mean and resting systolic pressure ratios < or = 0.61. Hyperemia is unnecessary and not useful for predicting > 50% stenosis. The rest-to-hyperemia percentage changes in systolic pressure ratios give poor results. Moderate (50%) stenosis is predicted with 95% confidence by resting pressure gradients > or = 34 mm Hg systolic and > or = 7 mm Hg mean, hyperemic mean pressure gradients > or = 30 mm Hg, and systolic pressure ratios < or = 0.73. Most published criteria have low accuracy, low predictive value, and a low optimal percentage of stenosis range. Simple pressure gradients give optimal results.

Arterial Occlusive Diseases↗
PubMed1994

Femoropopliteal bypass with either adequate ipsilateral reversed saphenous vein or obligatory polytetrafluoroethylene.

The results are presented of a 10-year experience with 312 femoropopliteal bypasses performed in 285 patients using ipsilateral autologous reversed greater saphenous vein when available and adequate and polytetrafluoroethylene (PTFE) when not. The indications for operation were severe claudication in 121 (39%), rest pain in 95 (30%), and minor tissue loss in 96 (31%) limbs. There were 235 (75%) saphenous vein bypasses, of which 157 were above and 78 below the knee, and 77 (25%) PTFE bypasses, 58 above and 19 below the knee. Of these, 232 (79%) saphenous vein and 62 (21%) PTFE bypasses were primary procedures. The 30-day mortality rate was 3% (7/285) and the 30-day amputation rate was 2% (6/312). Overall, 24 (10%) saphenous vein and 30 (39%) PTFE grafts ultimately failed. The cumulative primary patency of all bypasses was 77% +/- 4% (mean +/- 1 SE) (85% to 69%, 95% confidence interval) at 3 years and 75% +/- 4% (86% to 64%) at 5 years. Saphenous vein primary patency was superior to that of PTFE at 3 years, 87% +/- 4% (97% to 77%) vs. 54% +/- 12% (65% to 41%), (p < 0.01), and at 5 years, 81% +/- 6% (96% to 67%) vs. 48% +/- 16% (63% to 33%) (p < 0.01). Above-knee saphenous vein bypass primary patency was slightly better than below-knee patency at 3 years, 89% +/- 4% vs. 84% +/- 6%, and at 5 years, 83% +/- 7% vs. 80% +/- 8%. This was superior to above-knee PTFE patency at 3 years, 54% +/- 14%, and at 5 years, 34% +/- 16% (p < 0.01). The overall PTFE failure rate was three to four times that of the saphenous vein rate. These results strongly support the use of autologous greater saphenous vein for all femoropopliteal bypasses when it is available and of good quality. PTFE grafts are valuable secondary conduits when the vein is not available or is inadequate. This series was not randomized since PTFE was used only in patients with inadequate or unavailable ipsilateral greater saphenous veins. When this protocol was followed, the patency rate for greater saphenous vein was excellent and its use is recommended for femoropopliteal bypass when it is available and of good quality.

Aged↗
PubMed1994

Carotid endarterectomy when the distal internal carotid artery is small or poorly visualized.

PURPOSE: This is a report of the operative findings and results of carotid endarterectomy (CEA) when the conventional arteriogram demonstrates an internal carotid artery with a high-grade origin stenosis and a small or poorly visualized distal extracranial segment with an apparent diameter of 2 mm or less. METHODS: Eighteen CEA were performed on 17 patients with this preoperative finding and patent common and external carotid arteries. The indications for CEA were transient ischemia in seven patients, completed minor stroke in five and amaurosis fugax in four patients. One patient had bilateral findings and global cerebral ischemic symptoms. RESULTS: At CEA 16 internal carotid arteries had atherosclerotic very high-grade origin stenosis, and two had chronic occlusion. Ten of the 16 open arteries had true external diameters of 4 mm or more. Of these, seven were normal above the stenosis, two had a long, trailing intraluminal thrombus that was removed, and one had high-grade distal stenosis. Of the six arteries with true diameters of 3 mm or less (hypoplastic), two had a thick fibrotic wall. The carotid stump back pressure for the 16 open internal carotid arteries was 56 +/- 15 mm Hg (mean +/- SD). This was significantly higher than the 39 +/- 14 mm Hg back pressure measured in 1016 arteries without a string sign (p < 0.001). There was one 30-day postoperative death after a stroke. There was no systemic or neurologic morbidity. Post-CEA duplex scans demonstrated eight normal, five mildly stenotic, and five occluded internal carotid arteries. Two of the occlusions were found at CEA and the other three occluded arteries had low flow after CEA, two of which were hypoplastic and the other had a distal stenosis. CONCLUSIONS: Patients with symptoms with these findings on arteriograms should undergo CEA. However, the success of CEA in this setting depends on the internal carotid artery anatomy and disease, which is difficult to determine before CEA. Patients with a truly normal extracranial internal carotid artery have an excellent probability of a successful CEA, but this is not the case when the artery is small or fibrotic. Low internal carotid artery flow after a technically satisfactory CEA is a harbinger of thrombosis and should be managed by internal carotid artery ligation and external CEA.

Aged↗
PubMed1993

Carotid endarterectomy with reconstruction techniques tailored to operative findings.

PURPOSE: Reconstruction techniques tailored to operative findings were applied to 466 consecutive carotid endarterectomies (CEA) performed on 408 patients over 5 years. The choice of reconstructive technique was based on the extent of the arteriotomy incision required to obtain a complete internal CEA endpoint, the ability to obtain a complete endpoint, and the quality or redundancy of the endarterectomized internal carotid artery (ICA) segment. The hypothesis was that a complete internal CEA endpoint and a tapered, smooth, nonkinked reconstruction minimize complications. METHODS: Complete distal endpoint feathering was obtained in 437 (94%) CEA. Patch reconstruction was performed in the 429 (92%) CEA in which the arteriotomy extended distal to the ICA bulb. Before patching, 16 (3.4%) redundant endarterectomized ICA segments were shortened by transverse-eversion suture plication to prevent kinking. A saphenous vein interposition graft was used in nine (1.9%) CEA. The other 28 (6.0%) CEA had an arteriotomy that did not extend distal to the bulb and were primarily closed. RESULTS: Two (0.4%) patients died of myocardial infarction in the hospital; one of these patients also had a stroke. Three (0.6%) patients had nonfatal strokes in the hospital. Five patients had hyperperfusion syndrome after CEA, one of which occurred without complications in the hospital. The other four occurred after discharge from the hospital. Three of these patients had a stroke, and two with strokes died. The combined 30-day mortality and nonfatal stroke rate was 2.1% for CEA and 2.4% for patients. There were no patch ruptures, false aneurysms, or ICA occlusions. Three patients had a > 50% diameter carotid artery stenosis 6 months after CEA. CONCLUSIONS: These results support an aggressive attempt to obtain a complete or optimal ICA endpoint with reconstruction techniques based on operative findings. Recognition of patients at risk for and treatment of hyperperfusion syndrome after CEA remains a clinical challenge.

Adult↗
PubMed1992

Improved carotid hemodynamics with vertebral reconstruction.

This study tests the hypothesis that vertebral artery reconstruction improves carotid distribution hemodynamics during carotid occlusion. Twelve patients with vertebrobasilar symptoms underwent either direct (9) or indirect (3) vertebral reconstruction. There were six proximal vertebral to common carotid reimplantations, one proximal carotid-vertebral bypass and two distal carotid-vertebral bypasses, all with saphenous vein. Three patients with carotid-subclavian or axillo-axillary bypasses performed for symptomatic vertebral steal were studied at the time of carotid endarterectomy. During temporary ipsilateral carotid occlusion, vertebral reconstruction increased carotid back pressure from 39.3 +/- 10.2 mmHg to 46.8 +/- 9.5 mmHg (p less than 0.0001), increased cerebral perfusion pressure from 33.4 +/- 10.8 mmHg to 41.0 +/- 9.1 mmHg (p less than 0.0001), decreased the carotid collateral resistance to cerebral vascular resistance ratio from 1.68 +/- 0.90 to 1.24 +/- 0.64 (p less than 0.001), and increased the ratio of carotid back pressure to mean systemic arterial pressure from 0.452 +/- 0.122 to 0.515 +/- 0.118 (p = 0.0005). These results are presumed due to increased posterior-to-anterior blood flow in the posterior communicating arteries. Direct or indirect vertebral reconstruction may be a consideration in patients with cerebral ischemic symptomatic and nonreconstructible carotid occlusive disease.

Blood Pressure↗
PubMed1992

Influence of the first assistant on abdominal aortic aneurysm surgery.

The hypothesis that the type of first assistant who attends the surgeon influences the course and outcome of graft replacement for abdominal aortic aneurysm was tested. Surgical results were analyzed in 179 consecutive patients (149 men and 30 women; mean age, 69 +/- 7.5 years). All the operations were performed by the author-an experienced surgeon with a practice limited to general vascular surgery. The choice of first assistant was based solely on availability; 110 (61%) patients had a board-certified surgeon as the first assistant and 69 (39%) had an experienced registered nurse as the first assistant. Patients with intact aneurysms undergoing elective surgery were in Group 1, and patients with intact aneurysms undergoing urgent surgery were in Group 2. Group 3 patients included those who had ruptured aneurysms but were hemodynamically stable, and Group 4 patients had ruptured aneurysms and were in shock. The distribution of patients was similar in each first-assistant group, as was the use of straight and bifurcated graft reconstructions, associated visceral procedures, and other adjunctive procedures. The hospital mortality was 4% (6/149) for Group 1 patients, 12% (2/17) for Group 2,20% (1/5) for Group 3, and 50% (4/8) for Group 4 patients. The morbidity and mortality rates were independent of the type of assistant, as were the operative time, blood loss, and adjusted blood transfusion volume. These results suggest that the choice of either an MD-surgeon or an experienced RN as first assistant does not influence the course or outcome of abdominal aortic aneurysm surgery.

Journal Article↗
PubMed1992

Splenic artery stump back pressure.

Splenic arterial collateral hemodynamics were measured during splenic artery occlusion in 15 patients who had splenic to left renal artery bypass. The mean splenic artery stump back pressure during proximal splenic artery clamping was 48.0 +/- 9.8 mmHg (mean +/- ISD) and the mean collateral splenic perfusion pressure was 34.3 +/- 9.4 mmHg. The lowest measured back pressure was 39 mmHg and the lowest perfusion pressure was 30 mmHg. There were no spleen complications after operation. These measurements establish a normal range for collateral splenic perfusion pressure. These results may be helpful in clinical decisions about the adequacy of splenic circulation in operations that require division of the splenic artery or the short gastric arteries when there is celiac axis or splenic artery occlusive disease.

Blood Pressure↗
PubMed1991

Technique and clinical results of carotid stump back-pressure to determine selective shunting during carotid endarterectomy.

A method of confirming carotid back pressure accuracy, variability during carotid clamping, and the clinical results with a modified back pressure shunt criterion were evaluated in 665 carotid endarterectomies. Mean arterial pressure, back pressure, and internal jugular vein pressure were measured. Cerebral perfusion pressure (back pressure-jugular vein pressure) and the collateral to hemisphere vascular resistance ratio, (ratio = [arterial pressure-back pressure]/[back pressure-jugular vein pressure]) were calculated. A shunt was used when cerebral perfusion pressure less than 18 mm Hg. Back pressure accuracy was confirmed by test occlusion of the internal carotid artery distal to the plaque. Initial back pressure values were falsely high in 83 (12.5%) carotid endarterectomies. The mean SD (n = 665, mm Hg) were arterial pressure = 84.0 +/- 9.06, back pressure = 41.0 +/- 15.9, jugular vein pressure = 6.2 +/- 3.9, cerebral perfusion pressure = 35.1 +/- 5.7, and resistance ratio = 1.85 +/- 1.44. Perfusion pressure was less than 18 mm Hg in 82 (12.3%), of which 74 (11.1%) were shunted, and 8 (1.2%) had perfusion pressure increased greater than or equal to 18 mm Hg during carotid endarterectomy with phenylephrine. Back pressure was less than 25 mm Hg in 107 (16.1%), less than or equal to 25 in 114 (17.1%), and less than 50 mm Hg in 481 (72.3%). Pressures were continuously monitored during 28 carotid endarterectomies, and all had a positive linear relationship between arterial pressure and back pressure, and minimal variability in the back pressure/arterial pressure and resistance ratios. Only two patients (0.3%) had a new neurologic deficit in the first 12 hours after carotid endarterectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Hemodynamics analysis of a stenosed carotid bifurcation and its plaque-mitigating design.

Considering transient two-dimensional laminar flow in a diseased carotid artery segment with realistic inlet and outflow conditions, detailed velocity profiles, pressure fields, wall shear stress distributions and coupled, localized plaque formations have been simulated. The type of outflow boundary condition influences to a certain degree the extent of plaque build-up, which in turn reduces "disturbed flow" phenomena such as flow separations, recirculation zones, and wavy flow patterns in the artery branches during portions of the pulse. Based on computer experiments varying key geometric factors, a plaque-mitigating design of a carotid artery bifurcation has been proposed. Elimination of the carotid bulb, a smaller bifurcation angle, lower area ratios, and smooth wall curvatures generated a design with favorable hemodynamics parameters, leading to reduced plaque build-up by factors of 10 and 2 in the internal carotid and in the external carotid, respectively.

Blood Flow Velocity↗
PubMed1991

Early and late geometric changes after carotid endarterectomy patch reconstruction.

This study examines the degree and location of vessel wall geometric changes after carotid endarterectomy-vein patch reconstruction. The external diameters of the proximal common carotid, common carotid bulb, and internal carotid arteries were measured during operation with a caliper after 349 carotid endarterectomies. There were 309 saphenous vein reconstructions, 31 synthetic patch reconstructions, and 9 primary closures. One or more B-mode ultrasound studies with cross-sectional views for common and internal carotid cursor measurements were performed from 3 months to 5 years after operation. The intraoperative-to-postoperative common carotid diameters were unchanged for the three types of reconstructions. The internal carotid diameters increased 20% to 30% for both the vein and synthetic patched arteries. This dilation was present at 3 and 6 months and progressed slightly over 5 years. Wall thickening greater than or equal to 1 mm was present in 62% of the carotid endarterectomies, with concentric stenosis in 3% and eccentric stenosis in 59%. Eccentric stenosis was present at 3 to 6 months, located on the endarterectomized posterior-medial wall of the common and internal carotid arteries, was always less than 50%, and changed very little over 5 years. No aneurysms or internal carotid occlusions were identified. Carotid endarterectomy-vein patch reconstruction results in early, mild, nonaneurysmal dilation of the internal carotid patched segment, frequent mild eccentric restenosis, and rare hemodynamically significant concentric restenosis.

Aged↗