A temporary distal arteriovenous fistula improves venous hemodynamics in a model of venous occlusion.

The formation of a temporary distal arteriovenous fistula (dAVF) has been used clinically to palliate patients with symptomatic venous hypertension. This study tested the efficacy of a temporary dAVF for the treatment of venous hypertension in an experimental model. Twenty-four New Zealand white rabbits were divided into two experimental groups. Group I rabbits (n = 12) underwent standardized ligation of the iliac and femoral venous systems. Group II rabbits (n = 12) underwent standardized ligation of the iliac and femoral venous systems with the formation of a temporary dAVF. Venous obstruction was documented with venography, and venous hypertension was documented with femoral venous pressure measurements. Venous pressure, resistance, blood flow, vein circumference, vein cross-sectional area, vein wall thickness, and venography were compared between four rabbits from each group at 2, 4, and 8 weeks. The effect of differences in baseline venous pressures was eliminated by subtracting the venous pressure in the unobstructed rabbit limb from the pressure in the obstructed rabbit leg. Group II rabbits had a lower standardized venous pressure (4.4 +/- 2.2 versus 9.5 +/- 4.2 mm Hg, p less than 0.01) and venous outflow resistance (0.16 +/- 0.08 versus 0.36 +/- 0.18, p less than 0.05) than did group I rabbits. Group II rabbits also had a larger superficial femoral vein circumference (3.46 +/- 0.67 versus 2.57 +/- 0.08 mm, p less than 0.05) and cross-sectional area (0.66 +/- 0.31 versus 0.31 +/- 0.09 mm2, p less than 0.01) than did group I rabbits. The improvement persisted throughout the 6-week study, which suggested an improved venous outflow.

Hemodynamic effects of varied graft diameters in the venous system.

Both in vivo and mathematical models of venous hypertension were used to evaluate the hemodynamic effects of 4, 6, 8, and 10 mm diameter cross-femoral venous bypass grafts (CFBs). Eighteen grafts (length 138 +/- 3.4 mm) were tested in paired sequential fashion (four grafts, 4 and 8 mm; five grafts, 6 and 10 mm) in nine greyhounds (femoral vein diameter, 7.7 +/- 0.09 mm). Bilateral hindlimb venous pressures and flows were measured before and after unilateral iliofemoral venous ligation, 30 minutes after CFB insertion, and for 5 minutes after venous flow augmentation induced by stimulated muscle contraction. CFBs of all sizes were equally effective at relieving the occlusive venous hypertension at rest. Muscle contraction elevated venous pressure in all ligated hindlimbs (p less than 0.0001); however, the pressure returned to baseline by 3 minutes in dogs with 6, 8, and 10 mm grafts but remained elevated (p less than 0.05) with the 4 mm grafts even after 5 minutes. Peak graft flow (first 90 seconds after contraction) was significantly greater through the 8 mm grafts than through the 4 mm grafts (p less than 0.01), although no difference was noted in flow rates between 6 and 10 mm grafts. The pressure gradient across the graft as predicted by the mathematic model for 6 to 10 mm conduits was less than 5 mm Hg for flows up to 1000 ml/min, although the pressure gradient of the 4 mm graft exceeded 5 mm Hg at 200 ml/min and approached 30 mm Hg at 1000 ml/min. Therefore, data from both canine and mathematical models agreed that, at rates approximating human resting flow (1000 ml/min), no adverse short-term hemodynamic consequences result from CFB conduits of 6 to 10 mm diameter.

Long-term follow-up of the Palmaz stent for iliac occlusive disease.

BACKGROUND: Thirty-eight limbs with iliac occlusive disease were treated with Palmaz stents from 1987 through 1991. METHODS: Indications for stent utilization included dissection induced by percutaneous transluminal balloon angioplasty (PTA) (10), restenosis after PTA (nine), post-PTA residual stenosis (nine), multiple stenoses or occlusion (five), and unfavorable location (five). RESULTS: The ankle/brachial pressure index increased from 0.53 +/- 0.27 to 0.8 +/- 0.26 after stent deployment. The intraluminal pressure gradient decreased from 31.9 +/- 16.3 to 0.9 +/- 2.2 mm Hg after stent deployment. Complications included pseudoaneurysm (one), arteriovenous fistula (one), iliac perforation (one), groin hematoma (two), and occlusion (two). Follow-up arteriogram showed stenosis proximal or distal (n = 4) or within the stents (n = 4). These were treated with PTA or stents. Two patients required an aortobifemoral graft. Nine patients have died. Life table analysis showed a 1-, 3-, and 5-year primary and secondary cumulative patency of 87% +/- 5.9%, 74% +/- 8.2%, and 63% +/- 10% and 91% +/- 5.1%, 91% +/- 5.6%, and 86% +/- 7.6%, respectively. CONCLUSIONS: Palmaz stents, often required to salvage a PTA failure, appear to maintain overall patency at a high level. However, intimal hyperplasia and the progression of atherosclerotic disease may result in a need for additional procedures to obtain this favorable outcome.

Venous hemodynamics in a chronic venous valvular insufficiency model.

To develop a large-animal model of chronic venous valve incompetence, 13 greyhound dogs underwent unilateral hindlimb venous valve lysis with a valve cutter apparatus pulled retrograde through the iliac, femoral, and lateral saphenous veins. Bilateral venous pressures in the lateral saphenous vein were recorded before valve lysis, immediately after valve lysis, and at intervals from 1 to 14 weeks after valve lysis, with the dogs in the supine position and elevated 80 degrees semierect, as well as after stimulated hindlimb muscle contraction to empty the hindlimb veins. Passive venous filling time with elevation and 90% venous refilling time after muscle contraction were calculated. From immediately after through 14 weeks after valve lysis, a shortened venous filling time and 90% venous refilling time as well as an elevated poststimulation venous pressure were noted. This valve lysis method successfully produced a hemodynamically verified model of venous valvular insufficiency.

The natural history of intimal flaps in a canine model.

The natural history of arterial intimal flaps has not been well defined. This study characterizes the natural history of unrepaired intimal flaps. Thirty-nine 1-, 2-, and 3-mm hemispheric, distally based intimal flaps were made in 4- to 5-mm diameter canine femoral and carotid arteries. Twenty arteries had 2- and 3-mm intimal flaps and were monitored for short-term arterial thrombosis and flap extension. Nineteen had 1- and 2-mm intimal flaps and were monitored for thrombosis, long-term development of neointimal hyperplasia, arterial stenosis, and persistence of the flap. While 40% of the arteries with 3-mm intimal flaps developed thrombosis in 3 to 5 days, only 3% of the arteries with 1- or 2-mm intimal flaps developed thrombosis. Most 1- to 2-mm intimal flaps resolved and the subsequent development of neointimal hyperplasia or arterial stenosis was minimal. Arteries with hemodynamically significant stenoses from intimal flaps warrant repair, while arteries with smaller intimal flaps may not require repair.

The role of isolated profundaplasty for the treatment of rest pain.

This study was undertaken to determine the efficacy and durability of profundaplasty and define preoperative factors predictive of success. The hospital charts, vascular laboratory data, and arteriograms of 20 patients having 21 isolated profundaplasties for ischemic rest pain between 1979 and 1987 were reviewed. Follow-up extended to 72 months (mean, 26 months). Early success was achieved in 12 extremities (57%) and life-table analysis showed continued success to six years in 11 extremities (55%). Of the multiple preoperative factors assessed, only a low-thigh/ankle gradient pressure index (TAGI) of less than 0.55 was predictive of success. Life-table analysis for limbs with a TAGI of less than 0.55 showed an 89% success rate at six years compared with only a 32% success rate for limbs with a TAGI of more than 0.55. Isolated profundaplasty for the treatment of ischemic rest pain can be an efficacious and durable procedure when patients are selected based on objective hemodynamic measurements.

Clinical implications of combined hypogastric and profunda femoral artery occlusion.

From 1983 to 1990, nine patients with combined hypogastric (HA) and profunda femoral arterial (PFA) occlusive disease presented with five nonhealing hip disarticulations, three nonhealing above-the-knee amputations, perineal necrosis in six patients, buttock necrosis in four patients, visceral ischemia in two patients, and lumbosacral spinal ischemia in one patient. Obviously some patients had more than one regional complication. Five patients died from complications of HA/PFA ischemia. Survivors included two patients who required a hemipelvectomy, one patient who required an axillary-to-hypogastric artery bypass graft for stump salvage, and one patient who survived despite lumbosacral paralysis and complete cystectomy. The 56% mortality and 100% morbidity emphasize the critical significance of combined hypogastric/profunda femoral artery circulatory compromise. Efforts should be made to preserve or re-establish the HA and/or PFA circulation whenever possible. A hemipelvectomy may be required to allow the wounds to finally heal. Furthermore, the certainty of an above-the-knee amputation healing is not present in these patients; therefore, a hemodynamic assessment of the healing potential of an above-the-knee amputation is required.

Open transmetatarsal amputation in the treatment of severe foot infections.

Severe forefoot infections may lead to limb loss, even if addressed aggressively. Infection or gangrene that compromises the plantar skin flap may preclude a standard transmetatarsal or midfoot amputation, thereby culminating in a below-knee amputation. We report a series of forefoot infections with loss of the distal plantar skin. Open or guillotine amputation at the mid-metatarsal level led to a high rate of healing and a durable stump, provided that the level of infection did not extend beyond the metatarsal heads. Wound closure was obtained by wound contracture alone or by use of partial-thickness skin grafting. Rehabilitation was dependable. The association of diabetes mellitus or gangrene did not adversely affect outcome. Open transmetatarsal amputation is a safe surgical option preferable to midfoot or below-knee amputation for the treatment of severe forefoot infection that does not extend proximally beyond the metatarsal heads.

An experience with upper-extremity vascular trauma.

In this 6-year study of 101 limbs requiring surgical intervention for upper-extremity vascular trauma, most patients were male, young, and injured by penetrating objects. Injured vessels included 13 axillary/subclavian, 23 brachial, 40 radial, and 25 ulnar arteries. Concomitant injuries included nerve injury in 50 cases, tendon laceration in 29, and bony fracture in 11. Arterial repair was accomplished by primary repair in 54 limbs, vein graft in 26 limbs, and vein patch in 3 limbs. Seventeen arterial injuries were ligated. Ancillary procedures included 30 nerve or 27 tendon repairs. The limb salvage rate was 99%. No functional deficits were noted in those cases with only a vascular injury. In 64% and 25% of patients with nerve or musculoskeletal injury, respectively, the arm was functionally impaired. Prompt diagnosis and surgical intervention eliminate vascular injury as a factor in upper-extremity limb loss or disability. Functional deficits are the result of nerve or orthopedic injuries.

A nine-year experience with crossover femoro-femoro-popliteal sequential bypass.

Multisegmental arterial occlusive disease may require a combined inflow and outflow procedure for optimal treatment of limb ischemia. Twenty-one patients with unilateral iliac artery stenosis or occlusion and ipsilateral superficial femoral artery occlusion underwent crossover femoro-femoro-popliteal sequential bypass during a 9-year period. Seventeen operations were for limb salvage. Patency rates were determined separately for each segment of the bypass. Primary patency rates for the femoro-femoral segment were 89%, 83%, and 57% at 1, 2, and 5 years, respectively. Primary patency rates for the femoro-popliteal segments were 68%, 62%, and 40% at 1, 2, and 5 years, respectively. Limb salvage rates were 100%, 90%, and 77% at 1, 2, and 5 years, respectively. This experience indicates that femoro-femoro-popliteal bypass is an effective treatment in selected patients with severe ischemia due to combined iliac artery and superficial femoral artery disease.

Cerebral vascular reactivity assessed with acetazolamide single photon emission computer tomography scans before and after carotid endarterectomy.

BACKGROUND AND METHODS: In 64 patients, cerebral perfusion and vascular reactivity were assessed before and after carotid endarterectomy (CEA) using acetazolamide (ACZ)-enhanced single photon emission computer tomography (SPECT). Twenty-five patients were asymptomatic, whereas the remainder were symptomatic. Sixty-one patients had a > or = 70% ipsilateral internal carotid artery stenosis. RESULTS: Fifty SPECT scans revealed decreased vascular reactivity. Twenty-three showed infarcts. Fourteen patients had normal studies. Twenty of the SPECT scans of asymptomatic patients demonstrated poor vascular reactivity. After CEA, 39 patients had improved ipsilateral vasoreactivity. In 12 patients, contralateral improvement was also found. CONCLUSION: ACZ-enhanced SPECT scans, by assessing cerebral perfusion and vascular reactivity, may help to identify patients at risk of stroke should perfusion further diminish. Postoperative studies confirm improvement in vascular reactivity. ACZ-enhanced SPECT scans may provide objective evidence for the selection of patients with a high-grade asymptomatic carotid stenosis for CEA.

Acute mesenteric venous thrombosis. Revisited in a time of diagnostic clarity.

Historically, mesenteric venous thrombosis (MVT) has been found during laparotomy or at autopsy. Improvements in computed tomography (CT) and ultrasound (U/S) may identify patients earlier in their clinical course. How has this altered the treatment strategy of the authors? This 10-year retrospective study of acute MVT consisted of 12 men and three women (average age 43). Presenting signs and symptoms were nonspecific in 10/15 patients resulting in multiple diagnostic tests. All CT scans (10) and angiograms (4) revealed mesenteric clot. U/S exams detected clot in 6/9 patients. The remaining five patients exhibited clinical signs requiring operations rather than diagnostic studies. The only consistent laboratory abnormality was an elevated white blood cell count in 12/15 patients. Management of MVT varied. Five patients, heparinized once the diagnosis was made, did not experience dysfunction from MVT. Ten patients were not initially treated with heparin and were divided into three groups. Three patients received neither heparin nor surgery and have had no sequelae. MVT contributed to the death of two patients. The remaining five patients were diagnosed in the operating room following bowel resection. Two of these patients received postoperative heparin and had a favorable outcome. Two of the three patients not heparinized after surgery suffered additional bowel infarction. MVT can present as nonspecific abdominal pain, but also as peritonitis requiring operation. CT and U/S can identify patients with early MVT. It appears that heparin has both a primary therapeutic role in early disease and a postoperative adjunctive role in advanced disease. With such care, these patients can expect an acceptable prognosis (86% survival).

Vascular injuries during pancreatobiliary surgery.

Fourteen cases of vascular injury during pancreatobiliary surgery have been treated at our institution. The patients' mean age was 49 years, and nine were males. Six operations were performed for chronic pancreatitis, six for cancer, and two for an inflammatory process. Operations included 11 pancreatic resections and one laparoscopic cholecystectomy, one sphincteroplasty, and one pseudocyst drainage. Vessels injured included the portal vein (7), superior mesenteric vein (6), superior mesenteric artery (3), hepatic arteries (4), splenic vein (3). Six patients experienced more than one vascular injury. In all but one case, the injury was recognized and repaired during the initial operation. Primary repair was possible in seven cases. Six cases utilized autogenous tissue for repair. The one unrecognized injury was a right hepatic artery ligation, and a delayed repair was not possible. Follow-up demonstrated two occlusions, one following a portal vein repair without clinical sequela and a superior mesenteric artery repair which resulted in a small bowel stricture. The one unrecognized hepatic artery injury resulted in necrosis of the proximal common hepatic duct. Vascular injury following pancreatobiliary injury tends to occur in the presence of pancreatitis or cancer with its associated dense adhesions and inflammatory process. The variable anatomy of this area contributes to vascular injuries. Immediate recognition of the injury and repair appears to yield excellent results.

Arteriovenous fistulas as adjuncts to venous bypass grafts.

A canine model of occlusive hindlimb venous hypertension was used to determine which of two different, clinically applicable, adjunctive arteriovenous fistulas (AVFs), sequential or peripheral, would augment flow in autogenous cross-femoral venous bypass grafts (CFBs) with the least alteration of hindlimb hemodynamics. Unilateral venous hypertension was produced by iliofemoral venous ligation in three groups of five dogs: group I, venous ligation only (controls); group II, venous ligation followed by CFB with a sequential AVF; and group III, venous ligation with CFB and peripheral AVF. Bilateral hindlimb venous and arterial pressures and flows, and graft flows, were measured preoperatively and for 4 h postoperatively. Insertion of a CFB eliminated the venous hypertension in all 10 bypass dogs. Graft flow was augmented by addition of the sequential AVF (to 1167 +/- 309 mL/min from 92 +/- 12.3 mL/min: p less than .0001). However, this was accompanied, both in the limb ipsilateral to the AVF and in the contralateral limb, by the return of significant venous hypertension (p less than .001) and significant reduction (even reversal) of femoral vein flow caudad to the CFB (p less than .005). In contrast, adding the peripheral AVF augmented graft flow (to 200 +/- 62 mL/min from 65 +/- 43.7 mL/min; p less than .0001), but did not elevate venous pressure or impair venous flow in either hindlimb. The data from this short-term canine model suggest that a peripheral adjunctive AVF may effectively augment CFB graft flow without the potential for detrimental effects on venous hemodynamics characteristic of the sequential AVF.

Details of a canine venous insufficiency model.

Continued study of a chronic deep venous insufficiency (CDVI) model allows optimal comparison with the human condition. This study evaluates the model's long-term stability, its lack of observed clinical effect, and a simulated exercise study as a physiologic estimate of normal hindlimb walking. The time to maximal ankle venous pressure after standing (VFT), and to 90% of the venous refilling time after electrical stimulation, quadripedal, or hindlimb walking (VRT90), and the minimal pressure after exercise (AVP) were measured up to 10 months after CDVI model creation. The animals' intravenous resting pressure was obtained after standing stationary on all four limbs. Analysis of variance was used to determine statistical significance where indicated. VFT, AVP, and VRT90 measurements demonstrated values consistent with CDVI in animals studied up to 10 months after model creation and were statistically different from control limb values (p < or = .002, n = 8). Animals studied during quadripedal walking showed no difference in resting pressure, AVP, and VRT90 between model and control limbs (n = 5). There was no statistical difference in AVP or VRT90 measured under conditions of stimulated exercise or bipedal walking; and both conditions produced hemodynamic changes consistent with CDVI (n = 5). This animal model is a reliable long-term CDVI hemodynamic model. The normal venous hemodynamics recorded during quadripedic walking may explain the lack of clinical sequelae observed in this model. Lastly, the method of simulated exercise used in this study is a reliable test that reflects physiologic measurements obtained during bipedal walking.

Aortoiliac occlusive disease: a simple noninvasive method to determine significance.

This study was undertaken to develop a simple, noninvasive method for determining the hemodynamic significance of aortoiliac occlusive disease. In 14 dogs, 10-MHz Doppler recordings from the aorta and femoral arteries were made under normal (control) conditions and after construction of subcritical and critical iliac artery stenoses as documented by the papaverine test. The femoral waveforms obtained were analyzed for configuration (tri-, bi-, or monophasic) and pulsatility index. A ratio of time from ECG QRS peak to peak femoral flow divided by the time to peak aortic flow (TRFA) was calculated as was a ratio of the maximum rate of rise of the femoral Doppler signal to the aortic Doppler signal (MRRFA). These parameters were compared using Fisher's exact test and analysis of variance. TRFA and MRRFA accurately categorized the degree of iliac occlusive disease into statistically distinct groups. A TRFA less than 1.10 or a MRRFA greater than 0.70 identified a normal artery. MRRFA distinguished normal aortoiliac arteries from those with subcritical stenosis with a sensitivity of 0.93, a specificity of 1.00, and an accuracy of 0.96. TRFA distinguished normal aortoiliac arteries from those with a subcritical stenosis with a sensitivity of 0.86, a specificity of 0.86, and an accuracy of 0.86. Both TRFA and MRRFA separated normal aortoiliac arteries from those with a critical stenosis with a sensitivity of 1.00, a specificity of 1.00, and an accuracy of 1.00. The femoral Doppler waveform configuration and pulsatility index could not accurately categorize these differences (P = 0.100).

Neointimal hyperplasia following argon ion laser carotid endarterectomy: with and without endothelial cell seeding.

BACKGROUND AND OBJECTIVE: This study compares the development of neointimal hyperplasia following conventional and argon ion laser carotid endarterectomy and assesses the potential advantage of endothelial cell seeding. STUDY DESIGN/MATERIALS AND METHODS: Eight dogs underwent conventional endarterectomy in one carotid artery and an argon ion laser endarterectomy in the other. After 42 days, these arteries were harvested and the intimal thickness were compared. Six additional dogs underwent bilateral argon ion laser carotid endarterectomy with endothelial cell seeding on the one side only. These arteries were harvested after 65 days and their mean intimal thickness were compared. RESULTS: At 42 days, the mean intimal thickness in the conventional endarterectomy group was 0.070 +/- 0.007 mm; in the argon ion laser endarterectomy group it was 0.058 +/- 0.001 mm (P = 0.76, NS). At 65 days, the mean intimal thickness in the group without endothelial cell seeding was 0.125 +/- 0.003 mm vs. 0.061 +/- 0.001 mm on the seeded side (P = 0.043). CONCLUSION: Argon ion laser carotid endarterectomy results in no more neointimal hyperplasia than conventional endarterectomy. The neointimal hyperplasia is reduced by endothelial cell seeding.

Initial results of endothelial cell seeding following argon laser carotid endarterectomy.

This study evaluates the initial results of endothelial cell (EC) seeding following argon laser carotid endarterectomy. Venous endothelial cells were harvested from 12 dogs and cultured. A laser endarterectomy was performed on both carotids of each dog. One side was seeded with endothelial cells. Six dogs had both carotids harvested 1 hour after restoring blood flow. The others were harvested in 24 hours. The percentage of lumen covered with EC was evaluated by scanning electron microscopy. At 1 hour, the seeded arteries demonstrated 35 +/- 3 percent EC coverage, whereas the unseeded arteries had no EC coverage (P = 0.0002). At 24 hours, the seeded arteries had 58 +/- 15 percent EC coverage, whereas the unseeded arteries had no coverage (P = 0.01). Significant gross thrombus developed only in unseeded arteries (P = 0.047), two of which were occluded at 24 hours. EC seeding is beneficial following argon laser carotid endarterectomy resulting in improved patency and less surface thrombogenicity.

Drag reducing polymers may decrease atherosclerosis by increasing shear in areas normally exposed to low shear stress.

PURPOSE: Drag reducing polymers (DRPs) have been shown to decrease plaque formation. Their mechanism of action is unknown. Atherosclerosis tends to develop in areas of low shear stress. This study investigates whether DRPs increase shear stress in areas normally exposed to low shear stress. METHODS: Six dogs underwent surgical plication of the left half of the aorta. A specially modified 20-MHz Doppler ultrasound probe mounted at a 45-degree angle on a micromanipulator was used to measure blood flow velocity at six 4-mm intervals along both lateral sides of the aorta starting at the aortic wall and then at subsequent 0.1-mm depths moving into the lumen before and after administering DRP. Shear rates were calculated using linear regression and then compared using the paired t test. The blood viscosity remained constant at 0.04 poise during infusions of this amount of DRP. RESULTS: The maximum shear rate occurring during the cardiac cycle on the side of the aortic stenosis (plication) was 9.96 +/- 1.52/sec before the administration of the DRP and 14.27 +/- 2.01/sec after the administration of the DRP (P =.0240). The maximum shear rate on the side of the unstenosed aortic wall was 57.25 +/- 7.93/sec before the administration of the DRP and 44.80 +/- 6.23/sec after the administration of the DRP (P =. 0081). CONCLUSION: One of the ways that DRPs inhibit the development of atherosclerosis appears to be by increasing shear stress in areas normally exposed to low shear stress. Understanding this mechanism may lead to the development of pharmaceutical agents that inhibit the development of atherosclerosis.

The fate of unrepaired minor technical defects detected by intraoperative ultrasonography during carotid endarterectomy.

This report describes the natural history of unrepaired minor technical defects detected by intraoperative B-mode ultrasonography during carotid endarterectomy. Intraoperative ultrasonography was used to assess the technical adequacy of 80 carotid endarterectomies. Sixty-two arteries were normal on intraoperative ultrasound examination, whereas the remaining 18 arteries had a total of 21 minor residual technical defects. The 21 minor defects consisted of four internal carotid artery lesions, nine common carotid artery lesions, and eight external carotid artery lesions, 19 had 1 to 3 mm intimal flaps, and two had small stenoses. Sixteen of the 19 intimal flaps resolved before the first postoperative ultrasound study. These arteries had normal examination results, which indicated that these intimal flaps had healed. The two stenoses detected intraoperatively could not be detected by postoperative carotid duplex scanning at 1 month follow-up. No statistically significant relationship was found between the presence of a minor residual defect on intraoperative ultrasonography and the subsequent development of recurrent stenosis or occlusion in any of the arteries assessed. These data suggest that certain minor technical defects in the carotid artery that were detected by intraoperative ultrasonography are benign and may not require repeat exploration of the carotid artery for repair.