Deep venous thrombosis after percutaneous insertion of vena caval filters.

PURPOSE: A large multicenter study has recently questioned the overall clinical efficacy of vena caval filters, especially when inserted prophylactically, because of the subsequent development of deep venous thrombosis (DVT) at the insertion site. We examined the incidence of this complication with newer, smaller diameter percutaneous devices. METHODS: We reviewed our vascular surgery and interventional radiology clinical registries to identify patients in whom a femoral percutaneous vena caval filter had been placed from 1993 to 1998. This list was cross referenced with patients who had undergone lower extremity venous ultrasound scan examinations for the diagnosis of DVT in the vascular laboratory within a 60-day period before and after the insertion of the filter device. RESULTS: A total of 35 patients during this 5-year period had timely follow-up venous duplex scan studies performed. The indications for filter placement were DVT in 16 patients (46%), pulmonary embolus in 13 patients (37%), DVT and pulmonary embolus in three patients (9%), and prophylactically in three patients (9%) at high risk for thromboembolization. Of the patients with documented thromboembolic events, 91% (29 of 32) had contraindications to anticoagulation therapy, and the remaining 9% (3 of 32) represented failure of anticoagulation therapy. A Greenfield filter was used in 13 patients (37%), a Simon Nitinol filter was used in 11 patients (31%), and a VenaTech filter was used in nine patients (26%). The other two patients (6%) had a Bird's Nest filter inserted. At a mean follow-up period of 12 +/- 2 days (median, 6 days), there was a 40% (14 of 35) incidence of proximal DVT in venous segments without evidence of thrombus before filter insertion. The majority (71%; 10 of 14) occurred in the common femoral vein, with three located in the superficial femoral vein and one in the external iliac vein. The lowest incidence of DVT was seen with the Greenfield and Bird's Nest filters as compared with the smaller Simon Nitinol and VenaTech filters (20% vs 55%; P < .05). The highest incidence of thrombosis occurred in patients with pre-insertion pulmonary emboli (50%; 8 of 16) as compared with those patients with DVT (38%; 6 of 16) and prophylactic insertion (0%; 0 of 3). However, the subgroups were too small to attain statistical significance. CONCLUSION: There is a continuing and significant incidence of new DVT development ipsilateral to the percutaneous femoral insertion site of vena caval filters. The smaller diameter filters are not associated with a lower incidence of femoral thrombosis.

A national survey of practice patterns in the noninvasive diagnosis of deep venous thrombosis.

PURPOSE: Recent studies have recommended unilateral venous duplex scanning for the diagnosis of deep venous thrombosis (DVT) in patients who are unilaterally symptomatic. Vascular laboratory accreditation standards, however, imply that bilateral leg scanning should be performed. We examined whether actual practice patterns have evolved toward limited unilateral scanning in such patients. METHODS: A questionnaire was mailed to all 808 vascular laboratories in the United States that were accredited by the Intersocietal Commission for the Accreditation of Vascular Laboratories (ICAVL). To encourage candid responses, the questionnaires were numerically coded and confidentiality was assured. RESULTS: A total of 608 questionnaires (75%) were completed and returned. Most of the respondents (442; 73%) were either community-hospital or office-based laboratories, and the remaining 163 (27%) were university or affiliated-hospital laboratories. Most of the laboratories (460; 76%) had been in existence for 9 years or more, and 65% had been ICAVL-accredited in venous studies for 3 years or more. Board-certified vascular surgeons were the medical directors in 54% of the laboratories. Duplex ultrasound scanning was the diagnostic method used by 98% of the laboratories. In patients with unilateral symptoms, 75% of the laboratories did not routinely scan both legs for DVT. A large majority (75%) believe that bilateral scanning is not clinically indicated. Only 57 laboratories (14%) recalled having patients return with a DVT in the previously unscanned leg, with 93% of these laboratories reporting between one and five such patients. This observation correlated with larger volumes of venous studies performed by those laboratories (P <.05). Similarly, only 52 laboratories (12%) recalled having patients return with subsequent pulmonary emboli. Of these laboratories, only five reported proximal DVT in the previously unscanned legs of such patients. Of all these laboratories, therefore, only 1% (5 of 443) have potentially missed the diagnosis of a DVT that caused a preventable pulmonary embolus with such a policy. Among those laboratories that always perform bilateral examinations, 41% do so because of habit. Most (61%) of the laboratories that perform bilateral scanning would do unilateral scanning if it were specifically approved by ICAVL. CONCLUSION: Three quarters of the ICAVL-accredited vascular laboratories perform limited single-extremity scanning for the diagnosis of DVT in patients with unilateral symptoms. This broad clinical experience suggests that this practice is widespread in selected patients. Clinical protocols should be established to provide guidelines for local laboratory implementation.

Current applications of duplex ultrasonography and color Doppler imaging.

Duplex ultrasound is a noninvasive method of evaluating the function of the systemic arteries and veins. In this review, the physical principles of duplex ultrasonography are discussed and compared to other available noninvasive tests. The clinical applications of duplex ultrasound and color Doppler imaging are reviewed and diagnostic criteria stated. Newer and more controversial applications of duplex ultrasound are presented.

Influence of age on venous physiologic parameters.

PURPOSE: The incidence of deep venous thrombosis increases significantly with age. Attempts to explain this association have failed to identify factors that could be contributory. We hypothesized that age-related changes in venous physiologic parameters might contribute to an increased risk of deep venous thrombosis. METHODS: Air plethysmography was used to measure a number of physiologic parameters in two sets of patients. Group A consisted of 17 subjects (33 limbs), age range 23 to 40 years. Group B consisted of 11 subjects (22 limbs), age range 60 to 83 years. No subject in either group had peripheral vascular disease or a history of deep venous thrombosis. Parameters measured were venous volume, venous filling index, ejection volume, ejection fraction, residual volume fraction, and outflow fraction. RESULTS: Venous volume and ejection fraction were significantly reduced in Group B compared with Group A. Residual volume fraction was significantly increased in Group B compared with Group A. There were no statistically significant differences in outflow fraction, venous filling index, or ejection fraction between the two groups. CONCLUSIONS: These results suggest that the efficiency of the calf muscle pump diminishes with increasing age, possibly contributing to the increased incidence of deep venous thrombosis in the elderly.

Evaluation of celiac and mesenteric vascular disease with duplex ultrasonography.

A retrospective study of 25 patients was performed to evaluate the applicability of duplex ultrasonography to the celiac and superior mesenteric circulation. Lateral contrast aortograms were compared to the pulsed-Doppler spectral data from duplex examinations in fasting subjects. A significant correlation was identified between the celiac-aortic diastolic ratio and the degree of stenosis measured angiographically, but such a relationship could not be established for the superior mesenteric artery. These data suggest that duplex ultrasonography may not be a reliable screening test for mesenteric vascular disease.

Arterial reconstruction of the pancreatic allograft for transplantation.

The shortage of organs is particularly acute in whole pancreas transplantation, because the liver and pancreas often share a common arterial supply, making combined procurement of both organs difficult. A previously described technique of simultaneous whole liver and pancreas procurement depended on "classic" hepatic arterial anatomy, which is present just over half the time. We describe herein our experience with three Y-reconstructions of the splenic and superior mesenteric arteries of the pancreatic allograft using donor allograft internal and external iliac arteries. In situ Doppler ultrasound examination of the pancreatic allograft after surgery demonstrated a patent reconstruction without evidence of stenosis or turbulent flow patterns. We believe this reconstruction is a safe, alternative method to provide arterial flow to the whole donor pancreas.

Combined aortic and visceral arterial reconstruction: risks and results.

The indications, morbidity, and efficacy of combined reconstruction of the abdominal aorta and visceral arteries (renal and superior mesenteric; excluding suprarenal aortic aneurysms) were analyzed retrospectively in 29 consecutive patients who underwent surgery from June 1984 through February 1990. Seventeen men and 12 women ages 32 to 76 years (mean, 66 years) were studied. Follow-up was complete in all patients to either death or calendar year 1989 to 1990 (mean, 31.9 months; range, 2 to 66 months). All patients underwent bypass of angiographically proven severe lesions of one renal artery (19 patients), both renal arteries (8 patients), or the superior mesenteric artery and renal arteries (2 patients), in concert with synthetic distal aortic replacement for occlusive disease (10 patients) or aneurysm (19 patients). Indications for renal artery repair included severe hypertension in 13 patients, ischemic renal insufficiency in 8 patients, and lesion morphology alone in 8 patients. Operative mortality rate was 3 of 29 (10.3%), and each death was the result of multisystem organ failure. Nonfatal complications occurred in 11 of the 26 survivors (42%), and this group differed significantly from the uncomplicated 15 patients only in having a higher mean preoperative serum creatinine (2.5 +/- 1.1 mg/dl vs 1.6 +/- 0.9 mg/dl, p = 0.04, t test). The mortality rate of patients with preoperative serum creatinine greater than or equal to 2.0 mg/dl, was 15.4% (2/13 patients), compared to 6.2% (1/16) in patients with creatinine less than 2.0 mg/dl. Three late deaths occurred (2 stroke, 1 cancer). Hypertension control improved in 64% of patients overall, and in 7 of 9 patients whose major operative indication was renovascular hypertension. Renal function remained stable or improved in 12 of 15 patients (80%) with renal insufficiency, but 3 patients progressed to require dialysis. Long-term graft patency was demonstrated by angiography or on duplex scan in all studied survivors (21 patients). Although operative risks are clearly increased compared to less complex vascular procedures, careful patient selection and management will yield a favorable outcome in most patients with such combined lesions.

A rational approach to recurrent carotid stenosis.

To further characterize the incidence and morbidity of recurrent carotid stenosis, we reviewed 184 consecutive carotid endarterectomies performed in a university hospital between August 1983 and January 1988, in patients followed after operation with serial duplex ultrasonography. Recurrent stenosis of greater than 50% diameter reduction developed in eleven arteries (6.0%) at a mean interval of 10.2 +/- 7.8 months. Three of the eleven (1.6% of the total) had associated transient ischemic attack, and none had strokes. Restenosis was significantly more frequent in diabetic patients than in nondiabetic patients (13.3% vs 4.5%; p less than 0.05); and among patients whose primary stenoses had been symptomatic compared to asymptomatic (11.0% vs 1.5%; p less than 0.02). No statistically significant association with restenosis could be established for gender, hypertension, or smoking. Completion angiography and/or Doppler spectral analysis had been performed, and results were normal at the primary operation in 10 of the 11 patients. Only six of 184 arteries (3.3%) had vein patch closure, but none of these restenosed. Uneventful reoperation with patch closure was performed in three patients with transient ischemic attacks and two with preocclusive restenoses. Lesions were myointimal hyperplasia in four and atheroma in one. Three of the unoperated restenoses have shown regression on duplex scanning, but a fourth progressed to asymptomatic occlusion. Carotid restenosis is uncommon, even without routine use of vein patch angioplasty. Reoperation should be reserved for patients with associated symptoms or greater than 80% restenosis.

Evaluation of pancreatic allograft circulation using color Doppler ultrasonography.

In conclusion, color flow Doppler ultrasonography is a safe, noninvasive method to study perfusion in the pancreatic allograft. In trained hands, reproducibly quantitative measurements can be made of the circulation in the transplanted pancreatic allograft. With further experience, it is our hope that spectral analysis will elucidate rejection as it has for us with kidney transplants. Because the technique is noninvasive, it has a high degree of patient acceptance.

Physiologic and structural indices of vascular function in paraplegics.

In an effort to determine whether chronic physical forearm activity would increase both structural and physiologic indices of peripheral forearm vasodilation, we studied a group (N = 7) of individuals chronically performing high levels of arm work, young wheelchair-confined paraplegics, and compared them with ten young, able bodied control subjects. The index of vasodilator capacity was the flow response following the release of 10 min of arterial occlusion, the peak reactive hyperemic blood flow response (RHBF). The index of a structural effect of training on the vasculature was the brachial artery diameter (cm) derived by simultaneous measurement of velocity and forearm blood flow (area = flow.forearm volume.velocity-1). Vascular function differed significantly between the groups, with a greater RHBF (paraplegics, 53.8 +/- 3.7; controls, 38.2 +/- 1.5 ml.min-1.100 ml-1; P less than 0.05) and a larger brachial artery diameter at rest (paraplegics, 0.4 +/- 0.01 vs controls, 0.3 +/- 0.02 cm; P less than 0.05) in the paraplegics. We conclude that chronic upper extremity activity leads to an enhanced capability to vasodilate resistance vessels acutely and to a structural dilation of large conductance vessels.

Wound complications of autogenous subcutaneous infrainguinal arterial bypass surgery: predisposing factors and management.

To identify factors predisposing to wound infection and necrosis complicating in situ or other subcutaneous autogenous lower extremity vein bypass procedures, we retrospectively analyzed all such cases performed in our hospital between July 1983 and July 1988. Among 163 subcutaneous autogenous bypass grafts, wound complications developed in 28 (17%). According to progressive depth of involvement as defined in the text, 10 patients had grade I complications, six had grade II, and 12 had grade III complications with threatened or actual graft exposure. Factors significantly associated with wound morbidity were female gender, chronic steroid therapy, in situ bypass grafting, use of continuous incision (all p less than or equal to 0.05, chi square); diabetes mellitus, ipsilateral limb ulcer, limb salvage indication (all p less than 0.01); and bypass grafting to the dorsalis pedis artery (p less than 0.02). A logistic regression analysis identified four factors (in situ bypass grafting, steroid therapy, ipsilateral ulcer, and dorsalis pedis bypass grafting) that predicted a cumulatively increasing risk of wound complications, and in whose absence wound complications were rare. Grade I and II complications responded to standard regimens of wound care and intravenous antibiotics without loss of any graft or limb. In spite of aggressive efforts to provide secondary soft tissue coverage, grade III complications led directly to four major amputations and one death. Measures to prevent these morbid sequelae must include preoperative control of infection in the ischemic foot and meticulous attention to operative technique.

Hemodynamic performance of carotid artery shunts.

Although the use of shunts for carotid artery surgery remains controversial, the hemodynamics of the shunts currently available have not been carefully evaluated in vivo. We developed an animal model using contralateral carotid artery ligation, which produced ipsilateral carotid blood flows (640 +/- 44 ml/min) and internal carotid stump pressures (52 +/- 4 mm Hg) over a range commonly seen in carotid artery surgery. Seven shunts were tested and included Javid; 10F and 8F Brener; and 14F, 12F, 10F, and 8F Argyle shunts. The hemodynamic features evaluated for each shunt included maximum shunt flow, the pressure gradients occurring across each shunt, the increase in cerebral perfusion pressure over occlusion pressure associated with shunt placement, and the distal pressure pulse waveform. The larger diameter shunts were consistently better than the smaller diameter shunts. The correlation between shunt flow and the increase in distal pressure produced by shunt placement was high (r = 0.98, p less than 0.05), confirming that high flow rates maintained high perfusion pressure. By relating maximum shunt flow and the pressure gradient to the change in the pressure pulse contour for each shunt, it could be demonstrated that at the larger diameters, straight shunts displayed superior hemodynamic characteristics compared with tapered shunts, whereas at smaller diameters, tapered shunts were superior.

Dazoxiben, a thromboxane synthetase inhibitor, in Raynaud's phenomenon.

Dazoxiben, a specific thromboxane synthetase inhibitor, was evaluated in 21 patients with Raynaud's phenomenon in a double-blind, placebo-controlled crossover experiment. Total fingertip blood flows were measured by plethysmography and capillary blood flows were measured by 133Xe disappearance rate. Subjects were studied in both a warm (28 degrees) and a cold (20 degrees) room. Arteriovenous (AV) shunt flow was estimated by subtraction of capillary flow from total flow. Ex vivo production of thromboxane B2 (TXB2) and 6-keto PGF1 alpha was determined by specific radioimmunoassay in serum from venous blood incubated for 1 hr (37 degrees). Plasma concentrations of TXB2 and 6-keto PGF1 alpha were also monitored. Dazoxiben (100 mg 4 times a day for 14 days) inhibited ex vivo TXB2 production (from 463.1 +/- 69.9 to 101.8 +/- 13.4 ng/ml/hr; (means +/- SE], enhanced ex vivo 6-keto PGF1 alpha production (from 1.38 +/- 0.05 to 3.76 +/- 0.18 ng/ml/hr), reduced plasma TXB2 concentration (from 88.1 +/- 13.9 to 38.8 +/- 5.9 pg/ml). There were no changes in plasma concentration of 6-keto PGF1 alpha. Dazoxiben did not improve total digital blood flow, capillary flow, AV shunt flow, or forearm blood flow at 28 degrees or 20 degrees. There was no subjective improvement in frequency or severity of Raynaud's attacks (assessed by patient diaries). It is concluded that dazoxiben is a potent and specific thromboxane synthetase inhibitor capable of altering arachidonic acid metabolism, but is of little or no benefit in the treatment of Raynaud's phenomenon.