Lack of functional benefits following infrainguinal bypass in peripheral arterial occlusive disease patients

This study aimed to determine whether peripheral arterial occlusive disease (PAOD) patients with critical limb-threatening ischemia experienced functional benefits following lower extremity revascularization. Twenty ambulatory patients (aged 68 +/- 7 years) underwent infrainguinal revascularization to alleviate their symptoms. Peripheral hemodynamic and functional measures were obtained on each patient 1 week prior to and 3-4 months following revascularization. Critical limb-threatening ischemia was alleviated by surgery in all patients because the ankle/brachial index (ABI) increased 133% (p < 0.001) from 0.33 +/- 0.06 to 0.77 +/- 0.09. Despite the marked peripheral hemodynamic improvement following revascularization, little gains were noted in functional measures. The 6-min walking distance was unchanged (p = 0.739) from 85 +/- 9 m to 101 +/- 11 m. Additionally, the free-living daily physical activity, measured by an accelerometer worn over a 2-day period, was unchanged (p = 0.996) from 214 +/- 46 kcal/day to 215 +/- 83 kcal/day. In contrast, self-perceived ambulatory function improved by 142% to 271% (p < 0.001), and self-perceived physical activity increased 134% to 156% (p < 0.001). In conclusion, limb salvage following infrainguinal bypass does not translate into improvements in measured ambulation or in measured physical activity in PAOD patients, even though the patients perceive these measures to be better.

Improved functional outcomes following exercise rehabilitation in patients with intermittent claudication

BACKGROUND

The purposes of this study were to identify predictors of increased claudication distances following exercise rehabilitation in peripheral arterial occlusive disease (PAOD) patients with intermittent claudication and determine whether improved claudication distances translated into increased free-living daily physical activity in the community setting.

METHODS

Sixty-three patients were recruited (age, 68+/-1 years, mean +/- standard error). Patients were characterized on treadmill claudication distances, walking economy, peripheral circulation, cardiopulmonary function, self-perceived ambulatory function, body composition, baseline comorbidities, and free-living daily physical activity before and after a 6-month treadmill exercise program.

RESULTS

Exercise rehabilitation increased distance to onset of claudication pain by 115% (178+/-22 m to 383+/-34 m; p < .001) and distance to maximal claudication pain by 65% (389+/-29 m to 641+/-34 m; p < .001). The increased distance to onset of pain was independently related to a 27% increase in calf blood flow (r = .42, p < .001) and to baseline age (r = -.26, p < .05), and the increased distance to maximal pain was predicted by a 10% increase in peak oxygen uptake (r = .41, p < .001) and by a 10% improvement in walking economy (r = -.34, p < .05). Free-living daily physical activity increased 31% (337+/-29 kcal/day to 443+/-37 kcal/day; p < .001) and was related to the increases in treadmill distances to onset (r = .24, p < .05) and to maximal pain (r = .45, p < .001).

CONCLUSIONS

Increased claudication distances following exercise rehabilitation are mediated through improvements in peripheral circulation, walking economy, and cardiopulmonary function, with younger patients having the greatest absolute ambulatory gains. Furthermore, improved symptomatology translated into enhanced community-based ambulation.

External pneumatic compression and fibrinolysis in abdominal surgery

INTRODUCTION

External pneumatic compression (EPC) devices prevent lower extremity deep venous thrombosis by increasing venous flow and thereby reducing stasis. Early studies suggested that they also enhance systemic fibrinolytic activity and thus prevent thrombus formation; more recent studies have been conflicting. The hypothesis of this study was that EPC devices enhance systemic fibrinolysis or reduce postoperative fibrinolytic impairment in patients undergoing abdominal surgical procedures.

METHODS

Each of 48 patients (98% male; mean age, 67 years) undergoing major intra-abdominal surgical procedures (36 bowel procedures, 12 aortic reconstructions) was prospectively randomized to one of three treatments for deep venous thrombosis prophylaxis: subcutaneous heparin injections (HEP group), use of a thigh-length sequential EPC device (EPC group), or both (HEP + EPC group). Antecubital venous samples were collected for measurement of systemic fibrinolytic activity on the day before surgery, after induction of anesthesia but before prophylaxis was initiated, and on postoperative days 1, 3, and 5. Fibrinolysis was assessed through measurement of the activities of the rate limiting fibrinolytic activator, tissue plasminogen activator, and its inhibitor plasminogen activator inhibitor-1 with amidolytic methods.

RESULTS

On the day before surgery, plasminogen activator inhibitor-1 activity was elevated in all groups in comparison with that in age-matched and sex-matched controls (20.3 +/- 0.6 AU/mL). In the HEP group, plasminogen activator inhibitor-1 activity was further elevated above the value for the day before surgery on postoperative day 1 (28.5 +/- 4.3 AU/mL; P =.04) and postoperative day 3 (25.1 +/- 1.9 AU/mL; P =.07). No significant decrease in plasminogen activator inhibitor-1 activity occurred in either group treated with EPC devices in comparison with the HEP group at any time. There were no changes in tissue plasminogen activator activity postoperatively in the HEP group and no significant increases in either EPC group at any point.

CONCLUSIONS

Reduced systemic fibrinolytic activity ("fibrinolytic shutdown") occurred in these patients after abdominal surgery; it was manifested as increased plasminogen activator inhibitor-1 activity. EPC devices did not enhance systemic fibrinolysis or prevent postoperative shutdown either by decreasing plasminogen activator inhibitor-1 activity or by increasing tissue plasminogen activator activity. These data suggest that EPC devices do not prevent deep venous thrombosis by fibrinolytic enhancement; effective prophylaxis is achieved only when the devices are used in a manner that reduces lower extremity venous stasis.

The prevalence of carotid artery stenosis in patients undergoing aortic reconstruction

BACKGROUND

Coronary artery disease occurs frequently in patients undergoing aortic reconstruction, and it has been presumed that internal carotid artery occlusive disease is also common. This has led to the practice of screening for and repairing significant carotid lesions in asymptomatic patients prior to aortic reconstruction. The purpose of this study was to determine the true prevalence of internal carotid artery disease in these patients.

METHODS

The records of 240 patients who underwent duplex ultrasound screening for carotid artery disease prior to aortic reconstruction were reviewed. Surgery was performed for aortic aneurysm (AA) or aorto-iliac occlusive disease (AO). The prevalence of hyperlipidemia and coronary artery disease was similar between the two groups, but tobacco use, hypertension, and diabetes mellitus differed.

RESULTS

Internal carotid artery stenosis > or = 50% occurred in 26.7% of the total group (64 of 240 cases). Stenosis > or = 50% was more common in the AO group (40 of 101 cases, 39.6%) than the AA group (24 of 139 cases, 17.3%, P = 0.0001). Severe disease (70% to 99%) was also more common in the AO group than the AA group (9.9% versus 3.6%, P = 0.0464).

CONCLUSION

Internal carotid artery disease occurs commonly in patients undergoing aortic reconstruction, and screening is worthwhile. Significant disease is more common in patients with aorto-iliac occlusive disease than in those with aortic aneurysm, although atherosclerotic risk factors occur with varying frequency in the two groups. These findings suggest that additional factors may contribute to the higher prevalence of internal carotid artery stenosis in aorto-iliac occlusive disease.

Smoking history is related to free-living daily physical activity in claudicants

PURPOSE

To determine whether smoking history was related to free-living daily physical activity in peripheral arterial occlusive disease (PAOD) patients with intermittent claudication, and whether the effect of smoking history on physical activity level persisted after controlling for group differences in ambulatory function, peripheral circulation, and body composition.

METHODS

Patients were separated into three groups: those who never smoked (N = 35), those who had a lower pack-year history of smoking (< or =40 pack-yr; N = 33), and those who had a higher pack-year history (>40 pack-yr; N = 30). Free-living daily physical activity was assessed by activity monitors (an accelerometer and a pedometer) worn on each hip over 2 consecutive weekdays. Patients also were characterized on ambulatory function, peripheral circulation, and body composition because of their relationship with physical activity.

RESULTS

A progressive decline (P < 0.001) in free-living daily physical activity with increasing smoking exposure was obtained from the accelerometer in the nonsmokers (482 +/- 36 kcal x d(-1); mean +/- SE), smokers with a lower pack-year history (361 +/- 37 kcal x d(-1)), and smokers with a higher pack-year history (227 +/- 23 kcal x d(-1)). A similar decline was found with the pedometer data (P < 0.001). After controlling for group differences in 6-min walk distance and in calf transcutaneous heating power, group differences in free-living daily physical activity were no longer significant.

CONCLUSION

Progressive decrements in free-living daily physical activity with greater levels of smoking exposure in PAOD patients are primarily due to smoking-related impairments in ambulatory function and peripheral circulation.

Relationship between free-living daily physical activity and peripheral circulation in patients with intermittent claudication

The purpose of this study was to determine the relationship between free-living daily physical activity and peripheral circulation under resting, reactive hyperemia, and maximal exercise conditions in peripheral arterial occlusive disease (PAOD) patients with intermittent claudication. Sixty-one PAOD patients (age = 70 +/- 6 years, ankle/brachial index [ABI] = 0.57 +/- 0.24) were recruited from the Vascular Clinic at the Baltimore Veterans Affairs Medical Center and from radio and newspaper advertisements. Free-living daily physical activity was measured as the energy expenditure of physical activity (EEPA), determined from doubly labeled water and indirect calorimetry. Patients also were characterized on ankle/brachial index, calf blood flow, calf transcutaneous oxygen tension (TcPO2), and calf transcutaneous heating power (TcHP). ABI and calf blood flow served as markers of the macrocirculation of the lower extremity, while TcPO2 and TcHP served as markers of the microcirculation. The claudication patients were sedentary, reflected by a mean EEPA value of 486 +/- 274 kcal/day. EEPA was related to calf TcHP at rest (282 +/- 24 mW; r = -0.413, p = 0.002), after postocclusion reactive hyperemia (275 +/- 22 mW; r = -0.381, p = 0.004), and after maximal exercise (276 +/- 20 mW; r = -0.461, p<0.001). ABI, calf blood flow, and calf TcPO2 were not related to EEPA under any condition. In conclusion, higher levels of free-living daily physical activity were associated with better microcirculation of the calf musculature in older PAOD patients with intermittent claudication.

Brain-specific protein C activation during carotid artery occlusion in humans

BACKGROUND AND PURPOSE

Activation of plasma protein C (PC) zymogen by thrombin-thrombomodulin at the endothelial surface is an important endogenous antithrombotic mechanism. It is unknown whether activated protein C (APC) is generated in vivo in the cerebrovasculature, because there is only limited thrombomodulin expression in human brain vascular endothelium. Therefore, we tested the hypothesis that carotid occlusion produces brain-specific PC activation.

METHODS

Blood samples were simultaneously collected from the ipsilateral internal jugular vein and radial artery before and during carotid cross-clamping and on "de-occlusion" in 8 awake patients undergoing routine carotid endarterectomy. Plasma PC zymogen and circulating APC levels were measured using enzyme immunocapture assay and expressed as percent of pooled plasma controls.

RESULTS

Internal jugular vein APC levels increased 28% exclusively during carotid occlusion and then decreased 32% with de-occlusion (F=8.1, P<0.005). PC zymogen increased only 5.9% with occlusion (F=6.3, P<0.02), consistent with hemoconcentration. There were no changes in radial artery PC or APC levels.

CONCLUSIONS

These findings demonstrate brain-specific protein C activation in humans during carotid occlusion and suggest a protective role for endogenous APC generation during cerebrovascular occlusion.

Cigarette smoking shortens the duration of daily leisure time physical activity in patients with intermittent claudication

PURPOSE

The authors determined (1) whether peripheral arterial occlusive disease (PAOD) patients who smoke have a reduction in either the duration or intensity of daily physical activities compared with nonsmoking patients, and (2) whether group differences in the pattern of physical activity persisted after controlling for potential confounding variables.

METHODS

A total of 170 smokers and 201 nonsmokers who had quit smoking for at least 1 year prior to investigation were studied. Physical activity patterns were measured using the Minnesota Leisure Time Physical Activity (LTPA) questionnaire. Patients also were characterized on potential covariates such as demographics, comorbid conditions, cardiovascular risk factors, ambulatory measures, peripheral hemodynamics, and anthropometric measures.

RESULTS

The smokers were 37% less physically active than the nonsmokers (87 +/- 90 versus 139 +/- 121 kcal/day; P = 0.027). The reduced total LTPA in the smokers was due to a 28% shorter duration of performing activities (26 +/- 7 versus 36 +/- 22 min/day; P = 0.031), and a 3% lower mean intensity of the activities (3.3 +/- 1.0 versus 3.8 +/- 0.8 kcal/min; P = 0.038). The distance score on the Walking Impairment Questionnaire and the hip circumference were significant covariates of the LTPA measures. After adjusting for these covariates, the total LTPA remained 29% lower in the smokers (P = 0.039), the mean daily duration of LTPA remained 20% lower (P = 0.043), but the mean intensity of LTPA was no longer different between the groups.

CONCLUSION

Compared with their nonsmoking counterparts, claudicants who smoke have a reduced total LTPA because they engage in activities of similar intensity for a shorter duration of time.

Can intrarenal duplex waveform analysis predict successful renal artery revascularization?

PURPOSE

No currently available noninvasive test can preoperatively predict a successful outcome to renal revascularization. Resistance measurements from the renal parenchyma obtained with duplex sonography reflect the magnitude of intraparenchymal disease, and patients with extensive intrarenal disease may respond less favorably to revascularization. To address this question, we reviewed our (primarily) operative experience in patients undergoing renal artery revascularization, and compared the blood pressure (BP) and renal function response with resistance measurements obtained from the kidney both before and after revascularization.

METHODS

During a 56-month period, 31 consecutive renal artery revascularizations (25 surgical and 6 percutaneous angioplasties) were performed in 23 patients (21 atherosclerotic, 2 fibromuscular dysplasia). Duplex sonography was performed in each patient before and after revascularization, and parenchymal diastolic/systolic (d/s) ratios were calculated. BP and renal function response to intervention were compared with measurements of intrarenal flow patterns before and after revascularization.

RESULTS

Mean parenchymal peak systolic velocity was significantly higher after repair in all patients (pre-repair: 19.5 +/- 1.3, postrepair: 27.2 +/- 1.7; P < .0001). Despite this, there were no statistical differences between preoperative and postoperative parenchymal d/s ratios. A favorable (cured or improved) BP response was seen in 81% (17 of 21) of revascularizations performed for hypertension. Among these successes, parenchymal d/s ratios were in the normal range (ie, > or = 0.30) both before and after repair (mean prerepair: 0.34 +/- 0.03, mean postrepair: 0.31 +/- 0.03; not significant). In 4 patients in which BP failed to improve after intervention, the d/s ratio was abnormal before surgery (< 0.3), and remained so after revascularization (mean preoperative d/s ratio: 0.18 +/- 0.04, mean postoperative d/s ratio: 0.11 +/- 0.04; P = .003). Mean preoperative parenchymal d/s ratios were significantly higher in all patients with a successful BP response when compared with failures (P = .048). Similarly, among patients with single artery repairs, mean preoperative d/s ratios approached significance in successes vs. failures (success: 0.40 +/- 0.03, failure: 0.21 +/- 0.03; P = .054). A decrease in serum creatinine greater than or equal to 20% was seen in 8 of 18 patients (44%) with ischemic nephropathy. These patients also had normal d/s ratios preoperatively (mean 0.39 +/- 0.04), whereas the 10 patients who failed to improve had significantly lower ratios (mean 0.24 +/- 0.03; P = .041). Kidney length did not correlate with d/s ratio.

CONCLUSION

Although we do not believe that duplex sonographic measurement of intrarenal flow patterns alone is an accurate means of assessing main renal artery occlusive disease, the resistive indices seem to reflect the magnitude of intraparenchymal disease, and thus may provide important prognostic information for patients undergoing surgical revascularization. Our data suggest that a preoperative d/s ratio below 0.3 correlates with clinical failure relative to BP and renal function responses.

Relationship between free-living daily physical activity and ambulatory measures in older claudicants

The purpose of this study was to determine the relationship between free-living daily physical activity and ambulatory measurements in peripheral arterial occlusive disease (PAOD) patients with intermittent claudication. Thirty-four older, nonsmoking PAOD patients with intermittent claudication (age=69.0 +/- 6.0 years, ankle/brachial index [ABI] =0.63 +/- 0.18) were recruited from the Vascular Clinic at the Baltimore Veterans Affairs Medical Center and from radio and newspaper advertisements. Energy expenditure of physical activity (EEPA) was determined by using doubly labeled water and indirect calorimetry techniques. Patients were also characterized on claudication distances and peak oxygen uptake during a graded treadmill test, 6-minute walking distance, weight, body mass index, and percent body fat. The claudication patients were sedentary, as EEPA was 362 +/- 266 kcal/day. EEPA was related to the 6-minute walk distance (369 +/- 68 meters; r=0.629, P<0.001), to the number of steps taken during 6 minutes (605 +/- 99 steps; r=0.485, P=0.008), to the treadmill distance to maximal claudication (313 +/- 131 meters; r=0.470, P=0.010), and to the time to relief of pain (6:21 +/- 3:57 min:sec; r=-0.417, P=0.017). None of the other ambulatory and body composition measurements were correlated with EEPA. In conclusion, a reduction in free-living daily physical activity was associated with a decrease in ambulatory ability and with more severe intermittent claudication in older PAOD patients.

Progressive intermittent claudication is associated with impaired fibrinolysis

PURPOSE

Acute complications of atherosclerosis such as stroke and myocardial infarction are caused by thrombosis and may be associated with impaired fibrinolytic activity. The current study was performed to determine whether peripheral arterial disease (PAD) and its progression are also associated with impaired fibrinolysis, by measurement of tissue plasminogen activator (tPA, the activator of fibrinolysis) and its inhibitor plasminogen activator inhibitor-1 (PAI-1).

METHODS

The study group consisted of 80 men with a mean age of 69 years. This included 18 patients with mild intermittent claudication (MC, pain-free walking distance > or = 200 meters) and 51 patients with severe claudication (SC, walking distance <200 meters). Eleven age- and sex-matched patients without PAD served as controls. All patients had measurements of serum tPA antigen using an enzyme-linked immunoadsorbent assay. Serum levels of tPA and PAI-1 activity were assayed with an amidolytic method. Mean +/- SEM levels of the enzyme levels in patients with progressively more severe PAD were compared with normal controls.

RESULTS

Serum PAI-1 activity levels were significantly elevated in both PAD groups compared with normal controls (p < 0.02). There were no significant differences in the PAI-1 activity levels in groups with worsening degrees of PAD. There was a significant decrease in tPA activity levels in patients with SC (p = 0.01) relative to those with MC and the normal subjects. There was also a significant increase in tPA antigen level in the patients with SC compared with those with MC and the control subjects, as well as a significant inverse correlation between tPA antigen levels and pain-free walking time in patients with claudication (p = 0.001).

CONCLUSIONS

All patients with PAD in this study had significant reductions in endogenous fibrinolytic activity. Patients with SC had more impaired fibrinolytic activity than those with MC and the control subjects, suggesting that the progression to more severe levels of PAD may be associated with worsening endogenous fibrinolysis.

The effect of cigarette smoking on free-living daily physical activity in older claudication patients

The purposes of this study were (1) to determine whether peripheral arterial occlusive disease (PAOD) patients who smoke have a lower free-living daily physical activity than nonsmoking patients and (2) to determine whether the difference in physical activity persisted after controlling for potential confounders such as PAOD severity, age, body composition, and peripheral circulation. Thirty-four smokers (45.5 +/-9.8 years of smoking) and 43 nonsmokers (former smokers who had a smoking history of 35.0 +/- 13.1 years who quit 12.2 +/- 10.5 years prior to investigation) were studied. Patients wore a Caltrac accelerometer and a pedometer on each hip over two consecutive weekdays to assess free-living daily physical activity. Patients were also characterized on age, weight, body mass index (BMI), percent body fat, ankle/brachial index (ABI), calf blood flow, and exercise capacity. The smoking and nonsmoking claudication patients had a similar level of PAOD severity, for no group differences were noted in ABI (P=0.287) and treadmill time to maximal claudication pain (P=0.201). However, the smokers were 35% less physically active than the nonsmokers (264 +/- 123 vs 407 +/- 272 kcal/day; P<0.006), and they took 23% fewer steps (4,116 +/- 2,199 vs 5,329 +/- 2,924 steps/day; P<0.034). After adjustment for group differences in age, weight, BMI, percent body fat, and calf blood flow, the lower activity level of the smokers persisted. The adjusted daily energy expenditure was 27% lower (292 +/- 105 vs 400 +/- 214 kcal/day; P=0.021), and the adjusted amount of daily walking was 29% lower (4,039 +/- 1,760 vs 5,684 +/- 2,235 steps/day; P=0.003). Smoking PAOD patients had a less physically active lifestyle than nonsmoking patients, and the lower activity level of the smokers was independent of PAOD severity, age, body composition, and peripheral circulation.

Regression of proximal deep venous thrombosis is associated with fibrinolytic enhancement

PURPOSE

Recanalization after acute lower limb deep venous thrombosis (DVT) is well documented, but the precise mechanism and timing of these events has not been well characterized. Regression of DVT has been presumed to result from activation of the endogenous fibrinolytic system. This study was performed to compare measurements of the enzymatic components of the intrinsic fibrinolytic system (tissue plasminogen activator [tPA], plasminogen activator inhibitor [PAI-1]) with the observed morphologic changes in thrombosed venous segments using venous duplex ultrasound scanning (VDUS) at intervals after diagnosis of acute DVT.

METHODS

Nineteen patients with acute DVT underwent serial VDUS to assess regression of thrombus at intervals of 1 to 2 weeks, 3 to 6 weeks, 8 to 12 weeks, and 24 to 36 weeks. The extent of thrombus in each limb was quantitated at each interval by VDUS of the residual thrombus present in each of five major axial venous segments: the common femoral, superficial femoral, profunda femoris, popliteal, and tibial veins. Thrombus scores for the group at each interval were compared with baseline scores at diagnosis to calculate the percent residual thrombus. Endogenous fibrinolytic activity was determined at the same intervals by serologic assay of the biologic activities of tPA and its inhibitor PAI-1.

RESULTS

Thrombus regression was evident by VDUS at 1 to 2 weeks and progressed such that only 26% of residual thrombus remained at 24 to 36 weeks. Complete resolution of thrombus occurred in 10 of 18 patients (56%) who completed the 9-month study. Baseline mean tPA activity was 0.60 +/- 0.07 IU/ml and increased to 1.31 +/- 0.26 IU/ml at 1 to 2 weeks (p = 0.014). tPA activity remained significantly elevated through the 8 to 12 week interval and returned to baseline at 24 to 36 weeks. PAI-1 activity was elevated relative to an age-matched population at baseline (23.1 +/- 1.8 AU/ml) but remained unchanged throughout the study period. Progression of thrombus was observed in three patients (15.8%). Patients who experienced propagation of thrombus did not have the increased tPA activity that appeared to mark activation of intrinsic fibrinolysis.

CONCLUSIONS

Regression of acute DVT begins early and continues for at least 9 months. It is accompanied by significant enhancement of the endogenous fibrinolysis, which appears to be primarily mediated by increased tPA activity. Patients who have thrombus propagation in spite of standard antithrombotic therapy may have failure of activation of endogenous fibrinolysis.

A randomized, prospective trial of deep venous thrombosis prophylaxis in aortic surgery

OBJECTIVES

To study the incidence of postoperative deep venous thrombosis (DVT) in patients undergoing elective aortic reconstruction and to determine if aggressive DVT prophylaxis would reduce the incidence of DVT in these patients.

DESIGN

Randomized, prospective trial.

SETTING

University hospital and Veterans Affairs hospital.

PATIENTS

One hundred patients undergoing aortic reconstruction for aneurysmal or occlusive disease randomized to receive DVT prophylaxis (treatment group) or no prophylaxis (control group). Exclusion criteria included a history of DVT, long-term anticoagulant use, or a malignant neoplasm. During the study period, 12 patients were ineligible for follow-up. Ninety-eight patients completed the trial, including 50 patients in the treatment group and 48 patients in the control group. Two patients in the control group died postoperatively of unrelated causes.

INTERVENTION

Patients in the treatment group received DVT prophylaxis using a combination of low-dose heparin sodium therapy (5000 U every 12 hours) and calf-length intermittent mechanical compression devices. Control patients received no DVT prophylaxis.

MAIN OUTCOME MEASURES

The occurrence of acute lower extremity DVT diagnosed by interval venous duplex ultrasound scan surveillance performed on postoperative days 1, 3, and 7.

RESULTS

The overall incidence of proximal DVT in this study was 2%. One case of DVT occurred in the treatment group, and the other one occurred in the control group. There was no statistically significant difference (P = .99) in the incidence of DVT between the 2 groups. One patients in the control group had a nonfatal pulmonary embolus (1% of the patients overall).

CONCLUSIONS

The incidence of proximal DVT in patients undergoing elective aortic reconstruction is low compared with patients undergoing other major intraabdominal general surgical procedures. The use of aggressive DVT prophylaxis did not reduce the risk of postoperative proximal DVT in this study. The selective use of DVT prophylaxis in patients undergoing elective aortic surgery should be based on associated concomitant or evolving risk factors.

Defective fibrinolysis occurs after infrainguinal reconstruction

PURPOSE

Early thrombosis of infrainguinal bypass grafts may occur as a result of hypercoagulable states. Major surgical procedures are known to induce a procoagulant state that is manifested in part by reduced endogenous fibrinolytic activity or fibrinolytic shutdown. This study was performed to assess the timing and biologic mechanism of fibrinolytic shutdown after infrainguinal bypass procedures by direct assay of the serologic markers of in vivo fibrinolytic activity.

METHODS

Twenty patients underwent infrainguinal bypass procedures under epidural anesthesia. Endogenous fibrinolytic activity was assessed by measurement of tissue plasminogen activator (tPA) and its naturally occurring inhibitor, plasminogen activator inhibitor (PAI-1). The tPA and PAI-1 antigen (total protein) levels were determined using enzyme-linked immunosorbent assays, and measurements of in vivo biologic activity were performed using an amidolytic method. Measurements of tPA and PAI-1 were made before surgery, after surgery, and on postoperative days 1, 2, 7, and 30.

RESULTS

The mean preoperative PAI-1 activity was 20.6 +/- 1.4 arbitrary units (AU)/ml, which was higher than that of an age-matched population without severe atherosclerosis. PAI-1 activity rose significantly after surgery (29.6 +/- 2.2 AU/ml; p = 0.002) and remained elevated through the second day after surgery. Preoperative tPA activity level was 2.04 +/- 0.59 IU/ml and fell to 0.79 +/- 0.23 IU/ml (p = 0.046) immediately after the bypass procedure. All serologic indicators of fibrinolytic shutdown returned to baseline levels by 72 hours after surgery. No early graft thrombosis or other atherothrombotic complications occurred in these study patients.

CONCLUSIONS

Defective endogenous fibrinolytic activity occurs in the early postoperative period after infrainguinal bypass grafting procedures. Diminished endogenous fibrinolytic activity in these patients appears to be mediated by a combination of reduced tPA activity and significantly increased PAI-1 activity. No practical method is available to directly treat postoperative fibrinolytic shutdown, but postoperative antithrombotic therapy may be useful during this period to prevent early graft occlusion related to a relative hypercoagulable state.

Early duplex scan evaluation of four vena caval interruption devices

PURPOSE

Transvenous inferior vena cava (IVC) filters are used successfully for prevention of pulmonary embolism (PE), but early thrombotic complications such as insertion site thrombosis (IST) and inferior vena cava thrombosis (IVCT) may occur after placement. The frequency of these complications has been uncertain particularly for the wide variety of newer devices. This study was performed to prospectively evaluate IST and IVCT with color-flow venous duplex ultrasound scanning after four IVC filters were placed: the birds' nest filter, the titanium Greenfield filter, the stainless steel Greenfield filter, and the Simon nitinol filter.

METHODS

Percutaneous IVC filters were placed in 174 patients over a 21-month period. A birds' nest filter was used in 39 (22%) cases, a titanium Greenfield filter in 67 (39%) cases, a stainless steel Greenfield filter (25%) in 43 patients, and a Simon nitinol filter in 25 (14%) cases. Filters were placed for major deep venous thrombosis in 113 (63%) patients, after PE in 26 (15%) patients, and with prophylaxis in 35 (20%) patients. All patients had color-flow venous duplex ultrasound scanning of the insertion site and the inferior vena cava 7 to 10 days after placement or before discharge to document IST or VCT.

RESULTS

Early IST occurred in 43 (24.7%) cases, and early IVCT was observed in 20 (12%) cases in this series. No significant difference was found in the incidence of IST or IVCT among the four filter types used. The incidence of IVCT was significantly higher in patients having filters placed for PE. Men were more likely to receive a prophylactic filter than women in this study, but thrombotic complications were not related to patient sex. Thrombosis was seen with equal frequency at all insertion sites used. No patient died of PE after filter placement during the study period.

CONCLUSIONS

The incidence of thrombotic complications for all devices was higher than has generally been reported. No IVC filter used in this study demonstrated superior performance with regard to these thrombotic complications. As vena cava interruption devices are developed or significantly modified, prospective objective analysis of associated thrombotic complications will allow logical selection for clinical use.

Blue toe syndrome from a "coral reef" aorta

An endoaortic calcified mass, sometimes referred to as a "coral reef" aorta, is an unusual cause of distal leg microembolization. When discovered it is usually in the suprarenal aorta. We present an unusual case of infrarenal coral reef aorta with symptoms of distal atheroembolism. A review of the literature is also presented.

Venous hemodynamics during impulse foot pumping

PURPOSE

This study was designed to measure the effect of intermittent pneumatic compression of the plantar venous plexus on popliteal vein (PV) and common femoral vein (CFV) velocities measured by duplex ultrasound scanning.

METHODS

Thirty lower limbs in 15 healthy volunteers had venous duplex scanning measurement of PV and CFV velocities before and during foot pumping with an arteriovenous impulse foot pump system. Venous velocities were measured at two pump pressure settings (100 mm Hg, 200 mm Hg) and during two pump impulse durations (short = 1 second, normal = 3 seconds). All limbs were examined with the subjects in the supine position, and then measurements were repeated with subjects in the 15-degree reverse Trendelenburg position. The mean maximum venous velocity (MVV) produced by foot pumping was compared with resting venous velocity at each anatomic location and for each technologic variable.

RESULTS

Impulse foot pumping produced a statistically significant increase in MVV in both the PV and the CFV compared with resting velocities. This significant increase was observed for both pressure settings and both impulse durations, and no differences produced by these two individual variables could be detected. The increase in MVV produced by foot pumping was similar for limbs in the supine position and those examined in the reverse Trendelenburg position. The percentage increase in MVV produced by foot pumping was significantly higher in the PV than in the CFV.

CONCLUSIONS

Intermittent pneumatic compression of the plantar venous plexus produces measurable increases in venous outflow from the lower limbs of normal subjects. This study seems to justify further evaluation of the effectiveness of this technique for mechanical deep venous thrombosis prophylaxis in selected high-risk patient groups.

Early experience with a new ePTFE vascular prosthesis for hemodialysis

BACKGROUND

An expanded polytetrafluoroethylene (ePTFE) graft for hemodialysis designed for immediate cannulation was tested. The graft contains a cannulation segment consisting of a stretch ePTFE base tube surrounded by flat and round ePTFE fibers that are secured by a thin, perforated ePTFE cover. This study reports our early experience with this new vascular prosthesis.

PATIENTS AND METHODS

Between June 1994 and March 1995, 48 arteriovenous grafts were implanted in 47 patients for whom autogenous fistula construction was impossible. Mean patient age was 57 years (range 37 to 85), 86% of the patients were black, and 60% were men. Twenty-two (46%) grafts were in the forearm, 19 (39%) in the upper arm, and 7 (15%) in the groin. Unassisted and assisted patency rates were calculated by the Kaplan-Meier method. The times of first hemodialysis relative to implantation and the times to hemostasis after first decannulation were recorded. Explanted grafts were histologically evaluated with hematoxylin and eosin and Gram's stains.

RESULTS

The unassisted and assisted 6-month patency rate were 42% and 73%, respectively. Five of the first 10 graft were lost to management and technical errors, after which the respective patency rates were 56% and 82%. Eleven of 22 thrombosed grafts were salvaged, 9 with urokinase thrombolysis and 2 with surgical thrombectomy. Twenty-eight grafts were cannulated within 7 days. The time to hemostasis was usually 2 to 4 minutes and always less than 15 minutes. Histologic analysis of a graft explanted at 40 days showed good fibrous incorporation and capillary ingrowth between the cover and round fibers.

CONCLUSIONS

This new ePTFE vascular prosthesis can be safely cannulated immediately after implantation, avoiding the morbidity of temporary central venous catheter hemodialysis. After an initial period of familiarization, patency similar to that of other ePTFE arteriovenous grafts was achieved. For patients requiring urgent hemodialysis, this graft is an ideal alternative that allows immediate, safe cannulation.

Salvage of renal allograft function and lower extremity venous patency with thrombolytic therapy: case report and review of the literature

Five months after a cadaveric renal transplants a 69-year-old man was admitted with caval, iliac, and renal allograft vein thrombosis that occurred in the setting of a previously placed caval filter. The patient's urine output and renal function deteriorated rapidly. Thrombolytic therapy with urokinase was begun, and lysis of the thrombus occurred in 72 hours. The patient's renal function returned to baseline, and the transplant was salvaged. Moreover lower extremity venous patency and valvular function were maintained. We report the case and review the literature on thrombolytic therapy for renal allograft vein and lower extremity deep venous thrombosis.

Value of lower extremity venous duplex examination in the diagnosis of pulmonary embolism

PURPOSE

This study tests the hypothesis that the absence of deep venous thrombosis (DVT) on lower extremity color-flow venous duplex examination (LECFD) combined with a non-high-probability ventilation/perfusion (V/Q) scanning results rules out pulmonary embolus (PE). The use of LECFD as a diagnostic aid for PE is based on data that show that 90% of PE originate from lower extremity DVT, and therefore on the assumption that PE cannot be present if DVT is not present as the source.

METHODS

Over a 3-year period 51 patients with clinically suspected PE underwent LECFD and pulmonary angiography (PA) within 72 hours of each other. Forty-one patients also underwent V/Q scanning during the same time period. The results of LECFD and V/Q scans were compared with the results of PA, the gold standard for the diagnosis of pulmonary emboli.

RESULTS

Results of LECFD were positive for DVT in seven of 16 cases of angiographically documented PE. Thus the "sensitivity" of LECFD as a diagnostic aid in cases of suspected PE is 44%. The results of LECFD and V/Q scans were combined and compared with the results of PA. A high-probability V/Q scanning result was considered positive for PE. Intermediate- and low-probability scanning results were considered negative, because in the literature the decision to begin heparin therapy is not made on the basis of this result. The combination of test results was considered positive if either test result was positive and negative only if results of both were negative. With these criteria the combination of test results was positive in only 62% of cases of angiographically documented PE.

CONCLUSIONS

If treatment of suspected PE were based on LECFD alone or on duplex combined with V/Q scanning, 40% to 50% of patients with PE would remain untreated. In cases of suspected PE where these noninvasive tests do not confirm its presence, PA should be performed.

The "all-autogenous" tissue policy for infrainguinal reconstruction questioned

In 33% of patients referred for infrainguinal reconstruction for limb-threatening ischemia (mean preoperative ankle-arm index [AAI] = 0.26), no suitable autogenous reconstruction was possible. In 40% of cases, intraoperative pre-bypass contrast arteriography was necessary to identify a graftable tibial or pedal artery. The results of polytetrafluoroethylene (PTFE) and autogenous bypasses were compared after 1 to 3 years. After 1 year, patency was 85% and 67% for autogenous and PTFE bypasses, respectively. Limb salvage was 90% for autogenous bypass and 70% for PTFE bypass. Cumulative patency rates at 3 years were 80% for autogenous and 57% for PTFE grafts. Graft surveillance with duplex scanning and AAI was valuable in detecting failing grafts. For both types of reconstruction, secondary procedures were required to maintain patency. We attribute the excellent results with PTFE in part to long-term aspirin and warfarin therapy. In cases of combined superficial femoral and severe infra-popliteal occlusive disease, PTFE bypass is an excellent alternative when no autogenous conduit is available.

Surveillance of in situ infrainguinal bypass grafts: conventional vs. color flow duplex ultrasonography

Surveillance of in situ saphenous vein bypass grafts with duplex scanning detects graft abnormalities which may lead to graft thrombosis. Correction of these defects, while grafts are still patent, potentially improves overall graft patency. In this study we compared color flow and conventional duplex to determine whether color flow provided additional information not obtainable by conventional duplex examination. The primary patency rate (patency maintained without intervention) for all 51 cases was 76% (39/51). The secondary patency rate (patency maintained by identification and correction of graft defects before failure) was 88% (45/51). Duplex scanning reduced the graft failure rate by 50%. Color flow and conventional duplex examination provided the same information regarding incipient graft failure. In 20 patients monitored with both techniques, the same number of proximal (100%) and distal (90%) anastomoses were imaged. The same number of graft defects (three vein graft stenoses, one proximal femoral artery stenosis) were identified. Velocity data obtained using the two techniques (peak systolic velocity in an area of stenosis and the duplex velocity ratio) were not always the same, making calculation of percent stenosis from this data inaccurate. Color flow duplex is useful in monitoring graft patency, but provides no additional information over that provided by conventional scanning.

Diagnosis of deep venous thrombosis. A prospective study comparing duplex scanning to contrast venography

Duplex scanning has been proposed as a safe alternative to contrast venography for diagnosing deep venous thrombosis, but its accuracy has not been proved. In this prospective, double-blind study of 47 patients, the sensitivity and specificity of duplex scan criteria were determined relative to contrast venography for lower extremity deep venous thrombosis. Criteria considered to show the presence of deep venous thrombosis included visualization of thrombus (T), absence of spontaneous flow by Doppler ultrasonography (F), absence of phasicity of flow with respiration (P), and incompressibility of the vein with probe pressure (VC). When analyzed individually, the variables T and F had low sensitivities (50% and 76%) but high specificities (92% and 100%). VC had low values for both (79% and 67%, respectively). The best single variable was P (sensitivity and specificity = 92%). The best combinations of variables were T+P (sensitivity = 95%, specificity = 83%), T+F+P (sensitivity = 95%, specificity = 83%), F+P (sensitivity and specificity = 92%), and F+T (sensitivity = 92%, specificity = 87%). The low specificity of vein incompressibility was secondary to cases in which normal veins were difficult to compress in the thigh. All false-negative cases were from isolated calf vein thrombi. We conclude that isolated criteria from duplex scanning should not be used to diagnose deep venous thrombosis. In cases of suspected calf vein thrombosis, repeat duplex examination should be obtained in 3-4 days to determine the most appropriate therapy. In equivocal cases of proximal vein thrombosis, a contrast venogram should be obtained.

Spontaneous lysis of deep venous thrombi: rate and outcome

Ultrasonic duplex scanning was used to study the rates at which lysis of thrombi, valvular incompetence, and symptoms of the postthrombotic syndrome (edema) developed in 21 patients after deep venous thrombosis (DVT). Lysis of thrombi occurred rapidly in most patients. In 11 of 21 patients (53%), recanalization occurred in all segments by 90 days after presentation. In four patients, extension of the initial DVT occurred between 30 and 180 days, despite treatment with warfarin. Valvular incompetence developed in 13 patients during the study period. The number of patent venous segments with incompetent valves increased from the initial presentation to 180 days, at which time 25% of patent segments contained incompetent valves. Valvular incompetence developed in previously thrombosed segments that were initially competent after recanalization and in segments not previously thrombosed. This suggested that although incompetence may occur as a result of a direct effect of the thrombus on the valve, other mechanisms must also be involved. Patients with edema early after DVT (from 7 to 30 days) were more likely to have residual occlusion than valvular incompetence. The late development of edema (from 90 to 270 days) was more closely correlated with valvular incompetence.

Duplex imaging of in situ saphenous vein bypass grafts and late failure reduction

Duplex ultrasonic scanning was applied prospectively to 20 consecutive cases of in situ saphenous vein infrainguinal bypass 1, 3, 6, and 12 months postoperatively. All 20 (100 percent) and 17 of 19 (90 percent) of the proximal and distal anastomoses, respectively, could be imaged satisfactorily. Graft velocity ranged from 30 to 100 cm/s. Of three grafts with low velocity, one had impending graft failure and two had inherently low velocity but remained patent. Five defects in three grafts were detected. In three cases, intervention prevented graft failure. The primary patency rate was 80 percent, but was improved to 95 percent as a result of graft surveillance and simple revisions. Duplex scanning is a superior method for postoperative in situ saphenous vein bypass surveillance. We recommend that patients be studied 1 month postoperatively and every 3 to 6 months thereafter.

An objective assessment of the physiologic changes in the postthrombotic syndrome

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

Pathophysiology of venous claudication

Patients with chronic iliofemoral venous obstruction may develop severe thigh pain and a sensation of tightness with vigorous exercise (venous claudication). The discomfort requires 15 to 20 minutes to subside. In the seven patients studied the venous capacitance (VC) and venous outflow (VO) are lower than those of the unaffected limb even at rest. With exercise to the point of pain, the VO was unchanged but the VC decreased even further. The problem appears to rest with the venous collaterals, which have a high and fixed resistance. Because of this high outflow resistance, venous volume increases to near maximum during exercise. With this rise in venous volume, the amount the VC can increase during the period immediately following exercise is further reduced.

Developmental control of messenger RNA for hepatic tryptophan 2,3-dioxygenase

The enzyme tryptophan 2,3-dioxygenase [EC 1.13.11.11; L-tryptophan:oxygen 2,3-oxidoreductase (decyclizing)] first appears in the livers of young rats around the 15th postnatal day, and increases to the adult level by the 22nd day. Studies have shown that the appearance and subsequent development of the enzyme activity result from an increase in the rate of its synthesis and thus in the amount present in the liver. In this study, we have attempted to ascertain whether the appearance and development of tryptophan 2,3-dioxygenase mRNA coincided with, and thus led to, the development of enzyme activity, or whether the biosynthesis of this enzyme was due to a developmental event enabling translation of a preexisting, sequestered, reservoir of its mRNA. Using a cell-free protein-synthesizing system based on a wheat germ S30 supernatant, we measured the level of tryptophan 2,3-dioxygenase mRNA in the livers of rats between 0 and 22 days of age. We found that functional tryptophan 2,3-dioxygenase mRNA is not detectable in rat liver until the 15th postnatal day. It increases to the adult level by the 22nd postnatal day, in parallel with the enzyme. The appearance and development of tryptophan 2,3-dioxygenase are the direct consequence of the parallel appearance and development of its mRNA. It has been shown that glucocorticoids, which induce tryptophan 2,3-dioxygenase activity in adult rats, are capable of inducing the appearance of this enzyme precociously in 8- and 10-day-old rats. We have found that it is also possible to induce tryptophan 2,3-dioxygenase catalytic activity with hydrocortisone precociously in 4-day-old rats. Moreover, precocious induction of enzyme activity and the induction that occurs during the enzyme's normal developmental rise to the adult level between 15 and 22 days, are mediated through parallel increases in the level of tryptophan 2,3-dioxygenase mRNA. The present findings indicate that glucocorticoids are developmental hormones that act upon the postnatal hepatocyte to evoke elevated levels of the mRNA species coding for tryptophan 2,3-dioxygenase; the findings are compatible with the hypothesis that such hormones act by initiating and accelerating transcription of the structural genes coding for the alpha and beta protomers of this enzyme.