Prospective screening for postoperative deep venous thrombosis in patients undergoing infrainguinal revascularization.

PURPOSE: The incidence of deep venous thrombosis (DVT) in patients undergoing infrainguinal bypass graft procedures has not been well documented, and the need for routine prophylaxis remains controversial. The purpose of this study was to prospectively evaluate the risk of postoperative DVT complicating infrainguinal revascularization. METHODS: Seventy-four patients undergoing infrainguinal bypass graft procedures during a 12-month period were prospectively screened for DVT. Bilateral lower extremity venous duplex scan imaging was performed preoperatively and within 1 week and 6 weeks, postoperatively. Routine DVT prophylaxis was not used, with anticoagulation reserved for specific indications. RESULTS: Of the 74 patients screened, three patients (4.1%) had DVT identified on preoperative venous duplex scan imaging and were excluded from the study. Of the remaining 71 patients enrolled, only two patients (2.8%) had postoperative DVT. Postoperative DVT was ipsilateral to the bypass graft extremity in both patients, with involvement of the peroneal vein in one patient and the femoral vein in the other. Although routine prophylaxis was not used, 18 of these patients (25%) were anticoagulated for other indications, with DVT occurring in one patient (5.6%). Of the remaining 53 patients who did not receive postoperative anticoagulation, only one patient (1.8%) had DVT. CONCLUSIONS: According to this prospective study, the risk of postoperative DVT in patients undergoing infrainguinal revascularization is low. Routine prophylaxis is not recommended, with postoperative anticoagulation reserved for specific indications.

Efficacy of color flow duplex imaging for proximal upper extremity venous outflow obstruction in hemodialysis patients.

PURPOSE: The efficacy of color flow duplex imaging (CFDI) in detecting proximal upper extremity venous outflow obstruction in hemodialysis patients was compared with that of traditional contrast venography. METHODS: From 1993 through 1997, all hemodialysis patients who were evaluated for upper extremity venous outflow obstruction of the axillary, subclavian, or brachiocephalic veins with both CFDI and venography were identified. Medical history, hemodialysis access procedures, and indications for imaging were reviewed. The diagnostic accuracy of CFDI was compared with that of venography for proximal venous outflow obstruction, including focal stricture, partial obstruction, or complete occlusion. RESULTS: Sixty upper extremities in 42 hemodialysis patients were imaged with both CFDI and venography. Previous ipsilateral intravenous dialysis catheters had been present in 33 (55%) of the extremities imaged; current catheters were present in 16 (27%) of the extremities imaged; and 28 (67%) of the extremities imaged had a current ipsilateral arteriovenous (AV) shunt. Five (8%) of the 60 duplex scans were nondiagnostic because of artifact from intravenous dialysis catheters (3) or incomplete visualization of the subclavian or brachiocephalic veins (2) and were excluded from further analysis. In the remaining 55 duplex scans, proximal venous outflow obstruction was found in 18 (33%), compared with 21 (38%) identified by means of venography (P = not significant [NS]). Overall sensitivity, specificity, positive predictive value, and negative predictive value for CFDI were 81%, 97%, 94%, and 89%, respectively. CONCLUSION: CFDI is a reliable means of detecting proximal upper extremity venous outflow obstruction and should replace contrast venography as the initial imaging study in hemodialysis patients.

The role of air plethysmography in the diagnosis of chronic venous insufficiency.

PURPOSE: The role of air plethysmography (APG) in the diagnosis of venous disease is not well defined. We conducted this study to investigate the value of APG in the diagnosis of chronic venous insufficiency and to determine its correlation with the clinical severity of disease and the anatomic distribution of reflux. METHODS: We studied 186 lower extremities with duplex scanning and venography and measured the venous volume, venous filling index (VFI), ejection fraction, and residual volume fraction with APG. Limbs were categorized according to the Society for Vascular Surgery and International Society for Cardiovascular Surgery classification of clinical severity of disease and according to the anatomic distribution of valvular incompetence. RESULTS: Sixty-one limbs had no evidence of disease (class 0), 60 limbs had mild disease (classes 1, 2, and 3), and 65 limbs had severe disease (classes 4, 5, and 6). According to the results of duplex scanning and venography, there was no evidence of reflux in 56 limbs. Isolated superficial venous reflux occurred in 52 limbs, and perforator reflux, alone or in conjunction with superficial reflux, occurred in 30. Deep reflux, with or without superficial reflux, was found in 25 limbs. Deep and perforator reflux, with or without superficial reflux, was found in 19 limbs. The VFI had a sensitivity of 80% and 99% positive predictive value for any type of reflux. The VFI was significantly different between groups of limbs with different clinical severities of disease or different types of reflux. The incidence of deep or perforator reflux in limbs with a normal VFI value was 7%, and it was 82% in limbs with a VFI of more than 5. Among 86 limbs with VFI values not corrected with use of a thigh tourniquet, 28% did not have evidence of deep or perforator reflux, and among 15 limbs with VFI values corrected with the use of a tourniquet, 33% had perforator reflux, deep reflux, or both. All APG parameters had low positive predictive values for severe disease or ulceration. The ejection fraction and residual volume fraction did not influence the clinical severity of disease, did not discriminate between types of reflux, and in combination with the VFI did not improve the predictive value of APG. CONCLUSIONS: The VFI measured by APG is an excellent predictor of venous reflux, provides an estimate of the clinical severity of disease, and at high levels predicts deep reflux, perforator reflux, or both. Correction of an abnormal VFI with a thigh tourniquet is an unreliable predictor of the absence of deep or perforator incompetence. The predictive value of APG for severe disease or ulceration is poor. The ejection fraction and residual volume fraction, individually or in combination with the VFI, add little to the diagnostic value of APG, and their routine performance may not be clinically justified.

Predictive value of clinical criteria for the diagnosis of deep vein thrombosis.

BACKGROUND: The widespread use of ultrasonography for the diagnosis of deep vein thrombosis (DVT) has led to the overuse of ultrasonography with low diagnostic yield. We conducted this study to investigate the predictive value of clinical features in the diagnosis of DVT and their potential value as clinical guidelines for the use of ultrasonographic testing in the diagnosis of DVT. METHODS: The results of lower-extremity duplex ultrasonographic studies and clinical surveys prospectively obtained in 1526 patients suspected of having DVT were analyzed. RESULTS: There were 916 inpatients and 610 outpatients. Acute DVT was found in 16% of the inpatient duplex scans, and in 12% of the outpatient studies (p < 0.05). The incidence of acute DVT was not different between men and women in inpatient or outpatient populations. Acute DVT was found in the left leg in 60% of the outpatient studies, significantly more often (p < 0.001) than in the inpatients (35%). Bilateral DVT was more common (p < 0.05) in the inpatient population (35%) compared with the outpatient population (20%). No difference in the anatomic distribution of thrombosis was found between inpatients and outpatients. The presence of leg symptoms was associated with a significantly higher rate (p < 0.05) of positive studies compared with those patients without leg symptoms in both the inpatient and the outpatient populations. Individual symptoms, risk factors, and physical findings had low positive predictive value and sensitivity for the presence of acute DVT on duplex scan. A calf circumference discrepancy of less than 2 cm predicted the absence of DVT in 93% of inpatients and 85% of outpatients. The combination of a calf circumference discrepancy of less than 2 cm with the absence of recent operation, trauma, malignancy, previous history of DVT, or hypercoagulable state predicted the absence of DVT in 92% of the inpatients and 97% of the outpatients. CONCLUSIONS: Clinical symptoms, risk factors, and physical findings are poor predictors of the presence of acute DVT on duplex scan. However, the absence of a combination of objective clinical factors has high predictive value for the absence of acute DVT on duplex scan. These criteria may be used to establish clinical guidelines to reduce the use of duplex scanning for the diagnosis of DVT.

Noninvasive detection of iliac artery stenosis in the presence of superficial femoral artery obstruction.

In patients with superficial femoral artery obstruction, iliac disease may be difficult to diagnose by commonly used noninvasive techniques. We studied common femoral artery acceleration time (onset of systole to peak systole), as measured from a Doppler spectral display and expressed in milliseconds. Previous work has suggested that an acceleration time of 144 msec or greater is abnormal and is associated with iliac stenosis (greater than or equal to 75% diameter reduction) or occlusion. During a 2-year period, in 139 limbs with superficial femoral artery obstruction, acceleration times were measured immediately before angiography. The overall test accuracy was 94.2% (131/139). In the 112 sides with normal angiograms, the acceleration time correctly identified no disease in 109 patients (97.3% specificity), and in the 27 iliac stenoses or occlusions the test detected disease in 22 patients (81.5% sensitivity). This appears to be a good test that can be done with equipment usually available in most vascular laboratories.

Measuring ankle systolic blood pressure: validation of the Dinamap 1846 SX.

Clinical and epidemiologic situations requiring repeated measurements of blood pressure in the lower extremity are increasingly incorporating automated measurement devices; however, no device has been validated adequately for ankle blood pressure. This study evaluates the Dinamap 1846 SX against Doppler ultrasound in determining ankle systolic blood pressure (SBP) and compares a parallel with contour wrapping technique for applying the blood pressure cuff. Ankle SBP was measured on 71 adult volunteers by both devices simultaneously, for each cuff wrap. Averages of three readings were compared to evaluate Dinamap versus Doppler SBP estimates and to assess any cuff wrap effect. Multiple linear regression was used to assess potential effect modifiers. Instrument differences (Dinamap minus Doppler) for the parallel wrap (95% confidence intervals in parenthesis) were -1.5 mmHg (-3.1, 0.0) and -3.9 mmHg (-5.6, -2.2) for the contour wrap. Wrap effect differences (contour minus parallel) for the Doppler were -4.9 mmHg (-6.3, -3.5) and -7.2 mmHg (-8.7, -5.8) for the Dinamap. Degree of ankle taper was a strong modifier of cuff effect for the Dinamap but not for the Doppler: adjusted cuff effect with the Dinamap ranged from -3 to -10 mmHg. Measurement precision (within-person reproducibility, measured by within-person standard deviation [sigma 2] and reliability coefficient [R]) was higher for the Dinamap than the Doppler technique, lowest for the parallel wrap and Doppler configuration (sigma 2 = 5.4 mmHg, R = 0.88) and greatest for the contour wrap and Dinamap (sigma 2 = 4.0 mmHg, R = 0.94). In conclusion, cuff-wrapping technique can generate SBP differences of greater magnitude than instrument differences. Conditional on the use of the contour wrap, and by virtue of its high repeatability and ease of operation, the Dinamap is a useful tool for epidemiologic study and the clinical assessment of peripheral arterial disease.