Mesenteric and celiac duplex scanning: a validation study.

PURPOSE: To validate the accuracy of previously established duplex ultrasound criteria for > or =50% superior mesenteric artery (SMA) and celiac artery (CA) stenosis by comparison with arteriography. METHODS: Duplex criteria established retrospectively in our laboratory in 1991 identified an end-diastolic velocity (EDV) > or =45 cm/sec, or no flow signal, as highly sensitive (100%) and specific (92%) indicators for SMA stenosis > or =50% or occlusion. EDV was more accurate (95%) than peak systolic velocity (PSV), which had a maximal accuracy of 86% at a PSV > or =300 cm/sec, with low sensitivity (62%), but high specificity (100%). For CA, accurate velocity thresholds were not identified, but we subsequently noted that retrograde common hepatic artery flow direction from SMA collateral was highly predictive of severe CA stenosis or occlusion. Since publication of those findings, 243 mesenteric duplex scans were performed for clinical evaluation of suspected chronic mesenteric ischemia. Angiographic confirmation was available for a subset of 46. SMA and CA diameters were measured on lateral aortograms by observers blinded to the duplex results, and the original duplex diagnostic criteria were tested for accuracy. In addition, receiver operator characteristic curve analysis was performed on the velocity data to identify the most accurate velocity thresholds in the new data. RESULTS: Duplex was technically adequate in 98% of SMA, 96% of CA, and 89% of hepatic arteries, and arteriograms were adequate in 100% of SMA and 98% of CA. For the SMA, EDV > or =45 cm/sec again provided the best sensitivity (90%), specificity (91%), positive predictive value (90%), negative predictive value (91%), and overall accuracy (91%). As in the retrospective study, PSV > or =300 cm/sec provided low overall accuracy (81%), low sensitivity (60%), but high specificity (100%). Lowering the PSV threshold improved sensitivity but reduced accuracy. For CA, retrograde common hepatic artery flow direction was 100% predictive of severe CA stenosis or occlusion. Velocity data in CA provided accuracy not found in the original study. EDV > or =55 cm/sec or no flow signal had best overall accuracy (95%) with high sensitivity (93%) and specificity (100%). PSV > or =200 cm/sec or no signal also had excellent accuracy (93%), sensitivity (93%), and specificity (94%). In addition, three of four anatomic anomalies were correctly identified by duplex. These included one right hepatic and one common hepatic artery originating from the SMA, and one common celiacomesenteric trunk. CONCLUSION: This validation analysis confirms that duplex velocity criteria are accurate in the identification of mesenteric occlusive disease. Retrograde common hepatic artery flow direction correctly predicts severe CA stenosis or occlusion. Duplex ultrasound may also identify mesenteric anatomic variants that can influence study interpretation.

Carotid duplex criteria for a 60% or greater angiographic stenosis: variation according to equipment.

PURPOSE: The purpose of this study was to evaluate the carotid duplex criteria for a > or = 60% angiographic internal carotid artery (ICA) stenosis and the degree of variation among duplex scanners. METHODS: Carotid duplex criteria for a > or = 60% angiographic stenosis were evaluated in two ICAVL-accredited vascular laboratories with different brands of duplex scanners (Siemens-Quantum and Diasonics in Laboratory A, ATL and Diasonics in Laboratory B). Analysis was performed for 360 carotid bifurcations in 180 consecutive patients who had concurrent angiographic and duplex evaluation. Blinded angiogram evaluation was performed with precision electronic calipers on magnified views, with stenosis calculated by criteria of the Asymptomatic Carotid Atherosclerosis Study and the North American Symptomatic Carotid Endarterectomy Trial. Duplex data included internal carotid artery peak systolic velocity (ICA PSV), ICA end-diastolic velocity, and the ratio of ICA PSV to common carotid artery (CCA) PSV (ICA/CCA ratio). RESULTS: The most accurate determination of a > or = 60% ICA stenosis was obtained with ICA/CCA ratio and ICA PSV, but the optimal threshold differed for all four scanners. The optimal ICA/CCA ratio varied from 2.6 to 3.3, and the optimal ICA PSV varied from 190 to 240 cm/sec. All four scanners produced criteria that give a positive predictive value > 90% while maintaining accuracy at > or = 90%. Logarithmic transformation of duplex variables created a linear relationship between duplex values and angiographic stenosis, allowing statistical evaluation of scanner operating characteristics by linear regression analysis and analysis of covariance. This analysis revealed that the mathematic equation relating duplex values with angiographic percent stenosis was statistically different for one of the four scanners (p < 0.05). Scanner differences did not appear to be due to technologists, because the regression lines were nearly identical for the two Diasonics scanners despite use by different technologists. Ignoring the significant difference in operating characteristics for one of the four scanners would result in a mean error for predicting a 60% stenosis of 14% to 18% (equating a 46% or 78% stenosis with a 60% stenosis). CONCLUSIONS: We conclude that the correlation of duplex data with angiographic percent stenosis and the duplex criteria for a > or = 60% stenosis are machine-specific. Regression analysis can determine whether apparent differences are due to chance or significant differences in scanner characteristics. Future studies should include regression analysis according to equipment type.

Vascular laboratory cost analysis and the impact of the Resource-Based Relative Value Scale payment system.

PURPOSE: This study compares the actual cost of performing noninvasive laboratory studies with reimbursement under the previous Medicare Part B system and under current resource-based relative value scale (RBRVS) guidelines. METHODS: We calculated the cost to operate our own laboratory and estimated national costs for small- and large-model laboratories. Reimbursement under Medicare Part B was calculated for each Current Procedural Terminology code from average Medicare reimbursement allowances and national case volumes in 1990, which were obtained from the Health Care Financing Administration. All data were expressed as dollars per hour of study time to allow universal comparison of costs and reimbursement among tests that require differing lengths of time for completion. RESULTS: Technical costs for laboratory time ranged from $143 to $173 per study hour. The largest components of laboratory expenses were fixed costs, including personnel (37% to 46%), equipment (30% to 42%), and facilities (6% to 8%). Variable costs such as billing (9% to 10%) accounted for most of the remainder. More efficient allocation of equipment resulted in lower costs in large laboratories, whereas continued use of depreciated equipment resulted in lower costs in our own laboratory ($127/hr). CONCLUSIONS: We project that technical reimbursement under RBRVS will be $82/hr nationally and $80/hr locally, whereas global reimbursement (technical plus professional) will be $116/hr and $110/hr, respectively. On the basis of 1990 case volumes, the RBRVS system will decrease national global reimbursement by at least 35% compared with the previous Medicare Part B system. Under the new system, technical reimbursement will decrease by an estimated 27% nationally, whereas professional reimbursement will decrease by 52%. Revenue under RBRVS will not meet the cost to perform studies either nationally or locally. Technical reimbursement is 37% to 54% below actual technical costs, and even global reimbursement is 13% to 34% less than technical costs. Our analysis revealed that costs will exceed reimbursement despite maximization of operating efficiency. This analysis applies to outpatients only. A case mix including inpatients will further reduce reimbursement, because only the professional component is allowed. By setting reimbursement of vascular laboratories below actual costs, the new RBRVS system may ultimately reduce the availability of noninvasive vascular testing for elderly patients.

A blinded comparison of angiography, angioscopy, and duplex scanning in the intraoperative evaluation of in situ saphenous vein bypass grafts.

Angiography, angioscopy, and duplex scanning have each been advocated for intraoperative assessment of in situ saphenous vein grafts. We compared these three modalities during operation in a prospective, blinded study during the construction of 20 femoral-infragenicular in situ saphenous vein grafts. Each modality was used and interpreted by a surgeon blinded to the results of the other studies. Abnormalities requiring intervention were defined as (1) patent vein side branches, (2) residual valve cusps, and (3) anastomotic stenoses greater than 30%. Criteria, specific to the modality, corresponding to each category were prospectively defined. Fourteen residual valve cusps, 49 patent vein branches, and 6 anastomotic stenoses were suggested by at least one modality. Nine residual valve cusps, 32 patent vein branches, and no anastomotic stenoses were actually found (and corrected) by direct inspection. Sensitivity of detecting patent side branches for angiography, duplex scanning, and angioscopy was 44%, 12%, and 66%, respectively. Both angiography and angioscopy were significantly more sensitive than duplex scanning for detection of unligated side branches (p less than 0.01). Sensitivity of detecting residual valve cusps was 22% (angiography), 11% (duplex scanning), and 100% (angioscopy). Angioscopy was significantly more sensitive than either duplex scanning or angiography in detection of residual valve cusps (p less than 0.01). Since no anastomotic stenoses were confirmed, the false-positive rates for stenosis detection were 20% for angiography, 10% for duplex scanning, and 0% for angioscopy. Time requirement was 17 to 20 minutes and did not differ among the three modalities. No stenosis or arteriovenous fistula has been detected in any graft by postoperative duplex surveillance (mean, 10-month follow-up).(ABSTRACT TRUNCATED AT 250 WORDS)

Duplex ultrasonography in the diagnosis of celiac and mesenteric artery occlusive disease.

Duplex ultrasound criteria for the diagnosis of celiac and superior mesenteric artery (SMA) occlusive disease have not been well defined. We performed a blinded retrospective comparison of mesenteric duplex data with arteriography in 24 consecutive patients who underwent both studies. Arteriography revealed that eight superior mesenteric arteries were normal; five were minimally stenotic; eight had stenoses greater than or equal to 50%, and three were occluded. Nine celiac arteries were normal or minimally stenotic; 12 had stenoses greater than or equal to 50%, and three were occluded. Duplex scans were obtained after an overnight fast. In normal superior mesenteric arteries, peak systolic velocity (PSV) was 134 +/- 18 cm/sec and end-diastolic velocity (EDV) was 24 +/- 4 cm/sec. Superior mesenteric artery PSV in patients with minimal or no stenosis (171 +/- 22 cm/sec) was less than PSV in patients with severe (greater than 50%) stenosis (299 +/- 40 cm/sec, p = 0.006), and less than PSV in patients with patent superior mesenteric arteries who underwent revascularization (366 +/- 86 cm/sec, p = 0.017). Similarly, EDV was elevated in superior mesenteric arteries with severe stenosis (78 +/- 11 cm/sec, p = 0.001) and in patients who underwent revascularization (111 +/- 19 cm/sec, p less than 0.001) compared to those with less than 50% stenosis (30 +/- 6 cm/sec, p = 0.001). An EDV greater than 45 cm/sec was the best indicator of severe stenosis (sensitivity, 1.0; specificity, 0.92). Peak systolic velocity greater than 300 cm/sec was less sensitive (0.63), but highly specific (1.0) for severe superior mesenteric artery stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Preoperative assessment of the peripheral vascular disease patient for free tissue transfers.

Lower extremity reconstruction or salvage in patients with severe peripheral vascular disease is a unique challenge, requiring knowledge of the vascular anatomy, including the location of intraluminal irregularities and stenoses. In a retrospective study that includes four case reports, the authors describe the impressive ability of the Duplex imaging system, to assist in the proper selection of recipient vessels and of those areas within the vessels most suitable for anastomoses.