Original Articles
Can Duplex Scanning Replace Arteriography For Lower Extremity Arterial Disease? Ted R. Kohler, W., MD, George Andros, MD, John M. Porter, MD, Alexander Clowes, MD, Jerry Goldstone, MD, Kaj Johansen, MD, Edmond Raker, MD, Dale R. Nance, MD, D. Eugene Strandness, Jr, MD, Seattle, Washington
This preliminary study was undertaken to determine if surgeons would choose different intervention for lower extremity occlusive disease when given basic clinical information and data from either a duplex scan or arteriogram. Information on degree of stenosis from duplex scans and arteriograms of 29 patients was indicated on an anatomical line drawing along with the ankle blood pressures and a brief clinical description. Based on these data sheets, six vascular surgeons chose a clinical plan in a blinded fashion for each patient. Each plan was placed into one of eight possible categories for comparison using the kappa statistic. Intraobserver agreement between surgeons' decisions based on duplex scanning versus those based on arteriography was very good (mean kappa .70 with exact agreement in 76%). Interobserver agreement between different surgeons' decisions based on the same studies was significantly less (mean kappa 0.56, p < .05). Significant disparity in clinical approach occurred in 43% of the patients with nearly identical duplex scan and arteriogram reports, suggesting that much of the discrepancy lies in the clinical decision-making process. Clinical decisions made using duplex scans are very similar to those made using arteriograms. This technique can limit the need for arteriography in assessing patients with lower extremity arterial occlusive disease. (Ann Vasc Surg 1990;4:280-287) KEY WORDS: Arteries, stenosis or obstruction; arteries, extremities; angiography; ultrasound (US), doppler studies; ultrasound (US), comparative studies; clinical decision-making.
Duplex scanning is now accepted for reliable diagFrom the Departments of Surgery and Radiology, Veterans Administration Medical Center, the Department of Surgery, University of Washington School of Medicine, and the Department of Surgery, The Mason Clinic, Seattle, Washington; the Saint Joseph Medical Center, Burbank, California; the Division of Vascular Surgery. Department of Surgery, Oregon Health Sciences University, Portland, Oregon; and the Department of Surgery, University of California, San Francisco, California. Reprint requests: Ted Kohler, MD, Department of Surgery (112), Veterans Administration Medical Center, 1660 S. Columbian Way, Seattle, Washington 98108.
nosis of carotid artery stenosis, and several centers have begun to perform carotid endarterectomy without arteriography [ 1-6]. Our recent clinical experience suggests that duplex ultrasound can also accurately locate and quantify aortoiliac and femoropopliteal disease [7-9]. In a prospective clinical study, duplex scanning had a sensitivity of 82% and specificity of 92% in identifying significant arterial lesions [7]. In fact, it appeared that scanning was as accurate as two different radiologists grading the same arteriograms [9]. We undertook the current study to determine if surgeons would choose a significantly different intervention for treatment of lower extremity occlusive disease when
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given basic clinical information plus data from either a duplex examination or an arteriogram.
PATIENTS AND METHODS Duplex scans
Our technique for duplex scanning of the lower extremity arteries has been described previously [7]. Studies were performed with a Mark 600 or Ultramark 8 duplex scanner.* Patients are requested to limit their intake to a small, nonfatty meal on the evening prior to the examination and to take only a small amount of liquid with necessary medication on the morning of the study. Bowel preparation consists of a mild laxative taken on the evening prior to the study. The examination is begun with the patient supine. A 2.5 or 3 mHz transducer (or, in particularly asthenic individuals, a 5 mHz transducer) placed just below the xiphoid is used to image the aorta in the sagittal plane. The origin of the superior mesenteric artery is a convenient landmark seen originating from the anterior surface of the aorta. The aorta is followed distally to the iliac bifurcation, and each iliac artery is then followed separately to the groin level. The common femoral artery and the origin of the profunda femoris artery are examined next, followed by the proximal, mid, and distal superficial femoral artery. The patient is then turned to the prone position with the knees slightly flexed to study the popliteal artery. Velocity waveforms are recorded from each arterial segment and from any site of increased velocity or spectral broadening. Normal lower extremity arteries have a triphasic velocity waveform with a systolic forward flow peak followed by a brief reverse velocity component in early diastole and finally a second forward component. The normal waveform has a narrow spectral width, indicating a uniform flow pattern. Stenosis is detected on duplex scanning by an increase in velocity and broadening of the spectral waveform. Velocity signals are obtained from the center of the flow stream to minimize spectral broadening caused by the steep velocity gradient at the vessel wall. Criteria for grading the degree of stenosis have been described previously [7,8], and are summarized in Table I. Representative waveforms are shown in Figure I.
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TABLE I.--Classification criteria for estimating severity of stenosis in peripheral arteries Normal Triphasic waveform, no appreciable spectral broadening. 1-19% diameter reduction Normal waveform with slight spectral broadening and peak velocities increased no more than 30% greater than in the proximal adjacent segment. 20-49% diameter reduction Spectral broadening filling in the clear window under the systolic peak, peak velocity less than 100% greater than that of the next most proximal segment. 50-99% diameter reduction Peak systolic velocity 100% greater than proximal adjacent segment and reverse velocity component usually absent in the stenosis. Monophasic velocity waveform beyond the stenosis with reduced systolic velocity. Occlusion No flow in the imaged artery. Monophasic, preocclusive "thump" heard proximal to the occlusion; velocities markedly diminished and waveforms monophasic beyond the stenosis.
lower extremity occlusive disease during a two and one-half year period. Twenty-nine patients who had an arteriogram within three months of a duplex scan were selected. This is a subset of the patients reported in our most recent validation study [7]. The patients had a wide variety of disease severity ranging from simple stenosis to tandem occlusions and from claudication to gangrene. Duplex scans
a
s
Experimental design
This study used data from patients evaluated consecutively in our laboratory for symptomatic *Advanced Technology Laboratories, Inc., Bothell, Washington.
c
d
Fig. 1. Representative velocity waveforms from lower extremity arteries. (a) Normal; (b) 0-15% diameter reduction; (c) 16-49% diameter reduction; (d) 50-99% diameter reduction.
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and arteriograms were performed and interpreted in a blinded fashion, ie, without knowledge of the results of the other examination. For each arterial segment from the aorta to the popliteal artery, the observed disease was classified into one of the five categories outlined in Table I. A standard data sheet was prepared for both duplex scan and arteriogram results for each patient. Each contained a one sentence description of the patient's symptoms (claudication, rest pain, or ulceration), the anklearm indices, and results of treadmill testing, if done. This portion of the data sheet was identical for duplex scans and arteriograms. Also included was an anatomical line drawing of the lower limb arteries (Fig. 2). Results of the arteriogram or duplex scan were recorded on this drawing by the person who performed the study. Diseased segments were indicated by filling in the appropriate segments on the drawing; in addition, the disease category was tabulated next to the appropriate segment. It was not possible to determine by looking at an individual data sheet whether the results it depicted were obtained by duplex scanning or by arteriography and no information was provided to identify individual patients. Using the information contained in these data sheets, six of the authors (G.A., J.P., A.C., J.G., K.J., and E.R.) who were not previously familiar with the patients, their studies, or their treatment were asked to formulate a clinical plan. The reports were sent out in two separate mailings, each containing either a duplex scan or arteriogram report for each patient. On a random basis, either a duplex scan or arteriogram was sent first for each patient; consequently, the surgeons did not know if they were looking at data derived from a duplex scan or arteriogram. The second mailing was sent one month after completion for the first set and the data sheets were shuffled so they were not in the same order as before. The surgeons' plans were then placed into one of eight categories: o o o o o o o
No intervention Percutaneous angioplasty Operative endarterectomy Aortobifemoral bypass Femorofemoral bypass Femoropopliteal bypass Combined aortofemoral and femoropopliteal bypass o Other Comparisons were made using the kappa statistic, which measures the concordance between categorical data, adjusting for the extent of agreement expected by chance alone [10]. Kappa ranges from zero for only random agreement to one for perfect agreement. For each surgeon, the choice of intervention based on duplex scan results and arterio-
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DISABLING RIGHT A N D LEFT C A L F CLAUDICAT1ON
RIGHT
LEFT
20-49% 50-99%
. ~
20-49%
1-19%
1-19%
Brachial PT AT AAI
Right 188 100 100 53
Left
188 144 148 .78
Post Exercise
Right 0
Left 70
Fig. 2. Example of data sheet with sites of stenosis indicated on line drawing, brief clinical history at top, and ankle blood pressure data at bottom.
gram results were compared. Similarly, comparison was made between different surgeons' choices based on the same arteriogram or duplex scan reports.
RESULTS Table II lists intraobserver results for comparing the two decisions each surgeon made based on duplex scan or arteriogram reports. Kappa ranged from .61 to .90 for individual surgeons; the mean for the entire group was .70. Table III is the two-way contingency table for
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TABLE IV.--Kappa statistics for comparison of different surgeon's decisions based on the same arteriograms or duplex scans
TABLE II.--Kappa values for comparison of decisions based on duplex scanning versus arteriography Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon
.90
A B C D E F
.65 .73 .61 .66 .65
Combined Data n = 174
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.70
the combined data. Exact agreement occurred in 133 of 174 comparisons (76%). Table IV lists interobserver results for comparing different surgeons' decisions based on the same arteriogram or duplex scan reports. Kappa values ranged from .41 to .77, with a mean for arteriogram reports of .51 and for duplex scans of .61 (overall mean .56). The trend toward greater consistency from surgeon to surgeon with duplex scanning was significant (p < .05, Student's t-test). Kappa values for interobserver comparisons (Table IV) were significantly lower than those for intraobserver comparisons (Table II) (p < .05, Student's t-test). For 21 patients, the duplex scan and arteriogram reports were essentially the same (there were no disagreements regarding whether or not arterial segments of involved extremities had significant stenoses). F o r 12 of these patients (57%) all 72 of the clinical decision pairs were the same. In the remaining nine patients, 11 o f the 54 clinical decision pairs (20%) were different. In six pairs an angioplasty was advised in one case and not the other, in four the surgeons selected intervention in one instance and not the other, and in one the clinical decision was significantly different (profundaplasty alone versus profundaplasty with femoropopliteal bypass). There were significant differences in the duplex
Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon
A vs A vs A vs A vs A vs B vs B vs B vs B vs C vs C vs C vs D vs D vs E vs
Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon
Arteriogram
Duplex scan
.49 .64 .49 .45 .55 .41 .57 .57 .41 .57 .58 .48 .66 .41 .42
.53 .77 .64 .68 .60 .70 .56 .49 .56 .6t .74 .61 .65 .47 .54
.51 _+ .08
.61 -+ .09"
B C D E F C D E F D E F E F F
Mean _+ SD
*Arteriogram-arteriogram versus Duplex-duplex; p - .0002, paired t-test
scan and arteriogram data in the remaining eight patients. In one of these, an iliac segment in the asymptomatic extremity was deemed significantly stenotic by arteriography but not by duplex scan. This had no effect on the clinical decisions, which involved treatment of the symptomatic extremity only. In the remaining seven patients, 23 o f the 42 decision pairs (55%) were different. These cases are listed in Table V. There were five categories o f significant discrepancies between duplex scan and arteriogram data that resulted in these differences: (1) Iliac disease was more extensive on arteriogram than duplex scan (seven decision pairs in patients A and D); (2) iliac disease was more extensive on duplex scan than on arteriogram (four decision pairs in patients F and G); (3) aortic disease was more extensive on arteriogram than duplex scan (three decision pairs in patient B)" (4) femoral disease was more extensive on arteriogram than duplex scan (three decision pairs affected in patient E); (5) a
TABLE Ill.--Kappa table comparing decisions based on duplex scan versus arteriogram reports for all six surgeons--29 patients Duplex scan Arteriogram
Nothing
PTA*
Endarterectomy
Nothing PTA Endarterectomy Aortobifem Fem-fem Fem-pop Combined Other Totals
18 1 3 1 0 2 0 0 25
2 15 1 3 3 3 0 0 27
0 0 14 0 0 0 0 1 16
*Percutaneous transluminal arterioplasty n = 174 Kappa - 0,703
Aortobifem
Fem-fem
Fern-pop
Combined
Other
2 8 1 31 5 0 0 0 47
0 0 0 0 2 0 0 0 2
0 1 1 0 0 50 0 1 53
0 0 0 0 0 0 3 0 3
0 0 0 0 0 1 0 0 1
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TABLE V.mlnstances of significant disagreement based on arteriogram versus duplex scanning Clinical decision Patient A
Surgeon
Based on arteriogram
Based on duplex scan
E*~
Aortobifemoral bypass
Femoral endarterectomy
B*
Axillobifemoral bypass
lilac angioplasty
Reason for discrepancy Proximal lilac stenosis seen on arteriogram only More aortic disease on arteriogram, lilac disease on duplex scan
C
C*
Aortobifemoral bypass
lilac angioplasty
D§
No treatment
Aortobifemoral bypass
E§
lilac angioplasty
Femoropopliteal bypass
F§
Bilateral profundaplasties Angioplasty
Aortobifemoral bypass
Angioplasty Angioplasty Angioplasty Angioplasty
No treatment No treatment No treatment Aortobifemoral bypass
Angioplasty Angioplasty Angioplasty Angioplasty Angioplasty Aortobifemoral bypass Femoropopliteal bypass No treatment
Aortobifemoral Aortobifemoral Aortobifemoral Aortobifemoral Aortobifemoral No treatment No treatment
C*
D*
D
E* F* A*
B*
E
C* D* E* F* A*t D*t F*
F
B* Dt
G
B *t E**
Femorofemoral bypass Femorofemoral bypass Femorofemoral bypass Femorofemoral bypass
No treatment
More aortic disease on arteriogram, lilac disease on duplex scan More aortic disease on arteriogram, lilac disease on duplex scan lilac stenosis seen on duplex, ignored by surgeon Different clinical decisions Graft stenosis missed on duplex examination
More lilac disease seen on arteriogram, although none >50%
bypass bypass bypass bypass bypass
Angioptasty Aortobifemoral bypass Aortobifemoral bypass Aortobifemoral bypass Aortobifemoral bypass
Same Femoral stenoses on arteriogram only Disease appeared isolated to lilacs on duplex lilac stenosis on duplex scan only Same More lilac disease on duplex scan Same
*Cases in which duplex scanning would have lead to an unacceptable approach or outcome, assuming arteriography was correct *Cases in which arteriography would have lead to an unacceptable approach or outcome, assuming duplex scanning was correct §Cases where differences in approach do not coincide with differences in data
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graft stenosis later confirmed at surgery was missed on duplex scan (four decision pairs in patient C). One significant difference occurred when a surgeon ignored a significant iliac stenosis on one of the two studies (patient B). Table V also indicates which cases would have led to undesirable approaches or outcomes. If we assume that disease severity was always accurately assessed by arteriography, use of duplex scanning information would have led to an undesirable approach or outcome in 16 decisions involving five patients (17% of the patients). These included four decisions in one patient where duplex scanning missed a graft stenosis. Six of the remaining 23 cases in which decisions were significantly different would have led to acceptable outcomes. These generally involved attempting angioplasty instead of directly proceeding to aortobifemoral bypass grafting. If we assume that duplex scanning always accurately assessed disease severity (except the surgically-confirmed graft stenosis it missed), decisions based on arteriograms would have led to an undesirable approach or outcome in nine instances involving five patients (17% of the patients). Another interesting subset is the group in which surgeons decided to do nothing based on one examination and decided on intervention based on the other. This occurred in 11 decision pairs involving six patients (6% of all t74 comparisons). In five of these instances (45%), involved arterial segments were graded the same by duplex scan and arteriogram. In six decision pairs (55%), the decision to intervene in one case and not the other was based on the presence of disease detected on arteriogram and not on duplex scan (missed graft stenosis in four cases, and femoral artery stenosis in two cases).
DISCUSSION While arteriography has long been the definitive test for symptomatic aortoiliac and lower extremity arterial disease, its many limitations have stimulated the development of noninvasive testing. Contrast studies provide anatomic rather than physiologic data, and their interpretation is subject to considerable interobserver variability [11-15]. The arteriographic appearance of frequently eccentric atherosclerotic lesions may be misleading, particularly if only uniplanar views are obtained. Although direct measurement of pressure gradient is the best way to determine the hemodynamic significance of arterial lesions, this is often neither practical nor anatomically possible. Several groups have found that preoperative angiography does not visualize a third or more of crural or pedal arteries that are patent by Doppler examination or operative exploration [16-19], although others report that inflow
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occlusion balloon angiography [20] or antegrade femoral puncture can reduce the requirement for intraoperative angiography to less than 3% [21]. Finally, arteriography involves significant cost, including time, patient discomfort, and occasional morbidity [22-26], as well as the monetary expense. The concept of arterial reconstructive surgery without preoperative arteriography is not new. Many clinicians have questioned the use of routine preoperative arteriography in patients with abdominal aortic aneurysms [27-30]. After review of 110 patients who underwent routine abdominal aortography prior to abdominal aortic aneurysm resection, Couch and coworkers [27] concluded that such studies could be reasonably limited to patients with specific indications, including significant hypertension, impaired renal function, diminished or absent femoral pulses, suspected mesenteric ischemia, suspected suprarenal extension of the aneurysm, or suspected thoracic aneurysm. Similarly, several investigators have recently reported their experience performing carotid endarterectomy based on clinical criteria and noninvasive testing alone [1-5]. Reasons for proceeding to operation without arteriography include contrast allergy, renal failure, progression of disease in patients who have had previous arteriograms, patients fear of arteriography, severe aortoiliac disease making access to the arterial system difficult, and the urgent need to operate in patients with crescendo TIAs. Several groups have advocated planning lower extremity revascularization with a Doppler examination and intraoperative arteriogram [31,32]. Shearman and associates reported that they could eliminate arteriography in many patients with a combination of clinical history and bedside Doppler examination [33]. This group depends on the quality of the femoral pulse to predict adequacy of inflow and chooses the site for distal anastomosis based on the severity of symptoms, the patency of the tibial vessels at the ankle (assessed by continuous wave Doppler), and the ankle blood pressure. They use preoperative arteriography only when necessary to define aortoiliac disease, and they obtain an intraoperative arteriogram to confirm the suitability of the chosen outflow tract. This approach is said to save time, money, and patient discomfort while maintaining "good results" (not defined). Duplex scanning of lower extremity arterial disease has made the argument against routine arteriography even more compelling. The development of low frequency transducers with appropriate focal lengths has made it possible to study deep abdominal and pelvic structures, including the iliac arteries. With this technology, Jager and associates devised a classification scheme based on the extent of spectral broadening and increased velocity [8,9]. We used this scheme prospectively in our clinical vascular laboratory and compared ultrasonic du-
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plex scanning with arteriography for the localization and classification of arterial stenoses and occlusions in 32 patients (383 arterial segments). The agreement between duplex scanning and arteriography was not significantly different than the agreement between two different radiologists reading the same arteriograms (kappa of 0.55 versus 0.63). For determining if stenoses were greater than 50% diameter reducing, duplex scanning had a sensitivity of 82%, specificity of 92%, positive predictive value of 80%, and negative predictive value of 93%. This technique was particularly accurate for classifying iliac stenoses (sensitivity 89%, specificity 90%), which are the most difficult lesions to diagnose by any other noninvasive test. Recognizing that duplex scanning can localize and classify peripheral arterial stenoses nearly as well as arteriography, we undertook the current study to determine if clinical decisions based on duplex scan results would be significantly different from those based on arteriograms. We studied patients with a wide range of disease severity ranging from mild claudication to gangrene and from simple stenosis to tandem occlusions. We found little disagreement when comparing each surgeon's decisions based on duplex scanning with those based on arteriography (there was exact agreement in 76% of cases and the mean kappa was .70). The extent of this intraobserver agreement varied from surgeon to surgeon (kappa range .61 to .90). The highest kappa value of .90 may have resulted from surgeon A's propensity to select aortobifemoral bypass in a large number of cases, and the lower kappa values may reflect the relatively larger repertoire of the other surgeons or a tendency to focus on different aspects of the clinical situation at different times. Significant disparity among different surgeons' clinical decisions occurred in 43% of patients when there were no significant differences between duplex scan and arteriogram reports. These data suggest that much of the observed variability was caused by diversity in the surgeons' clinical approach to individual situations rather than disparity in classification of disease by the two techniques. We also found that surgeons agreed significantly more when their decisions were based on duplex scan results. The reason for this is not clear, but it is interesting to speculate that duplex scan reports tend to include less extraneous information than arteriograms because they are based on physiologic rather than anatomic data. Because hemodynamically significant lesions can be missed by either arteriography or duplex scanning, it is not always possible to know which examination gives the most accurate assessment of the patient's disease severity. In 17% of the patients, significant discrepancies in disease estimation by the two different techniques would have led to an inappropriate clinical approach by whichever
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test was inaccurate. Adverse outcomes are less likely when test results are combined with more complete clinical data than were presented to the surgeons in this study. For example, one significant error occurred in a case where duplex scanning missed a femoropopliteal graft stenosis. This error was evident to the clinicians following the patient, who noted decreasing ankle pressure. The best approach to clinical decision-making combines detailed history, physical examination, and simple noninvasive testing with duplex scanning and selective arteriography. What information is critical in clinical decisionmaking for lower extremity arterial insufficiency, and how should duplex scanning be used? The decision whether or not to intervene is based on the patient's overall health and evidence of disabling claudication, rest pain, or ulceration. If intervention is planned, the clinician must first determine if flow to the level of the groin is sufficient. Presence of a strong femoral pulse on physical examination usually indicates adequate inflow. When inflow is in question, a normal duplex scan reliably excludes the possibility of a significant iliac stenosis (negative predictive value 96%) [7]. When aortoiliac occlusive disease is extensive, aortofemoral bypass may be required, whereas percutaneous angioplasty may be attempted when duplex scanning detects relatively short, high-grade iliac stenosis. A reconstructive procedure below the groin is required when inflow is adequate. It is then necessary to decide if there is a suitable lesion for angioplasty or an adequate vessel for distal bypass. Although duplex scanning can assess popliteal patency, it has been difficult to determine the quality of the patent vessel or assess more distal, tibial arteries. Therefore, at present, duplex scanning alone cannot be used routinely to determine the exact level of distal anastomosis for lower extremity bypass.
CONCLUSIONS Previous work demonstrated that duplex scanning provides much of the same information about lower extremity arterial occlusive disease as arteriography, and the current study shows that clinical decisions based on duplex scanning are very similar to those based on arteriograms. Prospective trials using the actual duplex scans and arteriograms are needed to compare decisions based on the complete clinical history and physical examination. At present, noninvasive testing allows the clinician to choose intervention more wisely, be it a selective diagnostic arteriogram, percutaneous angioplasty, or surgery. As duplex scanning becomes more sophisticated, it may eliminate the need for routine preoperative contrast studies in the assessment of
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patients with lower extremity arterial occlusive disease.
ACKNOWLEDGMENT Supported by NIH Grant # H L 20898.
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16. SIMMS MH. HARDMAN J, SLANEY G. The relevance of pre-bypass pedal arch patency assessment. Br J Surg 1984; 71:381. 17. CAMPBELL WB, FLETCHER EL, HANDS LJ. Assessment of the distal lower limb arteries: a comparison of arteriography and Doppler ultrasound. Ann R Coll Surg Engl 1986 ;68: 37-39. 18. PATEL KR, SEMEL L, CLAUS RH. Extended reconstruction rate for limb salvage with intraoperative prereconstruction angiography. J Vasc Surg 1988;7:53t-537. 19. FLANIGAN DP, WILLIAMS LR, KEIFER T, SCHULER J J, BEHREND J. Prebypass operative arteriography. Surgeo' 1982;92:627-633. 20. CARDELLA JF, SMITH TP, DARCY MD, HUNTER DW, CASTANEDA-ZUNIGA W, AMPLAZ K. Balloon occlusion femoral angiography prior to in situ saphenous vein bypass. Cardiovasc lntervent Radiol 1987;10:181- t 87. 21. ANDROS G, HARRIS RW, SALLES-CUNHA SX, DULAWA LB, OBLATH RW, APYAN RL. Bypass grafts to the ankle and foot. J Vasc Surg 1988;7:785-794. 22. HUCKMAN MS, SHECK GI, NEEMS RL, TINOR T. Transfemoral cerebral arteriography versus direct percutaneous carotid and brachial arteriography: a comparison of complication rates. Radiology 1979;132:93-97. 23. KERBER CW, CROMWELL LD, DRAYER BP, BANK WO. Cerebral ischemia, 1. Current angiographic techniques, complications, and safety. Am J Roentgenol t978;130:10971103. 24. VITEK JJ. Femoro-cerebral angiography: analysis of 2,000 consecutive examinations, special emphasis on carotid arteries catheterization in older patients. Am J Roentgenol 1973;118:633-647. 25. HASS WK, FIELDS WS, NORTH RR, KRICHEFF II, CHASE NE, BAUER RB. Joint study of extracranial arterial occlusion. II. Arteriography. techniques, sites, and complications. JAMA 1968;203:159-166. 26. MANI RL. EISENBERG RL, McDONALD EJ Jr, POLLOCK JA, MANI JR. Complications of catheter cerebral arteriography: analysis of 5,000 procedures. 1. Criteria and incidence. Am J Roentgenol 1978;131:861-865. 27. COUCH NP, O'MAHONY J, McIRVINE A, WHITTEMORE AD, LOMBARA JA, MANNICK JA, The place of abdominal aortography in abdominal aortic aneurysm resection. Arch Surg 1983:118:1029-1034. 28. NUNO IN, COLLINS GM, BARDIN JA, BERNSTEIN EF. Should aortography be used routinely in the elective management of abdominal aortic aneurysm? A m J Surg 1982;144:53-57. 29. KWAAN JH, CONNOLLY JE, MOLEN RV, CONROY R. The value of arteriography before abdominal aneurysmectomy. Am J Surg 1977;134:108-114. 30. BREWSTER DC, RETANA A, WALTMAN AD, DARLING RC. Angiography in the management of aneurysms of the abdominal aorta. Its value and safety. N Engl J Med t975;292:822-825. 31. RICCO JB, PEARCE WH, YAO JST, FLYNN WR. BERGAN JJ. The use of operative pre-bypass arteriography with Doppler ultrasound recordings to select patients for extended femoro-distal bypass. Ann Surg 1983;198:646-653. 32. FLANIGAN DP, WILLIAMS LR, KEIFER T, SCHULER J J, BEHREND AJ. Pre-bypass operative arteriography. Surgeo' 1982;92:627-633. 33. SHEARMAN CP, GWYNN BR, CURRAN F, GANNON MX, SIMMS MH. Non-invasive femoropopliteal assessment: is that angiogram really necessary? Br Med J 1986;293:1086-t089.
Can Duplex Scanning Replace Arteriography For Lower Extremity Arterial Disease? Ted R. Kohler, W., MD, George Andros, MD, John M. Porter, MD, Alexander Clowes, MD, Jerry Goldstone, MD, Kaj Johansen, MD, Edmond Raker, MD, Dale R. Nance, MD, D. Eugene Strandness, Jr, MD, Seattle, Washington
This preliminary study was undertaken to determine if surgeons would choose different intervention for lower extremity occlusive disease when given basic clinical information and data from either a duplex scan or arteriogram. Information on degree of stenosis from duplex scans and arteriograms of 29 patients was indicated on an anatomical line drawing along with the ankle blood pressures and a brief clinical description. Based on these data sheets, six vascular surgeons chose a clinical plan in a blinded fashion for each patient. Each plan was placed into one of eight possible categories for comparison using the kappa statistic. Intraobserver agreement between surgeons' decisions based on duplex scanning versus those based on arteriography was very good (mean kappa .70 with exact agreement in 76%). Interobserver agreement between different surgeons' decisions based on the same studies was significantly less (mean kappa 0.56, p < .05). Significant disparity in clinical approach occurred in 43% of the patients with nearly identical duplex scan and arteriogram reports, suggesting that much of the discrepancy lies in the clinical decision-making process. Clinical decisions made using duplex scans are very similar to those made using arteriograms. This technique can limit the need for arteriography in assessing patients with lower extremity arterial occlusive disease. (Ann Vasc Surg 1990;4:280-287) KEY WORDS: Arteries, stenosis or obstruction; arteries, extremities; angiography; ultrasound (US), doppler studies; ultrasound (US), comparative studies; clinical decision-making.
Duplex scanning is now accepted for reliable diagFrom the Departments of Surgery and Radiology, Veterans Administration Medical Center, the Department of Surgery, University of Washington School of Medicine, and the Department of Surgery, The Mason Clinic, Seattle, Washington; the Saint Joseph Medical Center, Burbank, California; the Division of Vascular Surgery. Department of Surgery, Oregon Health Sciences University, Portland, Oregon; and the Department of Surgery, University of California, San Francisco, California. Reprint requests: Ted Kohler, MD, Department of Surgery (112), Veterans Administration Medical Center, 1660 S. Columbian Way, Seattle, Washington 98108.
nosis of carotid artery stenosis, and several centers have begun to perform carotid endarterectomy without arteriography [ 1-6]. Our recent clinical experience suggests that duplex ultrasound can also accurately locate and quantify aortoiliac and femoropopliteal disease [7-9]. In a prospective clinical study, duplex scanning had a sensitivity of 82% and specificity of 92% in identifying significant arterial lesions [7]. In fact, it appeared that scanning was as accurate as two different radiologists grading the same arteriograms [9]. We undertook the current study to determine if surgeons would choose a significantly different intervention for treatment of lower extremity occlusive disease when
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given basic clinical information plus data from either a duplex examination or an arteriogram.
PATIENTS AND METHODS Duplex scans
Our technique for duplex scanning of the lower extremity arteries has been described previously [7]. Studies were performed with a Mark 600 or Ultramark 8 duplex scanner.* Patients are requested to limit their intake to a small, nonfatty meal on the evening prior to the examination and to take only a small amount of liquid with necessary medication on the morning of the study. Bowel preparation consists of a mild laxative taken on the evening prior to the study. The examination is begun with the patient supine. A 2.5 or 3 mHz transducer (or, in particularly asthenic individuals, a 5 mHz transducer) placed just below the xiphoid is used to image the aorta in the sagittal plane. The origin of the superior mesenteric artery is a convenient landmark seen originating from the anterior surface of the aorta. The aorta is followed distally to the iliac bifurcation, and each iliac artery is then followed separately to the groin level. The common femoral artery and the origin of the profunda femoris artery are examined next, followed by the proximal, mid, and distal superficial femoral artery. The patient is then turned to the prone position with the knees slightly flexed to study the popliteal artery. Velocity waveforms are recorded from each arterial segment and from any site of increased velocity or spectral broadening. Normal lower extremity arteries have a triphasic velocity waveform with a systolic forward flow peak followed by a brief reverse velocity component in early diastole and finally a second forward component. The normal waveform has a narrow spectral width, indicating a uniform flow pattern. Stenosis is detected on duplex scanning by an increase in velocity and broadening of the spectral waveform. Velocity signals are obtained from the center of the flow stream to minimize spectral broadening caused by the steep velocity gradient at the vessel wall. Criteria for grading the degree of stenosis have been described previously [7,8], and are summarized in Table I. Representative waveforms are shown in Figure I.
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TABLE I.--Classification criteria for estimating severity of stenosis in peripheral arteries Normal Triphasic waveform, no appreciable spectral broadening. 1-19% diameter reduction Normal waveform with slight spectral broadening and peak velocities increased no more than 30% greater than in the proximal adjacent segment. 20-49% diameter reduction Spectral broadening filling in the clear window under the systolic peak, peak velocity less than 100% greater than that of the next most proximal segment. 50-99% diameter reduction Peak systolic velocity 100% greater than proximal adjacent segment and reverse velocity component usually absent in the stenosis. Monophasic velocity waveform beyond the stenosis with reduced systolic velocity. Occlusion No flow in the imaged artery. Monophasic, preocclusive "thump" heard proximal to the occlusion; velocities markedly diminished and waveforms monophasic beyond the stenosis.
lower extremity occlusive disease during a two and one-half year period. Twenty-nine patients who had an arteriogram within three months of a duplex scan were selected. This is a subset of the patients reported in our most recent validation study [7]. The patients had a wide variety of disease severity ranging from simple stenosis to tandem occlusions and from claudication to gangrene. Duplex scans
a
s
Experimental design
This study used data from patients evaluated consecutively in our laboratory for symptomatic *Advanced Technology Laboratories, Inc., Bothell, Washington.
c
d
Fig. 1. Representative velocity waveforms from lower extremity arteries. (a) Normal; (b) 0-15% diameter reduction; (c) 16-49% diameter reduction; (d) 50-99% diameter reduction.
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and arteriograms were performed and interpreted in a blinded fashion, ie, without knowledge of the results of the other examination. For each arterial segment from the aorta to the popliteal artery, the observed disease was classified into one of the five categories outlined in Table I. A standard data sheet was prepared for both duplex scan and arteriogram results for each patient. Each contained a one sentence description of the patient's symptoms (claudication, rest pain, or ulceration), the anklearm indices, and results of treadmill testing, if done. This portion of the data sheet was identical for duplex scans and arteriograms. Also included was an anatomical line drawing of the lower limb arteries (Fig. 2). Results of the arteriogram or duplex scan were recorded on this drawing by the person who performed the study. Diseased segments were indicated by filling in the appropriate segments on the drawing; in addition, the disease category was tabulated next to the appropriate segment. It was not possible to determine by looking at an individual data sheet whether the results it depicted were obtained by duplex scanning or by arteriography and no information was provided to identify individual patients. Using the information contained in these data sheets, six of the authors (G.A., J.P., A.C., J.G., K.J., and E.R.) who were not previously familiar with the patients, their studies, or their treatment were asked to formulate a clinical plan. The reports were sent out in two separate mailings, each containing either a duplex scan or arteriogram report for each patient. On a random basis, either a duplex scan or arteriogram was sent first for each patient; consequently, the surgeons did not know if they were looking at data derived from a duplex scan or arteriogram. The second mailing was sent one month after completion for the first set and the data sheets were shuffled so they were not in the same order as before. The surgeons' plans were then placed into one of eight categories: o o o o o o o
No intervention Percutaneous angioplasty Operative endarterectomy Aortobifemoral bypass Femorofemoral bypass Femoropopliteal bypass Combined aortofemoral and femoropopliteal bypass o Other Comparisons were made using the kappa statistic, which measures the concordance between categorical data, adjusting for the extent of agreement expected by chance alone [10]. Kappa ranges from zero for only random agreement to one for perfect agreement. For each surgeon, the choice of intervention based on duplex scan results and arterio-
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DISABLING RIGHT A N D LEFT C A L F CLAUDICAT1ON
RIGHT
LEFT
20-49% 50-99%
. ~
20-49%
1-19%
1-19%
Brachial PT AT AAI
Right 188 100 100 53
Left
188 144 148 .78
Post Exercise
Right 0
Left 70
Fig. 2. Example of data sheet with sites of stenosis indicated on line drawing, brief clinical history at top, and ankle blood pressure data at bottom.
gram results were compared. Similarly, comparison was made between different surgeons' choices based on the same arteriogram or duplex scan reports.
RESULTS Table II lists intraobserver results for comparing the two decisions each surgeon made based on duplex scan or arteriogram reports. Kappa ranged from .61 to .90 for individual surgeons; the mean for the entire group was .70. Table III is the two-way contingency table for
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TABLE IV.--Kappa statistics for comparison of different surgeon's decisions based on the same arteriograms or duplex scans
TABLE II.--Kappa values for comparison of decisions based on duplex scanning versus arteriography Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon
.90
A B C D E F
.65 .73 .61 .66 .65
Combined Data n = 174
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.70
the combined data. Exact agreement occurred in 133 of 174 comparisons (76%). Table IV lists interobserver results for comparing different surgeons' decisions based on the same arteriogram or duplex scan reports. Kappa values ranged from .41 to .77, with a mean for arteriogram reports of .51 and for duplex scans of .61 (overall mean .56). The trend toward greater consistency from surgeon to surgeon with duplex scanning was significant (p < .05, Student's t-test). Kappa values for interobserver comparisons (Table IV) were significantly lower than those for intraobserver comparisons (Table II) (p < .05, Student's t-test). For 21 patients, the duplex scan and arteriogram reports were essentially the same (there were no disagreements regarding whether or not arterial segments of involved extremities had significant stenoses). F o r 12 of these patients (57%) all 72 of the clinical decision pairs were the same. In the remaining nine patients, 11 o f the 54 clinical decision pairs (20%) were different. In six pairs an angioplasty was advised in one case and not the other, in four the surgeons selected intervention in one instance and not the other, and in one the clinical decision was significantly different (profundaplasty alone versus profundaplasty with femoropopliteal bypass). There were significant differences in the duplex
Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon
A vs A vs A vs A vs A vs B vs B vs B vs B vs C vs C vs C vs D vs D vs E vs
Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon Surgeon
Arteriogram
Duplex scan
.49 .64 .49 .45 .55 .41 .57 .57 .41 .57 .58 .48 .66 .41 .42
.53 .77 .64 .68 .60 .70 .56 .49 .56 .6t .74 .61 .65 .47 .54
.51 _+ .08
.61 -+ .09"
B C D E F C D E F D E F E F F
Mean _+ SD
*Arteriogram-arteriogram versus Duplex-duplex; p - .0002, paired t-test
scan and arteriogram data in the remaining eight patients. In one of these, an iliac segment in the asymptomatic extremity was deemed significantly stenotic by arteriography but not by duplex scan. This had no effect on the clinical decisions, which involved treatment of the symptomatic extremity only. In the remaining seven patients, 23 o f the 42 decision pairs (55%) were different. These cases are listed in Table V. There were five categories o f significant discrepancies between duplex scan and arteriogram data that resulted in these differences: (1) Iliac disease was more extensive on arteriogram than duplex scan (seven decision pairs in patients A and D); (2) iliac disease was more extensive on duplex scan than on arteriogram (four decision pairs in patients F and G); (3) aortic disease was more extensive on arteriogram than duplex scan (three decision pairs in patient B)" (4) femoral disease was more extensive on arteriogram than duplex scan (three decision pairs affected in patient E); (5) a
TABLE Ill.--Kappa table comparing decisions based on duplex scan versus arteriogram reports for all six surgeons--29 patients Duplex scan Arteriogram
Nothing
PTA*
Endarterectomy
Nothing PTA Endarterectomy Aortobifem Fem-fem Fem-pop Combined Other Totals
18 1 3 1 0 2 0 0 25
2 15 1 3 3 3 0 0 27
0 0 14 0 0 0 0 1 16
*Percutaneous transluminal arterioplasty n = 174 Kappa - 0,703
Aortobifem
Fem-fem
Fern-pop
Combined
Other
2 8 1 31 5 0 0 0 47
0 0 0 0 2 0 0 0 2
0 1 1 0 0 50 0 1 53
0 0 0 0 0 0 3 0 3
0 0 0 0 0 1 0 0 1
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TABLE V.mlnstances of significant disagreement based on arteriogram versus duplex scanning Clinical decision Patient A
Surgeon
Based on arteriogram
Based on duplex scan
E*~
Aortobifemoral bypass
Femoral endarterectomy
B*
Axillobifemoral bypass
lilac angioplasty
Reason for discrepancy Proximal lilac stenosis seen on arteriogram only More aortic disease on arteriogram, lilac disease on duplex scan
C
C*
Aortobifemoral bypass
lilac angioplasty
D§
No treatment
Aortobifemoral bypass
E§
lilac angioplasty
Femoropopliteal bypass
F§
Bilateral profundaplasties Angioplasty
Aortobifemoral bypass
Angioplasty Angioplasty Angioplasty Angioplasty
No treatment No treatment No treatment Aortobifemoral bypass
Angioplasty Angioplasty Angioplasty Angioplasty Angioplasty Aortobifemoral bypass Femoropopliteal bypass No treatment
Aortobifemoral Aortobifemoral Aortobifemoral Aortobifemoral Aortobifemoral No treatment No treatment
C*
D*
D
E* F* A*
B*
E
C* D* E* F* A*t D*t F*
F
B* Dt
G
B *t E**
Femorofemoral bypass Femorofemoral bypass Femorofemoral bypass Femorofemoral bypass
No treatment
More aortic disease on arteriogram, lilac disease on duplex scan More aortic disease on arteriogram, lilac disease on duplex scan lilac stenosis seen on duplex, ignored by surgeon Different clinical decisions Graft stenosis missed on duplex examination
More lilac disease seen on arteriogram, although none >50%
bypass bypass bypass bypass bypass
Angioptasty Aortobifemoral bypass Aortobifemoral bypass Aortobifemoral bypass Aortobifemoral bypass
Same Femoral stenoses on arteriogram only Disease appeared isolated to lilacs on duplex lilac stenosis on duplex scan only Same More lilac disease on duplex scan Same
*Cases in which duplex scanning would have lead to an unacceptable approach or outcome, assuming arteriography was correct *Cases in which arteriography would have lead to an unacceptable approach or outcome, assuming duplex scanning was correct §Cases where differences in approach do not coincide with differences in data
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graft stenosis later confirmed at surgery was missed on duplex scan (four decision pairs in patient C). One significant difference occurred when a surgeon ignored a significant iliac stenosis on one of the two studies (patient B). Table V also indicates which cases would have led to undesirable approaches or outcomes. If we assume that disease severity was always accurately assessed by arteriography, use of duplex scanning information would have led to an undesirable approach or outcome in 16 decisions involving five patients (17% of the patients). These included four decisions in one patient where duplex scanning missed a graft stenosis. Six of the remaining 23 cases in which decisions were significantly different would have led to acceptable outcomes. These generally involved attempting angioplasty instead of directly proceeding to aortobifemoral bypass grafting. If we assume that duplex scanning always accurately assessed disease severity (except the surgically-confirmed graft stenosis it missed), decisions based on arteriograms would have led to an undesirable approach or outcome in nine instances involving five patients (17% of the patients). Another interesting subset is the group in which surgeons decided to do nothing based on one examination and decided on intervention based on the other. This occurred in 11 decision pairs involving six patients (6% of all t74 comparisons). In five of these instances (45%), involved arterial segments were graded the same by duplex scan and arteriogram. In six decision pairs (55%), the decision to intervene in one case and not the other was based on the presence of disease detected on arteriogram and not on duplex scan (missed graft stenosis in four cases, and femoral artery stenosis in two cases).
DISCUSSION While arteriography has long been the definitive test for symptomatic aortoiliac and lower extremity arterial disease, its many limitations have stimulated the development of noninvasive testing. Contrast studies provide anatomic rather than physiologic data, and their interpretation is subject to considerable interobserver variability [11-15]. The arteriographic appearance of frequently eccentric atherosclerotic lesions may be misleading, particularly if only uniplanar views are obtained. Although direct measurement of pressure gradient is the best way to determine the hemodynamic significance of arterial lesions, this is often neither practical nor anatomically possible. Several groups have found that preoperative angiography does not visualize a third or more of crural or pedal arteries that are patent by Doppler examination or operative exploration [16-19], although others report that inflow
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occlusion balloon angiography [20] or antegrade femoral puncture can reduce the requirement for intraoperative angiography to less than 3% [21]. Finally, arteriography involves significant cost, including time, patient discomfort, and occasional morbidity [22-26], as well as the monetary expense. The concept of arterial reconstructive surgery without preoperative arteriography is not new. Many clinicians have questioned the use of routine preoperative arteriography in patients with abdominal aortic aneurysms [27-30]. After review of 110 patients who underwent routine abdominal aortography prior to abdominal aortic aneurysm resection, Couch and coworkers [27] concluded that such studies could be reasonably limited to patients with specific indications, including significant hypertension, impaired renal function, diminished or absent femoral pulses, suspected mesenteric ischemia, suspected suprarenal extension of the aneurysm, or suspected thoracic aneurysm. Similarly, several investigators have recently reported their experience performing carotid endarterectomy based on clinical criteria and noninvasive testing alone [1-5]. Reasons for proceeding to operation without arteriography include contrast allergy, renal failure, progression of disease in patients who have had previous arteriograms, patients fear of arteriography, severe aortoiliac disease making access to the arterial system difficult, and the urgent need to operate in patients with crescendo TIAs. Several groups have advocated planning lower extremity revascularization with a Doppler examination and intraoperative arteriogram [31,32]. Shearman and associates reported that they could eliminate arteriography in many patients with a combination of clinical history and bedside Doppler examination [33]. This group depends on the quality of the femoral pulse to predict adequacy of inflow and chooses the site for distal anastomosis based on the severity of symptoms, the patency of the tibial vessels at the ankle (assessed by continuous wave Doppler), and the ankle blood pressure. They use preoperative arteriography only when necessary to define aortoiliac disease, and they obtain an intraoperative arteriogram to confirm the suitability of the chosen outflow tract. This approach is said to save time, money, and patient discomfort while maintaining "good results" (not defined). Duplex scanning of lower extremity arterial disease has made the argument against routine arteriography even more compelling. The development of low frequency transducers with appropriate focal lengths has made it possible to study deep abdominal and pelvic structures, including the iliac arteries. With this technology, Jager and associates devised a classification scheme based on the extent of spectral broadening and increased velocity [8,9]. We used this scheme prospectively in our clinical vascular laboratory and compared ultrasonic du-
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plex scanning with arteriography for the localization and classification of arterial stenoses and occlusions in 32 patients (383 arterial segments). The agreement between duplex scanning and arteriography was not significantly different than the agreement between two different radiologists reading the same arteriograms (kappa of 0.55 versus 0.63). For determining if stenoses were greater than 50% diameter reducing, duplex scanning had a sensitivity of 82%, specificity of 92%, positive predictive value of 80%, and negative predictive value of 93%. This technique was particularly accurate for classifying iliac stenoses (sensitivity 89%, specificity 90%), which are the most difficult lesions to diagnose by any other noninvasive test. Recognizing that duplex scanning can localize and classify peripheral arterial stenoses nearly as well as arteriography, we undertook the current study to determine if clinical decisions based on duplex scan results would be significantly different from those based on arteriograms. We studied patients with a wide range of disease severity ranging from mild claudication to gangrene and from simple stenosis to tandem occlusions. We found little disagreement when comparing each surgeon's decisions based on duplex scanning with those based on arteriography (there was exact agreement in 76% of cases and the mean kappa was .70). The extent of this intraobserver agreement varied from surgeon to surgeon (kappa range .61 to .90). The highest kappa value of .90 may have resulted from surgeon A's propensity to select aortobifemoral bypass in a large number of cases, and the lower kappa values may reflect the relatively larger repertoire of the other surgeons or a tendency to focus on different aspects of the clinical situation at different times. Significant disparity among different surgeons' clinical decisions occurred in 43% of patients when there were no significant differences between duplex scan and arteriogram reports. These data suggest that much of the observed variability was caused by diversity in the surgeons' clinical approach to individual situations rather than disparity in classification of disease by the two techniques. We also found that surgeons agreed significantly more when their decisions were based on duplex scan results. The reason for this is not clear, but it is interesting to speculate that duplex scan reports tend to include less extraneous information than arteriograms because they are based on physiologic rather than anatomic data. Because hemodynamically significant lesions can be missed by either arteriography or duplex scanning, it is not always possible to know which examination gives the most accurate assessment of the patient's disease severity. In 17% of the patients, significant discrepancies in disease estimation by the two different techniques would have led to an inappropriate clinical approach by whichever
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test was inaccurate. Adverse outcomes are less likely when test results are combined with more complete clinical data than were presented to the surgeons in this study. For example, one significant error occurred in a case where duplex scanning missed a femoropopliteal graft stenosis. This error was evident to the clinicians following the patient, who noted decreasing ankle pressure. The best approach to clinical decision-making combines detailed history, physical examination, and simple noninvasive testing with duplex scanning and selective arteriography. What information is critical in clinical decisionmaking for lower extremity arterial insufficiency, and how should duplex scanning be used? The decision whether or not to intervene is based on the patient's overall health and evidence of disabling claudication, rest pain, or ulceration. If intervention is planned, the clinician must first determine if flow to the level of the groin is sufficient. Presence of a strong femoral pulse on physical examination usually indicates adequate inflow. When inflow is in question, a normal duplex scan reliably excludes the possibility of a significant iliac stenosis (negative predictive value 96%) [7]. When aortoiliac occlusive disease is extensive, aortofemoral bypass may be required, whereas percutaneous angioplasty may be attempted when duplex scanning detects relatively short, high-grade iliac stenosis. A reconstructive procedure below the groin is required when inflow is adequate. It is then necessary to decide if there is a suitable lesion for angioplasty or an adequate vessel for distal bypass. Although duplex scanning can assess popliteal patency, it has been difficult to determine the quality of the patent vessel or assess more distal, tibial arteries. Therefore, at present, duplex scanning alone cannot be used routinely to determine the exact level of distal anastomosis for lower extremity bypass.
CONCLUSIONS Previous work demonstrated that duplex scanning provides much of the same information about lower extremity arterial occlusive disease as arteriography, and the current study shows that clinical decisions based on duplex scanning are very similar to those based on arteriograms. Prospective trials using the actual duplex scans and arteriograms are needed to compare decisions based on the complete clinical history and physical examination. At present, noninvasive testing allows the clinician to choose intervention more wisely, be it a selective diagnostic arteriogram, percutaneous angioplasty, or surgery. As duplex scanning becomes more sophisticated, it may eliminate the need for routine preoperative contrast studies in the assessment of
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patients with lower extremity arterial occlusive disease.
ACKNOWLEDGMENT Supported by NIH Grant # H L 20898.
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