Contrast Arteriography Research Articles

Lower extremity revascularization without contrast arteriography: a prospective study of operation based upon duplex mapping

This study prospectively assessed the results of lower extremity surgical revascularization, which was performed on the basis of duplex arterial mapping in selected patients without preoperative contrast arteriography. Criteria were developed for patient selection. Among 158 patients requiring surgery for lower extremity ischemia over a 24-month period, 24 (15%) were selected for operation without current preoperative arteriography. Aorto-iliac and infrainguinal duplex arterial mapping were performed in an laboratory that was accredited by the Intersocietal Commission for Accreditation of Vascular Laboratories. Indications for surgery were minor gangrene (11), rest pain (7), or claudication (6). Operations included femoro-popliteal bypass (14), femoral endarterectomy (9) and femoral–femoral bypass (1). Mean length of stay was 4.5±2.0 days. Ankle–brachial index improved from 0.49±0.12 to 0.80±0.15 ( P<0.05). Primary patency was 91.7±9.4% and assisted primary patency was 100% at 18 months. There was no graft occlusion or limb loss. Mean follow-up was 16.7±7.0 months. These preliminary data support the safety and durability of duplex-guided lower extremity surgical revascularization without arteriography in selected cases. Success in a broader application of this approach requires the continuing development of patient selection criteria.

The use of duplex ultrasound arterial mapping as an alternative to conventional arteriography for primary and secondary infrapopliteal bypasses

Background: For more than 1 decade, duplex ultrasonography has been investigated as a potential replacement for invasive contrast arteriography (CA) prior to lower extremity revascularization. While some authors advocate the reliability of this methodology for infrainguinal imaging, revascularizations based on duplex ultrasonography alone are seldom reported. Our initial experience with duplex ultrasound arterial mapping (DUAM) for primary and secondary infrapopliteal bypasses performed without preoperative CA is reported in this series. Methods: Twenty-eight infrapopliteal bypasses based on DUAM alone (26) and combined DUAM and CA (2) were performed. Indications for surgery were tissue loss in 22 cases and rest pain in 6. Eight patients (29%) had at least 1 previous ipsilateral revascularization. A schematic anatomical drawing based on DUAM helped the selection of optimal inflow and outflow bypass sites. Bypasses originated from the femoral arteries in 17 cases, external iliac in 3, and popliteal in 4, and from a previous graft in 4. The distal anastomosis was to the dorsalis pedis in 12 cases, posterior tibial in 7, anterior tibial in 6, and peroneal in 3. Results: DUAM revealed unobstructed inflow in 24 cases, significant iliac stenosis in 1, and in 3 cases imaging was not possible owing to obesity. A pressure gradient of 15 mm Hg between donor and radial artery confirmed the stenosis diagnosed by DUAM, and was successfully treated with balloon angioplasty and stent placement. A single infrapopliteal runoff artery was identified by DUAM in 22 cases, 2 in 4 cases, and 3 in 2 cases. Preoperative CA was performed in 2 instances because of severe arterial calcification. Completion arteriography matched the run-off status predicted by DUAM in 25 out of 26 cases (96%). DUAM missed a significant anterior tibial artery stenosis that required a distal graft extension. One-, 3-, and 6-month patency rates were 96%, 85%, and 62%, respectively. Limb salvage rate was 86%. Conclusions: This early experience shows that DUAM may be a safe alternative to invasive conventional arteriography for the majority of patients (89%) presenting with critical ischemia and in need of infrapopliteal bypasses.

Surgical renal artery reconstruction without contrast arteriography: the role of clinical profiling and magnetic resonance angiography

Purpose: Contrast arteriography is the accepted gold standard for diagnosis and treatment planning in patients with atherosclerotic renovascular disease (RVD). In this study, the results of a selective policy of surgical renal artery reconstruction (RAR) with magnetic resonance angiography (MRA) as the sole preoperative imaging modality are reviewed. Methods: From May 1993 to May 1998, 25 patients underwent RAR after clinical evaluation, and aortic/renal MRA performed with a gadolinium-enhanced and 3-dimensional phase contrast technique. Clinical presentations suggested severe RVD in all patients and included poorly controlled hypertension (16 patients), hospitalization for hypertensive crises and/or acute pulmonary edema (13), and deterioration of renal function within one year of operation (15). Thirteen patients had associated aortic pathologic conditions (12 aneurysms, 1 aortoiliac occlusive disease), and eight of these patients also underwent noncontrast computed tomography scans. Significant renal dysfunction (serum creatinine level, ≥2.0 mg/dL) was present in all but 4 patients with 14 of 25 patients having extreme (creatinine level, ≥3.0 mg/dL) dysfunction. Results: Hemodynamically significant RVD in the main renal artery was verified at operation in 37 of 38 reconstructed main renal arteries (24/25 patients). A single accessory renal artery was missed by MRA. RAR was comprehensive (bilateral or unilateral to a single-functioning kidney) in 21 of 25 patients and consisted of hepatorenal bypass graft (3 patients), combined aortic and RAR (13 patients), isolated transaortic endarterectomy (8 patients), and aortorenal bypass graft (1 patient). Early improvement in both hypertension control and/or renal function was noted in 21 of 25 patients without operative deaths or postoperative renal failure. Sustained favorable functional results at follow-up, ranging from 5 months to 4 years, were noted in 19 of 25 patients. Conclusion: MRA is an adequate preoperative imaging modality in selected patients before RAR. This strategy is best applied in circumstances where the clinical presentation suggests hemodynamically significant bilateral RVD and/or in patients at substantial risk of complications from contrast angiography. (J Vasc Surg 1999;29:1012-21.)

Carotid artery disease: natural history, diagnosis, and therapy.

Stroke remains a major complication of atherosclerotic cerebrovascular disease, with extracranial carotid occlusive disease accounting for nearly one-third of all events. Although historical symptoms and physical examination findings are important, objective testing with carotid duplex ultrasonography and magnetic resonance arteriography represent the foundation for therapeutic decision making. Contrast arteriography is playing a decreasing role in the evaluation of patients with carotid artery disease. Options for therapy, based on the presence or absence of symptoms and degree of stenosis, include antiplatelet therapy with cardiovascular risk factor modification, carotid endarterectomy, and more recently, endovascular therapy.

Evaluation of Abdominal Aortic Aneurysms

The worldwide incidence of abdominal aortic aneurysms (AAAs) is increasing, and AAA remains a major source of mortality in our population. With a mortality rate of over 80% for AAA rupture, diagnosis and treatment of AAAs, although still asymptomatic, is imperative. Current techniques for eval uation of AAAs include clinical exam and radiologic modalities, which include contrast arteriography, ultrasound, computed tomography, and magnetic reso nance imaging. Controversy exists as to the most cost-effective technique(s) for timely diagnosis and management of AAAs. This article reviews the role of the various diagnostic techniques available for screening, nonoperative surveillance, and both open and endovascular repair of AAAs.

Can duplex scan arterial mapping replace contrast arteriography as the test of choice before infrainguinal revascularization?

Purpose: Arteriography is the diagnostic test of choice before lower extremity revascularization, because it is a means of pinpointing stenotic or occluded arteries and defining optimal sites for the origin and termination of bypass grafts. We evaluated whether a duplex ultrasound scan, used as an alternative to arteriography, could be used as a means of accurately predicting the proximal and distal anastomotic sites in patients requiring peripheral bypass grafts and, therefore, replace standard preoperative arteriography. Methods: Forty-one patients who required infrainguinal bypass grafts underwent preoperative duplex arterial mapping (DAM). Based on these studies, an observer blinded to the operation performed predicted what operation the patient required and the best site for the proximal and distal anastomoses. These predictions were compared with the actual anastomotic sites chosen by the surgeon. Results: Whether a femoropopliteal or an infrapopliteal bypass graft was required was predicted correctly by means of DAM in 37 patients (90%). In addition, both anastomotic sites in 18 of 20 patients (90%) who had femoropopliteal bypass grafts and 5 of 21 patients (24%) who had infrapopliteal procedures were correctly predicted by means of DAM. Conclusion: DAM is a reliable means of predicting whether patients will require femoropopliteal or infrapopliteal bypass grafts, and, when a patient requires a femoropopliteal bypass graft, the actual location of both anastomoses can also be accurately predicted. Therefore, DAM appears able to replace conventional preoperative arteriography in most patients found to require femoropopliteal reconstruction. Patients who are predicted by means of DAM to require crural or pedal bypass grafts should still undergo preoperative contrast studies to confirm these results and to more precisely locate the anastomotic sites. (J Vasc Surg 1999;29:100-9.)

Vascular surgery without arteriography: use of Duplex ultrasound

Although contrast arteriography has served as the historical `gold standard' for diagnosis of arterial disease, recent improvements in noninvasive diagnostic methods have made it possible to plan surgical treatment without subjecting patients to this invasive procedure. This approach avoids both the risks and costs associated with arteriography. Duplex scanning has become the standard noninvasive test for extracranial carotid artery disease, and it can also be used to directly evaluate the lower extremity arteries. In addition to the standard duplex criteria for classification of carotid stenosis, new criteria are available that reflect the stenosis thresholds identified in randomized clinical trials. Clinical experience has clearly shown that carotid endarterectomy can be performed safely based on the duplex scan alone in the majority of patients; however, arteriography is still indicated in selected cases. The evaluation of lower extremity arterial disease requires examination of multiple arterial segments, and most vascular surgeons still rely on the anatomic detail provided by arteriography for preoperative planning. Still, it may be possible to avoid formal preoperative arteriography in selected patients by using a combination of lower extremity duplex scanning and intraoperative arteriography. Further developments in noninvasive testing will continue to reduce the need for diagnostic arteriography prior to direct arterial surgery.

MAGNETIC RESONANCE ANGIOGRAPHY OF LOWER-EXTREMITY ARTERIAL DISEASE

Improvements in vascular technique have expanded the treatment options for patients with severe occlusive peripheral vascular disease. The decision to perform a major revascularization procedure in patients who are often at high risk for cardiovascular morbidity and mortality depends on the risk-benefit ratio. Detailed and accurate vascular imaging is essential and evaluating the likelihood of a successful revascularization with subsequent limb salvage. Although contrast angiography has been the time-honored reference standard imaging technique, the method is an invasive procedure with limitations and risks. MRA is a new, noninvasive vascular imaging technique that may now be added to the imaging options with the potential for improved sensitivity for finding patent runoff vessels, avoidance of morbidity, and cost equivalent to that of conventional contrast angiography. Magnetic resonance angiography is a rapidly developing and exciting new vascular imaging technique. As with any new technique, it is imperative that individual centers validate their MRA results and interpretations against the time-honored standard, which continues to be contrast arteriography. Several studies now indicate that MRA can be a cost-effective outpatient imaging technique sufficient for planning and successfully performing peripheral bypass procedures. As developments in hardware, software, and non-nephrotoxic contrast agents continue to increase, applicability of MRA in vascular surgery will continue to expand. Predictably, MRA will have a major role in the future of vascular imaging, and it is likely to supplant the need for conventional contrast angiography in the majority of patients.

CONTRAST-ENHANCED MR ANGIOGRAPHY: Theory and Optimization

It is now possible to perform contrast arteriography safely and rapidly by taking advantage of gadolinium contrast agents and three-dimensional MR imaging. Although the development of this approach to arteriography is in its infancy, the image quality already rivals conventional arteriography. As we continue to develop this technique by taking advantage of more pulse sequence tricks, improving hardware, and improving contrast agents, the field of vascular imaging will undoubtedly be transformed. This article discusses the fundamental concepts underlying this approach to angiography.

Safe and cost-effective approach to carotid surgery

To evaluate the safety and cost effectiveness of carotid surgery performed altering the perioperative protocol in an attempt to decrease resource utilisation. Department of vascular surgery in a large metropolitan teaching hospital in northern Italy. Prospective, non-selective study. Three hundred and eighty carotid procedures were performed in 1995 on 343 patients (274 males, 69 females, mean age 68.2 years, range 47-86 years). The most important cost containment measures, were: (i) limiting the use of contrast arteriography to cases of dubious ultrasonographic diagnosis; (ii) routine use of loco-regional anaesthesia; (iii) postoperative admission to an intensive care unit (ICU) only in selected cases; (iv) early postoperative discharge where possible. Mortality was 0.26% and neurological morbidity 1.58%. General anaesthesia was required in eight patients (2.1%), and only seven patients (1.8%) were admitted postoperatively to the ICU. Arteriography was performed in 56 cases (14.7%). The average hospital stay was 5 days with a global cost of 43,036 ECU, as compared with a cost of 6764 ECU for patients treated traditionally with routine arteriography, general anaesthesia and routine ICU admission. Selective use of arteriography and ICU, routine use of loco-regional anaesthesia and reduced hospital stay make it possible to lower the cost of carotid surgery without sacrificing quality.

Intraoperative prebypass arteriography for infrageniculate revascularization

Selection of the optimal distal target for infrageniculate arterial revascularization remains difficult in patients with multilevel occlusive disease due to poor visualization of the distal vasculature by preoperative arteriography. Prebypass, intraoperative arteriography (IOA) with direct injection of contrast into the infrageniculate arteries may improve distal arterial visualization and bypass target selection. One hundred fourteen extremities in 104 consecutive patients requiring infrageniculate bypass were prospectively studied. All patients underwent preoperative contrast arteriography (CA) of the aortoiliac and lower extremity arteries using iodinated and/or CO2 contrast and digital subtraction techniques. IOAs were obtained at operation to confirm the adequacy of the distal runoff from the predicted bypass target and to identify potentially superior targets. The preoperative plan formulated from the CA was compared to the actual procedure performed based on the IOA. The CA and IOA were also independently reviewed postoperatively by two blinded vascular surgeons to determine the number of patent vessel segments visualized and the number of segments with <50% stenosis. Revascularization was done in 105 of 114 extremities (92%), whereas amputation was required as the initial procedure in 9 patients (8%). The IOA altered the operative plan based on the CA in 27 of 144 patients (24%). Changes in the planned bypass procedures included selection of a more distal anastomotic site in 13 of 102 patients (13%), selection of a more proximal anastomotic site in 4 of 102 (4%), selection of a different artery for the distal anastomosis in 3 of 102 (3%), and amputation rather than bypass in 2 of 102 patients (2%) with no suitable distal bypass target on the IOA. The IOA also resulted in bypass rather than planned amputation in 5 of 12 patients (42%) deemed unreconstructable on the preoperative CA. A mean of 13 minutes was required for IOA and an adequate study was obtained on the first attempt in 98 of 144 patients (86%). On postoperative review, more patent vessel segments but fewer segments with <50% stenosis were identified on the IOA compared to the CA. Prebypass intraoperative arteriography facilitates selection of the optimal distal bypass target during infrageniculate revascularization and can result in initial limb salvage in select patients deemed unreconstructable by preoperative contrast arteriography.

Preoperative Sizing of Grafts for Transfemoral Endovascular Aneurysm Management: A Prospective Comparative Study of Spiral CT Angiography, Arteriography, and Conventional CT Imaging

Purpose: To define the impact of spiral computed tomographic angiography (CTA) with image reconstruction on graft selection for Transfemoral Endovascular Aneurysm Management (TEAM) by comparing it to conventional computed tomography (CT) and contrast arteriography. Methods: Twenty-one candidates for TEAM were included. The diameters of the superior and inferior aneurysm necks and lengths between the graft attachment sites were measured using the three imaging techniques. These measurements and their consequences on graft selection were studied. Results: The difference in length sizing between spiral CTA and arteriography never exceeded 1 cm; however, lengths measured by conventional CT scanning resulted in underestimation of graft length in 91% of patients. Graft diameters were chosen too small in 62% of the patients when based on arteriographic diameter measurements. A graft of similar diameter was selected by spiral CTA and conventional CT scanning in 81% of the patients, while minor oversizing by conventional CT scanning was found in 14%. Conclusions: Neither conventional CT scanning nor arteriography is adequate as a sole preoperative radiological investigation for TEAM graft sizing. Spiral CTA with image processing produces all information required for selection of tho-optimal graft size and should be regarded the method of first choice for this purpose.

Preoperative Testing before Carotid Endarterectomy: A Survey of Vascular Surgeons' Attitudes

Traditional surgical practice and published consensus statements from major vascular surgery specialty societies have considered contrast arteriography to be a routine part of the diagnostic evaluation prior to carotid endarterectomy (CEA). However, some surgeons now omit routine preoperative arteriography if a technically adequate carotid duplex scan is performed and indications for CEA are clear. To better establish current practice patterns and to characterize vascular surgeons' opinions about the role of preoperative arteriography, the Peripheral Vascular Surgery Society membership was surveyed by mail. Eighty-six percent of the members responded (430 of 502). Ninety-three percent of all patients considered for CEA are evaluated with duplex scanning; 82% with arteriography. While the majority of surgeons typically obtain both a duplex scan and an arteriogram, 70% have performed CEA without a preoperative arteriogram. Brain imaging studies (CT or MRI) are obtained in 26% and MR angiograms in 10% of cases. Seventy-five percent of the surgeons agreed with the statement that CEA without preoperative arteriography is an acceptable practice if appropriate indications for surgery are present. Furthermore, one third believed that CEA without a preoperative arteriogram is generally acceptable (acceptable more than half the time). Respondents were stratified by surgical experience time in practice and practice type. No significant differences in responses were found, suggesting the acceptance of CEA without preoperative arteriography is broad-based. This survey demonstrates changing attitudes among practicing vascular surgeons regarding the necessity for routine arteriography prior to CEA. Carotid endarterectomy on the basis of duplex scanning and clinical assessment should be considered an accepted alternative.

Value of Fast Gradient Echo Magnetic Resonance Angiography as an Adjunct to Coronary Arteriography in Detecting and Confirming the Course of Clinically Significant Coronary Artery Anomalies

We investigated the additional value of magnetic resonance (MR) angiography in 12 patients with clinically significant coronary anomalies. In 5 patients, the referring cardiologist requested additional evaluation because coronary arteriography was inconclusive about the course of the anomaly. For comparison, 7 patients with known anomalous coronary arteries were collected from our database. In these patients, there had been no doubt about the course of the anomalous coronary arteries. MR angiography provided the diagnosis in all 5 patients in whom the diagnosis was inconclusive beforehand. From the 7 patients in whom diagnosis had been established previously by contrast arteriography, the anomaly was confirmed in 5 by MR angiography. In 1 patient, the initial diagnosis at contrast arteriography had to be changed as a result of MR angiography. In 1 patient, the MR image was of insufficient quality to be conclusive.In conclusion, in patients with angiographically suspected coronary anomalies, fast gradient echo MR angiography is a helpful adjunct to coronary arteriography in identifying and confirming the origin and course of clinically significant coronary anomalies. The additional value of fast gradient echo MR coronary angiography is the visualization of both the artery and its surrounding structures.In 12 patients with angiographically suspected clinically significant coronary anomalies, we investigated the additional value of magnetic resonance angiography to delineate the course of the coronary artery. Fast gradient echo magnetic resonance angiography appeared to be a helpful adjunct to coronary arteriography in identifying and confirming the course of the clinically significant coronary anomalies.

Magnetic resonance angiography in the management of lower extremity arterial occlusive disease: a prospective study.

We conducted a prospective study to clarify the clinical utility of magnetic resonance angiography (MRA) in the treatment of patients with lower extremity arterial occlusive disease. During the interval of September 1993 through March 1995, 79 patients (43% claudicants, 57% limb-threatening ischemia) were studied with both MRA and contrast arteriography (ANGIO) and underwent intervention with either balloon angioplasty (9%), surgical inflow (28%), or outflow (63%) procedures. MRA and ANGIO were interpreted by separate blinded vascular radiologists, and arterial segments from the pelvis to the foot were graded as normal or with increasing degrees of mild (25% to 50%), moderate (51% to 75%), or severe (75% to 99%) stenosis or occlusion. Treatment plans were formulated by the attending surgeon and were based initially on hemodynamic, clinical, and MRA data and thereafter with ANGIO. Additional study surgeons formulated independent and specific treatment plans based on MRA or ANGIO alone. Indexes of agreement (beyond chance) for arterial segments depicted by MRA and ANGIO were assessed (kappa value), and treatment plans formulated were compared (chi-square). Precise agreement (%) and the percent of major discrepancies (segment classified as normal/mild stenosis on one study and severe stenosis/occlusion on the other) between MRA and ANGIO for respective arterial segments was as follows: common and external iliacs (n = 256) 77/3.5; superficial femoral and above-knee popliteal (n = 255) 73/6.7; below-knee popliteal (n = 131) 84/3.8; infrapopliteal runoff vessels (n = 864) 74/12.4; pedal vessels (n = 111) 69/19.8 Kappa values indicated moderate agreement (between MRA and ANGIO) beyond chance for all arterial segments. Treatment plans formulated by the attending surgeon, the MRA surgeon, and the ANGIO surgeon agreed in more than 85% of cases. Inability of MRA to assess the significance of inflow disease and inadequate detail of tibial/pedal vessels were the principal deficiencies of MRA in those cases where it was considered an inadequate examination. These findings suggest MRA and ANGIO are nearly equivalent examinations in the demonstration of infrainguinal vascular anatomy. MRA is an adequate preoperative imaging study (and may replace ANGIO), particularly in those circumstances when the risk of ANGIO is increased or when clinical and hemodynamic evaluation predict the likelihood of straightforward aortofemoral or femoral-popliteal reconstruction.

Arteries of the Foreflipper of the Harbor Seal (Phoca vitulina) as Represented by Contrast Arteriography.

Arteries of the Foreflipper of the Harbor Seal (Phoca vitulina) as Represented by Contrast Arteriography.

Use of magnetic resonance angiography for the preoperative evaluation of patients with infrainguinal arterial occlusive disease

This study was designed to determine whether magnetic resonance angiography (MRA) will allow preoperative management decisions without the need for contrast arteriography in patients with lower extremity ischemia caused by infrainguinal arterial occlusive disease. Forty-five patients with lower extremity ischemia in 50 limbs were evaluated by both two-dimensional time-of-flight MRA and intraarterial digital subtraction angiography (DSA) between February 1992 and June 1995. Independent management plans were based on clinical presentation, pulse volume recordings, and separate reviews of the MRA and DSA. Of 50 limbs, 23 required arterial bypass, 19 percutaneous transluminal angioplasty, 5 patch angioplasty, and 3 amputation. MRA and DSA correlated exactly in 89.5% of infrainguinal arterial segments, whereas interpretations disagreed in 10.5% of arterial segments. Mismatches that had an influence on patient treatment decisions occurred in only 8 (2.3%) of 352 arterial segments. Independent MRA- and DSA-based revascularization plans agreed in 45 (90%) extremities. MRA predicted the level of arterial reconstruction in all 23 limbs that required arterial bypass. MRA identified focal stenoses amenable to percutaneous transluminal angioplasty in 18 (94.7%) of the 19 limbs that ultimately underwent percutaneous transluminal angioplasty. A strategy of preoperative planning by MRA with confirmatory intraoperative arteriography would represent a 31% cost savings per patient at our institution while eliminating the morbidity of preoperative DSA. When used in combination with the patient's physical examination and segmental limb pressures with plethysmography, MRA is sufficient for planning infrainguinal arterial bypass procedures and selecting patients for percutaneous transluminal angioplasty.

The natural history of the external carotid artery after carotid endarterectomy: Implications for management

Most surgeons perform some type of endarterectomy of the external carotid artery (ECA) routinely during standard carotid endarterectomy (CEA). This approach has been shown to result in a small percentage of ECA occlusions, the clinical significance of which remains poorly understood. We have modified our approach to the management of the ECA during standard CEA by averting any attempt at external CEA. To evaluate the natural history of the untreated ECA after CEA, we reviewed the preoperative, postoperative, and follow-up duplex scans obtained from 232 CEAs over the past 4 years. Preoperative and postoperative carotid artery duplex examinations with specific evaluation of the extent of ECA stenosis were available for review on 114 CEAs performed between January 1991 and July 1994. All CEAs were performed for internal carotid artery stenosis greater than 75% as determined by duplex scanning, which was confirmed by either contrast arteriography or magnetic resonance angiography. Seventy-three (64.0%) procedures were performed for symptomatic lesions, whereas 41 (36.0%) were performed for asymptomatic stenosis. There were no perioperative strokes or transient ischemic attacks in this group, and there was one postoperative death (0.9%). Short- and intermediate-term follow-up demonstrated insignificant changes in ECA diameter after operation, with no cases of ECA occlusion and only five cases progressing to greater than 75% on the 1-year follow up duplex examination. We conclude from these data that averting external CEA during standard CEA does not result in significant progression of ECA stenosis or occlusion.

The fate of bypass grafts to angiographically occult runoff vessels detected by magnetic resonance angiography

Magnetic resonance angiography (MRA) is a noninvasive vascular imaging technique that is more sensitive than contrast arteriography (CA) for the detection of patent distal runoff vessels. This technique has facilitated performance of MRA-directed bypass procedures for patients who were believed not to be bypass candidates because of the absence of a suitable target vessel on the preoperative CA. The fate of bypasses to these angiographically occult runoff vessels is unknown, however, and it has been proposed that patients with angiographically occult runoff may have aggressive occlusive disease, rendering bypass procedures ultimately futile. Between April 1992 and February 1995, 212 autogenous vein infrageniculate bypasses were performed for limb-salvage indications, 22 (12%) to angiographically occult runoff vessels. Results of bypasses performed to angiographically occult vessels were compared with those of bypasses to CA-detected runoff vessels. Life-table analysis of graft-patency and limb-salvage rates was performed. The accuracy of the MRA-predicted patency of angiographically occult vessels was confirmed in every case by the operative findings. Life-table analysis revealed no significant difference in primary graft patency (p > 0.05) or limb-salvage (p > 0.05) rates between patients with bypasses to runoff vessels seen by MRA alone. At 35 months after surgery, the primary graft patency rate was 68% for bypasses to CA-detected vessel bypass and 67% for MRA-detected vessels. The limb salvage rate was 83% for CA-detected vessel bypass patients and 78% for patients with angiographically occult runoff. MRA can accurately identify patent runoff vessels not visualized by CA. Results of bypasses performed to angiographically occult runoff vessels are similar to those of bypasses performed to vessels detected by CA. MRA should be performed in patients in whom CA fails to reveal runoff vessels suitable for use in a limb-salvage procedure. The greater sensitivity of MRA may facilitate successful bypass surgery and improve the overall limb-salvage rate.

Observer variation in the interpretation of intra-arterial angiograms and the risk of inappropriate decisions about carotid endarterectomy.

To determine how often observer variation in the interpretation of intra-arterial angiograms might alter the decision whether or not to refer patients for carotid surgery. A prospective study was carried out in a consecutive series of 99 patients with transient ischaemic attacks and minor strokes. Interpretable angiographic films were available for 179 carotid artery bifurcations. Stenosis of the internal carotid artery was measured using mm scales, independently by three different radiologists (A, B, and C), using the European Carotid Surgery Trial method. An analysis of the grouped data showed good to moderate agreement by kappa statistics for radiologists A v B, B v C, and A v C of 0.68, 0.60, and 0.70 respectively. The mean absolute difference in the estimate of stenosis by each of the different radiologists (interobserver variation) was 9.5% and for each radiologist on two separate occasions (intraobserver variation) 8.4%. The degree of observer error was smallest among severely stenosed arteries. Although the absolute differences were small, "clinically important" differences which could change the treatment recommended from surgery to no surgery (or vice versa) occurred between radiologists A and B, B and C, and A and C in: seven (3.9%), six (3.4%), and 11 (6.1%) vessels respectively. Because observer variation affects all of the imaging methods (Doppler, duplex, contrast arteriography, and MR angiography) used to select patients with transient ischaemic attack and stroke, these findings are likely to be widely relevant. Any centre assessing patients with cerebrovascular disease will need to implement strict quality control measures in the interpretation of angiograms (and other vascular imaging procedures) to minimise observer error and thereby reduce the number of inappropriate decisions made to refer for carotid artery surgery or not.