Utility of magnetic resonance arteriography for distal lower extremity revascularization

Chapter II: Diagnostic methods

Non-invasive vascular studies can provide crucial information on the presence, location, and severity of critical limb ischaemia (CLI), as well as the initial assessment or treatment planning. Ankle-brachial index with Doppler ultrasound, despite limitations in diabetic and end-stage renal failure patients, is the first-line evaluation of CLI. In this group of patients, toe-brachial index measurement may better establish the diagnosis. Other non-invasive measurements, such as segmental limb pressure, continuous-wave Doppler analysis and pulse volume recording, are of limited accuracy. Transcutaneous oxygen pressure (TcPO(2)) measurement may be of value when rest pain and ulcerations of the foot are present. Duplex ultrasound is the most important non-invasive tool in CLI patients combining haemodynamic evaluation with imaging modality. Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) are the next imaging studies in the algorithm for CLI. Both CTA and MRA have been proven effective in aiding the decision-making of clinicians and accurate planning of intervention. The data acquired with CTA and MRA can be manipulated in a multiplanar and 3D fashion and can offer exquisite detail. CTA results are generally equivalent to MRA, and both compare favourably with contrast angiography. The individual use of different imaging modalities depends on local availability, experience, and costs. Contrast angiography represents the gold standard, provides detailed information about arterial anatomy, and is recommended when revascularisation is needed.

Aneurisma verdadeiro de artéria plantar medial: relato de caso

Os aneurismas periféricos merecem atenção pela sua baixa frequência e associação com outros aneurismas arteriais, principalmente o de aorta abdominal. O aneurisma de artéria plantar verdadeiro é ainda mais raro. A escassa literatura disponível concentra-se nos casos de pseudoaneurisma pós-traumático dessa artéria. Relata-se o caso de uma paciente do sexo feminino, 85 anos, com queixa de dor no pé direito ao deambular durante um ano, acompanhada de nódulo pulsátil em região plantar, próximo da base do primeiro pododáctilo. Não havia história prévia de trauma ou cirurgia na região plantar acometida. Realizou-se ecografia vascular e angiorressonância, que diagnosticaram aneurisma de artéria plantar. A paciente foi então submetida à aneurismectomia com ligadura das artérias nutricionais, apresentando boa evolução pós- operatória.

Duplex ultrasound scanning of peripheral arterial disease of the lower limb

OBJECTIVES

To assess the reliability and applicability of duplex ultrasound scanning (DUS) of lower limb arteries, compared with digital subtraction angiography (DSA), in patients with peripheral arterial disease (PAD).

DESIGN

A prospective, blinded, comparative study.

MATERIALS AND METHODS

A total of 169 patients were examined by DUS and DSA. Intermittent claudication (IC) was present in 42 (25%) patients and critical limb ischaemia (CLI) in 127 (75%) patients. To allow segment-to-segment comparison, the arterial tree was divided into 15 segments. In total, 2535 segments were examined using kappa (κ) statistics to test the agreement.

RESULTS

The agreement between DUS and DSA was very good (κ>0.8) or good (0.8 ≥ κ>0.6) in most segments, but moderate (0.6 ≥ κ>0.4) in the tibio-peroneal trunk and the peroneal artery. Agreement between the two techniques was significantly better in the supragenicular (κ=0.75 (95% confidence interval (CI): 0.70-0.80)) than in the infragenicular segments (κ=0.63 (0.59-0.67)) (p<0.001). Similarly, the technical success rate was significantly higher in the supragenicular segments (DUS: 100%; DSA: 99%) than in the infragenicular segments (both 93%) (p<0.001). DUS was the best technique for imaging of the distal crural arteries (92% vs. 97%; p<0.001) and DSA was the best technique for imaging of the proximal crural arteries (95% vs. 91%; p<0.01). Neither the agreement nor the technical success rate was influenced by the severity of PAD, that is, IC versus CLI.

CONCLUSION

The agreement between DUS and DSA was generally good, irrespective of the severity of ischaemia. DUS performed better in the supragenicular arteries than in the infragenicular arteries. However, DUS compared favourably with DSA in both tibial vessels, particularly in the distal part, which makes DUS a useful non-invasive alternative to DSA.

Quantification of blood flow velocity in stenosed arteries by the use of finite elements: an observer-independent noninvasive method

Interventions for peripheral arterial disease should be designed to treat a physiological rather than an anatomic defect. Thus, for vascular surgeons, functional information about stenoses is as important as the anatomic one. In case of finding a stenosis by the use of magnetic resonance angiography, it would be a matter of particular interest to derive automatically and directly objective information about the hemodynamic influence on blood flow, caused by patient-specific stenoses. We developed a methodology to noninvasively perform numerical simulations of a patient's hemodynamic state on the basis of magnetic resonance images and by the means of the finite element method. We performed patient-specific three-dimensional simulation studies of the increase in systolic blood flow velocity due to stenoses using the commercial computational fluid dynamic software package FIDAP 8.52. The generation of a mesh defining the flow domain with a stenosis and some simulation results are shown.

Aneurisma verdadeiro bilateral de artéria tibial posterior

Neste artigo, faz-se o relato de um caso de aneurisma verdadeiro bilateral da artéria tibial posterior em paciente de 57 anos. Os aneurismas surgiram em épocas diferentes. Os aspectos clínicos, diagnósticos e terapêuticos deste caso são discutidos. Este relato é importante, pois os autores não têm conhecimento de caso semelhante na literatura consultada.

Magnetic resonance imaging of the peripheral vasculature

BACKGROUND

Atherosclerotic disease of the peripheral vasculature is a prevalent condition for which catheter-based techniques have been considered to be the gold standard for diagnosis. However, because of their invasive nature, these techniques inherently have the potential for complications. Non-invasive diagnostic techniques have historically been limited by low accuracy and high operator dependence. Magnetic resonance angiography (MRA) is a new approach that has diagnostic accuracy comparable with invasive angiography.

METHODS

The literature on MRA for evaluation of carotid, mesenteric, renal, and lower-extremity arterial disease was extensively reviewed. Helpful diagnostic algorithms on the basis of the literature are also provided.

RESULTS

MRA is both sensitive and specific when compared with invasive angiography for the evaluation of peripheral arterial disease and avoids the potential for complications resulting from arterial puncture and use of iodinated contrast.

CONCLUSION

Current MRA techniques are diagnostically robust and have proven to be a highly accurate, safe, and convenient means of diagnosing atherosclerotic disease of the peripheral vascular system.

A Comparison of Magnetic Resonance Angiography, Contrast Arteriography, and Duplex Arteriography for Patients Undergoing Lower Extremity Revascularization

The objective of this study was to compare magnetic resonance angiography (MRA), contrast arteriography (CA), and duplex arteriography (DA) for defining anatomic features relevant to performing lower extremity revascularizations. From March 1, 2001 to August 1, 2001, 33 consecutive inpatients with chronic lower extremity ischemia underwent CA, MRA, and DA before undergoing lower extremity revascularization procedures. The reports of these tests were compared prospectively and the differences in the aortoiliac segment, femoral-popliteal, and infrapopliteal segments were noted. The vessels were classified as mild disease (<50%), moderate disease (50-70%), severe disease (71-99%), and occluded. These studies and treatment plans based on these data were compared. During this time period, 11 patients were not able to undergo MRA and therefore were excluded from the study. Thirty-three patients were included in this study. These patients underwent 35 procedures, as 2 patients underwent bilateral procedures. The mean age of the 33 patients was 76+/-10 years (SD). Indications for the procedures included gangrene (20), ischemic ulcer (8), rest pain (4), and severe claudication (1). Patients' medical history included diabetes mellitus (25), hypertension (20), and end-stage renal disease (5). No differences were noted between intraoperative findings and CA in this series. Two of the three differences between DA and CA were felt to be clinically significant whereas 9 of the 12 differences between MRA and CA were felt to be clinically significant. On the basis of these data in this series, MRA does not yet seem to be able to obtain adequate data on infrapopliteal segments, at least not for this highly selected population. When severe tibial calcification or very low flow states are identified, CA may be necessary for patients undergoing DA.

Contrast-enhanced peripheral MR angiography using SENSE in multiple stations: Feasibility study

PURPOSE

To investigate if the use of parallel imaging is feasible and beneficial for peripheral contrast-enhanced magnetic resonance angiography (CE-MRA).

MATERIALS AND METHODS

A total of 19 consecutive patients underwent peripheral CE-MRA using SENSE with two-fold reduction in the upper and lower leg stations. Conventional nonaccelerated imaging using constant level appearance (CLEAR) was used in the aortoiliac station. The findings were compared with those in a similar patient group that underwent peripheral CE-MR angiography using our standard imaging protocol without SENSE. Intraarterial digital subtraction angiography (IA-DSA) was used as the standard of reference. Lower extremity vessels were divided into anatomic segments (aortoiliac, upper legs, lower legs) for review. In each anatomic segment signal- and contrast-to-noise ratios (SNR, CNR), venous contamination, subjective image quality, as well as sensitivity and specificity, were determined for both patient groups.

RESULTS

SNR and CNR improved significantly for the aortoiliac and upper leg segments (all P-values < or = 0.001). Small reductions were seen in the frequency of disturbing venous enhancement (P = not significant). There were no significant differences with regards to subjective image quality or diagnostic accuracy (all P > 0.3). Overall sensitivity and specificity in the SENSE group were 81% and 95%, respectively. For the non-SENSE group, these values were 79% and 96%, respectively.

CONCLUSION

Preliminary results show that three-station peripheral CE-MRA using a full length peripheral arterial coil in combination with SENSE in the upper and lower leg stations is feasible and useful for further optimization of peripheral MRA. Using SENSE allows for routine, high-quality depiction of the entire peripheral vascular tree including the pedal arch. Higher SENSE factors are needed for further optimization.

Digital fluoroscopy as a valuable adjunct to open vascular operations

The increasing availability of and vascular surgeons' familiarity with digital cine-fluoroscopy in the operating room has been facilitated by the advent and growing popularity of endovascular aortoiliac aneurysm repair and other endovascular techniques that are being incorporated into vascular surgical practice. Digital cine-fluoroscopy can also be used as a valuable adjunct to standard open vascular procedures in several ways including: performance of completion angiography, fluoroscopically-assisted thromboembolectomy, intraoperative planning angiography, fluoroscopically-guided pressure gradient measurements, achieving vascular control of proximal arteries, intraoperative thrombolysis of compromised outflow tracts, and angioplasty and stenting of lesions detected intraoperatively. These techniques can improve the outcome of standard vascular procedures by permitting the identification of inflow, outflow, conduit, and anastomotic defects intraoperatively and guiding their repair. Additionally, in many cases they can reduce the amount of exposure required, reduce intraoperative blood loss, and minimize trauma to vessels during thrombectomy. Fluoroscopic guidance can facilitate and improve these and other aspects of standard open vascular procedures. Conversely, the ability to perform open interventions can facilitate the performance of many endovascular interventions. It is becoming increasingly important to be facile with both open and E fluoroscopically guided techniques in order to fully treat the spectrum of vascular disease in an optimum fashion.

Lower extremity stepping-table magnetic resonance angiography with multilevel contrast timing and segmented contrast infusion

OBJECTIVES

Standard lower extremity contrast-enhanced magnetic resonance angiography (LE-CEMRA) with single injection bolus-chase methods on the basis of a single pelvis timing run can be accurate for depicting most vascular occlusive lesions but may fall short of catheter-based angiography when imaging tibial and pedal vessels. Magnetic resonance angiography techniques with a second contrast timing bolus and separate acquisitions for the calves and the pelvis greatly improve reliability and reduce venous contamination to levels that may render conventional angiography obsolete.

METHODS

From July to December 2001, 60 consecutive patients underwent LE-CEMRA of the calves with separate stepping-table acquisitions of the pelvis and thighs. Forty-five (75%) had complete or partial angiographic correlation during an endoluminal intervention or operative completion study. Lower extremity vessels were divided into anatomic segments (aortoiliac, femoropopliteal, tibial-pedal) for review. Three blinded observers assessed magnetic resonance source partitions, maximum-intensity projections, and volume-rendered images. Disease per segment was graded from insignificant (<20%) to occluded (100%) in 10% increments. Segments were also scored for venous contamination (scale, 0 to 3) and diagnostic quality (scale, 1 to 5). Digital subtraction angiograms were assessed similarly but separately.

RESULTS

The combination dual-timing/dual-injection technique had an overall sensitivity, specificity, and accuracy of 99%, 97%, and 98%. Venous contamination and artifact were virtually eliminated with combined technique LE-CEMRA. Diagnostic quality of calf and foot vessels was significantly superior to conventional bolus-chase magnetic resonance techniques (P <.01).

CONCLUSION

Hybrid dual-acquisition LE-CEMRA allows complete timing specification that consistently produces high-quality, artifact-free images of the calf and pedal vessels. These techniques may be accurate enough to replace conventional digital subtraction angiogram for evaluation of lower extremity vascular occlusive disease.

Ultrasound imaging of infrainguinal arterial disease has a high interobserver agreement

OBJECTIVES

to evaluate and compare the operator dependency of duplex ultrasound and digital subtraction arteriography (DSA) in patients suffering from chronic lower limb ischaemia.

DESIGN

prospective and blinded validation study.

MATERIAL

twenty-six consecutive patients (13 male and 13 females) with severe claudication (n=6, 23%), rest pain (n=7, 27%) or tissue loss (n=13, 50%).

METHODS

two physicians independently performed a duplex scan of the lower limb from groin to foot (15 segments). Segments were classified as insignificantly (<50% stenosis) or significantly (>50% stenosis or occlusion) diseased. DSA was performed within 24h of the duplex scanning and was independently reported by two radiologists in the same manner. Interobserver agreement was assessed for both diagnostic methods. After 10 months the arteriograms were reassessed and the intraobserver agreement calculated.

RESULTS

for the limb as a whole the interobserver agreement was good and similar for both duplex and DSA, with kappa-values of 0.79 (95%-CI: 0.72-0.86) and 0.80 (0.74-0.87). In the femoral, crural and pedal segments the interobserver agreement was similar for both methods. The intraobserver agreement between the two DSA readings was 0.84 (0.79-0.90).

CONCLUSION

ultrasound is comparable to arteriography when visualising arterial occlusive disease in patients with chronic lower limb ischaemia.

Duplex selection facilitates single point-of-service endovascular and surgical management of aortoiliac occlusive disease

We attempted to optimize management of aortoiliac occlusive disease by using duplex imaging to aid in selection of favorable lesions for percutaneous transluminal angioplasty (PTA)/stenting, by avoiding nontherapeutic arteriography, and by providing single point-of-service care in which endovascular and open surgical reconstruction were combined. One-hundred consecutive patients with symptomatic (91 claudication, 9 limb threat) inflow occlusive disease based on clinical examination and physiologic testing underwent physician-directed duplex scanning of the infrarenal aorta through the femoral bifurcation. Iliac lesions suited to endovascular intervention were defined as focal (length <5 CM), high-grade stenoses with a peak velocity >300 cm/sec and velocity ratio >2 by duplex and were differentiated from unfavorable (diffuse/long iliac stenosis, occlusions, aneurysms, femoral occlusive disease) inflow lesions. Patients with favorable iliac lesions according to duplex were considered candidates for PTA/stenting in an endo-capable operating room, without prior diagnostic angiography. On the basis of duplex imaging, 38 patients possessed endovascularly favorable iliac lesions, 58 patients had unfavorable aortoiliofemoral disease, and 4 obese patients had inadequate studies. Duplex interpretation correctly classified disease distribution/severity in 92% of 50 patients who subsequently underwent intraoperative or diagnostic arteriography. Thirty-one of the 45 (69%) total interventions performed in this patient group were based on duplex findings alone. Of 29 patients with favorable lesions by duplex scanning who had intervention, 25 (86%) received iliac PTA/stenting, while 4 patients required inflow surgical reconstruction for nonfocal iliac disease demonstrated on operative arteriography. Duplex imaging correctly identified the need for concomitant outflow reconstruction/bypass in 11 of the 25 (44%) patients treated by iliac PTA/stenting. Primary and assisted patency rates of iliac PTA/stenting were 83% and 100% at 24 months by life-table analysis. Duplex imaging in patients with symptomatic aortoiliac occlusive disease can provide sufficient information to permit endovascular and surgical intervention without formal diagnostic arteriography in most patients.

MR angiography for assessment of peripheral vascular disease

Contrast-enhanced 3D MRA is emerging as a powerful noninvasive imaging modality for the assessment of patients with PVD. Its clinical utility using current technology has already been well established, and the continuous development of hard- and software will likely result in significantly improved performance. Thus, Gd-enhanced MRA is likely to emerge as the dominant noninvasive imaging modality for PVD worldwide.

Magnetic resonance angiography unmasks reliable target vessels for pedal bypass grafting in patients with diabetes mellitus

OBJECTIVE

The purpose of this study was to evaluate the performance of pedal bypass grafts to foot vessels detected by magnetic resonance angiography (MRA) that were occult in conventional angiography in patients with diabetes mellitus and severe arterial occlusive disease.

METHODS

Vascular surgery and radiology registries were reviewed for patients with pedal bypass grafts to arteries that were not detected with digital subtraction angiography but unmasked with MRA. From December 1997 to March 1999, 15 patients (mean age, 73 +/- 8 years) were identified and analyzed retrospectively. All the patients were diabetic, with 60% being insulin-dependent. Advanced tissue loss was the operative indication in all the cases. Distal anastomosis was performed to the dorsalis pedis artery in 10 cases and to the plantar artery in five cases, with ipsilateral greater saphenous vein as graft material in all the cases.

RESULTS

The perioperative mortality rate was 7% (1 of 15 cases). One graft occlusion resulted in a secondary patency rate of 93.1%. During a mean follow-up examination period of 22 months, no graft occlusions and one major amputation were noted, which resulted in a secondary patency rate of 93.1% and a limb salvage rate of 89.5% at 36 months.

CONCLUSION

Foot vessels that were occult in conventional angiography but could be detected with MRA were shown to be suitable target vessels for pedal bypass grafting with promising results.

Contrast enhanced MR angiography in the assessment of relevant stenoses in occlusive disease of the pelvic and lower limb arteries: diagnostic value of a two-step examination protocol in comparison to conventional DSA

INTRODUCTION/OBJECTIVES

Contrast-enhanced MRA (ce-MRA) has been claimed by many authors as a replacement of conventional angiography evaluating peripheral arterial occlusive disease. However, reliable detection of relevant stenoses (>70%) has to be provided for planning vascular interventions. Only few data in the literature focuses on this crucial problem. The purpose of this study was to evaluate this topic using a two-step body-coil-based MRA protocol.

METHODS AND PATIENTS

Forty three patients presenting with 82 stenoses >/=50% and 61 stenoses >70% on conventional catheter angiogram received fast Gadolinium-DTPA-enhanced high resolution 3D MR angiography at 1.5 T covering the pelvic and peripheral vascular tree in two examination steps using the body-coil. The data were evaluated double-blinded by three readers distinguishing moderate (50-70%) from severe stenoses (>70%).

RESULTS

Overall sensitivity/specificity/accuracy was 84/60/70% evaluating 143 segments. Specificity was rather poor in the iliac (58%) and crural (50%) region and moderate in the femoral and popliteal level (73%). The negative predictive value ranged between 78 and 91%. The grade of stenosis tend to be overestimated rather than underestimated in all levels with positive predictive values between 55 and 78%.

DISCUSSIONS AND CONCLUSIONS

Body-coil-based contrast-enhanced MRA has limited potential in distinguishing moderate from severe stenoses in peripheral occlusive disease. Overestimations are more common than underestimations. Both occur mainly in small-sized crural arteries but also in larger iliac arteries where vessel course in partition direction may cause inadequacy between voxel size and lumen diameter in severe stenosis.

Peripheral vascular surgery and magnetic resonance arteriography--a review

OBJECTIVES

to review the current status of lower limb MRA.

DESIGN

a literature review based predominantly on a MEDLINE database search of English-language publications from January 1991 to October 2000.

MATERIALS AND METHODS

twenty-eight articles, concerning non-enhanced MRA (13), gadolinium-enhanced MRA (14) or both (1), met the predefined requirement for quality. Results gadolinium-enhanced MRA (CE-MRA) seems to be more accurate, quicker and associated with fewer problems than non-enhanced (TOF) MRA. TOF-MRA has a sensitivity and specificity of 93% (range 64-100%) and 88% (range 57-100%) respectively, and CE-MRA presents values of 96% (range 71-100%) and 96% (63-100%), respectively, using conventional arteriography as the gold standard. Some articles report a substantial incidence of runoff vessels suitable for distal bypass visible on MRA but invisible on conventional arteriography. Gadolinium contrast is given intravenously and is generally well tolerated and has no known nephrotoxicity.

CONCLUSION

CE-MRA is accurate compared to conventional arteriography, has the potential to increase the limb salvage rate for selected patients, is non-invasive and well tolerated.

Peripheral magnetic resonance angiography

Peripheral vascular disease (PVD) is a common disorder in western society. Reflecting on the risks and costs of contrast arteriography, magnetic resonance angiography is a powerful noninvasive imaging modality for the diagnostic workup of patients with peripheral vascular disease. This article reviews the current state of the art of magnetic resonance angiography of the peripheral vasculature.

Interobserver Variation in Interpretation of Arteriography and Management of Severe Lower Leg Arterial Disease

OBJECTIVE

arteriography is the reference standard for the assessment of the lower leg arteries in patients with severe lower limb ischaemia. Interobserver variation in arteriography interpretation may cause disparities with non-invasive imaging modalities. We determined interobserver variation in lower leg artery assessment with intra-arterial digital subtraction angiography (IaDSA) and subsequent patient management.

MATERIALS

iaDSA studies of patients evaluated for severe claudication (n =5) or critical ischaemia ( n =43).

METHODS

arteriograms were independently judged by four observers. The popliteal and tibial arteries were graded as fully patent, severely diseased, occluded or non-diagnostic. The dorsalis pedis, common and deep plantar artery were graded as directly, indirectly or not filling the pedal arch or non-diagnostic. Agreement on grading arteries was expressed as kappa-values. Treatment plans (conservative, PTA, surgery, amputation, non-diagnostic) proposed by each observer based on clinical information and iaDSA were compared.

RESULTS

the rate of non-diagnostic judgements ranged from 1% in the popliteal to 22% in the pedal arteries. Overall agreement was good for grading the popliteal arteries (kappa=0.64), moderate for the tibial (kappa=0.47--0.54) and fair for the pedal arteries (kappa=0.39). Agreement was good to excellent for grading occluded or fully patent popliteal and tibial artery segments, and fair to moderate for grading severe disease. In 57% of cases at least 3 observers proposed identical treatment, which indicates fair overall agreement (kappa=0.33).

CONCLUSION

interobserver agreement on iaDSA is good to determine occluded or fully patent popliteal or tibial arteries, but not for severe disease. This should be taken into account when other diagnostic modalities are compared with iaDSA. Evaluation of diagnostic modalities as concordance in treatment plans is flawed by interindividual variation.

Cost Containment in Vascular Surgery

In the last decade, the delivery of health care and the role of the physician have undergone radical change. With the ad vent of managed care and the tightening of restrictions by Medicare and insurance companies, physicians have been required to review, re-engineer, and revitalize their role. Increasing financial pressures at the hospital level have caused administrators to cut costs at all levels. It is imper ative that physicians take an active role in cost containment so that the quality of care is not sacrificed. Cost containment in vascular surgery is an urgent priority in health care. Copyright © 2000 by W.B. Saunders Company.

Peripheral arterial disease: meta-analysis of the diagnostic performance of MR angiography

PURPOSE

To summarize the overall diagnostic performance of magnetic resonance (MR) angiography in the evaluation of peripheral arteriosclerotic occlusive disease and to identify the most important sources of variation in diagnostic accuracy between studies.

MATERIALS AND METHODS

A search strategy in MEDLINE and citation tracking were used to identify relevant English-language articles published since 1991. Each article was critically appraised for examination, patient, and study design characteristics. The accuracy data from different studies were analyzed by constructing summary receiver operating characteristic curves; multiple linear regression was used to examine the variation between study results.

RESULTS

Twenty-three studies were included. There was much heterogeneity in the study results, which could not be explained as differences in the threshold for a positive result. About half of the variation was due to the type of MR angiographic examination and the extent of image evaluation. The relative diagnostic odds ratio (DOR) for three-dimensional (3D) gadolinium-enhanced MR angiography compared with two-dimensional (2D) time-of-flight MR angiography was 7.46 (95% CI: 2.48, 22.20). The relative DOR for review of transverse source images or multiplanar reformations in addition to maximum intensity projections (MIPs) compared with the use of only MIPs for image evaluation was 4.53 (95% CI: 1.46, 13.87).

CONCLUSION

The diagnostic accuracy of 3D gadolinium-enhanced MR angiography is superior to that of 2D time-of-flight MR angiography. Also, the review of transverse source images or use of additional postprocessing techniques, such as multiplanar reformation, results in significantly better diagnostic performance.

Comparison of treatment plans for lower extremity arterial occlusive disease made with electrocardiography-triggered two-dimensional time-of-flight magnetic resonance angiography and digital subtraction angiography

BACKGROUND

The purpose of the study was to determine whether preoperative treatment plans for patients with lower extremity ischemia can be made with electrocardiography (EKG)-triggered two-dimensional (2D) time-of-flight (TOF) magnetic resonance angiography (MRA) as accurately as digital subtraction angiography (DSA).

METHODS

Forty patients were prospectively evaluated with the combination of EKG-triggered 2D TOF MRA, DSA, and pulse volume recordings. Blinded reviewers graded arterial segments for disease severity. Accuracy of separate MRA- and DSA-based treatment plans was compared with the procedures performed based on all available information.

RESULTS

There was an 86% exact match between MRA- and DSA-based plans (92% MRA and 94% DSA accuracy). The MRA-based plan accurately predicted 90% of suprainguinal and 95% of infrainguinal procedures, whereas the DSA-based plan accurately predicted 100% of suprainguinal and 85% of infrainguinal procedures. Two-year primary patency was 83% for all procedures. Radiologists' review of disease severity resulted in a mean exact correlation between studies of 81% (kappa = 0.64). The agreement between radiologists interpreting the MRA was 84% (kappa = 0.7) compared with 82% (kappa = 0.66) for the DSA.

CONCLUSIONS

MRA- and DSA-based preoperative management plans were of comparable efficacy. Significant interobserver variability was seen with the interpretations of both preoperative studies. EKG-triggered 2D TOF MRA can be used to plan arterial reconstructions; however, all patients require arterial pressure measurements prior to suprainguinal repair and confirmatory intraoperative angiography during infrainguinal revascularization.

Contrast-enhanced subtraction MR angiography in occlusive disease of the pelvic and lower limb arteries: results of a prospective intraindividual comparative study with digital subtraction angiography in 76 patients

PURPOSE

The purpose of this work was to evaluate the feasibility and clinical use of MR angiography (MRA) for examining the pelvic and lower limb arteries in patients with arterial occlusive disease.

METHOD

Seventy-six patients with clinical signs of peripheral arterial occlusive disease were included in the study. MRA was performed using a fast contrast-enhanced high-resolution 3D technique that covered the area from the distal abdominal aorta to the distal lower limbs in two examination steps.

RESULTS

In all patients, diagnostic images comparable with those of conventional intraarterial digital subtraction angiography (DSA) could be obtained. No false-negative findings were seen in the iliac, femoral, or popliteal arteries. Ten to 16% of the mild stenoses and 6-14% of the severe stenoses, mainly in the crural vessels, were overgraded compared with intraarterial DSA. Particularly in patients with proximal severe obstructions or occlusions, the crural segments could be depicted more clearly due to decreased arterial runoff in conventional angiography.

CONCLUSION

The consistency of the excellent depiction of the vascular territories of the distal aorta and the pelvic and lower limb arteries in a standardized setting suggests great potential for the use of MRA in the primary diagnosis of peripheral arterial occlusive disease.

Values and limitations of duplex ultrasonography as the sole imaging method of preoperative evaluation for popliteal and infrapopliteal bypasses

The purpose of this study was to evaluate whether duplex ultrasound arterial mapping (DAM) can reliably replace standard arteriography (SA) in the preoperative assessment of candidates for popliteal and infrapopliteal bypasses. This is the report of a two-phase study undertaken at our institution from July 1997 to May 1998. Carefully performed DAM averted the need for preoperative SA (51 of 58 procedures). The results of this study can be used as an impetus to initiate larger, multicenter protocols to further evaluate this newer noninvasive approach for patients presenting with severe lower-limb ischemia.

Duplex ultrasound scanning defines operative strategies for patients with limb-threatening ischemia

PURPOSE

To characterize the accuracy of color-flow duplex ultrasound (DUS) in planning lower extremity revascularization procedures, we prospectively compared operations predicted by means of DUS arterial scanning (DUSAS) and operations predicted by means of conventional angiography (CA) with actual operations performed in 36 patients undergoing 40 vascular reconstructions for critical (grade II/III) lower extremity ischemia.

METHODS

All patients were examined with lower extremity DUSAS followed by CA. DUSAS was performed from the aorta to the pedal vessels of the affected extremity. Adequacy of inflow was assessed, and the best distal target vessel with continuous, unobstructed flow was defined. An operative prediction was made and recorded based upon the DUSAS findings, and in a blinded fashion, based upon subsequent CA. The McNemar test for comparing correlated proportions was applied to test for the statistical significance of the difference (P < .05) between correct operations predicted by DUSAS and CA.

RESULTS

Of the actual operations performed, 83% were correctly predicted by means of DUSAS (95% CI; range, 77% to 89%). Seven operations were incorrectly predicted with DUSAS. Of the actual operations performed, 90% were correctly predicted by means of CA (95% CI; range, 81% to 99%). Four operations were incorrectly predicted with CA. The McNemar test determined that the difference between correct operations predicted by means of DUSAS and correct operations predicted by means of CA was not statistically significant (P = .50).

CONCLUSIONS

With few exceptions, DUSAS can be used to reliably predict infrainguinal reconstruction strategies. Vessels defined as adequate with DUSAS are rarely unfit for bypass. Prospective investigation of lower extremity revascularization based solely upon DUSAS is warranted.

Lower extremity vascular reconstruction and endovascular surgery without preoperative angiography

BACKGROUND

Recent studies have shown the feasibility of performing lower extremity revascularization based on noninvasive vascular studies alone.

METHODS

We undertook a prospective study of patients with lower extremity ischemia who underwent revascularization without preoperative angiography. Preoperative evaluation was done with noninvasive studies including segmental pressures, ankle arm index, duplex scan, and selective use of magnetic resonance angiography. Intraoperative angiography and intra-arterial pressure measurements were used prior to revascularization. Standard patency analysis and follow-up examination were performed.

RESULTS

In all, 47 patients underwent 65 procedures (27 iliac, 38 infrainguinal) over a 3-year period. Intraoperative angiography and operative findings correlated with the noninvasive studies. There was one immediate failure, and life table analysis demonstrated primary patency rates of 92% for iliac reconstruction (29 months) and 82% for infrainguinal reconstruction (40 months).

CONCLUSION

Preoperative evaluation for lower extremity revascularization utilizing only noninvasive vascular testing gives satisfactory results and is a safe and potentially durable alternative to routine preoperative angiography in most cases.

Intraoperative prebypass arteriography for infrageniculate revascularization

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.