A Prospective Feasibility Study of Duplex Ultrasound Arterial Mapping, Digital-Subtraction Angiography, and Magnetic Resonance Angiography in Management of Critical Lower Limb Ischemia by Endovascular Revascularization

A Prospective Feasibility Study of Duplex Ultrasound Arterial Mapping, Digital-Subtraction Angiography, and Magnetic Resonance Angiography in Management of Critical Lower Limb Ischemia by Endovascular Revascularization A.J. Lowery,1 N. Hynes,1 B.J. Manning,1 M. Mahendran,1 S. Tawfik,1 and S. Sultan,1,2 Galway, Ireland

Duplex ultrasound arterial mapping (DUAM) allows precise evaluation of peripheral vascular disease (PVD). However, magnetic resonance angiography (MRA) and digital-subtraction angiography (DSA) are the diagnostic tools used most frequently prior to intervention. Our aim was to compare clinical pragmatism, hemodynamic outcomes, and cost-effectiveness when using DUAM alone compared to DSA or MRA as preoperative assessment tools for endovascular revascularization (EvR) in critical lower limb ischemia (CLI). From 2002 through 2005, 465 patients were referred with PVD. Of these, 199 had CLI and 137 required EvR. Preoperative diagnostic evaluation included DUAM (n ¼ 41), DSA (n ¼ 50), or MRA (n ¼ 46). EvR was aortoiliac in 27% of cases and infrainguinal in 73%. Patients were assessed at day 1, 6 weeks, 3 months, and 6 months. Composite end points were relief of rest pain, ulcer/gangrene healing, and increase in perfusion pressure, as measured by ankle-brachial index (ABI) and digital pressures. Patency by DUAM, limb salvage, morbidity, mortality, length of stay, and cost-effectiveness were compared between groups using nonparametric t-test, analysis of variance, and Kaplan-Meier analysis. The three groups were comparable in terms of age, sex, comorbidity, and Society for Vascular Surgery/International Society of Cardiovascular Surgery clinical classification. Six-month mean improvement in ABI in the DUAM group was comparable to that in the DSA group (P ¼ 0.25) and significantly better than that in the MRA group (P < 0.05). Six-month patency rates for the DUAM group were comparable to those in the DSA group (P ¼ 0.68, relative risk [RR] ¼ 0.74, 95% confidence interval [CI] 0.18-2.99) and superior to that in the MRA group (P ¼ 0.022, RR ¼ 0.255, 95% CI 0.09-0.71). Length of hospital stay was lower in the DUAM group compared with the DSA group (P < 0.0001) and the MRA group (P ¼ 0.0003). The cost of DUAM is lower than that of both DSA and MRA. DUAM accurately identified the total number of target lesions for revascularization; however, MRA overestimated it. Our results indicate that DUAM is outstanding when compared with other available modalities as a preoperative imaging tool in a successful EvR program. DUAM is a minimally invasive preoperative evaluation for EvR and offers precise consecutive data with patency and limb salvage rates comparable to EvR based on DSA and superior to MRA. We believe that our feasibility study has established

1 Western Vascular Institute, University College Hospital, Galway, Ireland.

University College Hospital, Galway, Ireland, E-mail: sherifsultan@ esatclear.ie

2 Department of Vascular and Endovascular Surgery, Galway Clinic, Doughiska, Galway, Ireland.

Ann Vasc Surg 2007; 21: 443-451 DOI: 10.1016/j.avsg.2006.08.005 Ó Annals of Vascular Surgery Inc. Published online: February 26, 2007

Correspondence to: Sherif Sultan, MB, BCh, MCh, MD, FRCSI, DEVS, FISVS, DMD, FRCS (Gen-Vasc), EBQSeVASC, Department of Vascular and Endovascular Surgery, Western Vascular Institute,

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DUAM as an economically proficient primary modality for investigating patients with CLI that significantly shortens length of hospital stay.

INTRODUCTION Peripheral vascular disease (PVD) is a major cause of morbidity and mortality worldwide, particularly in Western society, where over 10% of the population over 65 years of age is affected.1 Elderly patients are most at risk of suffering from PVD and are more likely than younger patients to have significant comorbidity and an increased American Society of Anesthesiologists status. This limits the surgical therapeutic options available for the treatment of PVD in this cohort, who are frequently unsuitable for invasive or major reconstructive vascular surgery. This therapeutic challenge has largely been overcome by the introduction of minimally invasive endovascular procedures such as percutaneous transluminal angioplasty (PTA) and subintimal angioplasty (SIA). These are effective means of revascularization that have been shown to have outcomes comparable to reconstructive vascular surgery.2-5 Despite the trend toward minimally invasive therapeutic PTA and SIA in the treatment of PVD, preoperative imaging of these patients in many instances continues to be via invasive digital-subtraction angiography (DSA). Ideally, a minimally invasive strategy in the management of PVD patients should include noninvasive methods of mapping the arterial tree preoperatively. This would reduce exposure of the patient to potential complications associated with invasive imaging. Magnetic resonance angiography (MRA) has potential as a noninvasive imaging tool prior to lower limb revascularization.6-9 However, the patient’s clinical limitations are always a concern. The use of duplex ultrasound arterial mapping (DUAM) to image the lower limb arterial tree was first reported by Jager et al. in 1985.10 Since then, it has been shown to be an effective means of direct, noninvasive evaluation of arterial disease that can accurately discriminate between occluded, stenotic, and healthy vessels with accuracy comparable to DSA.11-15 To date, studies have demonstrated the efficacy of DUAM in the preoperative planning of lower limb arterial bypass.16-18 As a direct, bedside, noninvasive tool, DUAM would be an ideal sole imaging tool as a component of a minimally invasive management strategy in endovascular treatment of critical lower limb ischemia (CLI).

Prior to this study, DUAM was used in our institution as an adjunct to DSA or MRA for preoperative imaging of the lower limb vasculature and for postoperative assessment of graft patency as reported by others.19,20 From our earlier experience, we found that results from DUAM were as reliable as those from DSA or MRA and that DUAM also provided further useful information to allow planning of treatment strategies. This led to planning of endovascular revascularization (EvR) based solely on DUAM. In this study, we compared clinical pragmatism, hemodynamic outcomes, and cost-effectiveness when using DUAM alone compared to DSA or MRA as preoperative assessment tools for EvR in CLI. This was done to evaluate DUAM as a sufficient imaging modality for planning EvR in patients with CLI.

METHODS From 2002 through 2005, 465 patients were referred with PVD, of whom 199 had CLI, with 137 limbs requiring EvR. CLI was defined per the Society for Vascular Surgery (SVS) reporting standards.20 Patients who underwent bypass as the primary modality of treatment were not eligible for inclusion as the purpose of the study was to evaluate the efficacy of DUAM as a preoperative investigation for patients undergoing endovascular intervention. All patients for EvR underwent standard preoperative investigation including risk factor evaluation, physical examination, ankle-brachial indices (ABI), digital pressures, and imaging of the lower limb arterial tree (DUAM, DSA, MRA). In all patients with CLI, intervention was planned for the next available operating list. If MRA or DSA had not been carried out or was scheduled prior to this, EvR was undertaken based on the results from DUAM alone (DUAM was carried out as a rapid, noninvasive bedside tool preoperatively). DUAM was the sole preoperative imaging tool in 41 limbs. These patients were matched for comparison to patients who underwent EvR using either DSA or MRA for preoperative imaging during the same time period. There was no randomization, patients underwent DSA or MRA according to which investigation was most promptly available.

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Preoperative Imaging Techniques DUAM was carried out using an ATL HDI 5000 (Eindhover, The Netherlands) duplex scanner, by experienced vascular technologists who were blinded to any other radiographic findings. Arterial segments from the aorta to the pedal arteries were studied with B-mode and color flow imaging duplex ultrasound. The degrees of stenoses were calculated using peak systolic velocity (PSV) ratio criteria (ratio of PSV at the diseased segment to that of normal proximal segment) (Table I). Preoperative DUAM evaluation included arterial size, length and degree of stenoses or occlusion, and plaque characteristics in B mode (calcification and echolucency). As occluded areas were treated by SIA, in such instances, adequacy of length of normal vessel available for reentry was assessed. The examination was deemed inconclusive if an artery proximal or distal to the occlusion could not be visualized adequately due to calcification. At the conclusion of the procedure, the arterial tree was mapped and significant lesions were marked on the limb with indelible markers and targeted. All scans were reviewed by the principal investigator, who drew a three-dimensional reconstruction of the DUAM. The decision to proceed with EvR was based on the information regarding site of inflow and adequacy of outflow. MRA was performed with a SiemensÔ (Malvern, PA) Symphony 1.5 Tesla scanner to achieve highresolution images of the arterial system from the abdominal aorta to tibial vessels. Vascular imaging was achieved using contrast (gadolinium)-enhanced MRA. Images of the region of interest, i.e., lower limb arterial tree, were recorded with rapid-volume imaging sequences. MRA results were interpreted by interventional radiologists who were blinded to the results of other studies. Lesions targeted were those reported as significant by the radiologists. DSA was performed in the radiology department with informed consent. The volume of contrast material (iodixanol, VisipaqueÔ, Amersham Health, Princeton, NJ) administered ranged 60-200 mL and was dependent on the number of runs required to visualize the entire lower limb arterial tree. All patients had aortoiliac angiography, and most often bilateral angiography was performed at least to the knee level. The aortic films were taken in anteroposterior (AP) projection, followed by the iliac/pelvic images in AP and lateral projection. Selective angiography of the limb of interest was performed by advancing the catheter over the bifurcation in case of contralateral femoral puncture or by withdrawing the catheter into the ipsilateral iliac artery. In one case, access was obtained via the brachial artery

DUAM, DSA, and MRA for CLI 445

Table I. Relationship between the PSV ratio and percentage degree of diameter reduction PSV ratio

% Stenosis

<2 2.0-2.5 >2.5 Numerous lesions without any alteration in PSV or with PSV <2 Absence of flow

<50 50-60 >60 Diffuse disease Occluded

because the femoral pulse was impalpable bilaterally. Complete lower extremity images of the limb of interest were taken to include the tibial and pedal vessels in AP and lateral foot views. Adequate delay was allowed to visualize distal lesions. Studies were interpreted by the principal investigator and interventional radiologists. Target lesions were those identified as significant by the principal investigator and an interventional radiologist. DSA and MRA films were reviewed at a vascular conference by the principal investigator, and surgical options were discussed. Lesions to be targeted for revascularization were recorded preoperatively as suggested by the available DSA or MRA images. Patients were excluded from having EvR if there was echolucent material in the arterial tree, lack of a nipple in the superficial femoral artery (SFA) or common femoral artery (CFA) on DUAM, or a recent history of ischemia with an abrupt cutoff or filling defect on MRA or DSA. Those patients excluded from EvR were offered proximal or distal arterial revascularization bypass surgery.

EvR Techniques All procedures were performed in the operating theater using the OEC mobile c-arm imaging system (General Electric, Milwaukee, WI). The site of arterial puncture was always the ipsilateral CFA. A single part needle (Cook, Bloomington, IL) was used for arterial puncture to avoid posterior wall injury, and a 5F sheath (Cordis, Miami, FL) was placed in the CFA. Angiogram using Visipaque was performed in all patients as a road map. A 0.035 mm curved guidewire (Terumo, Tokyo, Japan) was used to cross the stenoses or create a subintimal plane at the site of occlusion. SmartÒ stents (Cordis) were used in the iliac artery when there was an occlusion or a recurrent or intractable lesion. Completion angiogram was performed in all cases. Line diagrams were included in the operative notes depicting intraoperative and postoperative

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findings of treated lesions that were analyzed and compared with duplex findings. These findings and digital images from the intraoperative angiograms were compared with images from MRA and DSA. All patients were prescribed aspirin, clopidogrel, and a hepatic hydroxymethylglutaryl coenzyme A reductase inhibitor postoperatively. Data Collection and Follow-Up Data were entered prospectively into Vascubase 5.1Ò (Consensus Medical, Vancouver, Canada) Patients were followed up postoperatively at day 1, week 6, 3 months, and 6 months according to our standard follow-up protocol. Patients’ symptomatic improvement was assessed by relief of rest pain and ulcer healing. ABI and digital pressures (ABI increase of >0.1 was considered significant) were measured to assess success of intervention, and duplex scan of the lower limb was carried out to assess for patency of the angioplasty site. Primary patency was defined as uninterrupted patency following the procedure. Our composite primary end points were patency, limb salvage, and mortality. Composite secondary end points were target lesion revascularization, increase in ABI, morbidity, cost-effectiveness, length of hospital stay, and number of hospital admissions related to the presenting complaint. Outcome parameters were compared between patients who were treated based on DUAM as the sole preoperative investigation and those who had preoperative MRA or DSA. Statistical Analysis Statistical analysis was performed using SPSS version 12.0.1Ò (SPSS Inc., Chicago, IL). Nonparametric t-test and analysis of variance (ANOVA) were employed as appropriate. Patency rates were evaluated using Kaplan-Meier analysis, and curves were compared using log-rank analysis. P < 0.05 was considered significant.

RESULTS During the study period, of 199 cases of CLI, 137 limbs were revascularized using endovascular techniques. The remaining 62 patients were deemed unsuitable for EvR and referred for reconstructive revascularization/bypass based on information obtained from the preoperative imaging. This information included the presence of echolucent material within the occluded segment lesion, the absence of

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Table II. Patient characteristics DUAM (n ¼ 41)

Sex Male Female Age (years) Mean Comorbidity and risk Diabetes Hypertension Smoking Renal impairment Presenting complaint Rest pain Ulceration Gangrene

MRA (n ¼ 46)

DSA (n ¼ 50)

16 (39%) 22 (48%) 22 (44%) 25 (61%) 24 (52%) 28 (56%) 75 factors 11 (27%) 25 (61%) 20 (49%) 4 (10%)

76 14 24 25 4

74 (30%) 13 (26%) (52%) 26 (52%) (54%) 29 (58%) (9%) 2 (4%)

38 (93%) 39 (85%) 38 (76%) 21 (51%) 18 (39%) 24 (48%) 4 (10%) 6 (13%) 5 (10%)

Table III. Procedures performed Procedure

DUAM

MRA

DSA

Iliac PTA Iliac SIA Femoral PTA Femoral SIA Popliteala Tibial/peroneala Total number of lesions

6 (3 stents) 17 (3 stents) 15 (6 stents) 1 1 0 20 (4 stents) 19 (1 stent) 25 (1 stent) 12 11 10 1 1 1 3 1 2 43 50 53

a

Distal lesions were frequently angioplastied in addition to a more proximal lesion.

a ‘‘nipple,’’ or the absence of a suitable inflow or outflow vessel for reentry. The indication for EvR in all cases was CLI,20 classified as Fontaine stage III-IV. Presenting complaints included rest pain 84%, ulceration 46%, and gangrene 11%. DUAM was the sole preoperative imaging investigation in 41 EvR limbs, DSA in 50 EvR limbs, and MRA in 46 EvR limbs. The three groups were comparable in terms of age (P ¼ 0.55), sex, comorbidity, and SVS/International Society of Cardiovascular Surgery clinical classification20 (Table II). EvR was aortoiliac in 27% of cases and infrainguinal in 73% (Table III). Patency and Limb Salvage Technical success of the procedure with a patency rate of 100% at day 1 was comparable between the DUAM and DSA groups. The MRA group had a poorer day 1 patency of 93.5% (Table IV). This

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DUAM, DSA, and MRA for CLI 447

Kaplan-Meier DUAM v CA

Table IV. Patency DUAM (%)

DSA (%)

MRA (%)

Day 1 Week 6 Month 3 Month 6

100 97.6 92.3 92.3

100 96 91.8 89.6

93.5 82.7 73.3 73.3

trend was evident throughout the follow-up period at 6 weeks, 3 months, and 6 months. The 6-month cumulative patency rate for the DUAM group (92.3%) was comparable to that of the DSA group (89.6%; P ¼ 0.68, relative risk [RR] ¼ 0.74, 95% confidence interval [CI] 0.18-2.99) and superior to that of the MRA group (73.3%; P ¼ 0.022, RR ¼ 0.255, 95% CI 0.09-0.71) (Figs. 1 and 2). In the DUAM group, three patients were not patent at the 6-month follow-up. One of these patients required a femoropopliteal bypass, and one had a below-knee amputation. The third patient had symptomatically improved due to the development of large collaterals and had no further intervention at the 6-month follow-up. In the DSA group, five patients were not patent at the 6-month follow-up. Two of these patients had above-knee amputation, one had below-knee amputation, and two had reconstructive vascular surgery (femorodistal bypass). In the MRA group, three angioplasties were unsuccessful and not patent at day 1. One of these patients required above-knee amputation, and one had reconstructive vascular surgery. The third patient was arteriopathic and suffered a myocardial infarction intraoperatively, requiring transfer to the cardiothoracic unit for coronary artery bypass grafting. This patient underwent subsequent further assessment of his PVD and was deemed not suitable for EvR. A further nine patients in the MRA group were not patent at 6-month follow-up. Two of these patients had further angioplasty, three had reconstructive vascular surgery, two had below-knee amputation, and two required above-knee amputation. ABI The increase in ABI at follow-up was comparable between the DUAM group and the DSA group (P ¼ 0.25). The MRA group had a significantly poorer ABI increase (P < 0.05) (Table V). Target Lesion Revascularization: Accuracy Comparison between the preoperative imaging investigation and the diagrammatic representation of

100

95 90 DUAM

85

CA

80 0

30

60

90

120

151

Days

Fig. 1. Kaplan-Meier life table comparing patency of the DUAM and Conventional Angiography (CA) groups.

Kaplan-Meier DUAM vs MRA

100

Cummulative Patency Rate

Time

Cummulative Patency Rate

105

80 60 40 20

DUAM MRA

0 0

30

60

90

120

151

Days

Fig. 2. Kaplan-Meier life table comparing patency of the DUAM and MRA groups.

intraoperative findings was carried out to identify the accuracy of the preoperative investigation in identification of target lesions. In the DUAM group, 43 lesions were identified and marked at the time of preoperative DUAM, all of which were treated at angioplasty. In the DSA group, 53 lesions identified preoperatively were treated at angioplasty. In the MRA group, 58 lesions were identified as requiring treatment on the preoperative MRA. Only 50 of these required angioplasty. Of the eight lesions that were overestimated by the preoperative MRA, six were infrainguinal, and two of these were infragenicular. This indicates that DUAM is accurate in predicting lesions that will require treatment (100%) as decided intraoperatively. DSA similarly predicted the lesions requiring treatment with 100% accuracy. MRA, on the other hand, tended to overestimate these lesions (only 86% of lesions

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Table V. Mean ABI increase (three-way ANOVA) Time

DUAM DSA

MRA

Day 1

0.291 0.301 0.158

Week 6

0.315 0.349 0.179

Month 3 0.318 0.307 0.170 Month 6 0.300 0.310 0.172

Significance DUAM vs. MRA P < 0.05 DUAM vs. DSA NS DSA vs. MRA P < 0.05 DUAM vs. MRA NS DUAM vs. DSA NS DSA vs. MR P < 0.05 DUAM vs, MRA P < 0.05 DUAM vs, DSA NS DSA vs, MRA P < 0.05 DUAM vs. MRA P < 0.05 DUAM vs. DSA NS DSA vs. MRA P < 0.05

NS, nonsignificant.

identified by MRA as target lesions were deemed as requiring intervention at the time of EvR). Suboptimal Imaging In our series, one patient was unable to tolerate lying supine for MRA due to severe respiratory disease, and another claustrophobic patient was unable to lie still for the duration of the procedure and had a suboptimal scan. In addition, six patients had suboptimal MRA of the infragenicular vessels in the presence of venous contamination. In the DUAM group, a similar number of patients had suboptimal below-knee images due to heavy calcification (n ¼ 5) and severe lower limb ulceration (n ¼ 1). However, our protocol manages to overcome this issue by performing an on-table angiogram and proceeding with EvR if appropriate. Morbidity The most common complication was groin hematoma (n ¼ 7), and there was no significant difference between the groups. Two hematomas occurred in the DSA group, one following preoperative angiogram and the other after completion of EvR, that needed surgical evacuation. Other hematomas were minor and occurred postoperatively, two in the DUAM group and three in the MRA group. These resolved spontaneously. One patient in the MRA group had myocardial infarction during angioplasty and was subsequently referred for coronary revascularization. One patient in the MRA group developed bibasal pneumonia and septicemia postoperatively. Mortality Seven patients died in the 6-month follow-up period. Two of these deaths occurred within 30 days

postoperatively. One patient in the DSA group died of cardiac failure 1 week postoperatively, and one patient in the DUAM group died due to complications of a lower respiratory tract infection 3 weeks postoperatively. This occurred after discharge from hospital. The remaining five deaths occurred more than 30 days postoperatively, following discharge from hospital. Three late deaths occurred in the DUAM group, two from cardiac arrest and one from pneumonia. The other two late deaths occurred in the MRA group. One occurred in a patient with chronic congestive heart failure, complicated by pulmonary edema and respiratory tract infection. The other death was due to cardiac arrest. Hospital Stay and Cost There was a statistically significant difference (P < 0.001) in the mean number of days spent in hospital by those in the DUAM group (4 days) and in the MRA (9 days) and DSA (9 days) groups. The cost of a single DUAM scan was V65, which is appreciably lower than that of DSA, V655, or MRA, V415.

DISCUSSION Accurate mapping of the lower limb arterial tree is essential prior to revascularization. DSA has traditionally been favored due to its ability to provide the operating surgeon with a precise visual display of the vascular system. The high rate of complications associated with DSA (4-9%), including hematoma, anaphylaxis, arterial injury, and renal failure,21-25 as well as the increased cost24 have led to increasing awareness and interest in less invasive procedures. Management of CLI demands intervention with minimal morbidity. An ideal noninvasive imaging technique in evaluating lower limb ischemia should achieve the accuracy of DSA without the associated risks or limitations. For a duplex ultrasound-experienced endovascular surgeon, DUAM fulfills these criteria and identifies the required inflow, outflow, and hemodynamics of the target level revascularization, which can be obtained and laid as a visual display. The decision to perform angioplasty based on DUAM alone was taken at our institution based on the validation of our vascular laboratory and previous observation on the accuracy of DUAM. The accuracy of DUAM has previously been reported;10-13 DUAM has high rates of sensitivity and specificity when compared to DSA11,26-28 and MRA.29,30 It has good interobserver agreement31 and can be

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reproduced by trained vascular technologists. Legemate et al.32 reported sensitivity and specificity of 100% for the aortoiliac segment, with sensitivity of 90% and specificity of 98% for the femoropopliteal vessels when DUAM was compared with DSA. Davies et al.33 compared DUAM and DSA imaging of the SFA/popliteal vasculature and reported a sensitivity of 96-97% and specificity of 98%. The precision of DUAM is continuously improving due to the advancement of ultrasound technology. In our series, DUAM identified the number of lesions requiring angioplasty with 100% accuracy. London et al.34 suggested that DUAM be considered the first-line investigation for patients with lower limb arterial disease. This reflects our view and approach to preoperative management of patients with CLI. In addition to its accuracy in detection of stenoses and occlusions, DUAM offers potentially useful hemodynamic information that is not available with other imaging techniques. It is able to visualize both the vessel wall and the lumen and identify sites of turbulent or decreased blood flow.13,35 It also identifies stenotic plaques with echolucent material or echolucency in areas of occlusion, which we consider a contraindication for EvR due to potential for distal embolization and immediate rethrombosis or early PTA failure.36 The successful use of DUAM as the sole preoperative imaging modality for reconstructive vascular surgery has been reported by Ascher et al.16,17 and others.18 This study focused on preoperative imaging for patients undergoing EvR. Levy et al. in 199830 found that clinical success in endovascular procedures was possible using either preoperative MRA or DUAM. However, they did not differentiate between patients who underwent DUAM and MRA when assessing clinical outcome. In our series, we successfully used DUAM to evaluate lesions in native vessels, and the outcomes in DUAM and MRA patients were analyzed separately. Bostrom et al.37 reported that femoropopliteal lesions can be reliably selected for PTA based on duplex findings; this is supported by our findings that patients who underwent angioplasty based on DUAM findings had technical and clinical success rates comparable to those whose revascularization was based on DSA. There are reports of successful percutaneous angioplasty using DUAM alone both preoperatively and intraoperatively.38 Our series differs from previous reports by the fact that a large proportion of the lesions were treated by SIA. SIA enables endovascular treatment of long occlusions that are not suitable for PTA, thus expanding the role of endovascular management2,5,39

DUAM, DSA, and MRA for CLI 449

to be an effective alternative to bypass in patients with PVD with TransAtlantic Intersociety Consensus score C and D lesions. Before SIA can be undertaken, specific information regarding plaque morphology is required together with accurate measurement of the vessel distal to the occlusion. DUAM is unique in that it provides all this information with a single noninvasive scan. In our series of patients, those who underwent angioplasty with DUAM as the sole preoperative investigation had better technical and clinical outcomes than those who had preoperative MRA. The use of MRA as a noninvasive investigation for evaluation of lower extremity arterial disease has been quite extensively studied and shown to be an effective means of evaluating the aortoiliac system8,40 and the infrainguinal vessels.6 Carpenter et al.9 and Cambria et al.7 have reported successful use of MRA as the sole preoperative imaging modality for both angioplasty and bypass grafting in lower limb ischemia. Unlike our series, these studies concentrated on DSA and MRA and did not evaluate DUAM as an alternative noninvasive imaging modality. Leiner et al.,41 in a comparison of DUAM and MRA, found that MRA predicted treatment plans more accurately overall; this was in contrast to our findings. However, on subgroup analysis, Leiner et al.41 did find that DUAM was better for predicting femoral PTA. Hingorani et al.42,43 compared MRA, DSA, and DUAM and reported that MRA findings were more likely to disagree with DSA than DUAM. This mirrored our findings that DUAM is comparable to DSA in planning EvR. They experienced similar problems with MRA as were experienced by us, such as difficulty assessing the degree of stenoses and patency of distal vessels due to venous contamination, low flow or signal dropout, and poor patient tolerance. In our series, one patient was unable to tolerate lying supine due to severe respiratory disease and another claustrophobic patient was unable to lie still for the duration of the procedure and had a suboptimal scan. Soule et al.29 found that MRA was not a suitable replacement for DSA as a preoperative imaging modality due to under- and overestimation of lesions, resulting in only 82% agreement between MRA and intraoperative findings. In our study, MRA identified more areas requiring treatment than were actually treated at angioplasty, indicating a certain degree of overestimation of lesions. This may be attributable to factors such as calcification, tortuosity, and signal dropout. These limitations of MRA as an imaging investigation may have negatively impacted on the

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planning of the revascularization procedure and thus contributed to the poor outcomes in the MRA group. More relevant, however, is the fact that MRA did not accurately identify plaque characteristics such as echolucency. This is easily identifiable using DUAM, and echolucency is a contraindication to EvR due to the possibility of distal embolization and early failure.36 In the DUAM group, patients with echolucent plaques were referred for reconstructive bypass procedures. In the MRA group, patients with plaque echolucency may not have been as easily identified and so were referred for an endovascular procedure that perhaps would not have been attempted had echolucency been identified on a preoperative DUAM. DUAM is not without limitations as an imaging investigation. Larch et al.44 and Allard et al.45 have reported poor visualization of the infragenicular vessels by DUAM, which is further compromised in the presence of heavy calcification. These limitations were encountered in our series, where some patients had suboptimal below-knee scans due to heavy calcification (n ¼ 5) and severe lower limb ulceration (n ¼ 1). However, our protocol manages to overcome this issue by performing an on-table angiogram and proceeding with EvR if appropriate. Notably, similar numbers (n ¼ 6) in the MRA group in our series had suboptimal study of infragenicular vessels in the presence of venous contamination as previously reported.29,42,43 The significant findings of this study evaluating DUAM as a preoperative imaging modality for patients with CLI are as follows: 1. DUAM is comparable to DSA in planning the management strategy and achieving technical success and clinical improvement. 2. Patients who had preoperative DUAM as the sole imaging investigation had a significantly lower length of hospital stay and incurred less cost than those who underwent alternative preoperative imaging techniques (DSA, MRA) 3. In our series of patients, those who underwent angioplasty based on preoperative MRA had poorer rates of technical success, patency, and limb salvage. 4. Preoperative MRA frequently overestimated the extent of disease and number of lesions requiring revascularization. We have previously shown that endovascular techniques significantly reduce the hospital stay, number of hospital admissions, and cost of treatment.2,5 In this study, patients who were investigated with DUAM as an imaging technique prior

Annals of Vascular Surgery

to endovascular intervention had a further reduced hospital stay and reduced number of hospital admissions related to the presenting complaint. This reflects reduced waiting time and time to perform DUAM compared with DSA or MRA. In addition, there was a need for postprocedure recovery care in patients who had preoperative DSA. The cost of DUAM in terms of equipment, staff requirements, and time is significantly lower than that of DSA and MRA. However, reduced hospital stay and cost of procedure have obvious economic benefits. Our results indicate that DUAM is superior to other available modalities as the preoperative imaging tool in a successful EvR program. DUAM is a minimally invasive preoperative evaluation for EvR and offers precise consecutive data with patency and limb salvage rates comparable to EvR based on DSA and superior to MRA. We believe that our feasibility study has established DUAM as an economically proficient, lower-cost primary modality for investigating patients with CLI that significantly shortens the length of hospital stay. REFERENCES 1. Coni N, Tennison B, Troup M, et al. Prevalence of lower extremity arterial disease among elderly people in the community. Br J Gen Pract 1992;42:149-152. 2. Holm J, Baum A, Jivegard L, et al. Chronic lower limb ischaemia: a prospective randomised controlled study comparing the 1-year results of vascular surgery and percutaneous transluminal angioplasty (PTA). Eur J Vasc Surg 1991;5:517-522. 3. Wilson SE, Wolf GL, Cross AP. Percutaneous transluminal angioplasty versus operation for peripheral arteriosclerosis. Report of a prospective randomized trial in a selected group of patients. J Vasc Surg 1989;9:1-9. 4. Nasr Mk, McCarthy RJ, Hardman J, Chalmers A, Horrocks M. The increasing role of percutaneous transluminal angioplasty in the primary management of critical limb ischaemia. Eur J Vasc Endovasc Surg 2002;23:398-403. 5. Hynes N, Akhtar Y, Manning B, et al. Subintimal angioplasty as a primary modality in the management of critical limb ischaemia: comparison to bypass grafting for aortoiliac and femoropopliteal occlusive disease. J Endovasc Ther 2004;11:460-471. 6. Carpenter J, Owen R, Baum R, et al. Magnetic resonance angiography of peripheral run off vessels. J Vasc Surg 1992;16:807-815. 7. Cambria R, Yucel E, Brewster D, et al. The potential for lower extremity revascularization without contrast arteriography: experience with magnetic resonance angiography. J Vasc Surg 1993;17:1050-1057. 8. Carpenter J, Owen R, Holland G, et al. Magnetic resonance angiography of the aorta, iliac and femoral arteries. Surgery 1994;116:17-23. 9. Carpenter J, Baum R, Holland G, et al. Peripheral vascular surgery with magnetic resonance angiography as the sole pre-operative imaging modality. J Vasc Surg 1994;20: 861-871.

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