Outcomes of prosthetic upper arm arteriovenous graft vs brachiobasilic fistula for hemodialysis access.

OBJECTIVE: Primary arteriovenous access such as radiocephalic and brachiocephalic fistulas are initial choices for creating vascular access in dialysis patients. When neither of these choices is an option, upper arm arteriovenous graft or brachiobasilic transposition is recommended. Although primary fistula is better than prosthetic graft for suitable patients, there is little data to guide the best treatment strategy in the absence of suitable vein for primary access creation. This study identifies factors that influence patency rates and compares outcomes of patients treated with brachiobasilic fistula vs upper arm graft in patients who have failed forearm access or are not candidates for primary access. METHODS: A prospectively maintained database of patients with dialysis-dependent renal failure from 2010 to 2022 was analyzed. Primary, primary assisted, and secondary patency rates were calculated. Incidence rates of complications and reinterventions were compared. RESULTS: There were 148 patients with brachiobasilic fistulas and 157 patients with upper arm grafts. The graft group was older (70.1 ± 14.7 vs 62.5 ± 14.6 years; P = .003) and had a higher incidence of pacemakers (11.9% vs 4.1%; P = .005). Brachiobasilic fistulas had higher 6-month (77.0% vs 64.3%; P = .02) and 1-year (68.2% vs 55.4%; P = .03) primary-assisted patency. Secondary patency rates were better for upper arm grafts at 1-year (82.2% vs 72.3%; P = .05). Access complications of non-maturation and aneurysm were higher in basilic vein transposition (21.6% vs 1.3%; P < .0001; 15.5% vs 6.4%; P = .017). Grafts had higher rates of occlusion (58.0% vs 25.7%; P < .0001). In terms of interventions, upper arm grafts had higher rates of thrombectomy (50.3% vs 18.9%; P < .0001), but there was no difference seen in angioplasty, stent, surgical revision, or steal procedures. Basilic vein transpositions had longer time to cannulation (104.6 ± 81.1 vs 32.5 ± 22.4 days; P < .0001), longer total catheter days (251.1 ± 181.7 vs 72.9 ± 56.3 days; P < .0001), and higher number of procedures to aid maturity (0.7 ± 0.7 vs 0.1 ± 0.3; P < .0001). CONCLUSIONS: In this retrospective analysis, when forearm access or primary arteriovenous access is not an option, basilic vein transposition and upper arm grafts have fairly equivalent primary patency. Primary assisted patency is slightly better in basilic vein fistulas, but secondary patency is better in upper arm grafts at 1 year. Basilic fistulas also had longer time to cannulation, longer total catheter days, and more procedures to aid maturity.

Initial experience with a modified "candy-plug" technique for false lumen embolization in chronic type B aortic dissection.

Background: Persistent distal false lumen (FL) perfusion after thoracic endovascular aortic repair (TEVAR) for type B aortic dissection (TBAD) can lead to aneurysmal degeneration and an increased risk of rupture. We have presented our initial experience using a modified "candy-plug" (CP) technique for FL embolization. Methods: From February 2021 to July 2022, we treated six patients using the modified CP technique. All the patients had undergone prior or simultaneous TEVAR for chronic TBAD with persistent FL perfusion and aneurysm expansion. Bilateral common femoral artery access was obtained, and intravascular ultrasound was used to confirm wire access in the true lumen (TL) and FL. A conformable TAG device (W.L. Gore & Associates, Flagstaff, AZ) was used in four cases and an Excluder aortic cuff (W.L. Gore & Associates) in two cases. The device was modified by placing a constraining "napkin-ring" suture through the middle segment of the device. Femoral sheaths were placed in the TL and FL. A standard TL TEVAR extension was performed at the level of the celiac artery (zone 5). Next, the CP device was advanced and deployed in the FL, distally aligning it with the TL device. An appropriately sized Amplatzer II plug (Abbot Vascular, Santa Clara, CA) was then deployed in the constrained segment of the modified stent graft. Completion angiography was performed to confirm successful FL embolization. Results: Technical success was defined as successful deployment of the CP device in the FL. The technical success rate was 100% (six of six patients). Clinical success was defined as the cessation of aneurysm growth on follow-up computed tomography angiography. No 30-day mortality, myocardial infarction, stroke, spinal cord ischemia, access site complications, or aortic-related reinterventions occurred. Surveillance imaging at a mean follow-up of 10 months confirmed clinical success (stable aneurysm size or shrinkage) for all five patients with follow-up data available. Conclusions: The modified CP embolization technique is a promising solution for persistent distal FL perfusion after TEVAR for TBAD. Further investigation is required to determine the long-term durability of this technique as an adjunct to TEVAR to promote aortic remodeling.

The first commercial use of the Valiant Navion stent graft system for endovascular repair of a descending thoracic aortic aneurysm.

OBJECTIVES: Thoracic endovascular aortic repair (TEVAR) is the standard of care for descending thoracic aortic aneurysms (DTAA), and newer generation stent grafts have significant design improvements compared to earlier generation devices. METHODS: We report the first commercial use of the Medtronic Valiant Navion stent graft for treatment of an 85-year-old woman with a 5.8 cm DTAA and a highly tortuous thoracic aorta. RESULTS: A percutaneous TEVAR was performed using a two-piece combination of the Valiant Navion FreeFlo and CoveredSeal stent graft configurations for zones 2-5 coverage. The devices were successfully delievered through highly tortuous anatomy and deployed, excluding the entire length of the aneurysm with precise landing, excellent apposition and no evidence of endoleak. The patient tolerated the procedure well and has had no stent graft-related complications through one-year follow-up. CONCLUSIONS: Design enhancements such as a lower profile delivery system, better conformability, and a shorter tapered tip are some of the improvements to this third-generation TEVAR device. Coupled with the multiple configuration options available, this gives physicians a better tool to treat thoracic aortic pathologies in patients with challenging anatomy. The early results are encouraging, and evaluation of long-term outcomes will continue.

Thoracic Endovascular Aortic Repair in Octogenarians and Nonagenarians.

BACKGROUND: The oldest segments of the population are expanding rapidly, and the number of thoracic endovascular aortic repairs (TEVARs) performed in the elderly parallels this trend. We describe our institutional TEVAR experience in octogenarians and nonagenarians. METHODS: All patients 80 years and older undergoing TEVAR at a single institution were reviewed using a prospectively maintained database. Baselines demographics, operative details, and outcomes were retrospectively analyzed. RESULTS: Twenty-five octogenarians and nonagenarians (age, 84.8 ± 3.7 years; 64% male) underwent TEVAR between January 2014 and January 2019. The most common preoperative comorbidities were hypertension (n = 24; 96%) and tobacco use (n = 18; 72%), and the mean modified frailty index was 0.32 ± 0.17. Degenerative aneurysms constituted the majority of aortic pathologies (60%), and most patients were symptomatic (64%), with a mean maximal aortic diameter of 62.7 ± 15.6 mm. Endoleaks were noted in 3 (12%) patients. Intensive care unit length of stay was 2.0 (1.5, 3.0) days, and the total length of stay was 5.0 (3.0, 7.0) days. In-hospital mortality was 12% (n = 3), while the overall 30-day mortality was 16% (n = 4). The median follow-up was 469.0 (76.0, 586.0) days. On univariate analysis, the presence of a postoperative complication was associated with a significantly increased risk of 30-day mortality (P < 0.01). CONCLUSIONS: Despite the inherently elevated operative risk among the elderly, this study demonstrates reasonable success rates for TEVAR in octogenarian and nonagenarian patients. In properly selected patients, advanced age alone should not be a prohibitive factor for TEVAR.

Use of a Dual-Filter Cerebral Embolic Protection Device in Thoracic Endovascular Aortic Repair.

BACKGROUND: The risk of periprocedural stroke after thoracic endovascular aortic repair (TEVAR) ranges from 3% to 8%. Although cerebral embolic protection devices (CEPD) are widely utilized in transcatheter aortic valve replacement, there are currently no Food and Drug Administration approved CEPDs for use in TEVAR. We report our initial experience with the off-label use of a dual-filter CEPD in patients undergoing TEVAR. METHODS: Two patients at high risk for embolic stroke underwent TEVAR for descending thoracic aortic aneurysms (DTAAs) at a single institution. A dual-filter CEPD (Sentinel; Boston Scientific, Marlborough, MA) was used in an off-label fashion in both cases. Patient 1 was a 62-year-old woman with a 6.2-cm DTAA, extending from the left subclavian artery (LSCA) to the diaphragm (Zones 3-5) and associated with extensive atherosclerotic disease of the aortic arch. Patient 2 was a 78-year-old woman with a 6.3-cm DTAA, extending from the LSCA (Zone 2) to the sixth intercostal space (Zone 4) with associated mural thrombus. Given the proximity of the aneurysm to the LSCA, a left carotid-subclavian bypass was performed for planned LSCA coverage. RESULTS: Through a percutaneous right radial artery approach using a 6F sheath, the Sentinel dual-filter CEPD was delivered over a 0.014″ guidewire into the thoracic aorta. Under fluoroscopic guidance, the 2 filters were sequentially deployed in the innominate and left common carotid arteries, respectively. Appropriately sized devices were successfully delivered and deployed in the proximal and distal landing zones, respectively. Two devices were used for each patient. Completion angiograms showed successful exclusion of the DTAAs in both cases, without evidence of endoleak. The CEPD filters were retrieved in standard fashion without difficulty. Pathology demonstrated successful capture of embolic debris and fibrin clot in both patients. Neither patient exhibited neurological deficits or device-related complications. Both patients remained neurologically intact at 1- and 2-month follow-up, respectively. Surveillance angiograms revealed successful exclusion of the aneurysm without any evidence of endoleak. CONCLUSIONS: We report the novel off-label use of a dual-filter CEPD in 2 patients undergoing TEVAR. Pathological confirmation of embolic debris in the filters makes this a potential tool for stroke prevention during TEVAR in high-risk patients.

MR imaging of iliofemoral peripheral vascular calcifications using proton density-weighted, in-phase three-dimensional stack-of-stars gradient echo.

PURPOSE: The presence of vascular calcifications helps to determine percutaneous access for interventional vascular procedures and has prognostic value for future cardiovascular events. Unlike CT, standard MRI techniques are insensitive to vascular calcifications. In this prospective study, we tested a proton density-weighted, in-phase (PDIP) three-dimensional (3D) stack-of-stars gradient-echo pulse sequence with approximately 1 mm3 isotropic spatial resolution at 1.5 Tesla (T) and 3T to detect iliofemoral peripheral vascular calcifications and correlated MR-determined lesion volumes with CT angiography (CTA). METHODS: The study was approved by the Institutional Review Board. The prototype PDIP stack-of-stars pulse sequence was applied in 12 patients with iliofemoral peripheral vascular calcifications who had undergone CTA. RESULTS: Vascular calcifications were well visualized in all subjects, excluding segments near prostheses or stents. The location, size, and shape of the calcifications were similar to CTA. Quantitative analysis showed excellent correlation (r2 = 0.84; P < 0.0001) between MR- and CT-based measures of calcification volume. In one subject in whom three pulse sequences were compared, PDIP stack-of-stars outperformed cartesian 3D gradient-echo and point-wise encoding time reduction with radial acquisition (PETRA). CONCLUSION: In this pilot study, a PDIP 3D stack-of-stars gradient-echo pulse sequence with high spatial resolution provided excellent image quality and accurately depicted the location and volume of iliofemoral vascular calcifications. Magn Reson Med 77:2146-2152, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Embolization of Onyx Causing Acute Limb Ischemia.

We present the case of a patient with a refractory type II endoleak treated with translumbar Onyx with passage of the Onyx material into the endograft and subsequent embolization to the infrainguinal vasculature. This report represents a new complication of Onyx embolization that, to our knowledge, has not previously been described in the literature.

Arterial spin labeled carotid MR angiography: A phantom study examining the impact of technical and hemodynamic factors.

PURPOSE: To quantify the accuracy of three-dimensional (3D) radial arterial spin labeled (ASL) magnetic resonance angiography (MRA) using vascular models of carotid stenosis. METHODS: Eight vascular models were imaged at 1.5 Tesla using pulsatile flow waveforms at rates found in the internal carotid arteries (100-400 mL/min). The impacts of the 3D ASL imaging readout (fast low angle shot (FLASH) versus balanced steady-state free precession (bSSFP)), ultrashort echo time imaging using a pointwise encoding time reduction with radial acquisition (PETRA), and model stenosis severity on the accuracy of vascular model display at the location of stenosis were quantified. Accuracy was computed vis-à-vis a reference bSSFP volume acquired under no flow. Comparisons were made with standard-of-care contrast-enhanced MRA (CEMRA) and Cartesian time-of-flight (TOF) MRA protocols. RESULTS: For 50% and 70% stenoses, CEMRA was most accurate (respective accuracies of 81.7% and 78.6%), followed by ASL FLASH (75.7% and 71.8%), ASL PETRA (69.6% and 70.6%), 3D TOF (66.6% and 57.1%), ASL bSSFP (68.7% and 51.2%), and 2D TOF (65.1% and 50.6%). CONCLUSION: Flow phantom imaging studies show that ASL MRA can improve the display of hemodynamically significant carotid arterial stenosis compared with TOF MRA, with FLASH and ultrashort echo time readouts being most accurate.

Randomized trial of a dry-powder, fibrin sealant in vascular procedures.

OBJECTIVE: Topical hemostats are important adjuncts for stopping surgical bleeding. The safety and efficacy of Fibrocaps, a dry-powder, fibrin sealant containing human plasma-derived thrombin and fibrinogen, was evaluated in patients undergoing vascular surgical procedures. METHODS: In this single-blind trial (clinicaltrials.gov: NCT01527357), adult patients were randomized 2:1 to Fibrocaps plus gelatin sponge (Fibrocaps) vs gelatin sponge alone. Results are presented for the patient subset undergoing vascular procedures with suture hole bleeding. The primary efficacy endpoint compared time to hemostasis (TTH) over 5 minutes. Safety follow-up continued to day 29. RESULTS: A total of 175 patients were randomized and treated (Fibrocaps, 117; gelatin sponge, 58). Patients were predominately male (69%) and underwent arterial bypass (81%), arteriovenous graft formation (9%), or carotid endarterectomy (9%). Fibrocaps significantly reduced TTH compared with gelatin sponge (hazard ratio [HR], 2.1; 95% confidence interval [CI], 1.5-3.1; median TTH, 2 minutes; 95% CI, 1.5-2.5 vs 4 minutes; 95% CI, 3.0-5.0; P < .002). Significant reductions were also observed in patients receiving concomitant antiplatelet agents alone (HR, 2.8; 95% CI, 1.0-7.4; P = .03; n = 33), anticoagulants alone (HR, 2.0; 95% CI, 1.0-4.0; P = .04; n = 43), or both antiplatelet agents and anticoagulants (Fibrocaps vs gelatin sponge, HR, 2.3; 95% CI, 1.2-4.3; P = .008; n = 65). Incidences of common adverse events (procedural pain, nausea, constipation) were generally comparable between treatment arms. Anti-thrombin antibodies developed in 2% of Fibrocaps-treated patients and no-gelatin-sponge patients. CONCLUSIONS: Fibrocaps, a ready-to-use, dry-powder fibrin sealant, was well-tolerated and reduced TTH in patients undergoing vascular procedures, including those receiving antiplatelet agents and/or anticoagulants, demonstrating its safety and usefulness as an adjunct to hemostasis.

The FINISH-3 trial: a phase 3, international, randomized, single-blind, controlled trial of topical fibrocaps in intraoperative surgical hemostasis.

BACKGROUND: This Phase 3, international, randomized, single-blind, controlled trial (FINISH-3) compared the efficacy and safety of Fibrocaps, a ready-to-use, dry-powder fibrin sealant containing human plasma-derived thrombin and fibrinogen, vs gelatin sponge alone for use as a hemostat for surgical bleeding in 4 indications (ie, spinal, hepatic, vascular, soft tissue dissection). STUDY DESIGN: Adults with mild to moderate surgical bleeding (randomized 2:1; Fibrocaps vs gelatin sponge) were treated at a single bleeding site (day 1). Time to hemostasis (TTH) during 5 minutes was compared (log-rank statistic) within each indication. Safety follow-up continued to day 29. RESULTS: Patients were treated (Fibrocaps, n = 480; gelatin sponge, n = 239) when undergoing spinal (n = 183), vascular (n = 175), hepatic (n = 180), or soft-tissue (n = 181) procedures. Fibrocaps was applied by spray device in 53% of all procedures (94% of hepatic and soft-tissue procedures). Fibrocaps significantly reduced TTH compared with gelatin sponge; estimated hazard ratios were 3.3, 2.1, 2.3, and 3.4 for the 4 surgical indications, respectively (each p < 0.001; primary end point). Fibrocaps significantly reduced median TTH for each indication (p < 0.001) and was superior for secondary efficacy end points of restricted mean TTH (p < 0.001) and probability of hemostasis at 3 (p < 0.001) and 5 (p ≤ 0.002) minutes. Adverse event incidences were generally similar between treatment arms. Non-neutralizing, anti-thrombin antibodies developed in 2% of Fibrocaps-treated and 3% of gelatin sponge-treated patients. CONCLUSIONS: Fibrocaps was well tolerated and significantly reduced TTH relative to gelatin sponge alone in all 4 surgical indications. These findings demonstrate the broad utility of Fibrocaps as a hemostatic agent for mild to moderate surgical bleeding.

Management and outcomes of dialysis access-associated steal syndrome.

OBJECTIVE: Dialysis access-associated steal syndrome (DASS) complicates arteriovenous access surgery. We describe a 10-year experience with the surgical management of DASS. METHODS: DASS operations were retrospectively reviewed from July 2003 to July 2013 from a single academic institution. Demographics, symptoms, surgical details, and outcomes were collected. RESULTS: A total of 201 patients had 218 episodes of DASS. Mean age was 65 years, and 62% were women. DASS was caused by 175 arteriovenous fistulas (80%), 41 upper extremity prosthetic grafts (19%), and two thigh grafts (1%); 87% were brachial artery based. A portion (22%) were referred for DASS from outside practices. All patients had grade 2 (48%) or grade 3 (52%) DASS; 92% (185) were available for follow-up, with a median time to first follow-up of 23 days. Surgical procedures included ligation (73), distal revascularization with interval ligation (DRIL) (59), revision using distal inflow (RUDI) (21), banding (38), proximalization of arterial inflow (12), and distal radial artery ligation (13). There were no differences in preoperative comorbidities between treatment groups. The 30-day complications included continued steal, thrombosis, bleeding, infection, and mortality. Ligation and DRIL were performed most often for grade 3 steal. Ligation and banding were performed most acutely (median time to intervention after access creation of 39 and 24 days vs DRIL and RUDI at 97 and 100 days). Fistula preservation was 0% for ligation, 100% for DRIL, 95% for RUDI, and 89% for banding (P < .01). Improvement of symptoms ranged from 75% (banding) to 98% (DRIL) (P = .005). Women were less likely to have DRIL but more likely to have ligation (P = .001). Complications were highest in the banding (49%) and RUDI (37%) groups. Average mortality was 3.5%, with no significant differences among groups. During the study period, 3287 access procedures were performed, and access volume steadily increased (2003-2008, 1312 access creations; 2008-2013, 1975). Percentage of fistulas (79% vs 86%), incidence of steal (4% vs 6%), and percentage of DRILs (25% vs 28%) were consistent across the two study periods. CONCLUSIONS: DRIL and ligation were performed in patients with the most severe symptoms. Compared with ligation, DRIL has equal symptom resolution, no increase in complications, and fistula preservation. Compared with banding, DRIL resulted in superior fistula preservation and fewer complications. DRIL should be considered the preferred procedure for management of DASS in patients with a functioning autologous fistula who can tolerate a major operation.

Nonenhanced arterial spin labeled carotid MR angiography using three-dimensional radial balanced steady-state free precession imaging.

PURPOSE: To optimize and preliminarily evaluate a three-dimensional (3D) radial balanced steady-state free precession (bSSFP) arterial spin labeled (ASL) sequence for nonenhanced MR angiography (MRA) of the extracranial carotid arteries. MATERIALS AND METHODS: The carotid arteries of 13 healthy subjects and 2 patients were imaged on a 1.5 Tesla MRI system using an undersampled 3D radial bSSFP sequence providing a scan time of ∼4 min and 1 mm(3) isotropic resolution. A hybridized scheme that combined pseudocontinuous and pulsed ASL was used to maximize arterial coverage. The impact of a post label delay period, the sequence repetition time, and radiofrequency (RF) energy configuration of pseudocontinuous labeling on the display of the carotid arteries was assessed with contrast-to-noise ratio (CNR) measurements. Faster, higher undersampled 2 and 1 min scans were tested. RESULTS: Using hybridized ASL MRA and a 3D radial bSSFP trajectory, arterial CNR was maximized with a post label delay of 0.2 s, repetition times ≥ 2.5 s (P < 0.05), and by eliminating RF energy during the pseudocontinuous control phase (P < 0.001). With higher levels of undersampling, the carotid arteries were displayed in ≤ 2 min. CONCLUSION: Nonenhanced MRA using hybridized ASL with a 3D radial bSSFP trajectory can display long lengths of the carotid arteries with 1 mm(3) isotropic resolution.

Projection MR imaging of peripheral arterial calcifications.

PURPOSE: Both CT and MR angiography are accurate for the evaluation of luminal abnormalities in peripheral arterial disease (PAD). However, only CT (requiring exposure to potentially hazardous ionizing radiation) provides a reliable means to detect vascular calcifications. In this study, we demonstrate the feasibility of detecting peripheral arterial calcifications with MRI. METHODS: The institutional investigational review board approved the study. Seven patients with PAD and iliofemoral arterial calcifications shown by prior CT angiography (CTA) were studied. The imaging techniques included: 1) dual-echo three-dimensional (3D) gradient recalled echo (GRE) pulse sequence using flow compensation and in-phase echo times (TE); and 2) prototype version of 3D point-wise encoding time reduction with radial acquisition (PETRA), which enables imaging with an ultra-short TE. RESULTS: With both techniques after grayscale inversion, vascular calcifications appeared bright, as did cortical bone, and were readily distinguished from the vessel lumen and surrounding soft tissues. The location and conformation of the calcifications corresponded with CT. The second echo GRE provided the highest contrast-to-noise ratios; whereas PETRA was best suited for the creation of thick projection images. CONCLUSION: In this pilot study, MRI was able to detect vascular calcifications. Projection imaging using PETRA provided a similar appearance to, and allowed direct comparison with, CT.

Endovascular treatment of iatrogenic injury to the retrohepatic inferior vena cava.

Iatrogenic injury of the inferior vena cava (IVC) is a rare event with potentially devastating sequelae. Only a handful of case reports are available in the literature describing successful endovascular techniques to manage this complication. We present the case of a patient with injury to the retrohepatic IVC resulting in life-threatening hemorrhage which was controlled with endovascular stent grafts.

Complications of indwelling retrievable versus permanent inferior vena cava filters.

OBJECTIVE: Retrievable inferior vena cava (IVC) filters are appealing because they are designed for either retrieval or long-term use. However, the long-term safety of indwelling retrievable compared with permanent filters is largely unknown. This study was undertaken to compare complication rates and types associated with indwelling retrievable and permanent filters. METHODS: A retrospective review identified 1234 IVC filters (449 retrievable, 785 permanent) placed in 1225 patients from 2005 to 2010. Patients with retrievable filters removed electively were excluded, yielding 383 patients in whom retrievable filters were left in place. These patients with indwelling retrievable filters were compared with those with permanent filters with respect to demographics, comorbidities, survival, and complication rate and type. Differences in patient characteristics were tested with χ(2), Fisher exact, and Wilcox rank-sum tests. Logistic regression was used to identify predictors of complications. Because there were differences in the characteristics of the patients with indwelling retrievable filters and permanent filters, an additional propensity score analysis was performed yielding 319 patients in each group. RESULTS: Patients with indwelling retrievable filters were younger than those with permanent filters (mean age, 62 vs 75 years; P < .0001). Patients with indwelling retrievable filters had significantly more complications than those with permanent filters (9% vs 3.0%; P < .0001) after mean follow-up of 20 months (range, 0-86 months). Filter complications were categorized as thrombotic, device related, or systemic. While the most common complication type with both indwelling retrievable and permanent filters was thrombotic (4.4% vs 2.2%; P = NS), device-related complications were significantly more common with indwelling retrievable filters compared with permanent filters (3% vs 0.5%; P < .006). Propensity score analysis demonstrated that even in the matched groups, indwelling retrievable filters were associated with significantly more complications than permanent filters (9.1% vs 3.5%; P = .0035). CONCLUSIONS: Indwelling retrievable IVC filters were associated with significantly higher complication rates than permanent filters. Both thrombotic and device-related complications were more common with retrievable filters. Long-term use of retrievable filters should be avoided, especially considering the younger population in whom they are placed.

Peripheral arterial disease in a symptomatic diabetic population: prospective comparison of rapid unenhanced MR angiography (MRA) with contrast-enhanced MRA.

OBJECTIVE: The joint guidelines of the American College of Cardiology and American Heart Association support the use of contrast-enhanced MR angiography (CEMRA) to diagnose the location and degree of stenosis in patients with known or suspected peripheral arterial disease (PAD). The high prevalence of chronic renal impairment in diabetic patients with PAD and the need for high doses of gadolinium-based contrast agents place them at risk for nephrogenic systemic fibrosis. The purpose of our study was to evaluate the accuracy of the rapid technique of quiescent-interval single-shot (QISS) unenhanced MR angiography (MRA) compared with CEMRA for the diagnosis in diabetic patients referred with symptomatic chronic PAD. SUBJECTS AND METHODS: This prospective two-center study evaluated 25 consecutive diabetic patients with documented or suspected symptomatic PAD. Both centers used identical imaging protocols. Images were independently analyzed by two radiologists. A subgroup analysis was performed of patients who were also assessed with digital subtraction angiography (DSA) as part of the standard-of-care protocol before revascularization. RESULTS: For this study, 775 segments were analyzed. On a per-segment basis, the mean values of the diagnostic accuracy of unenhanced MRA compared with reference CEMRA for two reviewers, reviewers 1 and 2, were as follows: sensitivity, 87.4% and 92.1%; specificity, 96.8% and 96.0%; positive predictive value, 90.8% and 94.0%; and negative predictive value, 95.5% and 94.6%. Substantial agreement was found when overall DSA results were compared with QISS unenhanced MRA (κ = 0.68) and CEMRA (κ = 0.63) in the subgroup of patients who also underwent DSA. There was almost perfect agreement between the two readers for stenosis scores, with Cohen's kappa values being greater than 0.80 for both MRA techniques. CONCLUSION: The results of our study indicate that QISS unenhanced MRA is an accurate noncontrast alternative to CEMRA for showing clinically significant arterial disease in patients with diabetes with symptomatic PAD.

Nonenhanced extracranial carotid MR angiography using arterial spin labeling: improved performance with pseudocontinuous tagging.

PURPOSE: To compare pulsed arterial spin labeling (PASL) and pseudocontinuous arterial spin labeling (PCASL) for nonenhanced extracranial carotid MR angiography (MRA). MATERIALS AND METHODS: Parametric signal equations for PASL and PCASL MRA were formulated and compared. Volunteer imaging (n=7) at 1.5 Tesla was performed to compare the methods over a broad range of repetition and labeling times. Empirical results were compared with theoretical predictions. The feasibility of the optimal method was investigated in patients (n=2) with sonographically documented carotid artery disease. RESULTS: In volunteers, PCASL provided significantly improved signal than PASL (range: 32-255% improvement; P<0.01), and better supported the use of long labeling times and short repetition times. Excellent agreement between theory and experiment was found (intraclass correlation coefficient=0.966; P<0.001). PCASL provided excellent depiction of the carotid arteries in initial patient studies. CONCLUSION: Compared with pulsed tagging, pseudocontinuous tagging provides improved performance for nonenhanced extracranial carotid MRA and warrants further clinical investigation.

Evaluation of peripheral arterial disease with nonenhanced quiescent-interval single-shot MR angiography.

PURPOSE: To assess the diagnostic performance of quiescent-interval single-shot (QISS) magnetic resonance (MR) angiography, a nonenhanced two-dimensional electrocardiographically gated single-shot balanced steady-state free precession examination for the evaluation of symptomatic chronic lower limb ischemia. MATERIALS AND METHODS: For this prospective institutional review board-approved, HIPAA-compliant study, the institutional review board waived the requirement for informed patient consent. The QISS nonenhanced MR angiography technique was evaluated in a two-center trial involving 53 patients referred for lower extremity MR angiography for suspected or known chronic peripheral arterial disease (PAD), with contrast material-enhanced MR angiography serving as the noninvasive reference standard. The accuracy of stenosis assessments performed with the nonenhanced MR angiography sequence was evaluated relative to the reference standard. Per-segment, per-region, and per-limb sensitivities and specificities were calculated, and assessments were considered correct only if they were in exact agreement with the reference standard-derived assessments. Generalized estimating equation (GEE) modeling with use of an unstructured binomial logit analysis was used to account for clustering of multiple measurements per case. The sensitivity and specificity of QISS MR angiography for the determination of nonsignificant (<50%) versus significant (50%-100%) stenosis were compared with the sensitivity and specificity of the reference standard. RESULTS: The diagnostic performance of nonenhanced MR angiography was found to be nearly equivalent to the diagnostic performances of contrast-enhanced MR angiography and digital subtraction angiography. Non-GEE segment-based analysis revealed that for the two reviewers, nonenhanced MR angiography had sensitivities of 89.7% (436 of 486 segments) and 87.0% (423 of 486 segments) and specificities of 96.5% (994 of 1030 segments) and 94.6% (973 of 1028 segments). CONCLUSION: QISS nonenhanced MR angiography offers an alternative to currently used imaging tests for symptomatic chronic lower limb ischemia, for which the administration of iodinated or gadolinium-based contrast agents is contraindicated.