The limitations of magnetic resonance angiography in the diagnosis of renal artery stenosis: comparative analysis with conventional arteriography.

PURPOSE: Gadolinium-enhanced magnetic resonance angiography (MRA) is commonly used as a screening modality for the detection of renal artery stenosis. However, evidence supporting its utility in clinical practice is lacking; few rigorous studies have compared MRA with contrast arteriography (CA). After making anecdotal clinical observations that MRA sometimes overestimated the degree of renal artery stenosis, we decided to determine the interobserver variability, sensitivity, specificity, and diagnostic accuracy of MRA compared with CA. METHODS: From September 1999 to April 2003, we evaluated 68 renal arteries in 34 patients with clinically suspected renal artery stenosis using both MRA and CA. All studies were independently reviewed by four blinded observers. Renal arteries were categorized by MRA as normal, <50%, and >50% stenosis/occlusion. The sensitivity, specificity, and accuracy of MRA detection of renal artery stenosis were compared to CA as the gold standard. Interobserver variability (kappa) was also calculated. RESULTS: MRA demonstrated 87% sensitivity, 69% specificity, 85% accuracy, 95% negative predictive value, and 51% positive predictive value for the diagnosis of renal artery stenosis. Interobserver agreement was moderate for MRA (kappa = 0.53) and good for CA (kappa = 0.76). In 21 arteries (31%), MRA was falsely positive. CONCLUSIONS: In patients with a high clinical suspicion of renal artery stenosis, MRA is 87% sensitive in the detection of >50% stenosis. However, MRA is relatively nonspecific compared with CA and results in significant overestimation of renal artery stenosis in nearly one third of patients. To reduce unnecessary CA, clinicians should consider supplemental studies.

Endovascular therapy in prevention and management of coronary-subclavian steal.

BACKGROUND: The optimal management of patients undergoing coronary artery bypass grafting (CABG) who have proximal subclavian artery stenosis (SAS) is not well established. SAS may lead to flow reversal through a patent in situ internal mammary artery graft, resulting in myocardial ischemia (coronary-subclavian steal). We review our experience in prevention and management of coronary-subclavian steal. METHODS: The medical records of patients who received treatment of symptomatic coronary-subclavian steal were reviewed. Patients who underwent subclavian artery revascularization before CABG were also included in our review. Patient demographic data, findings at presentation, imaging and treatment methods, and short-term and intermediate-term results were analyzed. RESULTS: Over 4 years, 14 patients with combined subclavian and coronary artery disease were identified. Nine patients had angina (n = 8) and/or congestive heart failure (n = 2) after CABG (post-CABG group). Four patients underwent treatment of SAS and one underwent treatment of recurrent stenosis before or during CABG (pre-CABG group). Among this pre-CABG group, one patient had symptoms of left arm claudication; the other four patients had no symptoms. A blood pressure gradient was commonly noted between both arms. An angiogram confirmed the proximal location of SAS in all patients, and established the presence of flow reversal in a patent internal mammary artery graft in the post-CABG group. Operative management consisted of percutaneous transluminal angioplasty (PTA) and stenting of the subclavian lesion in 11 patients, PTA only in 2 patients, and carotid-subclavian bypass grafting in 1 patient. No known perioperative complications or morbidity was encountered in either group. Mean follow-up was 29 months, during which stenosis recurred in two patients, along with associated cardiac symptoms. In both patients repeat angioplasty was successful, for an assisted primary patency rate of 100%. CONCLUSION: PTA and stenting to treat SAS appears to provide effective protection from and treatment of coronary-subclavian steal over the short and intermediate terms. A surveillance program is essential because of the risk for recurrent stenosis. Continued follow-up is necessary to determine long-term efficacy of this treatment compared with more conventional surgical approaches.

The AneuRx stent-graft since FDA approval: single-center experience of 230 cases.

PURPOSE: To compare a single-center experience with the AneuRx stent-graft system before and after FDA approval to results from the multicenter phase II clinical trial. METHODS: The medical records of 230 consecutive patients (218 men; mean age 74 years) undergoing AneuRx stent-graft implantation for abdominal aortic aneurysm (AAA) exclusion since September 1999 were reviewed to collect patient characteristics, aneurysm morphology, procedure variables, perioperative morbidity, mortality, and short-term outcome. These data were compared to the 30 patients treated at our institution during the AneuRx phase II clinical trial and to the overall multicenter trial data. Stent-graft difficulty was categorized from 1 (straight neck and access of appropriate size) to 4 (proximal neck <10 mm long or angulated >60 degrees and/or difficult access) based on aneurysm morphology. RESULTS: Data from the 30 patients enrolled in the phase II trial at our institution were comparable in terms of patient characteristics and procedure variables to patients treated after FDA approval and to the multicenter data. However, the proportion of cases involving aneurysms with a more complex morphology (levels 3 and 4) rose 22% after FDA approval, reflecting a change in referral patterns. Our postoperative endoleak and morbidity rates increased nonsignificantly with respect to our own phase II experience (17% versus 6%, 18% versus 11%, respectively); however, they were not significantly different from the multicenter data. Reintervention was performed in 15 of 38 endoleak cases, mostly type I. Only 5 (2.1%) cases had a persistent endoleak at the time of discharge. CONCLUSIONS: Since FDA approval of the AneuRx device, our endovascular practice has changed toward the management of increasingly more complex AAAs. Although we are attempting more challenging cases, we are able to maintain similarly high short-term success rates while offering stent-grafting to an increasing number of patients. These results suggest that more patients may be candidates for endoluminal graft placement than determined by the clinical trial selection criteria, provided that strict surveillance and long-term follow-up is maintained.