Multidetector computed tomography for acute pulmonary embolism.

BACKGROUND: The accuracy of multidetector computed tomographic angiography (CTA) for the diagnosis of acute pulmonary embolism has not been determined conclusively. METHODS: The Prospective Investigation of Pulmonary Embolism Diagnosis II trial was a prospective, multicenter investigation of the accuracy of multidetector CTA alone and combined with venous-phase imaging (CTA-CTV) for the diagnosis of acute pulmonary embolism. We used a composite reference test to confirm or rule out the diagnosis of pulmonary embolism. RESULTS: Among 824 patients with a reference diagnosis and a completed CT study, CTA was inconclusive in 51 because of poor image quality. Excluding such inconclusive studies, the sensitivity of CTA was 83 percent and the specificity was 96 percent. Positive predictive values were 96 percent with a concordantly high or low probability on clinical assessment, 92 percent with an intermediate probability on clinical assessment, and nondiagnostic if clinical probability was discordant. CTA-CTV was inconclusive in 87 of 824 patients because the image quality of either CTA or CTV was poor. The sensitivity of CTA-CTV for pulmonary embolism was 90 percent, and specificity was 95 percent. CTA-CTV was also nondiagnostic with a discordant clinical probability. CONCLUSIONS: In patients with suspected pulmonary embolism, multidetector CTA-CTV has a higher diagnostic sensitivity than does CTA alone, with similar specificity. The predictive value of either CTA or CTA-CTV is high with a concordant clinical assessment, but additional testing is necessary when the clinical probability is inconsistent with the imaging results.

Percutaneous Orthotopic IVC Construction in a Pediatric Patient with Symptomatic IVC Agenesis.

Inferior vena cava agenesis is an uncommon condition usually attributed to embryologic dysgenesis. When symptomatic, unprovoked deep venous thrombosis and/or lower extremity venous congestion are the most frequent manifestations. Its rarity has precluded consensus regarding appropriate management. Symptomatic chronic venous congestion requires surgical construction of auxiliary venous pathways, which may involve substantial morbidity, prolonged recovery and extensive scarring. We report successful minimally invasive management via percutaneous endovascular orthotopic inferior vena cava construction in a pediatric patient, thereby obviating the need for surgery and its associated morbidity. LEVEL OF EVIDENCE: Level IV, case study.

Atherosclerotic renal artery stenosis in the post-CORAL era part 2: new directions in Transcatheter Nephron Salvage following flawed revascularization trials.

Unlike endovascular therapeutic studies for atherosclerosis in many other vascular beds, major trials regarding endovascular renovascular revascularization have resulted in a stagnating equipoise. However, every major trial completed for this topic thus far has suffered from major methodological flaws that limit the validity and external generalizability of their results. Furthermore, certain patient populations who are known to benefit from renovascular revascularization may never be studied because they cannot be ethically withheld from life-saving treatment. Forthcoming percutaneous techniques may one day complement angioplasty and stenting in a burgeoning era of cellular modulation and endovascular-directed renal regeneration.

Atherosclerotic renal artery stenosis in the post-CORAL era part 1: the renal penumbra concept and next-generation functional diagnostic imaging.

After three neutral trials in which renal artery stenting failed to improve renal function or reduce cardiovascular and renal events, the controversy surrounding diagnosis and treatment of atherosclerotic renal artery stenosis and renovascular hypertension has led to paradigm shifts in the diagnostic algorithm. Noninvasive determination of earlier events (cortex hypoxia and renal artery hemodynamic changes) will supersede late sequelae (calcific stenosis, renal cortical thinning). Therefore, this review proposes the concept of renal penumbra in defining at-risk ischemic renal parenchyma. The complex field of functional renal magnetic resonance imaging will be reviewed succinctly in a clinician-directed fashion.

Brachial Artery Access.

Low brachial artery access is a safe alternative approach for the interventionalist when the femoral artery approach is not feasible or desirable. One important advantage of upper extremity access is the favorable route of entry from above into the caudally oriented visceral arteries. Although the risk of complications is low for experienced operators, meticulous attention to technique and knowledge of local anatomy are imperative to safely use brachial artery access. Adequate anticoagulation with heparin and use of lowest-profile devices may minimize complications. Following these procedures, patients must be carefully evaluated immediately and trained to self-monitor for up to 2 weeks for signs and symptoms of bleeding and nerve compression. This article describes the indications, procedural steps, expected outcomes, and tips on overcoming technical challenges of brachial artery access.

Renal artery stenosis: imaging options, pitfalls, and concerns.

Renal artery stenosis can be diagnosed with multiple imaging modalities, each one having different risk vs accuracy tradeoffs. Catheter angiography with pressure gradient measurements is the definitive gold standard but also the most invasive and thus reserved primarily for imaging at the time of renal revascularization. Ultrasonography is the safest and least expensive but also the least accurate and most operator-dependent. Contrast-enhanced computed tomographic angiography and magnetic resonance angiography are intermediate (between ultrasound and catheter angiography) with respect to accuracy and expense. Exciting new advances in magnetic resonance that include new contrast agents, which eliminate nephrogenic systemic fibrosis risk, and techniques to characterize the hemodynamic significance of renal artery stenoses are now becoming available. In addition, magnetic resonance angiography without any contrast has become more accurate and rivals contrast-enhanced techniques in some patients. This review explores these techniques for renal artery stenosis imaging.

Diagnostic pathways in acute pulmonary embolism: recommendations of the PIOPED II investigators.

PURPOSE: To formulate comprehensive recommendations for the diagnostic approach to patients with suspected pulmonary embolism, based on randomized trials. METHODS: Diagnostic management recommendations were formulated based on results of the Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) and outcome studies. RESULTS: The PIOPED II investigators recommend stratification of all patients with suspected pulmonary embolism according to an objective clinical probability assessment. D-dimer should be measured by the quantitative rapid enzyme-linked immunosorbent assay (ELISA), and the combination of a negative D-dimer with a low or moderate clinical probability can safely exclude pulmonary embolism in many patients. If pulmonary embolism is not excluded, contrast-enhanced computed tomographic pulmonary angiography (CT angiography) in combination with venous phase imaging (CT venography), is recommended by most PIOPED II investigators, although CT angiography plus clinical assessment is an option. In pregnant women, ventilation/perfusion scans are recommended by many as the first imaging test following D-dimer and perhaps venous ultrasound. In patients with discordant findings of clinical assessment and CT angiograms or CT angiogram/CT venogram, further evaluation may be necessary. CONCLUSION: The sequence for diagnostic test in patients with suspected pulmonary embolism depends on the clinical circumstances.

Three-dimensional MR angiography in imaging platinum alloy stents.

PURPOSE: To evaluate visualization inside platinum stents with three-dimensional contrast-enhanced magnetic resonance angiography (CE-MRA). MATERIALS AND METHODS: Breath-hold three-dimensional gadolinium (Gd) MRA was performed on 18 patients with 22 platinum stents in the renal (n = 18), celiac (n = 1), superior mesenteric (n = 1), and iliac (n = 2) arteries. Electronic calibers were used to measure the lumen diameter within the stent and just distal to the stent to calculate percent stenosis. MRA accuracy was determined from the difference between percent stenosis measured on MRA and digital subtracted angiography (DSA). The patients were imaged at flip angles of 45 degrees , 60 degrees , 75 degrees , 90 degrees , and 150 degrees . RESULTS: MRA demonstrated the stent lumen in all of the patients, with a mean difference between MRA and DSA of 21%. For stents oriented parallel to B0 (iliac arteries) the difference was only 10%, as compared to 22% for stents perpendicular to B0. The flip angle with the best agreement between MRA and DSA was 75 degrees (16%). CONCLUSION: The lumen of a platinum stent can be imaged with three-dimensional CE-MRA, although grading of restenosis has limited accuracy. The best results were obtained with a flip angle of 75 degrees and for stents in the iliac arteries parallel to B0.