Diagnostic accuracy of contrast-enhanced magnetic resonance angiography and duplex ultrasound in patients with peripheral vascular disease

To screen or not to screen? The development of a prediction model for aorto-iliac stenosis in kidney transplant candidates

Screening for aorto‐iliac stenosis is important in kidney transplant candidates as its presence affects pre‐transplantation decisions regarding side of implantation and the need for an additional vascular procedure. Reliable imaging techniques to identify this condition require contrast fluid, which can be harmful in these patients. To guide patient selection for these imaging techniques, we aimed to develop a prediction model for the presence of aorto‐iliac stenosis. Patients with contrast‐enhanced imaging available in the pre‐transplant screening between January 1st, 2000 and December 31st, 2018 were included. A prediction model was developed using multivariable logistic regression analysis and internally validated using bootstrap resampling. Model performance was assessed with the concordance index and calibration slope. Three hundred and seventy‐three patients were included, 90 patients (24.1%) had imaging‐proven aorto‐iliac stenosis. Our final model included age, smoking, peripheral arterial disease, coronary artery disease, a previous transplant, intermittent claudication and the presence of a femoral artery murmur. The model yielded excellent discrimination (optimism‐corrected concordance index: 0.83) and calibration (optimism‐corrected calibration slope: 0.91). In conclusion, this prediction model can guide the development of standardized protocols to decide which patients should receive vascular screening to identify aorto‐iliac stenosis. External validation is needed before this model can be implemented in patient care.

Accuracy of duplex ultrasonography in estimation of severity of peripheral vascular disease

Duplex ultrasonography (DUS) is a safe, noninvasive method for imaging vasculature when compared with conventional angiography. Our goal is to assess the accuracy of DUS compared with angiography of the lower extremities. We reviewed a total of 373 lesions in 278 patients from July 2005 through June 2010. Patients underwent DUS followed by angiography within 30 days. Peak systolic velocities (PSV) were stratified into one of four categories and compared with the angiographic findings. Seventy-five chronic total occlusions were found. Of the remaining 298 lesions, a significant relationship was found between PSV and degree of angiographic stenosis (p < 0.001). DUS was found to demonstrate a sensitivity of 79.7%, specificity of 79.2%, positive predictive value of 88.2%, and negative predictive value of 66.7% for lesions ≥ 70%. The 66.7% of the false-negative lesions with the lowest velocities were below the knee joint. DUS of the lower extremities is accurate in determining the degree of stenosis ranging from mild-to-severe disease. Some limitation may exist in estimating the degree of stenosis below the knee.

Improved characterization of popliteal aneurysms using gadofosveset-enhanced equilibrium phase magnetic resonance angiography

Although standard magnetic resonance angiography (MRA) has many advantages in the evaluation of peripheral artery disease, it has poorer spatial resolution compared with computed tomographic angiography and digital subtraction angiography. The MRA blood pool contrast agents have an extended half-life. By allowing longer imaging times, MRA enables the acquisition of high-resolution images as well as providing simultaneous visualization of both arteries and veins. Two cases of popliteal artery aneurysm are presented, in which MRA with a blood pool contrast agent provided critical clues to the correct diagnosis: a traumatic pseudoaneurysm of the popliteal artery caused by a femoral osteochondroma and a large fusiform popliteal aneurysm compressing the adjacent popliteal vein, causing venous congestion and leg pain.

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.