Ferumoxytol-enhanced MR Angiography for Vascular Access Mapping before Transcatheter Aortic Valve Replacement in Patients with Renal Impairment: A Step Toward Patient-specific Care

Abstract

Purpose To assess the technical feasibility of the use of ferumoxytol-enhanced (FE) magnetic resonance (MR) angiography for vascular mapping before transcatheter aortic valve replacement in patients with renal impairment. Materials and Methods This was an institutional review board-approved and HIPAA-compliant study. FE MR angiography was performed at 3.0 T or 1.5 T. Unenhanced computed tomographic (CT) images were used to overlay vascular calcification on FE MR angiographic images as composite fused three-dimensional data. Image quality of the subclavian and aortoiliofemoral arterial tree and confidence in the assessment of calcification were evaluated by using a four-point scale (4 = excellent vascular definition or strong confidence). Signal intensity nonuniformity as reflected by the heterogeneity index (ratio between the mean standard deviation of luminal signal intensity and the mean luminal signal intensity), signal-to-noise ratio, and consistency of luminal diameter measurements were quantified. Findings at FE MR angiography were compared with pelvic angiograms. Results Twenty-six patients underwent FE MR angiography without adverse events. A total of 286 named vascular segments were scored. The image quality score was 4 for 99% (283 of 286) of the segments (κ = 0.9). There was moderate to strong confidence in the ability to assess vascular calcific morphology in all studies with complementary unenhanced CT. The steady-state luminal heterogeneity index was low, and signal-to-noise ratio was high. Interobserver luminal measurements were reliable (intraclass correlation coefficient, 0.98; 95% confidence interval: 0.98, 0.99). FE MR angiographic findings were consistent with correlative pelvic angiograms in all 16 patients for whom the latter were available. Conclusion In patients with renal impairment undergoing transcatheter aortic valve replacement, FE MR angiography is technically feasible and offers reliable vascular mapping without exposure to iodine- or gadolinium-based contrast agents. Thus, the total cumulative dose of iodine-based contrast material is minimized and the risk of acute nephropathy is reduced. ^© RSNA, 2017 Online supplemental material is available for this article.

Figure 1.

Conventional and emerging alternative vascular access sites for transcatheter aortic valve replacement (TAVR) are depicted in the ferumoxytol enhanced MRA image. Transfemoral and transapical approaches have been most widely used. Emerging alternative vascular access routes include transaortic, trans-subclavian, and transcaval.

Figure 2.

Qualitative assessment of image quality and vascular characteristics. Image quality was evaluated on a 4-point scale (1: non-diagnostic; 2: poor definition such that only gross features such as overall patency are evaluable; 3: good definition such that pathology can be confidently visualized or excluded; 4: excellent definition such that detailed anatomy is clearly visualized with sharp borders). A 4-point scale was also used to assess confidence in vessel tortuosity, calcific burden, calcific morphology, and atheroma (1: no confidence, 2: mild confidence, 3: moderate confidence, 4: strong confidence).

Figure 3.

FE-MRI for annular measurements and valve sizing. Multiplanar reformatted FE-MRA images are displayed and can be manipulated using a (a) double oblique technique to estimate transcatheter valve size and other vascular access sites. (b) Distance of the coronary arteries to the annular plane can also be assessed. White arrows show both right and left coronary ostia.

Figure 3.

FE-MRI for annular measurements and valve sizing. Multiplanar reformatted FE-MRA images are displayed and can be manipulated using a (a) double oblique technique to estimate transcatheter valve size and other vascular access sites. (b) Distance of the coronary arteries to the annular plane can also be assessed. White arrows show both right and left coronary ostia.

Figure 4.

FE-MRA at 3.0T. 89-year-old male with severe AS and chronic kidney disease (creatinine 1.7 mg/dL, stage 3b) presented for TAVR evaluation. 3D volume rendered and multiplanar reformat FE-MRA images demonstrate significant tortuosity of the iliofemoral vessels and areas of atheromatous changes (white arrows) near the bifurcation of the infrarenal abdominal aorta and bilateral iliac arteries. Fused 3D volume rendered and non-contrast CT image provide additional information on calcific morphology, location, and burden. Catheter angiogram of the right common iliac confirmed the diagnostic accuracy of the FE-MRA. A 26mm Edwards Sapien XT valve was successfully deployed via the transfemoral approach without complications.

Figure 5.

FE-MRA at 3.0T. 84-year-old male with severe AS and moderate renal impairment (creatinine of 1.7 mg/dL, stage 3b) presented for TAVR evaluation. First-pass and steady state (a) 3D volume rendered and (b) multiplanar reformat (MPR) FE-MRA of the entire aorta and pelvic access vessels show significant tortuosity. There is comparable luminal vascular enhancement between first-pass vs steady state imaging. (c) Post-contrast black blood HASTE imaging depicts atheromatous plaque morphology (red arrowhead) at the transverse aortic arch and incidental multiple renal cysts (black arrowhead). This patient had successful transfemoral placement of a 26mm Edwards Sapien valve.

Figure 5.

FE-MRA at 3.0T. 84-year-old male with severe AS and moderate renal impairment (creatinine of 1.7 mg/dL, stage 3b) presented for TAVR evaluation. First-pass and steady state (a) 3D volume rendered and (b) multiplanar reformat (MPR) FE-MRA of the entire aorta and pelvic access vessels show significant tortuosity. There is comparable luminal vascular enhancement between first-pass vs steady state imaging. (c) Post-contrast black blood HASTE imaging depicts atheromatous plaque morphology (red arrowhead) at the transverse aortic arch and incidental multiple renal cysts (black arrowhead). This patient had successful transfemoral placement of a 26mm Edwards Sapien valve.

Figure 5.

FE-MRA at 3.0T. 84-year-old male with severe AS and moderate renal impairment (creatinine of 1.7 mg/dL, stage 3b) presented for TAVR evaluation. First-pass and steady state (a) 3D volume rendered and (b) multiplanar reformat (MPR) FE-MRA of the entire aorta and pelvic access vessels show significant tortuosity. There is comparable luminal vascular enhancement between first-pass vs steady state imaging. (c) Post-contrast black blood HASTE imaging depicts atheromatous plaque morphology (red arrowhead) at the transverse aortic arch and incidental multiple renal cysts (black arrowhead). This patient had successful transfemoral placement of a 26mm Edwards Sapien valve.