Ferumoxytol MRA for transcatheter aortic valve replacement planning with renal insufficiency

Abstract

Background Computed tomography angiography (CTA) is the test of choice for pre-procedure imaging of transcatheter aortic valve replacement (TAVR) candidates. The iodinated contrast required, however, increases the risk of renal dysfunction in patients with pre-existing renal failure. Ferumoxytol is a magnetic resonance imaging (MRI) contrast agent that can be used with renal failure. Its long vascular resonance time allows gated MRA sequences that approach CTA in image quality. We present respiratory and cardiac gated MRA enabled by ferumoxytol that can be post-processed in an analogous fashion to CTA. Methods Seven patients with renal failure presenting for TAVR were imaged with respiratory and cardiac gated MRA at 3T using ferumoxtyol for contrast. Aortic annulus, root and peripheral access dimensions were calculated in a fashion identical to that used for CTA. Of these, 6 patients underwent a TAVR procedure and 5 had intraoperative valve assessment with transesophageal echocardiograph (TEE) using standard clinical protocols that employed both two- and three-dimensional techniques. Results Good correlation between MRA aortic annulus measurements and those from TEE were shown in 5 patients with mean annulus area of 392.4 mm2 (290–470 range) versus 374.1 mm2 (285–440 range), with a pairwise correlation coefficient of 0.92, p=0.029. All patients received Sapien valve implants (one 20 mm, three 23 mm, and two 26 mm valves). Access decisions were guided by MRA with no complications. Annulus sizing resulted in no greater than trace/mild aortic regurgitation in all patients. Conclusions Ferumoxytol MRA is a safe alternative to CTA in patients with renal failure for pre-TAVR analysis of the aortic root and peripheral access.

Gated thoracic magnetic resonance angiography at 3T: noncontrast versus blood pool contrast

“…With its T1-shortening effect and long intravascular residence time of over 12 h, it is well suited for the steady-state imaging that longer respiratory and cardiac sequences require [15]. In a small cohort of patients, ferumoxtyol-enhanced MRA has shown promise for TAVR planning [8]. An alternative blood pool MRI contrast agent, gadofosveset (Ablavar, Lantheus Medical), was withdrawn from production in 2016.…”

“…Furthermore, we included a CTA reference for reproducibility of measurements to provide context for our data. In a previous publication, we found USPIO MRA had comparable measurement of aortic annulus area with trans-esophageal echocardiography (TEE) as the gold standard using a similar 3D MRA protocol [8]. The blood pool contrast agent used (ferumoxtyol) has a higher reported incidence of anaphylaxis than gadolinium (1:10,000) [16].…”

“…A standard T2 preparation (40 ms) was used for the non-contrast MRA to improve contrast between the lumen and surrounding tissues [6, 7]. An inversion recovery preparation (200 ms) was used for the contrast-enhanced MRA to enhance the lumen to background contrast, as the contrast media has short T1 values [8]. The non-contrast MRA had a TR/TE of 6.3/3.1 ms, a bandwidth of 399 Hz/pixel, a flip angle of 12°, an echo train length of 45, resulting in a 283 ms acquisition window acquired during diastole.…”

“…Instead, gated native (noncontrast) three-dimensional (3D) MRA approaches have been employed and correlate well with CTA for aortic annulus sizing [6, 7]. A separate approach that has shown promise for TAVR planning is the use of a non-gadolinium blood pool contrast agent with a long enough intravascular resonance time to allow high-resolution, gated 3D MRA [8]. A unique advantage of this iron-based blood pool contrast agent (ferumoxtyol) is that it is appropriate for patients with renal failure.…”

3D transesophageal echocardiography in TAVR

“…Small studies have compared its use in TAVR sizing with 3D TEE and CT and found comparable efficacy with no differences in significant PVL or mortality. 13,14 Increasing availability of this technique will add options for those unable to undergo CT planning.…”