MRA With Feraheme in HHT

Overview

Magnetic resonance (MR) imaging is performed with contrast agents to highlight the blood vessels and allow interpretation and diagnosis of blood vessel abnormalities. HHT (Hereditary Hemorrhagic Telangiectasia) is a disease of blood vessels, and can suffer fatal bleeding if abnormal blood vessels are not detected and treated early. Patients with HHT also require many imaging studies through their lifetimes for surveillance of blood vessels. Many HHT patients also have co-existing iron deficiency anemia from bleeding in their nose and gastrointestinal tract, and receive daily iron therapy. Ferumoxytol is an alternative MR contrast agent, which is FDA (Food and Drug Administration) approved for the treatment of iron deficiency anemia. In addition, it is not associated with the risks to the kidneys of the other agents. The use of ferumoxytol for MR imaging may benefit the patients who do not currently receive imaging due to the contraindications of the conventional contrast agents. It avoids the use of ionizing radiation. Also, the conventional contrast agents are associated with risks. Iodinated contrast in CT is associated with significant risks of kidney damage. Another imaging technique, MR, uses gadolinium based contrast agents. Gadolinium, if used in patients with pre existing kidney dysfunction (defined as GFR \< 30ml/min) is associated with the development of another devastating disease called nephrogenic systemic fibrosis. As HHT patients will require repeated scans throughout their lifetimes, this study will provide them a safer alternative. Ten patients from the HHT clinic in whom the use of ferumoxytol as an MR agent is clinically indicated will be invited to participate in this study, which will determine if MR with ferumoxytol is able to detect and characterize vascular malformations in HHT.

The safety of the use of gadolinium based contrast agents in MR is a concern for the FDA, with risks of development of nephrogenic systemic fibrosis and the more recent discovery of accumulation of gadolinium in the brain in patients who have received multiple prior MR scans. Hereditary hemorrhagic telangiectasia (HHT) manifests with multiple vascular malformations (VMs) in the skin, mucous membranes and solid organs affecting the spine, brain, liver, gastrointestinal tract, pancreas, and lungs. The disease has an autosomal dominant inheritance and affects 1 in 5000 individuals. Cerebral vascular malformations occur in 23 % of HHT patients, with a bleeding risk of 0.5% per year. Pulmonary AVMs occur in 15-50% of HHT patients, with a complication rate of 50% ranging from fatal hemoptysis or hemothorax to stroke or cerebral abscess. Liver vascular malformations are present in 32-78% of HHT patients. The rationale for screening for vascular malformations is detection of a treatable lesion prior to the development of a fatal complication. The international guidelines currently recommend different first line screening tests in each organ: MRI for cerebral VMs, transthoracic echocardiography for pulmonary VMs, endoscopy for gastrointestinal VMs, Doppler US or CT for liver VMs. Contrast enhanced magnetic resonance angiography (CE-MRA) may play an important role in the simultaneous whole body screening of vascular malformations. The advantages of CE-MRA include visualization of the entire body vasculature in one examination, high spatial resolution comparable to CT, no ionizing radiation and easy of multiplanar reconstructions. Substituting a conventional gadolinium based contrast agent (GBCA) with an ultra small, super paramagnetic iron oxide agent (USPIO) e.g ferumoxytol, will eliminate any potential risk of developing nephrogenic systemic fibrosis. Since 2009, ferumoxytol ('Feraheme' Advanced Magnetics, Cambridge, MA) has been FDA approved for the treatment of iron deficiency anemia in adult patients with chronic kidney disease. The results of prior studies suggest that ferumoxytol is comparable to standard GBCAs for CE- MRA. Our experience with use of ferumoxytol to date suggests that it will be a superior agent for detection of vascular malformations in a range of vascular territories and that it will be uniquely capable of interrogating multiple territories in one sitting, due to its highly stable intravascular residence time.