A Novel Ferumoxytol-enhanced Cardiac Magnetic Resonance Imaging for the Detection of Intracardiac Thrombus

Overview

The incidence of thrombosis in ventricular aneurysm was reported to be 35%-40%, which may lead to systemic thromboembolism. Patients with ventricular aneurysm without detectable thrombus are not routinely treated with anticoagulation. Therefore, the accuracy of intracardiac thrombus detection has an important impact on clinical management decisions. Currently, transthoracic echocardiography is the most commonly used method to detect intracardiac thrombus, but its sensitivity and positive predictive value are low. Cardiac magnetic resonance has a higher diagnostic accuracy for intracardiac thrombus, and its sensitivity and positive predictive value are higher than those of transthoracic echocardiography and CT. However, the gadolinium-based contrast agents commonly used for enhanced magnetic resonance imaging have some problems such as nephrogenic systemic fibrosis, gadolinium deposition in the brain, and short imaging time. Ferumoxytol, a superparamagnetic iron oxide nanoparticle, can be used for off-label enhanced magnetic resonance imaging. Its long intravascular half-life makes it suitable for enhanced magnetic resonance imaging with complex scanning procedures and long repetitive scans. Ferumoxytol is cleared from the blood pool by macrophages of the reticuloendothelial system, mainly in the spleen and lymph nodes. Therefore, ferumoxytol has a favourable safety even in adults and children with end-stage renal failure. The aim of this study is to evaluate the effectiveness of a novel ferumoxytol-enhanced cardiac magnetic resonance in detecting intracardiac thrombus in patients with ventricular aneurysm and after percutaneous ventricular reconstruction.

Ferumoxytol is a member of ultrasmall superparamagnetic iron oxide particles with an average diameter of 30 nm, originally developed as an intravascular contrast agent for MRI. Ferumoxytol was approved by the FDA in 2009 for the intravenous treatment of iron deficiency anaemia in adults with chronic kidney disease, and has also been used off-label as a non-gadolinium contrast agent for whole-body magnetic resonance imaging. Its iron oxide core is coated with dextran, which reduces immunogenicity and delays phagocytosis and the release of elemental iron from the core. As a result, ferumoxytol has a long intravascular half-life of approximately 15 hours and is slowly taken up by the macrophages of the reticuloendothelial system. Because of its long half-life, ferumoxytol is suitable for enhanced magnetic resonance imaging with complex scanning procedures and long repetitive scans. Ferumoxytol has been proved to be safe even in adults and children with end-stage renal failure. As feraheme is not available in the Chinese market, we experimentally synthesised a new formulation of ferumoxytol, which is identical to ferumoxytol in terms of physicochemical structure, pharmacokinetics and toxicological effects, at the request of Chia Tai Tianqing Pharmaceutical Group Co, Ltd (Nanjing, China) in 2014. This study is a single-centre, prospective, observational, non-randomised study. The study will enrol patients with ventricular aneurysm and after percutaneous ventricular reconstruction. The aim of this study is to evaluate the effectiveness of ferumoxytol-enhanced cardiac magnetic resonance imaging in detecting intracardiac thrombus in patients with ventricular aneurysm and left ventricular thrombus in the dynamic chamber and static chamber in patients 180±30 days after percutaneous ventricular reconstruction by comparing the detection rate of intracardiac thrombus with ferumoxytol-enhanced cardiac magnetic resonance imaging and transthoracic echocardiography, and to provide a clinical basis for the development and application of the new generation of magnetic resonance contrast agents in China. The echocardiography and magnetic resonance imaging experts were blinded to each other's results.