Noninvasive Assessment of Myocardial Inflammation by Cardiovascular Magnetic Resonance in a Rat Model of Experimental Autoimmune Myocarditis
Background—Limited availability of non-invasive and biologically precise diagnostic tools poses a challenge for the evaluation and management of patients with myocarditis.
Methods and Results—The feasibility of cardiovascular magnetic resonance (CMR) imaging with magneto-fluorescent nanoparticles (MNPs) for detection of myocarditis and its effectiveness in discriminating inflammation grades were assessed in experimental autoimmune myocarditis (EAM) (n = 65) and control (n = 10) rats. After undergoing CMR, rats were administered with MNPs, followed by a second CMR 24 hours later. Head-to-head comparison of MNP-CMR with T2-weighted, early and late gadolinium enhancement CMR was done in additional EAM (n=10) and control (n=5) rats. Contrast-to-noise ratios (CNRs) were measured and compared between groups. Flow cytometry and microscopy demonstrated infiltrating inflammatory cells engulfed MNPs, resulting in altered myocardial T2* effect. Changes in CNR between pre- and post-MNP CMR were significantly greater in EAM rats (1.08 ± 0.10 vs. 0.48 ± 0.20; P < 0.001). In addition, CNR measurement in MNP-CMR clearly detected the extent of inflammation (P < 0.001) except for mild inflammation. As compared with conventional CMR, MNP-CMR provided better image contrast (CNR change 8% vs. 46%, P < 0.001) and detectability of focal myocardial inflammation. Notably, MNP-CMR successfully tracked the evolution of myocardial inflammation in the same EAM rats.
Conclusions—MNP-CMR permitted effective visualization of myocardial inflammatory cellular infiltrates and distinction of the extent of inflammation compared with conventional CMR in a preclinical model of EAM. MNP-CMR performs best in EAM rats with at least moderate inflammatory response.
- Received October 23, 2011.
- Accepted April 16, 2012.
- Copyright © 2012, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited