Noninvasive Assessment of Myocardial Inflammation by Cardiovascular Magnetic Resonance in a Rat Model of Experimental Autoimmune MyocarditisClinical Perspective
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Background—Limited availability of noninvasive 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 performed in additional EAM (n=10) and control (n=5) rats. Contrast-to-noise ratios were measured and compared between groups. Flow cytometry and microscopy demonstrated that infiltrating inflammatory cells engulfed MNPs, resulting in altered myocardial T2* effect. Changes in contrast-to-noise ratio between pre- and post-MNP CMR were significantly greater in EAM rats (1.08±0.10 versus 0.48±0.20; P<0.001). In addition, contrast-to-noise ratio measurement in MNP-CMR clearly detected the extent of inflammation (P<0.001) except for mild inflammation. Compared with conventional CMR, MNP-CMR provided better image contrast (CNR change 8% versus 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—Magneto-fluorescent nanoparticle 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. Magneto-fluorescent nanoparticle CMR performs best in EAM rats with at least moderate inflammatory response.
- Received October 23, 2011.
- Accepted April 16, 2012.
- © 2012 American Heart Association, Inc.