Non-invasive assessment of early and acute myocarditis in a rat model using cardiac magnetic resonance tissue tracking analysis of myocardial strain.

Abstract

Myocardial strain analysis can provide diagnostic and prognostic information for myocarditis. The aim of the present study was to assess early and acute myocarditis in a rat model using cardiac magnetic resonance tissue tracking (CMR-TT) for myocardial strain analysis. We compared the strain's findings with the histological and immunohistochemical results. Experimental autoimmune myocarditis (EAM) was induced by footpad injections of porcine cardiac myosin. The rats were examined by 7.0T preclinical CMR at day 14 (n=15) and day 21 (n=16) after EAM induction and the two control groups (each n=15) were also examined at day 14 and day 21, respectively. Using CMR-TT, we found a global peak systolic radial strain (ErrSAX) and a circumferential strain (EccSAX) from the short-axis cine views and a radial strain (ErrLAX) and a longitudinal strain (EllLAX) from the long-axis cine views, which were calculated by dedicated TT software. Subsequently, histological and immunohistochemical evaluations were performed. EllLAX significantly decreased in early myocarditis compared with the control (-23.40%±1.48% vs. -22.02%±0.81%, P<0.05). ErrSAX, EccSAX, ErrLAX, and EllLAX values significantly reduced in acute myocarditis compared with the controls (ErrSAX: 34.27%±9.80% vs. 49.76%±4.97%, EccSAX: -18.98%±3.69% vs. -24.13±1.23, ErrLAX: 33.21%±10.24% vs. 49.59%±5.69%, and EllLAX: -17.75%±3.58% vs. -23.39%±1.48%; P<0.001, respectively). The receiver operating characteristic curve showed that myocardial strain analysis had a good diagnostic performance in early and acute myocarditis. The pathological evaluation revealed that inflammatory lesions began to appear in early myocarditis and peaked in acute myocarditis. The CMR-TT strain analysis allowed accurate and reliable evaluation of early and acute myocarditis in a rat model, and has the potential to serve as a diagnostic indicator for the assessment of myocardial dysfunction in myocarditis.