Abstract 15985: Myocardial Infarct Characterization Using Magnetic Resonance Imaging Without Contrast Agents
Introduction: Late gadolinium enhanced (LGE) MRI is frequently used to evaluate myocardial viability, estimate total infarct size and transmurality, but is uncomfortable, unsuitable for short-term follow-up, and contraindicated in patients with renal failure because of the risk of nephrogenic systemic fibrosis (NSF).Hypothesis: Endogenous contrast (T1ρ) MRI can be used to accurately quantify myocardial infarct size.
Methods: 3D short-axis LGE and T1ρ MRI (3 T TIM Trio; Siemens Healthcare, Erlangen, Germany) was performed in vivo in Yorkshire swine (N=5) 8 weeks following surgical induction of apical MI via left thoracotomy. Swine were sacrificed and hearts excised and splayed for photographic planimetry (PLN). Infarct size was computed from MR and optical images using a gradient descent segmentation algorithm interfaced to ImageJ (NIMH, Bethesda, MD). Statistical analysis was performed by 2-Way ANOVA and differences analyzed by a Bland-Altman test (Matlab 2010b, The Mathworks, Natick, MA).
Results: Infarct size measured by T1ρ MRI (21.1 ± 1.4%) was not significantly different from LGE MRI (22.2 ± 1.5%) or planimetry (21.1 ± 2.7%; p<0.05). There was excellent agreement between the three techniques (Fig. 1), although mean infarct size difference was smaller between tomographic LGE- and T1ρ-MRI scans than between MRI and planimetry (Fig. 2). The latter underestimates infarct size at the endocardial surface.
Conclusion: The positive outcome of this investigation strongly suggests that T1ρ accurately depicts myocardial infarct size. Future study is essential in patients recommended for surgical revascularization or in quantitative studies of LV remodeling.
- © 2011 by American Heart Association, Inc.