Tissue Characterization in Cardiology: Moving Beyond Function.

Cardiovascular Magnetic Resonance (CMR) offers accurate and highly reproducible tissue characterization, beyond cardiac function. Late gadolinium enhancement (LGE), although represents a noninvasive biopsy for fibrosis quantification, it is unable to detect diffuse myocardial disease. Native T1 mapping and extracellular volume fraction (ECV) are able to provide important information about processes involving both myocardial cells and interstitium that otherwise cannot be identified. Changes in myocardial native T1 mapping reflect cardiac diseases such as acute coronary syndromes, myocardial infarction, myocarditis, diffuse fibrosis, systemic disease such as cardiac amyloidosis, all presented with high T1 and Anderson-Fabry disease and siderosis, presented with low T1 mapping. The ECV, an index generated by native and postcontrast T1 mapping, introduces a new way to measure the cellular and extracellular interstitial matrix (ECM). ECV has a prognostic value equal to Left ventricular ejection fraction (LVEF); however, LVEF underscores the interstitial matrix. This myocyte-ECM dichotomy has important implications for identifying therapeutic targets that are of great value for heart failure (HF) treatment. Furthermore, T2 mapping is superior compared with myocardial T1 and ECM for assessing the activity of myocarditis in recent-onset HF. These indices will affect significantly the clinical decision making. However, there is still lack of multicenter studies and community-wide approach including MRI vendors, clinicians, fundings, softwares, and contrast agent manufacturers.