Imaging of Cardiac Fibrosis: An Update, From the AJR Special Series on Imaging of Fibrosis.

Myocardial fibrosis (MF) is defined as excessive production and deposition of extracellular matrix (ECM) proteins, resulting in pathologic myocardial remodeling. Three types of MF have been identified: replacement fibrosis from tissue necrosis, reactive fibrosis from myocardial stress, and infiltrative interstitial fibrosis from progressive deposition of non-degradable material such as amyloid. While echocardiography, nuclear medicine, and CT play important roles in the assessment of MF, MRI is pivotal in the evaluation of MF, using the late gadolinium enhancement (LGE) technique as a primary endpoint. The LGE technique focuses on the pattern and distribution of gadolinium accumulation in the myocardium and assists the diagnosis and establishment of the etiology of both ischemic and non-ischemic cardiomyopathy. LGE MRI aids prognostication and risk stratification. In addition, LGE MRI is used to guide management of patients being considered for ablation for arrhythmias. Parametric mapping techniques, including T1 mapping and extracellular volume measurement, allow detection and quantification of diffuse fibrosis, which may not be detected by LGE MRI. These techniques also allow monitoring of disease progression and therapy response. This review provides an update on imaging of MF, including prognostication and risk stratification tools, electrophysiologic considerations, and disease monitoring.