Cardiac Magnetic Resonance Assessment of Myocardial Fibrosis

> I do not seek. I find.> > Pablo Picasso Diffuse interstitial myocardial fibrosis (DMF) and replacement myocardial fibrosis (or scar) are common features of a wide variety of pathological conditions of the heart and play an important role in the progression of heart failure. Recent advances in cardiac magnetic resonance (CMR) techniques now permit assessment of DMF as well as the commonly used scar imaging, or late gadolinium enhancement (LGE) methods.1 Recent work has shown the prognostic value of detecting DMF in patients with valvular heart disease and early diabetic cardiomyopathy.2,3 Although conventional LGE techniques can successfully identify replacement fibrosis in conditions such as acute and chronic myocardial infarction and hypertrophic cardiomyopathy, they are less suitable imaging methods for detecting DMF because there may be little normal myocardium available to compare with affected areas. Fibrosis shortens the postcontrast longitudinal relaxation time (T1) properties of myocardium, and this feature may be exploited in DMF because T1 can be directly measured by CMR, using specific pulse sequences in a strategy known as T1 mapping. Among them, the modified Look-Locker inversion recovery (MOLLI) sequence has been used extensively by Messroghli and his colleagues in ischemic cardiomyopathy patients, whereas validation with histological analyses of fibrosis has been scarce. In their article published in this issue of Circulation: Cardiovascular Imaging , Messroghli and colleagues4 applied a custom MOLLI technique in a rat model of DMF to better account for potential weaknesses in the technique such as sensitivity to motion and heart rate.5 In addition to comparing T1 relaxation times before and after a 2-week infusion of angiotensin II to induce DMF, they also derived myocardial extracellular volume from hematocrit and T1 of blood and myocardium. The authors found a very …