No abstract

Background-Extracellular matrix expansion is a key element of ventricular remodeling and a potential therapeutic target. Cardiovascular magnetic resonance (CMR) T 1 -mapping techniques are increasingly used to evaluate myocardial extracellular volume (ECV); however, the most widely applied methods are without histological validation. Our aim was to perform comprehensive validation of (1) dynamic-equilibrium CMR (DynEq-CMR), where ECV is quantified using hematocrit-adjusted myocardial and blood T 1 values measured before and after gadolinium bolus; and (2) isolated measurement of myocardial T 1 , used as an ECV surrogate. Methods and Results-Whole-heart histological validation was performed using 96 tissue samples, analyzed for picrosirius red collagen volume fraction, obtained from each of 16 segments of the explanted hearts of 6 patients undergoing heart transplantation who had prospectively undergone CMR before transplantation (median interval between CMR and transplantation, 29 days). DynEq-CMR-derived ECV was calculated from T 1 measurements made using a modified Look-Locker inversion recovery sequence before and 10 and 15 minutes post contrast. In addition, ECV was measured 2 to 20 minutes post contrast in 30 healthy volunteers. There was a strong linear relationship between DynEq-CMR-derived ECV and histological collagen volume fraction (P<0.001; within-subject: r=0.745; P<0.001; r 2 =0.555 and betweensubject: r=0.945; P<0.01; r 2 =0.893; for ECV calculated using 15-minute postcontrast T 1 ). Correlation was maintained throughout the entire heart. Isolated postcontrast T 1 measurement showed significant within-subject correlation with histological collagen volume fraction (r=−0.741; P<0.001; r 2 =0.550 for 15-minute postcontrast T 1 ), but between-subject correlations were not significant. DynEq-CMR-derived ECV varied significantly according to contrast dose, myocardial region, and sex. Conclusions-DynEq-CMR-derived

No abstract