Dynamic-equilibrium CMR-derived extracellular volume strongly correlated with histological collagen volume fraction (within-subject r=0.745, P<0.001; between-subject r=0.945, P<0.01).
Observational (n=36)
Effect estimate: r=0.745 (within-subject); r=0.945 (between-subject)
p-value: p=<0.001
BACKGROUND: Extracellular matrix expansion is a key element of ventricular remodeling and a potential therapeutic target. Cardiovascular magnetic resonance (CMR) T1-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 T1 values measured before and after gadolinium bolus; and (2) isolated measurement of myocardial T1, 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 T1 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 between-subject: r=0.945; P<0.01; r(2)=0.893; for ECV calculated using 15-minute postcontrast T1). Correlation was maintained throughout the entire heart. Isolated postcontrast T1 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 T1), 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 ECV shows a good correlation with histological collagen volume fraction throughout the whole heart. Isolated postcontrast T1 measurement is insufficient for ECV assessment.
Miller et al. (Thu,) conducted a observational in Patients undergoing heart transplantation and healthy volunteers (n=36). Dynamic-equilibrium CMR (DynEq-CMR) and isolated myocardial T1 measurement vs. Histological collagen volume fraction was evaluated on Correlation between CMR-derived ECV/T1 and histological collagen volume fraction (r=0.745 (within-subject); r=0.945 (between-subject), p=<0.001). Dynamic-equilibrium CMR-derived extracellular volume strongly correlated with histological collagen volume fraction (within-subject r=0.745, P<0.001; between-subject r=0.945, P<0.01).