Abstract 14728: Assessment of Myocardial Wall Thickness and T1 Mapping is Highly Reproducible in Multi-Center Trials: The Multi-Ethnic Study of Atherosclerosis (MESA)

Abstract

BACKGROUND: Myocardial wall thickness and extracellular volume in subclinical heart disease may be associated with alterations in myocardial tissue composition. The reproducibility of these parameters by cardiac MRI (CMR) in a multi-center study has not been assessed.

PURPOSE: We sought to test the reproducibility of two novel measurements, wall thickness by 3D modeling and T1 mapping, and to relate them to myocardial stiffness with cardiac tagging.

METHODS: MESA subjects who underwent CMR with tagging, T1 mapping and hematocrit data were included (n=605, mean age 67 +/- 8.7 years, 48% male); 10% (n=60) were randomly selected for reproducibility analysis. Mid-ventricular mid-wall global radial strain (Err) was obtained from myocardial tagging (HARP software, Diagnosoft). Wall thickness was obtained from cine images (CIM, Auckland MRI Research Group). T1 mapping was obtained from MOLLI sequences before / after (12, 25 min) 0.15 mmol/kg gadolinium. Extracellular volume fraction (ECV) was derived from T1 data as an index of interstitial fibrosis. Two independent readers assessed inter-reader reproducibility.

RESULTS: Segmental analyses of 960 myocardial regions (n=60) were used to assess reproducibility. Linear regression demonstrated strong inter-reader correlation for mid-ventricular wall thickness measurement with a very small bias (0.48 mm) by Bland-Altman analysis (Figure). Inter-reader ECV showed significant correlation (r=.91, p< 0.05). Mean wall thickening extracted from 3D models demonstrated significant correlation with radial strain (p=0.026, n=605). Myocardial wall thickness and radial strain showed inverse correlation with ECV (r= -0.13 and r= -0.45, respectively, p< 0.001).

CONCLUSIONS: Myocardial wall thickness and extracellular volume are both highly reproducible and related to increased myocardial stiffness. Our results suggest radial strain correlates better with ECV as expected, due to increasing myocardial fibrosis.