Abstract 18832: High-Resolution, Whole Heart T1 Mapping in a Chronic Atrial Fibrillation Model

Abstract

Introduction: Cardiac fibrosis is a marker of adverse remodeling of the heart. Cardiac T1 mapping is the only non-invasive method to assess diffuse myocardial fibrosis. However, existing T1 mapping techniques are not applicable for whole heart mapping with adequate spatial resolution to accurately evaluate the thin atrial wall. We have developed a novel, high-resolution, whole heart T1 mapping technique which can be used to characterize fibrosis in all cardiac chambers simultaneously. Methods: We applied the whole heart T1 mapping technique to study fibrosis progression in a canine, chronic atrial fibrillation (AF) model. Dogs (n=8) were subjected to rapid atrial pacing (RAP) and underwent baseline (n=8) and 8-month RAP MRIs (n=4) to evaluate myocardial fibrosis. Whole heart T1 mapping was performed on a 3 Tesla MRI scanner during slow contrast infusion (0.05 micromol/kg/sec of Gd-BOPTA). Spatial resolution of T1 mapping scans was 1.25x1.25x2.5 mm. T1 mapping was performed at least 30 minutes after start of slow contrast infusion to achieve steady-state for contrast distribution. Results: Figure 1a shows representative image of cardiac T1 maps that visualize the myocardium of all cardiac chambers clearly. Myocardium of LV and LA has similar T1 values in baseline scans (p=NS), which decreased significantly in the LV and LA 8 months after initialization of RAP (p<0.05, Fig. 1b). This change in T1 indicates increased fibrosis of left ventricle and atrium after 8 months of AF. Conclusions: High-resolution, whole heart T1 mapping technique can be used to non-invasively assess diffuse myocardial fibrosis in all cardiac chambers. T1 mapping indicates that 8-months RAP results in increased LV and LA fibrosis.