T1-MAPPING BY CARDIAC MAGNETIC RESONANCE IMAGING: FROM HISTOLOGICAL VALIDATION TO CLINICAL IMPLICATION

Abstract

Background: Extracellular volume (ECV) expansion is a key feature of heart failure. CMR T1-mapping has recently been developed as a non-invasive technique to estimate the ECV. However, the diagnostic and prognostic impact of this technique is not well established. Methods: 473 consecutive patients referred to CMR (49.5% female, 57.8±17.1 years) without hypertrophic cardiomyopathy, cardiac amyloidosis, or Anderson-Fabry disease were studied. T1-mapping using the Modified Look-Locker Inversion recovery (MOLLI) sequence was used for ECV calculation (CMR-ECV). For methodological validation, 36 patients also underwent left ventricular biopsy and ECV was quantified by TissueFAXS analysis (TissueFAXS-ECV). To assess the prognostic value of CMR-ECV, its association with hospitalization for cardiovascular reasons / cardiac death was tested in a multivariable Cox-regression model. Results: TissueFAXS-ECV was 26.3±7.2% and was significantly correlated with CMR-ECV (r=0.493, p=0.002). Patients were followed for 13.3±9.0 months and divided into CMR-ECV tertiles for Kaplan-Meier analysis (tertiles: ≤25.7%, 25.8-28.5%, and ≥28.6%). Significantly higher event rates were observed in patients with higher CMR-ECV (log-rank: p=0.013). By multivariable Cox-regression analysis, CMRECV was independently associated with outcome among imaging variables (p=0.004) but not after adjusting for clinical parameters. Conclusions: CMR T1-mapping allows accurate non-invasive quantification of ECV, and is independently associated with event-free survival among imaging parameters. Its prognostic value on top of established clinical risk factors warrants further investigation in long-term studies.