Abstract 16863: Cardiac Magnetic Resonance T1 Mapping as a Window Into the Myocardium in Friedreich Ataxia

Abstract

Introduction: Left ventricular (LV) remodeling and hypertrophy are common findings in Friedreich Ataxia (FA) and associated with a poorer prognosis. Cardiac magnetic resonance (CMR) T1 mapping, a technique used to assess myocardial fibrosis, may be able to identify cardiomyopathic changes in FA at an early stage of the cardiac disease process. We hypothesized that T1 mapping variables would demonstrate myocardial involvement in FA independently of the recognized LV structural and functional changes. Methods: A standardized CMR protocol including T1 mapping and measurements of LV mass, LV end-diastolic volume, native T1 time, post gadolinium (PostGad) T1 time, and calculation of the LV mass/volume ratio (LVMVR), partition coefficient (PC), and extracellular volume (ECV) was performed at two sites on FA subjects who were homozygous for GAA repeats in the FXN gene. GAA repeat length in the shorter allele (GAA1) of the frataxin gene ( FXN ) was used as a surrogate for the degree of frataxin deficiency. Results: Ninety-five FA subjects (56% males, median age 22 yrs, age of onset 10 yrs, GAA1 700) were scanned. Nine FA subjects had a LV ejection fraction (EF) <55%; their T1 variables were not different than those with preserved LVEF. Fifty-three subjects had an elevated LVMVR (>1.20); their T1 variables were not different from those without an elevated LVMVR. On multivariate analysis, GAA1 correlated with native T1 time (p=0.009), PostGad T1 time (p=0.003), PC (p<0.001), and ECV (p<0.001) after adjusting for sex, age and site. LVMVR was a correlate of native T1 time when adjusted for sex, age and site (p=0.019), but not when also adjusted for GAA1, whereas GAA1 still predicted native T1 when adjusted for sex, age, site, and LVMVR (p=0.018). Conclusion: T1 mapping provides information about the myocardium in FA which is correlated with the degree of frataxin deficiency and is independent of LV remodeling. Study of the relationship between T1 variables and cardiac outcomes is now needed to help determine the utility of this technique as a monitoring and prognostic biomarker for this rare disease.