The Impact of advanced tissue characterization techniques using cardiac magnetic resonance imaging on the assessment of cardiac remodeling in patients with non-ischemic cardiomyopathies

Introduction Interstitial myocardial fibrosis and myocardial oedema are major contributors to cardiac remodeling and the development of heart failure in patients with cardiomyopathy (CMP). Purpose This study is based on the hypothesis that native T1 time, which measures interstitial myocardial fibrosis, and T2 time, which quantifies myocardial edema, correlate with disease progression in patients with non-ischemic CMP and, consequently, with various parameters of cardiac structure and function. Method We retrospectively analyzed a cohort of patients with non-ischemic CMP who underwent CMR at two medical centers, between January 2021 and March 2022. Out of the 594 patients who underwent CMR examinations, 272 met the criteria for non-ischemic CMP. All CMR studies were performed using a 1.5 Tesla scanner (Siemens, Erlangen, Germany). T1 time was assessed at the level of the interventricular septum, excluding areas of focal fibrosis. T2 time was analyzed at the level of the interventricular septum or as the mean between it and areas of hypersignal. Results Regarding cardiac structure and function parameters, native T1 time was inversely correlated with left ventricular ejection fraction (LVEF) (r = -0.2576, p = 0.0001) and positively correlated with indexed left ventricular volumes (LVEDVi (r = 0.296, p < 0.0001)and LVESVi (r = 0.3378, p < 0.0001)) and indexed left ventricular (LV) mass (r = 0.2183, p = 0.0126). However, native T1 time, did not correlate with the presence of focal fibrosis (r = 0.0623, p = 0.3353), instead, was correlated with the number of focal scars (r = 0.321, p < 0.001). T2 time significantly correlated with the presence of focal fibrosis (r = 0.1697, p = 0.0068) and its extent (r = 0.2949, p < 0.0001). T2 time also correlated with indexed LV mass (r = 0.266, p = 0.0024) and LVEF (r = 0.1291, p = 0.0402). Notably, native T1 time was significantly prolonged in symptomatic patients, correlating with NYHA functional class (r = 0.437, p = 0.001). Conversely, T2 time did not show a significant correlation with NYHA functional class (r = 0.118, p = 0.061). Conclusions Native septal T1 time, demonstrated a significant correlation with cardiac structure and function parameters such as LVEF, LV volumes, and LV mass in patients with non-ischemic CMP. Additionally, native T1 time correlated with the extent of focal fibrosis and NYHA functional class. T2 time showed a weak but statistically significant correlation with indexed LV mass and indexed LVESV. Furthermore, it correlated with both the presence of focal fibrosis and its extent, supporting the hypothesis that myocardial edema plays a key role in myocyte apoptosis and fibrosis development. These findings emphasize the importance of monitoring both native T1 and T2 times for a comprehensive assessment of myocardial pathology and disease progression in non-ischemic CMP patients.