Abstract 18808: Relationship Between Myocardial Extracellular Volume and Myocardial Scar in Non-ischemic Cardiomyopathy Patients

Abstract

Background: Delayed Enhancement (DE) Cardiovascular magnetic resonance (CMR) has been established as the reference standard for assessment of myocardial replacement fibrosis (RF) in ischemic heart disease. However DE-CMR is unable to identify diffuse interstitial fibrosis (IF). Recently, T1 mapping of the myocardium following the administration of gadolinium contrast has been shown to identify increased extracellular volume (ECV) which occurs in the setting of IF. For this study we sought to evaluate the relationship between RF and IF in patients with nonischemic cardiomyopathy (NICMP). Method: We enrolled 80 consecutive patients with NICMP who underwent DE-CMR and T1 mapping using a modified look-locker inversion recovery (MOLLI) technique. The extent of RF was determined by analysis of DE-CMR images. The ECV was estimated from the concentration of extracellular contrast agent in the myocardium relative to the blood in the dynamic steady state. Care was taken to avoid measuring ECV in regions with RF detected on DE-CMR. Results: The cohort consisted of 61.3% of patients with RF. In RF group, the mean scar burden was 7.4±9.9% of left ventricle myocardium. Patients with RF had higher ECV compared to those without RF (36.1±10.7 and 31.9±6.7 respectively; p=0.04). The left ventricular ejection fraction (LVEF) and stroke volume (SV) were significantly lower in patients with increased ECV (p<0.005). Same relation held true for patients with RF (p<0.005). There was a significant increase in ECV for patients with RF of more than 5% of LV myocardium (p<0.001). In linear regression analysis, ECV is positively associated with scar burden (Beta weight=0.527, p<0.001). Conclusion: This study suggests that LVEF and SV are significantly lower in patients with increased ECV and for those with RF. There is a positive relationship between increased ECV and RF in patients with NICMP. There appears to be a threshold effect where the largest increase in IF occurs when there is more than 5% RF.