Abstract： Objective:To explore whether left ventricular interstitial fibrosis is associated with left atrial enlargement and left atrial dysfunction in patients of hypertrophic cardiomyopathy(HCM) with preserved ejection fraction.Methods:From October 2018 to September 2021, 59 HCM including 30 with enlarged maximal left artrial volume index (LAVI max), 29 with normal LAVI max and 28 age-and gender-matched controls were retrospectively enrolled. Imaging protocol included cine sequence, late gadolinium enhancement and T 1 mapping.The relationships between left ventricular mass index (LVMI), quantitative myocardial fibrosis and left atrial-related indexes were analyzed. One-way analysis of variance with Bonferroni post hoc correction or Kruskal-Wallis was performed for continuous variables. Categorical variables were assessed using the Chi-square test or Fisher′s exact test. Pearson or Spearman analysis was used for linear or monotonic nonlinear correlations. Results:The left ventricular end-diastolic volume index, left ventricular end-systolic volume index, left ventricular cardiac output and LVMI of HCM with enlarged LAVI max group were higher than HCM with normal LAVI max group and control group( P<0.05).Correlation analysis showed that LVMI correlated positively with LAVI max( r=0.780, P<0.001) and minimal left artrial volume index (LAVI min) ( r=0.816, P<0.001), extracellular volume correlated positively with LAVI max( r=0.462, P<0.001) and LAVI min( r=0.483, P<0.001),%LGE was correlated positively with LAVI max( r=0.311, P<0.05) and LAVI min( r=0.327, P<0.05),left ventricular index interstitial volume was correlated negatively with left atrial ejection fraction of reservoir ( r=-0.669, P<0.001),left atrial ejection fraction of conduit ( r=-0.472, P<0.001),left atrial ejection fraction of pump ( r=-0.518, P<0.001)and left atrial expansion index( r=-0.626, P<0.001). Conclusion:There is association between LVMI and fibrosis and left atrial enlargement and phases dysfunction in HCM with preserved ejection fraction.