Objective:To investigate the changes of strains based on feature tracking in patients with hypertrophic obstructive cardiomyopathy (HOCM) after surgical myectomy and the potential factors that influenced post-myectomy global strains.Methods:A total of 27 patients with HOCM who underwent septal myectomy in Fuwai Hospital from June 2014 to July 2017 were retrospectively collected. They all received cardiac MR (CMR) cine acquisitions before and after surgery. Their preoperative and postoperative strain parameters, including radial strain (RS), circumferential strain (CS), and longitudinal strain (LS) of the global left ventricle, septum, and lateral wall, were assessed by feature tracking. Comparisons of pre-myectomy and post-myectomy imaging parameters were performed using paired-samples t-test or Wilcoxon matched-pairs signed-ranks test. Pearson or Spearman correlation analysis and linear regression analysis were utilized to find the correlated factors of postoperative global strains. Results:Compared with preoperative strains, postoperative global LS, septal LS, lateral RS, lateral CS, and lateral LS increased statistically (all P<0.05); postoperative global RS, global CS, and septal CS decreased (all P<0.05); no statistically significant difference was observed in septal RS ( P=0.165). Age at surgery ( r=0.428, P=0.026) and preoperative myocardial maximum ventricular wall thickness ( r=-0.587, P=0.001) were both linearly related to postoperative global RS; the further multivariate stepwise linear regressions showed that only preoperative myocardial maximum ventricular wall thickness might be correlated with postoperative global RS (adjusted R 2=0.287, P=0.002). Only myocardial maximum ventricular wall thickness was linearly related to global CS ( r=0.679, P<0.001) and global LS ( r=0.588, P=0.001), respectively; univariate linear regression revealed that preoperative myocardial maximum ventricular wall thickness might be correlated postoperative global CS (adjusted R 2=0.337, P=0.001) and postoperative global LS (adjusted R 2=0.281, P=0.003), respectively. Conclusions:Cardiac surgery definitely relieves left ventricular outflow tract obstruction and generally improves longitudinal and lateral strains, but a negative impact may occur in global and septal CS and RS. Preoperative maximum ventricular wall thickness may affect postoperative global strains.