4.6 Study limitations
Data for this study were collected retrospectively from single center database. Accordingly, our study included some limitations. First, there were the numerous factors influencing our results such as the sample size as well as the risk for selection bias and the observer bias. Our study sample size was small, especially patients who had significant increase in LVOT gradient after the TMVI, leading to the statistical limitation to examine the impact of variables on LVOT narrowing. In addition, the population was very heterogeneous in terms of TMVI settings (ViV, ViR, and ViN). Further, the measurer could not measure all the parameters blindly because the measurer knew that a prosthetic valve was placed. Second, the current study evaluated the LVOT narrowing after the balloon-expandable transcatheter aortic valves implantation in the mitral position. The data would differ if a different transcatheter mitral valve was used.