4.1 Study Limitations
The limitations of our study that need to be addressed. First, this was a single-center retrospective study with a small sample size. Second, in this study, we estimated the EOA using the PHT. There are several methods that can be used to calculate the EOA, and, depending on the cases, the PHT may not accurately reflect the actual EOA, which can result in an inaccurate diagnosis of PPM. Third, because this study did not have a randomized design, it is possible that unidentified confounders or selection bias may have influenced the results. Fourth, the preoperative values of the LA and LV diastolic diameters could not be obtained in several patients. Thus, further prospective studies are necessary to determine the impact of PPM on late outcomes.