2.2 Study design
70 patients who met the above criteria were enrolled between February 2016 and December 2018, with the last follow-up in December 2019. Patients were randomly assigned to the FLS group (n=35) or the conventional group (n=35). Randomized numbers were generated by professional statisticians according to random digit table. 10 patients were excluded from the study for the following reasons: sudden death before operation (n=3), withdrawal of consent (n=5), admission to an intensive care unit (ICU) for mechanical ventilation (n=1), and violation of protocol (n=1). In addition, 2 patients in the FLS group and 1 patient in the conventional group underwent concomitant aortic annular enlargement due to a small aortic annulus mismatched with BSA. Therefore, 28 (28/30) patients in the FLS group and 29 (29/30) patients in the conventional group were included in per-protocol analysis.