1.1 Clinical data Sixty-two patients with 19-gauge aortic valve replacement (referred to as the 19-mm valve group) accounted for 1.2% of the simultaneous valve replacements (62 cases/5167 cases), including 26 cases of rheumatic heart valve disease, 15 cases of degenerative lesions, and 21 cases of congenital lesions. Another 62 patients were selected for simultaneous replacement of mechanical valves of 21 or more (referred to as the 21 mm valve group), including 38 cases of rheumatic heart valve disease, 20 cases of degenerative lesions, and 4 cases of congenital lesions. 1.2 Surgical methods The surgeries were performed under medium and low temperature extracorporeal circulation, with cold crystalloid high-potassium stopping solution instilled in the aortic root and ice chips placed in the pericardial cavity for myocardial protection. The aortic annulus was replaced with a mechanical valve by interrupted mattress sutures with 2-0 valve replacement thread, and no patients underwent annular enlargement. There was no difference in aortic block time and extracorporeal circulation time between the two groups, and all patients were completed by the same physician. 1.3 Follow-up and Data Collection All patients were followed up by letter, telephone, or in-hospital review. 51 patients were followed up in the 19-mm valve group and 48 patients were followed up in the 21-mm valve group. The follow-up period ranged from 2 to 101 months (56.3±37.2 months), with a total of 743.1 person-years of follow-up. The follow-up included postoperative echocardiographic changes, improvement of cardiac function, clinical symptoms and signs, etc. 1.4 Echocardiography The changes of left ventricular ejection fraction, left ventricular end-diastolic diameter, posterior wall thickness, weight index, aortic transvalvular pressure difference and other left heart function indexes in the two groups were detected before, 1 year and 5 years after surgery using HPSonos 5500 echocardiographic diagnostic instrument, and were compared and analyzed. 1.5 Statistical analysis The measurement data were expressed as mean ± standard deviation (±SD), and the paired t-test was used to compare the measurement data of the two groups of patients. The survival rate analysis of the two groups of patients was calculated by Kaplan-Meier survival curve, and the Log-rank test was used to compare the survival rates of the two groups. p<0.05 was considered a statistically significant difference. 2, Results No surgical death, 4 patients died one year after surgery in the 19 mm valve group, 1 died of left heart failure; 1 died of cerebral hemorrhage, the reason was related to the patient's previous history of cerebral hemorrhage, and oral warfarin was not rechecked for prothrombin time for half a year after surgery. 2 cases died of unknown causes. Sixteen patients died 5 years after surgery, including 7 cases of left heart failure, 4 cases of anticoagulation complications, and 4 cases of unexplained death.