2.3 Surgical procedure
The operations were performed by the same surgeon. Both groups of patients underwent MIAVR via an upper sternum approach. Briefly, an upper hemisternotomy to the right side was performed in the midline and the third or fourth intercostal space guided by the preoperative chest computer tomography (CT), forming a J-shape incision. The distal ascending aorta was cannulated. Multi-stage venous cannulation (Medtronic, Minneapolis, MN) was performed through the femoral vein. The ascending aorta was cross-clamped and crystalloid was perfused antegrade through the aortic root soon after initiating CPB, while letting the nasopharyngeal temperature drip to 32-34°C. If the patient has combined aortic valve insufficiency, the crystalloid was perfused through the coronary artery sinus after the ascending aorta was incised. A transverse incision was made 1 cm above the sinotubular junction, and 3 traction sutures were drawn on the upper and lower edges of the incision to expose the aortic valve. In the FLS group, scissor was used to cut off as many diseased leaflets as possible, and a nerve hook was used to incise a gap at the base of the calcified nodule to loosen the connective tissue of the spongiosa layer, then the fibrosa layer at the calcified tissue could be completely peeled off easily (Fig. 1 and the Supplementary Video S1). This method ensures complete removal of the calcified tissue on the valve stump and the annulus. In the conventional group, calcified tissue on the valve stump and annulus was mechanically crushed by rongeur forceps, before the calcified debris was carefully removed. Once the diseased valve was excised and annulus debrided, a Carpentier-Edwards Perimount Magna aortic pericardial valve (Edwards Lifesciences, Irvine, CA) was implanted with continuous or interrupted suturing. The traction sutures were removed and the aortotomy was closed. Once the patient was weaned from CPB, transesophageal echocardiography was employed to assess effective orifice area (EOA), mean gradient, correct positioning of the prosthesis and possible paravalvular leak (PVL). A single mediastinal drainage tube was placed into the anterior mediastinum before the closure of chest.