2.4 Surgical procedures
Operations were guided by intraoperative transesophageal echocardiography (TEE), with particular attention paid to ventricular septal anatomy as well as thickness, MV anatomy as well as function, and mitral subvalvular anatomy. The patient was put in the reverse Trendelenburg and left lateral decubitus position. Under general anaesthesia, the heart and ascending aorta were exposed by a median incision with sternotomy, and cardiopulmonary bypass with ascending aortic and right atrial cannulation was established with a left ventricular vent placing via the right superior pulmonary vein. Through a low oblique aortotomy approximately 7-10 mm above the right coronary ostium, the aortic valve leaflets were pulled up to gain access to the outflow tract, the hypertrophic cardiac muscle, anterior MV leaflet, and mitral subvalvular apparatus. A head lamp and loupe magnification were used to achieve better inspection of the left ventricular cavity. Special surgical instruments (as shown in Figure 1) were used during the resection. Scalpel resection was usually started at the nadir of the right cusp, 5 mm below the aortic valve and extending leftwards to the left trigone. The area of septal excision was lengthened beyond the bases of PMs and toward the apex of the heart. The depth of resection was up to 50% of the basal thickness of the septum. The excision of the hypertrophic muscles as a whole mass was required. In addition, mitral subvalvular anomalies were also corrected, including false cords cutting, retracted secondary chordae cutting, and hypertrophic PM release and/or resection. After resections were completed, the bases of the PMs should be seen by looking through the incision of the aortic root. And then, the outflow tract, mitral and aortic valves were carefully and thoroughly reexplored.
TEE was used after weaning off bypass to measure the maximum gradients and the severity of MR following myectomy. A repeat procedure was immediately performed if there was residual LVOT obstruction and/or residual moderate or more MR or if a ventricular septal defect or a left ventricular free wall rupture was observed. Residual obstruction was defined as a maximum gradient following myectomy > 30 mmHg.