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.