2.2 Preoperative evaluation
Preoperative transthoracic echocardiography (TTE) examination was
performed to define (1) the location and magnitude of any left
ventricular pressure gradient, both at rest and with provocation; (2)
the distribution and severity of myocardial hypertrophy; (3) MV anatomy
and function; (4) the presence of mitral subvalvular anomalies including
abnormal chordae tendineae attached to the ventricular septum or free
wall (false cords), fibrotic and retracted secondary chordae inserted on
the anterior mitral leaflet body, and papillary muscle (PM)
abnormalities (hypertrophy, and direct insertion into the anterior
mitral valve leaflet); and (5) the presence of intrinsic MV disease
including lesions of mitral leaflets and mitral annulus. Resting LVOT
velocity was measured by continuous-wave Doppler of the outflow tract
from an apical window, and the resting LVOT pressure gradient was
estimated by using the modified Bernoulli equation (i.e.,
gradient = 4v2, where v = peak LVOT velocity). In
patients with resting LVOT gradients < 30 mmHg, maneuvers such
as the Valsalva maneuver and stand-to-squat were frequently used. In
addition, cardiac magnetic resonance was frequently used to measure
basal septal thickness and for characterization of PM morphology and
location within the left ventricular cavity, PM thickness, and PM
mobility.