2.2. Echocardiographic studies and image acquisition
The device used for conventional 2DE and RT3DE was the Philips IE33
system with a matrix array ultrasonographic transducer (X4.1 transducer;
Philips Medical Systems, Bothell, WA, USA). We used Simpson’s
biplane method for measurement of ejection fraction with in an apical 4
and 2 chamber views according to recent guidelines (7). After
endocardial tracing of borders at end systole and end diastole was
performed, we calculated LVEF with the formula by using LV end-diastolic
(EDV) and LV end-systolic volumes (ESV) as follows: EF = (EDV-ESV) ⁄
EDV.
To achieve optimal Real-time 3D echocardiographic acquisition of the
left ventricle, images were optimized by managing the gain, compress,
and time-gain compensation controls. Sector width and depth at two
dimensional setting and we switched to xPlane imaging to detect the
quality of endocardial borders at orthogonal view. After obtaining a
satisfactory image which included all segments of myocardium clearly,
full-volume acquisition with capturing of 4 adjacent ECG gated
sub-volumes over 4 consecutive cardiac cycles in a pyramidal scan was
performed during patients end-expiratory apnea within single breathhold
to prevent stitching artifacts. Acquisition of each sub‐volume was
triggered to the ECG R‐wave of every other heartbeat to allow sufficient
time for the probe to be recalibrated and each subvolume stored.
Post processing analysis of volumes and EF were performed using Qlab
software (Version 9.0; Philips Medical Systems) by two expert
echocardiographer with extensive training in 3D echocardiography. The
multiplanar view was aligned to maximize the LV cavity long- and
short-axes in the 2- and 4-chamber views. End- diastole was defined as
the first frame after mitral valve closure and end- systole was defined
as the first frame after aortic valve closure. After first identifying
the apex and mitral annulus on the end-diastolic and end-systolic
frames, transverse plane was adjusted at the level of papillary muscles
and saggital plane was adjusted from the midline of mitral annulus to
apex. Then automatic endocardial border definition was performed by
applying 4 mitral annular and 1 apical points: septal, lateral,
anterior, inferior annular, and apex (Figure 1). Manual corrections of
the LV endocardial borders including papillary muscles and
trabeculations were performed if the operator judges the automatically
detected surface as suboptimal. Sequence analysis were performed and
checked for correct border detection frame- by- frame. At the end of
analysis LVEDV, LVESV, LVEF, stroke volume, cardiac output, 16 segments
and 12 segments SDI were obtained (Figure 2) (8).