Echocardiographic assessment
All examinations are performed by senior doctors according to the
standard procedure within the first 24 hours in ICU. Mindray-M9 portable
color Doppler ultrasound and a P4-2s probe (2‒4 MHz) were used to
perform echocardiography. Measurements
of
interventricular septal
end-diastolic thickness (IVSd), left ventricular end-diastolic dimension
(LVDd), left ventricular ejection fraction (LVEF), pulmonary artery
systolic pressure (PASP), and left ventricular diastolic function were
obtained from each echocardiographic examination. With the guidance of
tricuspid regurgitation detected by color Doppler, continuous wave
Doppler was used to measure the maximum velocity of
tricuspid regurgitation and the
tricuspid valve regurgitation
pressure gradient (TRPG). The PASP was estimated by TRPG plus
right atrial pressure (RAP). The
right ventricular inflow tunnel section, parasternal short axis,
parasternal four chamber, apical four-chamber or five-chamber sections
were selected according to the clarity of the image in each patient.
According to the collapsibility of
inferior vena cava (IVC), RAP was
valued as 5, 10, or 15 mmHg, respectively6. In the case of mechanical
ventilator usage, central venous pressure (CVP) was considered to be
equal to RAP. The highest PASP value was used for statistical analysis.
In order to ensure accuracy and repeatability, the echocardiographic
data were collected by two independent senior doctors.