Echocardiography
A comprehensive transthoracic echocardiography (TTE), which included
two-dimensional, M-mode, Doppler echocardiography was performed
according to the recommendation of the American Society of
Echocardiography.14 TTE
examinations were performed using a Vivid 7 Ultrasound System (GE
Healthcare, Horten, Norway). From the parasternal long axis view, we
recorded the LV end-diastolic and end-systolic diameters. The LV
end-diastolic volume (EDV), LV end-systolic volume (ESV) and LVEF were
calculated using the biplane method of the disk summation. The stroke
volume was calculated using the outflow tract diameter measured at the
base of the aortic leaflet in the parasternal long axis view and the
pulsed Doppler velocity integral obtained at the same level in the
five-chamber or apical long axis view.
LDSE was performed before surgery. Dobutamine was infused intravenously
in 10-min stages at incremental doses of 5 and 10 g/kg/min while
monitoring a single-lead electrocardiogram and blood pressure. EDV, ESV,
LVEF and stroke volume were obtained at each stage.