Preoperative examination of bilateral IMAs
Each patient was examined in the supine position with a Philips EPIQ7
Ultrasound Machine (United States) with L12-3 frequency of 3–12 MHz,
connected to electrocardiography. To examine the left IMA, the probe was
placed on the fourth intercostal space on the left side of the sternum
and moved to the left to search for IMA. Luminal diameter was measured
in the two-dimensional image. The angle between the sound beam and the
blood flow was adjusted to <60°. Spectral Doppler ultrasound
was used to measure the peak systolic velocity (PSV), peak diastolic
velocity (PDV), systolic velocity–time integral (sVTI, integrating
instantaneous speed with time to obtain distance of systolic blood
flow), and diastolic velocity–time integral (dVTI, integrating
instantaneous speed with time to obtain distance of diastolic blood
flow) and to calculate resistance index (RI=PSV/PDV) and diastolic
velocity–time integral fraction [dVTIF = dVTI/(dVTI + sVTI)]. The
mean values of three cardiac cycles were then used for analysis.
Examination of the right IMA was performed using the same method as in
the left IMA.