Assessment of IMA initial segment after the operation
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. The probe was placed on the left neck region, along the axis of the vertebral artery to visualize the beginning of the vertebral artery in the supraclavicular fossa. The probe was then rotated 90° to the opposite side of the vertebral artery (inferior wall of the subclavian artery) to detect the opening of the left IMA and to measure the angle between the left IMA and the subclavian artery. The luminal diameter of the IMA was measured at a distance of 0.5–1.0 cm from the opening. Spectral Doppler ultrasound was used to find the spectrum of the initial segment of the IMA after the operation, to measure PSV, PDV, sVTI, and dVTI, and to calculate RI, dVTIF, and PDV/PSV ratio (D/S). The mean values of three cardiac cycles were then used for analysis. The flow of IMA was calculated using to the luminal diameter.
All operations were performed by the same deputy chief physician.