CCTA examination
All of the participants underwent CCTA on a SIEMENS Force Dual-source Instrument with prospective electrocardiogram gating. The scanning range covered the whole heart and coronary artery from the tracheal bifurcation to the diaphragmatic surface level at the cardiac base. The scanning methods were as follows: after plain scanning, the scanning was enhanced with the contrast agent trace method and an area-of-interest region (the ascending aorta) was set with a threshold value of 100 Hu; when the threshold value was reached, the scanning was automatically trigged. The scanning parameters included automatic tube voltage, automatic detector width, the acquisition layer of 0.75 mm, the interlayer spacing of 0.4 mm, the rotating time of 0.25 s, and the mean time to scan a whole heart of 3–6 s. The median cubital vein was injected with 370 mgI/mL iopromide (ultravist, Bayer AG, Leverkusen, Germany) or 350 mgI/mL iohexol (General Electric Company, Fairfield, Connecticut, USA) at a flow rate of 4–5 mL/s or with 50–60 mL normal saline. After examination, the patient was advised to stay for 0.5-h observation. Patients left without discomfort.