This retrospective observational study included 105 patients with a history of CABG who underwent CTCA between January 2015 and March 2020. Patients with uninterpretable images or implanted metallic cardiac devices, which might interfere with image quality, were excluded from the analysis.

CTCA Protocol: All scans were performed on a 64-slice Philips Ingenuity CT scanner using retrospective ECG-gating. The scanning range extended from the thoracic inlet to the lung bases to include the origin of internal mammary arteries and bypass grafts. Non-ionic, low-osmolar contrast (iohexol 350 mg/ml) was injected intravenously at a rate of 5 ml/sec, followed by a saline flush. A dual-head pressure injector was used to administer 80–100 ml of contrast. Image acquisition was triggered using real-time contrast bolus tracking, with scanning initiated once contrast was visualized in the descending aorta. Diagnostic images were reconstructed with a slice thickness of 1 mm to minimize artifacts. Images were excluded if motion artifacts interfered with evaluation.

Image Analysis:Native vessels and grafts were evaluated using axial, multi-planar reformatted (MPR), thin-slab maximum intensity projection (MIP), and volume-rendered (VR) images.

• Native Vessel Analysis: Patency of the left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA) was assessed. Stenosis was classified as <50%, 50–70%, 70–90%, or >90%, with significant stenosis defined as ≥50%.
• Graft Analysis: Grafts were assessed for type, diameter, patency, and occlusion site. Patency was categorized as normal, diseased (<50% narrowing), or occluded. Correlations were drawn between graft patency and factors such as native artery stenosis, calcium scores, and graft origin distance from the aortic annulus. Branch artery grafts were categorized with their corresponding major artery (e.g., diagonal artery with LAD).

Statistical Analysis: Continuous variables were expressed as mean ± standard deviation or median, while categorical data were presented as frequencies (%). Independent samples t-tests, ANOVA, and Fisher’s exact tests were used to compare variables. A p-value of <0.05 was considered statistically significant.