Background: The femoral, radial, or ulnar arteries can be used for coronary angiography, which has emerged as the gold standard for diagnosing and treating coronary artery disease. Objectives: The aim of the current study is to compare radial artery diameter pre and post-radial coronary angiography by duplex ultrasound to evaluate the effect of pre-medication at the diameter of the radial artery and analyze the predictors that can cause radial artery spam (RAS) to avoid it. Patients and Methods: A one-arm clinical trial was carried out on 92 patients eligible for trans-radial procedures. All patients were subjected to medical history (demographic data, comorbidities, current medications especially cardiac drugs, and history of ischemic heart disease and its course), clinical examination, echocardiographic data, ECG, laboratory investigations, duplex on radial artery pre and post-trans-radial angiography. Results: There was a significant statistical difference between radial artery diameter change and the number of radial puncture attempts (P value 0.001). The relation between data of percutaneous coronary intervention (PCI) and radial artery diameter change shows a significant statistical difference in the number of stents used at PCI (P value 0.039). While the guiding catheter used, wires used, the number of balloons used, and the types of stents used showed non-significant statistical differences (P values 0.195, 0.352, 0.995, and 0.434, respectively). Conclusion: RAS is still an important problem in trans-radial access. During this study, we found the predictors which decrease radial artery diameter change and induced radial artery spasm in patients who underwent trans-radial coronary angiography.