A 38-year-old man who had a history of percutaneous coronary artery coil occlusion was admitted to our hospital with chest pain and shortness of breath. His complaint was chest pain, which is typical. ST depressions were observed during the treadmill exercise stress test. Coronary angiography demonstrated the persistence of a coronary arteriovenous fistula and coils in the fistula. Primarily, additional coil placement inside the arteriovenous fistula was decided as the mode of treatment. The coil was first placed inside the arteriovenous fistula and then an attempt was made to detach it. However, it was unsuccessful after four trials and electrical detachment of more than 3 minutes. Finally, a 2.5 × 18-millimetre graft stent was deployed at 20 atmospheric pressure. Electrocardiographic recordings showed bizarre ST segment changes during the electrical detachment of the coil. In this report, we discuss the concealed bizarre electrocardiographic changes that were seen during coronary arteriovenous fistula occlusion.