A 74-year-old male was admitted with atypical chest pain. Transradial coronary angiography revealed that there was no obstructive disease in left anterior descending artery (LAD) or circumflex artery (LCX; figure A). When performing right coronary angiography with a five French Tiger shaped universal catheter (Terumo Corporation, Japan), the conus branch was super selected. Furthermore, expansion of conus branch was observed after overfilling with contrast medium (white arrow in panel B of the Figure). The catheter was removed immediately. Visualisation of expanded conus branch persisted for about 40 s, then the stain disappeared radically (Figure C). Under the circumstances, there was no significant change in symptoms, vital signs or electrocardiogram. Then the angiography was continued and revealed a nearly normal right coronary artery and conus branch (Figure D). Serial ultrasound cardiogram tests were performed and no pericardial effusion were found. We deduced that expansion of conus branch should be attributed to the artery overfilling with contrast medium. Special curve of the universal catheter facilitated super selection of conus branch when performing right coronary angiography, and overfilling with contrast medium could result in conus branch expansion, rupture, malignant arrhythmia, etc. This is a profound example of this phenomenon. And as far as we know, this is the first report in the literature. We should do our best to avoid super selection of conus branch and overfilling with contrast medium in order to decrease such complications.