Contrast injected, scan triggered, but where has contrast gone?
A 56-year-old diabetic male with a history of atypical chest pain was referred for CCTA. An intravascular access with an 18-G cannula was achieved relatively easily in the right cubital fossa and the tubing of the pressure injector was connected to the cannula. Planning of retrospective electrocardiographic ECG-gated CCTA (Somatom Definition, Siemens, Germany) was done with a bolus tracking technique, with the region of interest (ROI) placed in the upper descending aorta. The Hounsfield value (HU) for automatic triggering was set at 100. However, an unexpected delay was noted in the triggering of the scan. Meanwhile, the patient moved his right upper limb. The scan was abandoned and the patient was examined. While the patient's vital signs were stable, his right upper extremity was cold. There was no swelling at the injection site. The patient was shifted to the observation room where his vitals and the status of right arm were constantly monitored.\nReview of the limited CCTA images revealed no contrast in the coronary arteries and ascending aorta []. Streaks of contrast were noted in the arch of aorta and the descending aorta, with faint opacification of the right cardiac chambers []. Whereas there was no contrast in the right brachiocephalic vein or superior vena cava, there was opacification of the right subclavian and right common carotid arteries. These imaging findings could be explained by an inadvertent intra-arterial injection of contrast, with retrograde flow of contrast into the right upper limb arterial circulation and aorta. Some venous return from the distal circulation of the right upper limb could explain the faint appearance of contrast in the right heart chambers.