Ideal positioning of the catheter tip is a few millimeters into the vessel of interest (either left main or RCA), oriented coaxially with the lumen. Challenges with anatomy can make this difficult resulting in the catheter being either too shallow or too deep.
LAO showing disengagement of the catheter tip shortly after beginning to inject. Subsequently, the catheter re-engages the RCA and continues moving in and out in an unstable position.
When the catheter is not deeply engaged enough, it can actually disengage during injection resulting in non-selective injection of contrast into the aortic root. This results in poor opacification of the vessel of interest.
AP caudal showing tenuous catheter engagement. About halfway through the injection, the catheter disengages before bouncing back in. Engagement remains unstable throughout the clip.
On the other hand, it is also possible to have the catheter seated too deeply. This can result in poor opacification of the portion of the vessel proximal to the catheter tip, and in subselective engagement of either the LAD or LCx resulting in poor opacification of the unselected vessel.
RAO caudal showing subselective engagement of the LCx resulting in poor opacification of the LAD (seen at the top of the screen).
LAO caudal showing a non-selective “root shot” due to completely disengaged catheter.
LAO caudal showing a non-selective “root shot” due to completely disengaged catheter.
In some cases, the catheter is completely disengaged from the coronary artery resulting in a non-selective injection of the aortic root.
In an effort to spare contrast, angiographers try not to inject more dye than necessary for diagnosis. Sometimes this results in injection of too little dye making the angiogram difficult to interpret due to poor opacification.
AP caudal with insufficient contrast injection resulting in poor opacification of vessels.
AP caudal with insufficient contrast injection resulting in poor opacification of vessels.