Final answer:
Left ventriculography is a procedure used in cardiac catheterization to determine the severity of aortic insufficiency by assessing heart function via contrast dye and X-ray imaging.
Step-by-step explanation:
The technique used in the cardiac catheterization laboratory that determines the severity of aortic insufficiency is C. Left ventriculography. This procedure involves injecting a contrast dye into the left ventricular chamber of the heart and then taking X-ray images. These images help in assessing the structure and function of the heart's chambers and valves, particularly the aortic valve. Left ventriculography is particularly useful for evaluating the severity of aortic insufficiency, which occurs when the aortic valve does not close properly, allowing blood to flow backward into the left ventricle.