Cardiac catheter Cardiac catheterization is when a thin plastic tube (catheter) into an artery or vein in the leg (or arm). From there it can be advanced into the chambers of the heart or into the coronary arteries. It can measure blood pressure within the heart and how much oxygen is in the blood. It's also used to get information about the pumping ability of the heart muscle. Catheters are also used to inject dye into the coronary arteries.
