Invasive Vascular Testing
The modalities of invasive vascular testing are Digital Subtraction Angiography (DSA) , CT angiography and Magnetic Resonance Angiography (MRA).
DSA involves placement of a catheter into a vein or artery followed by the injection of a contrast agent (Radiocontrast agent). A series of xrays are then taken while the contrast agent is in the vascular system to provide information about the anatomy and physiology of the area that is being examined.
CT angiography is a similar procedure with the difference being that the x-rays are conducted on a CT scanner.
MRA is performed in a magnetic resonance imaging scanner. This is a large magnetic coil in which the patient is placed while the magnet is turned on and off repeatedly. This test often involves the administration of a contrast agent called Gadollinium.
The risks associated with invasive vascular testing relate to the injection into the blood vessel and the administration of contrast agent.
When a needle or catheter is placed into an artery or vein there can be resulting damage to that blood vessel which can lead to bleeding or occlusion of that blood vessel. The incidence of significant blood vessel damage is very much less than 1% of tests performed.
Other risks involve allergic reactions to contrast agents. If you have had an allergic reaction in the past to contrast agent you should inform the doctor performing the procedure. It may be possible to obtain appropriate information using another technique or using another contrast agent such as carbon dioxide or pre treating you with a course of prednisone to suppress the allergic reaction.
Radiocontrast agent is excreted through the kidneys. Some people who have underlying conditions that affect their kidneys may be predisposed to renal failure as a result of the contrast that is used. These conditions are pre existing chronic renal failure, diabetes mellitus , age, multiple myeloma and dehydration. If you have any of these conditions it is important to have precautionary measures taken before the performance of these tests. These measures may involve intravenous prehydration , administration of sodium bicarbonate and acetylcysteine. Your doctor can also reduce the amount of contrast agent give or perform the test using carbon dioxide.