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| Angiography | |
|---|---|
 Angiogram of the brain showing atransverse projection of thevertebrobasilar andposterior cerebral circulation. | |
| ICD-9-CM | 88.40-88.68 |
| MeSH | D000792 |
| OPS-301 code | 3–60 |
Angiography orarteriography is amedical imaging technique used to visualize the inside, orlumen, of blood vessels and organs of the body, with particular interest in thearteries,veins, and theheart chambers. Modern angiography is performed by injecting a radio-opaquecontrast agent into the blood vessel and imaging usingX-ray based techniques such asfluoroscopy. With time-of-flight (TOF) magnetic resonance it is no longer necessary to use a contrast.
The word itself comes from theGreek words ἀγγεῖονangeion 'vessel' and γράφεινgraphein 'to write, record'. The film or image of theblood vessels is called anangiograph, or more commonly anangiogram. Though the word can describe both anarteriogram and avenogram, in everyday usage the terms angiogram and arteriogram are often used synonymously, whereas the term venogram is used more precisely.[1]
The term angiography has been applied toradionuclide angiography and newer vascular imaging techniques such asCO2 angiography,CT angiography andMR angiography.[2] The termisotope angiography has also been used, although this more correctly is referred to asisotope perfusion scanning.
The technique was first developed in 1927 by thePortuguese physician and neurologistEgas Moniz at theUniversity of Lisbon to provide contrasted X-raycerebral angiography in order to diagnose several kinds of nervous diseases, such as tumors, artery disease andarteriovenous malformations. Moniz is recognized as the pioneer in this field.[3] He performed the first cerebral angiogram in Lisbon in 1927, andReynaldo dos Santos performed the first aortogram in the same city in 1929. In fact, many current angiography techniques were developed by the Portuguese at the University of Lisbon. For example, in 1932,Lopo de Carvalho performed the first pulmonary angiogram via venous puncture of the superior member. In 1948 the first cavogram was performed bySousa Pereira. With the introduction of theSeldinger technique in 1953, the procedure became markedly safer as no sharp introductory devices needed to remain inside the vascular lumen. Radial access technique for angiography can be traced back to 1989, whenLucien Campeau first cannulated the radial artery to perform a coronary angiogram.[4]
Depending on the type of angiogram, access to the blood vessels is gained most commonly through thefemoral artery, to look at the left side of the heart and at thearterial system; or thejugular orfemoral vein, to look at the right side of the heart and at the venous system. Using a system ofguide wires andcatheters, a type ofcontrast agent (which shows up by absorbing theX-rays), is added to the blood to make it visible on the X-ray images.
The X-ray images taken may either be still, displayed on animage intensifier or film, or motion images. For all structures except the heart, the images are usually taken using a technique calleddigital subtraction angiography or DSA. Images in this case are usually taken at 2–3 frames per second, which allows theinterventional radiologist to evaluate the flow of the blood through a vessel or vessels. This technique "subtracts" the bones and other organs so only the vessels filled with contrast agent can be seen. The heart images are taken at 15–30 frames per second, not using a subtraction technique. Because DSA requires the patient to remain motionless, it cannot be used on the heart. Both these techniques enable the interventional radiologist or cardiologist to seestenosis (blockages or narrowings) inside the vessel which may be inhibiting the flow of blood and causing pain.
After the procedure has been completed, if the femoral technique is applied, the site of arterial entry is either manually compressed, stapled shut, or sutured in order to prevent access-site complications.[5]
One of the most common angiograms performed is to visualize thecoronary arteries. A long, thin, flexible tube called acatheter is used to administer the X-ray contrast agent at the desired area to be visualized. The catheter is threaded into an artery in theforearm, and the tip is advanced through the arterial system into the major coronary artery.X-ray images of the transientradiocontrast distribution within the blood flowing inside the coronary arteries allows visualization of the size of the arteryopenings. The presence or absence ofatherosclerosis oratheroma within the walls of thearteries cannot be clearly determined.
Coronary angiography can visualize coronary arterystenosis, or narrowing of the blood vessel. The degree of stenosis can be determined by comparing the width of the lumen of narrowed segments of blood vessel with wider segments of adjacent vessel.[5]
The coronary angiography is performed under local anaesthesia. The patient is awake during the procedure. An incision is made in the groin, wrist, or arm, and a catheter is inserted into the artery through it. An X-ray is used to guide the catheter to the area of blockage. A dye is inserted through the catheter to make the places of blockage visible.
When the catheter is in position, a thin wire with a balloon is guided to the place of blockage. The balloon is inflated to widen the artery, allowing the blood to flow freely. Often, a stent is used, and as the balloon is inflated, the stent in place expands and holds open the artery. The balloon is then deflated and removed, leaving the stent in place.
After the completion of the procedure, the catheter is removed, and the plug area is sealed using angio-seal.
The procedure takes around two hours, and the patient can be discharged after an overnight stay in the hospital, depending on the condition.[6]
Cerebral angiography provides images of blood vessels in and around the brain to detect abnormalities, includingarteriovenous malformations andaneurysms.[7] One common cerebral angiographic procedure is neuro-vasculardigital subtraction angiography.[8][9]
Pulmonary angiography is used to visualise the anatomy of pulmonary vessels. Pulmonary angiography may be used during embolization ofpulmonary arteriovenous malformations.[10] In addition, pulmonary angiography may be performed during treatment ofpulmonary embolisms.[11]
Angiography is also commonly performed to identify vesselsnarrowing in patients with leg claudication orcramps, caused by reduced blood flow down the legs and to the feet; in patients with renal stenosis (which commonly causes high blood pressure) and can be used in the head to find and repair stroke. These are all done routinely through the femoral artery, but can also be performed through the brachial or axillary (arm) artery. Any stenoses found may be treated by the use of balloon angioplasty, stenting, oratherectomy.
A common indication for angiography is to evaluate and guide treatment for internal (e.g. gastrointestinal) bleeding.[12] Angiography may also be used duringhemorrhoidal artery embolization for treatment of symptomatichemorrhoids.[13]
Fluorescein angiography is a medical procedure in which a fluorescent dye is injected into the bloodstream. The dye highlights the blood vessels in the back of the eye so they can be photographed. This test is often used to manage eye disorders.[14]
Optical coherence tomography (OCT) is a technology usingnear-infrared light to image the eye, in particular penetrate the retina to view the micro-structure behind the retinal surface.Ocular OCT angiography (OCTA) is a method leveraging OCT technology to assess the vascular health of the retina.[15]
Microangiography is commonly used to visualize tiny blood vessels.
Post mortem CT angiography for medicolegal cases is a method initially developed by avirtopsy group. Originating from that project, both watery[16] and oily[17] solutions have been evaluated.
While oily solutions[17] require special deposition equipment to collect waste water, watery[16] solutions seem to be regarded as less problematic. Watery solutions also were documented to enhance post mortem CT tissue differentiation whereas oily solutions were not. Conversely, oily solutions seem to only minimally disturb ensuing toxicological analysis, while watery solutions may significantly impede toxicological analysis, thus requiring blood sample preservation before post mortem CT angiography.[18]
Angiography is a relatively safe procedure. But it does have some minor and very few major complications. After an angiogram, a sudden shock can cause a little pain at the surgery area, but heart attacks and strokes usually do not occur, as they may in bypass surgery. The risk of complications from angiography can be reduced with a prior CT scan by providing clinicians with more information about number and positioning of the clots in advance.[19][20]
Major complications in cerebral angiography such as indigital subtraction angiography or contrast MRI are also rare but includestroke, anallergic reaction to theanaesthetic other medication or the contrast medium, blockage or damage to one of the access veins in the leg, pseudoaneurysm at the puncture site; orthrombosis andembolism formation.Bleeding orbruising at the site where the contrast is injected are minor complications, delayed bleeding can also occur but is rare.[21]
The contrast medium that is used usually produces a sensation of warmth lasting only a few seconds, but may be felt in a greater degree in the area of injection. If the patient is allergic to the contrast medium, much more serious side effects are inevitable; however, with new contrast agents the risk of a severe reaction is less than one in 80,000 examinations. Additionally, damage to blood vessels can occur at the site of puncture/injection, and anywhere along the vessel during passage of the catheter. Ifdigital subtraction angiography is used instead, the risks are considerably reduced because the catheter does not need to be passed as far into the blood vessels; thus lessening the chances of damage or blockage.
Antibiotic prophylaxis may be given in those procedures that are not clean, or clean procedures that results in generation ofinfarcted ornecrotic tissues such asembolisation. Routine diagnostic angiography is often considered a clean procedure. Prophylaxis is also given to prevent infection from infected space into blood stream.[22]
There are six risk factors causing thrombosis after arterial puncture: low blood pressure, small arterial diameter, multiple puncture tries, long duration of cannulation, administration of vasopressor/inotropic agents,[23] and the usage of catheters with side holes.[24]
