Angiography is an invasive imaging technique for visualizing arteries and veins using contrast media. The conventional version is performed under radiographic control with fluoroscopy and the production of serial radiographs. Today, this form of angiography is increasingly being replaced by the more modern procedures of magnetic resonance imaging (MRI) or computed tomography (CT). The term angiography or angio is used to describe the following procedures:
- Catheter angiography – radiographic imaging of the vessels by invasive application of contrast medium through a catheter (plastic tube). This form of angiography is described in detail later in this text.
- CT angiography – after the injection of the contrast agent, the vessels are then displayed three-dimensionally by means of the computer (see exemplary under cardio-CT).
- MRI angiography – primary magnetic resonance examination with imaging of the vessels with or without contrast agent.
Angiography of the arteries is called arteriography and imaging of the venous vessels is called phlebography.
Indications (areas of application)
- Atherosclerosis (arteriosclerosis; hardening of the arteries) with vascular stenoses (vasoconstrictions).
- Acute vascular occlusion – for example, in myocardial infarction (heart attack), cerebral infarction (stroke).
- Aneurysm (vascular outpouchings)
- Angiomas (vascular malformation)
- Apoplexy (stroke; insult, cerebral infarction).
- Vascular injuries
- Vascular malformations
- Embolism – partial or complete occlusion of a blood vessel by, for example, fat droplets, blood clots and air bubbles.
- Coronary heart disease (CHD)
- Varices (varicose veins)
- Peripheral arterial occlusive disease (PAD) or peripheral arterial occlusive disease (PAOD); colloquially known as “shop window disease”; it is a disorder of arterial blood flow to the extremities (legs).
- Stenoses – vasoconstrictions, for example, of the carotids (carotid stenosis, stenosis of the carotid artery; carotid artery stenosis), the renal arteries or the remaining arteries in the head, body and extremities.
- Thrombosis – vascular disease in which a blood clot (thrombus) forms in a vessel.
Contraindications
When using an iodine-containing contrast agent, the following contraindications should be noted: Iodine allergy, hyperthyroidism (hyperthyroidism), and impaired renal function. If any of these contraindications are present, the use of a non-iodine-containing contrast agent is required.
The procedure
Because contrast media have a high allergic potential, the patient’s tolerance should be tested beforehand with a small amount. Through a catheter, the contrast agent is now injected into the vascular area to be examined. The catheter is inserted percutaneously (through the skin) beforehand and the corresponding vessel is probed. In arteriography, this is often done via the femoral artery, i.e., as transfemoral catheter angiography. In survey angiography (unselective angiography), the contrast agent is injected into the aorta, allowing visualization of the aorta and the great vessels and their branches. In selective angiography, on the other hand, the contrast medium is applied in the immediate vicinity of the vascular system to be depicted and this is shown together with the associated organ system. In this case, vascular stenoses (vascular constrictions), vascular obliterations (vascular occlusions) or aneurysms (vascular bulges) can be diagnosed particularly well. When imaging venous vessels, the contrast medium is applied to a peripheral vein in the hand or foot. The contrast agent penetrates into the deep venous system and allows visualization of thrombosis (blood clots). As a rule, 1-2 X-ray images are taken per second so that the blood flow can be adequately visualized. With the help of digital catheter technology, it is possible to take up to 6 images per second. This is done simultaneously with fluoroscopy, which allows visual inspection. Both the imaging function, the fluoroscopy and the electrical pressure syringe, through which the contrast medium is applied, are electronically interconnected, so that optimal coordination is possible.The so-called digital subtraction angiography (DSA) is a special procedure for isolated imaging of the vessels. Beforehand, a mask is taken, which means that a native X-ray image of the area to be examined is taken without contrast medium. Subsequently, the image is taken with contrast medium. All structures visible on the mask are now subtracted from the contrast image so that only the vessels are visible. This image is called a pure angiogram. During angiography, so-called interventions can be performed. These are the following therapeutic interventions:
- PTA – Percutaneous transluminal angioplasty is a procedure called balloon dilatation. Stenoses (narrowing of the vessel) are dilated under radiographic control by inflating a small balloon in the lumen of the vessel. This leads to a controlled injury of the vessel intima (inner layer of the wall of blood vessels) with bursting of the vascular plaques (deposits on the vessel wall) and overstretching of the intima and media (middle layer of blood vessels, consisting of muscle cells and fibers of elastic connective tissue).
- PTCA – percutaneous transluminal angioplasty of coronary arteries (arteries that surround the heart in a coronary shape and supply blood to the heart muscle).
- Local lysis – When a vessel is occluded by a thrombus, thrombus-dissolving pharmaceuticals (drugs) are applied directly into the vessel so that locally high concentrations are achieved to dissolve the thrombus and recanalize the vessel.
- Stent implantation – To keep narrowed vessels open, a stent (vascular support) can be inserted through the catheter.
Because angiography is an invasive procedure, the patient must be informed about possible complications. These include bleeding, hematoma (bruising), thrombosis, infection and the risk of contrast intolerance. Catheter angiography has the following advantages for the patient:
- Direct invasive vascular imaging via catheters is somewhat more time-consuming for the patient, but the imaging is still more precise than in all other examinations, such as computed tomography or magnetic resonance imaging.
