Overview of Angiography
Medical imaging, which allows us to visualize the inside of the body, has seen a lot of advancements over the last 50 years. One of these advancements involves a process called angiography. This technique allows doctors to see the inner structure of blood vessels in the body. They do this by injecting a special substance into a blood vessel and then taking a series of x-ray images. This method allows them to see the walls of the vessel and how blood is flowing through it.
Angiography started out only as a way to diagnose problems, but over the years, it has also become a method to treat certain conditions. It has progressed from creating a simple image on film to a real-time moving image on a screen and even a three-dimensional image from a CT scan. Angiography also allows doctors to perform treatments at the initial diagnosis time.
The traditional angiography, which provides real-time images and treatment options, is invasive, meaning it involves a certain level of intrusion into the body. Nevertheless, it continues to be the most trusted method for diagnosing most blood vessel-related diseases. In recent years, doctors have improved angiography techniques to include non-invasive options using CT scans and magnetic resonance imaging technologies.
CT angiography, or CTA, is a specific type of angiography that uses a CT scan along with a substance injected into a vein to take detailed images. Although it provides a lot information and images of the heart and surrounding areas, it isn’t as helpful for smaller areas, such as the blood vessels in the extremities (arms and legs), because they’re so small. However, interventional angiography is able to take high-resolution images and detect even small changes in these tiny vessels.
Magnetic Resonance Angiography (MRA) is another important technique trending in clinical practice as it offers a unique advantage. MRA, which uses a magnetic field instead of radiation, is gaining traction especially now when advancements in imaging techniques are happening so rapidly. It is based on the natural magnetic properties of body tissues and doesn’t require harmful radiation exposure. However, the detailed working principles of CTA and MRA are complex and beyond the scope of this discussion.
Anatomy and Physiology of Angiography
The detailed structure of our body’s blood vessel system is very complex. This article will discuss the important parts related to angiography, a medical imaging technique used to visualize the inside of blood vessels.
Let’s start with the aorta, the main and largest artery in our body. Its beginning part is called the aortic root, which is usually around 4.3 cm wide in healthy individuals. The aorta gives off the left and right main arteries that supply the heart, then it continues upward before bending into the aortic arch.
Three significant arteries branch off from the arch:
1. The brachiocephalic trunk splits into the right common carotid artery (which goes to the head) and the right subclavian artery (which goes to the arm).
The left common carotid artery further breaks down into the internal and external carotid arteries. The internal one, along with the vertebral artery, forms the circle of Wilis, a vital circle of arteries at the base of the brain. The external carotid artery gives off many branches that supply the areas around the neck, face, and head.
The subclavian artery, which supplies our upper body, is divided into three sections by a muscle called the scalenus anterior muscle. The first section gives off the vertebral artery, which also contributes to the supply of blood to the brain via the circle of Willis. It also gives rise to the internal mammary artery and the thyrocervical trunk, supplying the chest and neck areas respectively. The second part gives off the costocervical trunk while the dorsal scapular artery comes from the third part. After the subclavian artery passes over the first rib, it changes its name to the axillary artery, which supplies the upper arm.
The abdominal aorta, a part of the aorta that’s in the belly, has six major branches. Three of these supply the organs in the belly and include the coeliac axis (which further breaks down into the hepatic, splenic, and left gastric arteries) and two other arteries called the superior and inferior mesenteric arteries. The abdominal aorta also gives off the suprarenal, renal, and the testicular or ovarian arteries, which supply the respective organs. The abdominal aorta finishes as common iliac arteries, which split into the internal and external iliac arteries. The internal one provides blood to the pelvic and perineal organs, while the external one forms the femoral artery, supplying the lower leg.
The femoral artery in the leg and the radial artery in the forearm are common places where doctors insert a catheter to take images of your blood vessels, a process called angiography.
However, angiography does have one limitation: it can’t fully show the inside wall of your blood vessels, especially if there is a condition called arterial calcification. Other advanced techniques, like intravascular ultrasound, are often needed for this purpose.
Why do People Need Angiography
Angiography is an X-ray imaging test that uses a dye to view the blood vessels in various systems of the body. Certain conditions might make it necessary for a doctor to recommend angiography. Here are a few examples from different categories:
Brain and skull (Neuroangiography)
For external brain conditions, this could include a specific type of abnormal blood vessel connection (cavernous-carotid fistula), narrowing of the carotid artery (extracranial carotid stenosis), nosebleeds that won’t stop (epistaxis), and a certain disorder that affects blood flow to the brain (subclavian steal syndrome).
This method is also used for internal brain conditions. These include bleeding inside the brain not due to injury (subarachnoid hemorrhage), malformed and nuisance blood vessels in the brain (cerebral arteriovenous malformations and aneurysms), a constriction of brain arteries (cerebral vasospasm), a sudden loss of brain function (acute stroke), or to help plan brain surgery (WADA test).
Heart and blood vessels (Cardiovascular)
Angiography can be used to look for bulging and tearing in large blood vessels, like the aorta (thoracic and abdominal aortic aneurysm and dissection), to diagnose and treat blockages in the heart’s blood vessels (coronary artery disease), heart blood vessels that are bulged (coronary artery aneurysms), and peripheral vascular disease, which is another name for poor circulation of the blood.
Lungs (Pulmonary)
Angiography can also be employed when there is bleeding in the lungs (pulmonary hemorrhage).
Digestive system (Gastrointestinal System)
When there is lack of blood flow to the intestines (mesenteric ischemia) or severe internal bleeding in the digestive system, then angiography comes in handy.
Kidneys (Renal)
It’s helpful in diagnosing high blood pressure caused by kidney disease (renovascular hypertension), and for the care and upkeep of a special blood vessel connection used in kidney dialysis (dialysis fistula mapping and maintenance angioplasty).
Reproductive system
Angiography might be used to treat swollen veins on the testicles (varicoceles) or painful ovarian veins (pelvic congestion syndrome), and overgrowth of the muscle tissue in the uterus (fibroids).
Cancer (Oncology)
Angiography remains a crucial tool in treating cancers of the liver (hepatomas), colon and rectum (colorectal liver metastases), specific kind of tumors (carcinoid tumors), and kidney cancers (renal cell carcinoma).
Injury (Trauma)
And finally, it’s used when there’s a severe injury to the arteries in the limbs or uncontrollable internal bleeding following certain types of severe injury.
When a Person Should Avoid Angiography
There are some conditions which may prevent somebody from having an angiography. An angiography is a medical procedure used to view blood vessels and organs in the body. However, not everyone is eligible.
People who weigh more than 350 pounds may be unable to have an angiography because several machines used in North America have a weight limit for safety purposes.
If a person is pregnant, they might usually not be able to have angiography. However, in extreme cases where the mother’s life might be at risk due to severe bleeding it can be performed.
People who have had a severe reaction to iodinated contrast medium might not be able to safely have angiography. This reaction includes symptoms such as breathing problems (bronchospasm), voice box spasms (laryngospasm), swelling under the skin (angioedema), and sudden drop in blood pressure and heart rate (cardiovascular collapse). For these people, another method named carbon dioxide angiography might be used. Those with history of mild allergic reactions can also be given steroids and antihistamines before the procedure.
Patients who have kidney problems or dehydration might also be at risk. This is because they may have an increased risk of further damaging their kidneys after being exposed to the contrast medium, a substance used to make the structures inside your body show up clearer. For those patients, using very low or no contrast might be an alternative.
Patients with coagulopathy (a condition that affects the body’s blood clotting), an INR (International Normalized Ratio) value more than 2, or a platelet count less than 50,000 are at a higher risk of bleeding. However, there are devices that can help reduce this risk.
Patients with diabetes who take metformin (a diabetes medication), especially those with kidney problems, might have an increased risk of kidney problems and lactic acidosis (a buildup of acid in your body).
Finally, patients who are very anxious or cannot lay still might need to be sedated during the procedure.
Equipment used for Angiography
The room where doctors perform angiography, a medical test used to visualize the inside, or lumen, of blood vessels and organs of the body, and related treatments needs to be big enough to fit all necessary machines and medical personnel.
The crucial equipment needed for traditional angiography includes:
- A set of catheters and guide wires: These are thin, flexible tubes that doctors use to access your blood vessels and direct medical tools to the exact area they need to examine or treat.
- An autoinjector : This device automatically injects the contrast material (dye) that makes your blood vessels visible on the X-ray images.
- An image intensifying screen: This device captures and magnifies the images of your blood vessels, making it easier for doctors to see details.
- A sliding table: This is a movable table on which you lie during the procedure. It can be adjusted to help position you correctly for the angiography.
- Remote computerized equipment: These are computers and software that are used to control other devices and analyze the X-ray images.
- Biplane C-arm digital imaging: This is an advanced type of X-ray machine that can take images from two different directions. It helps doctors get a more comprehensive view of your blood vessels.
- A generator: This device provides the power for the X-ray machine.
Who is needed to perform Angiography?
The process of angiography is usually carried out by a skilled medical team led by doctors with special training in critical care and technical know-how. These doctors could be experts in different fields such as interventional radiology (that involves using imaging technology to guide medical procedures), vascular surgery (surgeries involving blood vessels), interventional neuroradiology (using imaging to guide procedures in the nervous system), or interventional cardiology (using imaging to guide heart treatments), depending on what the procedure requires.
Nurses and nurse managers in the angiography lab also have a vital role in the procedure. Their job is to keep you safe before, during, and after the procedure. They are skilled in critical care, which involves looking after patients with serious health disorders, and also in monitoring your heart’s function using special equipment. Radiology technicians in the lab are trained in using imaging equipment to get clear pictures of your blood vessels and monitoring your heart to ensure your safety.
Preparing for Angiography
Before having an angiography (a medical imaging procedure used to visualize the inside of blood vessels), patients are given individual preparations based on their unique characteristics, the type of angiography to be performed, and its purpose.
It’s important that all patients are well-hydrated to reduce the risk of kidney damage caused by the contrast medium, a dye injected into the bloodstream to make the blood vessels visible on the images. Some patients may also need to avoid eating or drinking for 6 to 8 hours before the procedure, depending on the situation.
Extra precaution is needed for certain groups of patients. This includes those with kidney problems, people with diabetes who are taking metformin (a medicine used to control blood sugar), those taking antiplatelet or anticoagulant drugs (medicines that prevent blood clots), and those who have previously had an allergic reaction to iodinated contrast (the type of dye used). These individuals need special evaluation before undergoing angiography to ensure their safety during the procedure.
How is Angiography performed
Angiography is a medical imaging technique used to visualize the inside of blood vessels and organs of the body. It involves the injection of a contrast medium to reveal the vessels in X-ray images. Now, where the doctor accesses your body for this procedure depends on what blood vessels or body part needs to be examined.
For example, if the process requires observing areas such as the vessels in the pelvic area, chest, arms, and the head and neck, the procedure usually starts from your thigh’s large artery, also known as the femoral artery. This artery is a popular choice because it’s large and allows the use of bigger instruments like stents or occlusive aortic balloons that can stop or control blood flow in an emergency.
However, when dealing with your heart vessels, the angiography often begins at the radial artery located in your wrist. This access point has a less risk of complications compared to starting at the arteries in the thigh or arm. Even larger size medical tubes or ‘sheaths’ can still easily be inserted through the thigh area. Doctors can conveniently use special skin-stitching tools and collagen plugs, a material to stop bleeding at the thigh site.
For the lower leg vessels’ examination, doctors can either choose to start at the femoral artery or from a lower leg artery known as the popliteal artery.
During the procedure, a suitable catheter, a thin flexible tube, is inserted at the access site. Helping doctors navigate this tube is a system of soft flexible wires. This catheter is carefully moved to the correct blood vessel that needs to be checked. After reaching the location, a fluid known as a contrast medium is put in to highlight the blood vessels for the X-ray machine. The X-ray images can either be still or dynamic, using a technique called digital subtraction angiography that clicks images a few times every second. This helps doctors identify how narrow or abnormal the blood vessels have become.
When imaging the chest’s main artery, called the thoracic aorta, doctors first look at the aortic root, then the upper aorta, the aortic arch, and finally the upper descending aorta. During this process, your head might be tilted to the right and lifted for better imaging. As a start, doctors often take an image at an angle, allowing them to understand the type of aortic arch you have. This helps them predict the procedure’s complexity, particularly since certain arch types make the procedure more challenging.
While imaging the abdominal aorta, the main artery in the stomach area, you would be lying on your back. Doctors take images from the back and the side views. The initial images typically span from the top of your diaphragm to the edge of the hipbones. The first round of imaging is usually carried out with the catheter at the level of your first lumbar vertebra, a bone in your lower back. The catheter is then moved to the point where the aorta split or the aortic bifurcation, and the pelvic vessels are imaged using tilted projections.
In simple terms, it’s a careful, guided procedure that helps doctors understand the state of your arteries and deal with any abnormalities, thanks to advancements in medical technology!
Possible Complications of Angiography
Angiography, a test that helps to take detailed images of your blood vessels, is generally safe, but there’s a slightly higher risk of complications for certain groups of people. This includes older people, people with weak hearts, stiff arteries with calcium buildup, kidney disease, and those with multiple health problems.
There can be minor and major complications from this procedure.
Minor complications are usually less severe, and they may include:
* Bruising
* Feeling sick to your stomach
* Pain where the needle was inserted
* Minor allergic reactions like rash, itching, or hives
* A temporary decrease in kidney function
* A quick feeling of heat or a burning sensation
Major complications are less common but more serious. They may include:
* Serious bleeding or a lump of clotted blood (hematoma), a false aneurysm (an outward bulging in the wall of an artery), which happens in less than 5% of the tests. In some extreme cases, some patients require overnight supervision, while others might need further treatment or blood transfusion to control the bleeding.
* Severe allergic reaction
* Sudden kidney failure.
In some cases, the dye used in angiography can affect the kidneys, leading to a condition called Contrast-Induced Nephropathy (CIN). This might require short-term kidney treatment. However, this can be mitigated through proper hydration before the procedure and using the smallest possible amount of dye.
One way used to estimate the safe amount of contrast dye to use is a formula where 5 times the body weight in kilograms is divided by the serum creatinine (a waste product found in the blood). However, the maximum dose should not exceed 300ml. Still, this formula is less helpful for high-risk patients like those with anemia, diabetes, heart failure, and cardiogenic shock, and it is not often used in medical settings.
Another way is to ensure that the volume of contrast used is less than twice the amount of creatinine the kidneys can clear from the body. If it exceeds thrice this amount, the risk of CIN significantly increases.
What Else Should I Know About Angiography?
Noninvasive imaging techniques, such as CT angiography (CTA) and magnetic resonance angiography (MRA), have largely taken the place of traditional invasive angiography for diagnosing vascular conditions. These procedures can assess the state and function of our blood vessels without needing to insert a catheter into the body. Just like traditional angiography, these techniques can deliver information about the structure and health of your blood vessels.
Studies have shown that an aspect of CT angiography, known as computed tomography fractional flow reserve (CT-FFR), is roughly 82% as accurate as invasive FFR in diagnosing conditions. However, this accuracy level drops to about 46% when the measurements are in a specific range (specifically, between 0.70 and 0.80). In these cases, traditional invasive methods are deemed necessary.
Despite the usefulness of noninvasive imaging options, invasive angiography remains important, especially considering the rapidly advancing field of minimally invasive treatments. Some examples of these treatments include percutaneous coronary intervention (which is a procedure to open up blocked heart arteries), clot removal for strokes (mechanical thrombectomy), placement of stents in peripheral and renal arteries, and targeted chemotherapy delivery (transarterial chemoembolization).
Recent advancements have seen the introduction of metrics derived from images captured during angiography. These metrics have proven to be highly accurate in comparison to the results derived from invasive pressure wire methods which measure blood flow (known as FFR).
