What is coronary angiography?
Coronary angiography is visualization of the blood vessels of the heart (coronary arteries) by injecting radiocontrast ‘dye’ into them. Conventionally this is achieved by entering these blood vessels using small tubes known as catheters, introduced through blood vessels in the wrist or groin. In addition to this ‘invasive coronary angiography’, there is also another form of coronary angiography known as CT coronary angiography.
What is CT coronary angiography?
CT coronary angiography is a less invasive form of coronary angiography which does not require introduction of a catheter into the coronary artery. It uses multi slice computerized tomography (MSCT), also known as multi detector CT (MDCT) to capture images of coronary arteries after injecting radiocontrast into the blood vessels (veins) of the forearm. It can be done as an outpatient procedure. The scanner captures images timed to contractions and relaxations of the heart triggered by an electrocardiogram (ECG). For accurate triggering to occur the heart rate has to be stable and low. This is often achieved with the help of medications which are given before the test. Three dimensional reconstructions of the coronary arteries can be obtained by this technique. All the major branches can be seen by CT coronary angiography.
What are the downsides of CT coronary angiography?
Though CT coronary angiography is less invasive and quite convenient for the subject, the details obtained are not as good as conventional coronary angiography. It is at the best a good screening test to exclude significant coronary artery disease. Once significant coronary artery disease is detected by CT coronary angiography, conventional angiography is undertaken to decide on what type of treatment – whether coronary angioplasty (removal of blocks from coronary arteries using balloons and stents) or coronary bypass surgery is needed.
What is angiography?
Angiography is visualisation of a blood vessel with or without injecting a contrast (‘dye’) into its lumen. Most of us are now familiar with coronary angiography used to visualise the blood vessels supplying oxygenated blood to the heart. Usually visualization of each blood vessel is named after it: e.g. renal angiography – visualisation of renal (kidney) vessels; cerebral angiography – visualization of blood vessels of cerebral (brain) vessels; peripheral angiography – visualisation of the blood vessels of the limbs and other peripheral organs.
What are the different techniques of angiography?
Angiography can be divided into invasive and non invasive depending how much invasion is done into the body structures for visualising the vessels. Magnetic resonance angiography (MR angiography) can be considered as the truly non invasive angiography as there is no need to inject any contrast into the blood vessel to visualize the vessels. The hydrogen ions in the water content itself acts as the contrast for MR angiography. Hence MR angiography is also known as ‘dyeless angiography‘. In computerized tomographic (CT) angiography, iodinated contrast is injected into the peripheral veins (blood vessels carrying deoxygenated blood to the heart) of the forearms. X-ray equipment then captures the movement of the contrast into various parts of the body. If if captures the coronary blood vessels, then it is called CT coronary angiography. If it captures the blood flow to the lungs, it is called CT pulmonary angiography. In truly invasive angiography like coronary angiography, the contrast is injected directly into the blood vessels of the heart (coronary arteries). This is done by introducing small tubes known as catheters under local anaesthesia through the blood vessels at the wrist or groin and tacking them under X-ray fluoroscopic guidance to the coronary arteries through the aorta (largest blood vessel carrying oxygenated blood, arising from the heart).
What is fluorescein angiography?
Fluorescein angiography is used to visualise the blood vessels of the eye by injecting fluorescent dye into the blood vessels. The images of the inner eye are then photographed, to study the blood vessels of the retina, the light sensitive inner coating of the eye which senses our visual information and transmits it to the brain.