Cardiac catheterisation is a way to find out detailed information about your heart and coronary arteries. Some 'operations' are also possible during cardiac catheterisation.
It is a special x-ray study of the heart that involves the insertion of soft narrow plastic tubes called catheters via blood vessels into the heart. This procedure is carried out at the Cardiac Catheterisation Laboratory to determine the function of the heart and its surrounding blood vessels through x-ray imaging. Local anaesthetic is injected into the skin to numb the area. A puncture is then made with a needle in either the femoral artery in the groin or the radial artery in the wrist, (Seldinger technique), before a guidewire is inserted into the arterial puncture. A plastic sheath (with a stiffer plastic introducer inside it) is then threaded over the wire and pushed into the artery. The wire is then removed and the side-port of the sheath is aspirated to ensure arterial blood flows back. It is then flushed with saline. This arterial sheath, with a bleedback prevention valve, acts as a conduit into the artery for the duration of the procedure.
Catheters are inserted using a guidewire and moved towards the heart. Once in position above the aortic valve the guidewire is then removed. The catheter is then engaged with the origin of the coronary artery (either left coronary artery or right coronary artery) and x-ray opaque iodine-based contrast is injected to make the coronary vessels show up on the x-ray fluoroscopy image.
When the necessary procedures are complete, the catheter is removed. Firm pressure is applied to the site to prevent bleeding. This may be done by hand or with a mechanical device. Other closure techniques include an internal suture and plug. If the femoral artery was used, the patient will probably be asked to lie flat for several hours to prevent bleeding or the development of a hematoma. If the arm is used, the patient can ambulate sooner. Cardiac interventions such as the insertion of a stent prolong both the procedure itself as well as the post-catheterization time spent in allowing the wound to clot.
"Cardiac catheterization" is a general term for a group of procedures that are performed using this method, such as coronary angiography, as well as left ventricle angiography. Once the catheter is in place, it can be used to perform a number of procedures including angioplasty, PCI (percutaneous coronary intervention) angiography, balloon septostomy, and an Electrophysiology study.
It is usually carried out after preliminary tests such as electrocardiogram (ECG), echocardiography, treadmill exercise test (stress test), and Holter Ambulatory ECG monitoring, show evidence of an abnormal heart rate or rhythm. During cardiac catheterisation, your physician will insert a long, thin tube into a blood vessel in your groin or arm. The tube will be gently directed to the heart and to the origin of the coronary arteries. Dye is then injected into the coronary artery while x-ray pictures are taken producing special "pictures" of the arteries that supply blood to the heart (the coronary arteries) and of the main pumping chamber of the heart (the left ventricle).
There may be several injections of the dye, and the catheter may be moved around during the procedure. This is necessary to get different views of your heart and coronary arteries.
The entire time in the cath lab will probably be less than one hour. These images can reveal if one or more of the coronary arteries are blocked or if the left ventricle is functioning properly and pumping blood throughout the body.
Additional information can be obtained about the pressure in the different chambers of the heart and about whether the heart valves are working normally. The dye in the coronary arteries is seen by the x-ray as a white line. A disruption of the white line may signify an area of plaque build-up inside the wall of the artery. For most patients, the primary determining factor is whether a partial or complete blockage in the coronary arteries is present. The doctor and patient must decide whether these blockages should be treated with angioplasty (the balloon procedure) or bypass surgery. The patient must decide whether he or she is willing to undergo one of these revascularisation procedures. If the patient is not willing, there is often little reason to undergo a cardiac catheterisation.
Generally accepted reasons for patients to undergo a cardiac catheterisation include the following:
- Angina pains (i.e., the discomfort from blocked coronary arteries), that are not easily controlled with medication or that interfere daily life.
- Chest pains of uncertain cause that repeatedly recur and defy diagnosis despite other tests
- Angina that occurs at rest despite medical therapy
- Recurrent angina after a heart attack
- Markedly abnormal stress test results
- Heart failure, when the suspected cause is coronary artery disease
- Disease of one or more of the heart valves causing symptoms such as shortness of breath
The risks of cardiac catheterisation are low, but sound medical reason should always determine whether to undergo a cardiac catheterisation procedure.
Occasionally, patients have an allergic reaction to the iodine-based dye used during cardiac catheterisation. People who have had a previous reaction to intravenous dye or who have allergies to shellfish are at increased risk for allergic reaction. The doctor should be aware of the patient's risk for allergic reactions before performing the procedure. Such patients usually are given a steroid and other medications before the procedure to reduce the chance of serious allergic reaction to the dye.
In rare cases, the dye used during the procedure can produce kidney damage, including kidney failure requiring dialysis. People with an increased risk for this complication include those with diabetes or pre-existing kidney disease. Patients at higher risk of dye-induced renal failure are sometimes admitted to the hospital the night before the procedure to receive intravenous hydration beforehand. Good hydration before and during the procedure may decrease the chances of dye-induced kidney failure.
In general, the risk for serious complications, such as stroke, heart attack or death, is very low - approximately one in 1000 in the general population.
Although cardiac catheterisation is regarded as a relatively safe procedure, complications do occasionally occur. These can include:
- Bleeding at the site of sheath insertion.
(This commonly produces a small bruise in the groin, but in rare cases, can lead to more serious internal bleeding).
- Infection at the site of sheath insertion
- Damage to the blood vessels in the groin
- Allergic reaction to the iodine-based dye
- Kidney damage and/or kidney failure
- Heart attack