Definition Stent
A stent is an artificial vessel support and is used to keep occluded vessels open for a long time. In addition, stents can also be used in other hollow organs if there are occlusions or unnatural connections to other organs or if there is a threat of occlusion due to a disease process. In most cases, stents are used in vessels or hollow organs if the function is impaired by an occlusion (stenosis) of various causes.
The decision to implant a stent in a blood vessel is made when a vessel is so narrowed that the tissue behind it or even a whole organ or body part can no longer be adequately supplied. Most frequently, stents are implanted in the coronary arteries. This is often necessary when, in the course of coronary heart disease, the blood supply to the heart muscle is no longer guaranteed, resulting in restrictions in heart function or even a heart attack.
In addition to the application on the heart, further indications are vascular occlusions in the area of
- Renal arteries
- Large basin vessels or the
- Carotid arteries, which are responsible for supplying the brain and whose function is therefore vital.
Stents can hold open not only vessels but also other hollow organs of the body. They are thus an important support in the therapy of various types of cancer. One such example is esophageal cancer, in the course of which tumor growth can lead to oesophagus closure.
The implantation of a stent can keep the esophagus open and thus prevent a considerable reduction in the patient’s quality of life, since an obstruction of the esophagus does not allow the patient to eat independently and swallow saliva. Stents can also be helpful in the symptomatic treatment of other cancers that displace structures such as the bile ducts or respiratory tract and prevent complications. Another indication is an esophago-tracheal fistula, an unnatural opening between the esophagus and trachea.
This can be closed with a stent. When implanted in a vessel, the stent is usually inserted via the groin with the help of a catheter, so that no large wound is made during the operation. The patient is awake during this procedure, only the puncture site where the doctor punctures the vessel is locally anesthetized and the patient is given a sedative.
The inner walls of the vessel do not contain pain receptors, so the stent itself is not painful. First, an artery in the groin region, or more rarely, in the arm is located and punctured. Now a so-called airlock is placed to prevent blood loss through the lesion at the artery.
It seals the punctured area in the vessel and keeps it open. A catheter can now be inserted into the vessel through the airlock. First, a guide wire is inserted, with the help of which the affected area of the vessel can be located.
This is done by taking advantage of the fact that the metal wire can be seen very clearly in an X-ray image. To check the position of the wire, the physician can take X-rays again and again during the intervention and thus always knows exactly where it is located in the vessel. Once the catheter has reached the correct position, it can now be inserted via the wire.
In order to be able to assess the degree of constriction once again, contrast medium can be injected through the catheter, so that the vessel can be well visualized. In the case of stent implantation in the heart, patients often experience the administration of contrast medium as a warm feeling in the chest. After selecting a suitable stent, the stent is then inserted on a balloon and advanced to the narrowed area in the vessel.
The vessel is dilated (expanded) several times by inflating the balloon under very high pressure. Once the affected area has reached the desired inner diameter, the catheter and balloon are pulled out again and the stent remains in the previously constricted area and keeps it open. There are also stents that do not require a balloon in the vessel to expand them, as they can unfold on their own.
However, the narrowed area must be sufficiently dilated with a balloon before implantation, since the stent alone is not capable of doing this. After implantation, a pressure dressing is applied over the puncture site to prevent secondary bleeding. This pressure dressing should not be removed for 24 hours after a physician has thoroughly examined the site and found it to be unremarkable.To do this, the doctor uses a stethoscope to listen to the vessel and search for hematomas to detect any damage to the vessel.
This stent implantation takes place under general anesthesia. In the case of a tumor that reduces the diameter of the hollow organ, the position and size of the hollow organ must first be precisely examined by means of X-ray. It is advisable to mark the dimensions, for example on the patient’s thoracic wall, with metal markers in order to find the optimal location with the help of an X-ray image when implanting the stent.
The stent must be as long as the area covered by the tumor to ensure that the organ remains open for a long time. If necessary, during the operation prior to implantation, the affected constriction is first dilated with a balloon and then the stent is inserted. Depending on the location of the stenosis, stents of different materials are used.
Once the stent is placed in the appropriate location, it expands, this takes some time and is only completely closed after one day. Then the stent has reached its maximum strength. The implantation of a stent in a vessel is a low-risk procedure that rarely leads to serious complications.
At the puncture site, bleeding or hematoma may occur as mentioned above. In order to avoid infection, it is essential to work under sterile conditions. The skin area above the artery to be punctured should be well disinfected so that no skin germs enter the body when the skin is punctured.
An arteriovenous fistula can also occur at the puncture site. This is an unnatural connection between an artery and a vein, which must be removed by laser or vascular surgery. The contrast medium used to visualize the vessels can cause allergic reactions.
Caution is required in the case of pre-existing kidney damage. Contrast media are excreted via the kidney and can further worsen limited renal function, which is why the renal function is checked before use. Some contrast media contain iodine.
These must not be used in the case of thyroid diseases, as a hyperthyroid crisis may occur. Due to these risks, the thyroid gland is also tested for its function in addition to the kidney before an operation. Other very rare complications are cardiac arrhythmia during the implantation of a stent in the heart, which usually disappears after the operation, but in the worst case, a patient may have to be resuscitated.
Since the stent is a foreign body in the vessel, a blood clot may form. This thrombus can, under certain circumstances, clog downstream vessels, which leads to the formation of an infarct in the affected tissue. In the example of the heart, a heart attack can be triggered in this way.
To prevent this complication, the patient is administered highly effective anticoagulants during the intervention, which prevent the formation of a blood clot. However, these drugs also have side effects, such as an increased risk of bleeding due to poor coagulation and intolerance reactions. When implanting in hollow organs, bleeding may occur due to tissue damage caused by the doctor.
Bleeding or tissue damage in the area of the stent is also possible. A further risk is the slippage of the stent, which, depending on its position in the oesophagus for example, can lead to damage to the gastrointestinal tract. The stent in the esophagus can also constrict the windpipe, which can lead to shortness of breath. This topic may also be of interest to you: The Bypass
