A stent is a small mesh tube that is inserted into an artery to keep it open and improve blood flow. Stents are commonly used to treat blockages in arteries caused by coronary artery disease. While stents are generally effective, in some cases stents can fail over time. Recognizing the symptoms of a failing stent is important so that appropriate treatment can be sought.
What is a stent?
Stents are tiny mesh tubes that are inserted into arteries to keep them open. They are commonly made of metal alloys or plastics and come in a variety of shapes and sizes. Stents act like scaffolds to support the inner walls of arteries that have become narrowed or blocked due to plaque buildup. This plaque buildup is called atherosclerosis and happens when cholesterol and other substances accumulate along the arterial walls.
When an artery becomes severely narrowed due to plaque buildup, it can restrict blood flow. This lack of blood flow is called ischemia and can cause symptoms like chest pain or shortness of breath. To treat blocked arteries and improve blood flow, stents are often implanted during an angioplasty procedure. During angioplasty, a catheter with a balloon on the end is threaded through the blood vessels to the site of the blockage. The balloon is inflated to compress the plaque and widen the artery. The stent is then deployed and expanded to hold the artery open.
Stents provide mechanical support to the arterial wall to keep the artery open and prevent it from collapsing or becoming blocked again. There are two main types of stents:
- Bare metal stents – made of surgical stainless steel or other metal alloys.
- Drug-eluting stents – have medication embedded in the stent to help prevent renarrowing of the artery.
Stents are used in multiple blood vessels throughout the body but are most commonly placed in the coronary arteries that supply blood to the heart. Placing a stent in a blocked coronary artery can help treat coronary artery disease and its complications like angina and heart attacks.
How do stents fail?
While stents are designed to remain in place permanently, they can sometimes fail over time leading to recurrent narrowing or blocking of the stented artery. There are two main ways that stents can fail:
Re-stenosis
Re-stenosis refers to the renarrowing of the stented artery that occurs due to tissue growth. Even with a stent in place, abnormal tissue growth can still occur along the inner lining of the artery leading to plaque buildup. As this tissue grows, it can gradually re-narrow the artery.
Drug-eluting stents were designed to reduce re-stenosis by slowly releasing medication to inhibit tissue growth. However, re-stenosis can still occur even with drug-eluting stents. The renarrowing typically happens slowly over months to years after stent placement.
Stent thrombosis
Stent thrombosis is the formation of a sudden blood clot inside the stent. This is a rare but serious complication that can occur in the days, weeks or even years after a stent procedure.
When a clot rapidly forms inside the stented area of the artery, it can completely block blood flow leading to a heart attack or stroke. Stent thrombosis tends to occur more frequently with bare metal stents compared to drug-eluting stents.
Risk factors for developing stent thrombosis include:
- Not properly taking prescribed anti-platelet medications like aspirin or clopidogrel
- Having a condition that predisposes to increased blood clotting like inherited clotting disorders
- Prematurely discontinuing anti-platelet medications
- Having stents placed in emergency situations like a heart attack
What are the symptoms of a failing stent?
The symptoms of a failing stent depend on the underlying cause and which artery has the stent.
Coronary artery stent failure
For stents placed in the coronary arteries of the heart, the most common symptom of stent failure is recurrent chest pain, also called angina. Angina occurs when there is not enough blood flow to meet the heart’s needs. Just like prior to the original stent placement, decreased blood flow through a failing stent can cause angina.
Angina typically causes pressure, tightness, heaviness, shooting pain, or burning sensation in the chest. It may radiate to the jaw, neck, shoulders, back, or arms. Angina is often provoked by physical exertion or emotional stress and relieved by rest.
Other symptoms of a failing coronary stent may include:
- Shortness of breath
- Abnormal heart rhythms
- Fatigue, weakness
- Lightheadedness, dizziness
A failing coronary stent may also show signs and symptoms of a heart attack if a blood clot rapidly forms within the stent leading to a complete blockage. Heart attack symptoms can include:
- Severe central chest pain
- Pain that radiates to the arms, neck, jaw, back or stomach
- Shortness of breath
- Sweating, nausea, vomiting, anxiety
- Lightheadedness, dizziness, loss of consciousness
Carotid artery stent failure
For stents placed in the carotid arteries of the neck, which supply blood to the brain, symptoms of a failing stent may include:
- Transient ischemic attacks (TIAs) – brief stroke-like symptoms that resolve within 24 hours, often called mini-strokes. TIAs may cause sudden weakness, numbness, vision changes, difficulty speaking, or dizziness.
- Stroke – longer lasting symptoms of slurred speech, weakness on one side, vision loss, difficulty walking, severe headache.
- Fainting
- Dizziness
These symptoms are caused by decreased blood flow to parts of the brain supplied by the stented carotid artery.
Peripheral artery stent failure
In the arms or legs, symptoms of a failing stent in the peripheral arteries can include:
- Pain, cramping or fatigue in the muscles of the arms or legs when using them that is relieved by rest – this is called claudication
- Foot or leg pain at rest that disturbs sleep
- Skin wounds on the arms or legs that are slow to heal or will not heal
- Gangrene or skin ulcers on the limbs
Decreased blood flow through a failing peripheral artery stent reduces oxygen supply to the muscles and skin.
Renal artery stent failure
For stents placed in the renal arteries that supply the kidneys, there are often no symptoms of stent failure. Decreased blood flow through a failing renal stent can lead to high blood pressure that requires medication to control, but this is usually without specific symptoms.
Rarely, a completely blocked renal stent can cause sudden flank pain, nausea and vomiting.
Diagnosing a failing stent
If symptoms and history suggest a stent may be failing, diagnostic tests can confirm stent failure and determine the location and extent of the problem:
- Angiogram – This special x-ray imaging procedure injects dye into the blood vessels to visualize flow through the stented artery. Blockages, narrowing, or blood clots within a stent can be identified.
- Intravascular ultrasound – A tiny ultrasound probe is threaded into the stented artery to provide detailed imaging of the inside of the stent and artery wall.
- Optical coherence tomography – Advanced imaging similar to intravascular ultrasound but uses light waves instead of sound waves to give very detailed artery images.
- Blood tests – Certain blood tests like cardiac enzyme tests can help diagnose heart attack. Blood clotting tests may be done to assess for clotting disorders.
- Stress testing – Tests like a treadmill stress test, stress echocardiogram or nuclear stress test can reveal decreased blood flow through a failing cardiac stent.
- CT or MR angiogram – These less invasive imaging scans require injection of contrast dye to visualize artery/stent blood flow.
Identifying the location and cause of stent failure will guide appropriate treatment.
Treating a failing stent
The main options for treating a failing stent include:
Medical therapy
Maximizing medical therapy involves:
- Taking anti-platelet medications like aspirin and clopidogrel to prevent blood clots
- Using drugs to lower blood pressure and cholesterol
- Controlling diabetes through diet, exercise, and medication
- Stopping smoking to halt further artery damage
This helps slow the progression of plaque buildup and development of symptoms. However, medical therapy alone is often insufficient to treat a severely failed stent causing worsening symptoms.
Repeat angioplasty
A repeat angioplasty can be done to re-expand the narrowed stented segment using a balloon catheter. Often another stent is placed inside the old stent at the same time (stent-in-stent placement). This can help improve blood flow through a severely narrowed stent due to tissue growth.
Bypass surgery
Coronary artery bypass grafting (CABG) open heart surgery involves grafting a healthy artery or vein to bypass the blocked stented artery. This can restore blood supply to the heart or other organs supplied by severely blocked stents that cannot be reopened by angioplasty.
Thrombectomy
If a stent thrombosis has occurred due to development of a large blood clot within the stent, emergency treatment is needed. Thrombectomy techniques can be done to remove the clot and restore blood flow. This may be done surgically or using catheter-based techniques.
Stent removal and replacement
If a stent shows evidence of fracture, shifting position, or has developed recurrent clots despite medication, surgery may be done to remove the stent and replace it with a new one. This is rare and only considered when absolutely necessary.
Deciding on the appropriate treatment approach depends on the severity of stent failure, risks of repeat procedures, and the patient’s preferences. Monitoring closely for any symptoms of stent failure is key, as prompt repeat intervention leads to better outcomes when stents begin to fail.
Preventing stent failure
While stents can fail for various reasons, the following measures can help reduce the likelihood of stent failure:
- Carefully following provider instructions regarding anti-platelet medications like aspirin and clopidogrel after stent placement. These medications reduce the risk of dangerous blood clots forming within the stent.
- Making dietary changes and exercising to reach optimal cholesterol and blood pressure levels, and control other cardiovascular risk factors like diabetes.
- Quitting smoking and avoiding secondhand smoke, which damages blood vessels.
- Reporting any potential stent-related symptoms promptly to the healthcare provider.
- Attending regular follow-up appointments to monitor the stented artery.
- Following the recommended exercise/activity guidelines provided after the procedure to allow proper stent healing.
While no stenting procedure is completely free of complications, adhering closely to medical therapy and lifestyle changes can help stents remain open for longer.
Conclusion
Stents are designed to remain in place permanently, but in some cases these tiny mesh tubes implanted in arteries can fail over time. This leads to recurrent narrowing or sudden blocking of the stented artery. Depending on the type of stent and location in the body, symptoms of a failing stent can include angina, leg pain with activity, strokes, high blood pressure, or even heart attack or kidney failure if complete blockage occurs.
If stent failure is suspected, tests like an angiogram or CT scan can assess blood flow through the stent. Treatment options for a failing stent range from medication and lifestyle changes to repeat artery opening procedures or bypass surgery in severe cases. While a perfect solution to prevent stent failure doesn’t exist, medications, diet, exercise, and smoking cessation go a long way in extending the life of artery stents.