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Carotid Percutaneous Transluminal Angioplasty
A procedure to prevent stroke by opening a narrowed segment of carotid artery using a small balloon

Stroke is diagnosed one half million times each year and consumes a tremendous amount of medical resources, costing over fifteen billion dollars a year. In the early 1990's several well-designed studies clearly demonstrated the advantage of carotid endarterectomy over medical therapy in patients in which the carotid artery is narrowed by 60-70% in selected patients. In certain circumstances, such as a person with severe heart disease or other medical problems that makes carotid endarterectomy risky or if the area of narrowing is high in the neck, angioplasty and/or stenting become an option. The narrowed vessel is first dilated using a small balloon passed through a catheter to the point of stenosis (percutaneous transluminal angioplasty- PTA) and held open with a stent (a small flexible wire mesh brace} not unlike those used in coronary catheterization (percutaneous transluminal stenting- PTS).

Anatomy and Physiology

  • Blood leaving the heart enters the aorta, the main central artery of the body (Figure 1)
  • The first arterial branches off of the aorta are the innominate artery (also called the brachiocephalic trunk), left common carotid artery and the left subclavian artery
  • The innominate artery gives rise to the right common carotid and subclavian arteries. In the neck the common carotid arteries branch into the internal and external carotid arteries, the internal carotid arteries extending upwards in the front of the neck to feed the front of the brain including the frontal, parietal and temporal lobes (see Craniotomy). The vertebral arteries on each side pass upwards in the back of the neck to feed the back part of the brain
Figure 1 - Arteries leading from the aorta to the internal carotid arteries

 

Pathology

  • Arteries become narrowed (stenosis) by the formation of a plaque
  • The plaque is composed of a fatty material and occasionally contains calcium
  • It is sometimes coated with small pieces of clot
  • For some unknown reason a common place for a stenosis to occur is at the point where the internal carotid artery branches from the common carotid artery, though the plaque can be anywhere in the carotid or vertebral circulation
  • When a plaque narrows the vessel lumen (inside of the vessel) by 60-70%, the chance of a major stroke is statistically less with surgery or angioplasty than with medication
  • The chance of a major stroke is also greater if the patient has had a previous small stroke than if he has not had a small stroke. The stroke may occur because
    1. The stenosis in the artery limits the flow of blood to the brain
    2. A blood clot forms in a brain artery (thrombosis)
    3. A small piece of blood clot or plaque breaks off and lodges in one of the arteries in the brain (embolus)
  • When an artery to a part of the brain is blocked, the region that the artery feeds dies (an infarct). This produces the symptoms of a stroke (Figure 2)
  • A hemorrhagic stroke occurs when there is also bleeding into the brain
Figure 2a - CT scan showing an area of dead brain (infarct) in the distribution of the right middle cerebral artery due to a stroke Figure 2b - MRI showing an infarct in the distribution of the right middle cerebral artery due to a stroke

 

History and Examination

  • There are various risk factors that heighten the incidence of stroke. They are:
    1. Increased age
    2. Male
    3. African-American
    4. Family history of stroke
    5. Diabetes mellitus
    6. High blood cholesterol
    7. Obesity
    8. Inactivity
    9. High blood pressure
    10. Smoking
    11. Being overweight
    12. Family history of stroke
    13. Heart disease
    14. Radiation therapy to the neck
  • A patient may or may not have symptoms of a small stroke (transient ischemic attack (TIA) or mini-stroke). The symptoms of a TIA include
    1. Sudden numbness or weakness of the face, arm or leg on one side of the body
    2. Loss of speech, trouble talking or trouble understanding speech
    3. Sudden dimness or loss of vision in one eye
  • Additional symptoms that may represent a stroke are:
    1. Unexplained dizziness, unsteadiness, or fall
    2. Severe, unexplained headache
    3. Double vision
    4. Drowsiness
    5. Nausea and vomiting
  • Using a stethoscope the doctor may hear a bruit (swishing sound synchronous with the heart pulse) over the carotid artery.
    1. The bruit usually means that there is a significant stenosis of the carotid artery
    2. When there are no associated symptoms, this is designated as an asymptomatic carotid stenosis
    3. The stenosis is designated as symptomatic when associated with symptoms of a stroke
  • There may be weakness of one side of the body (the side opposite the stenosis)
  • Speech may be garbled or not understood
  • There may be a loss of vision in one eye
  • The blood vessels of the retina of the eye may show tiny spots that are very small emboli
  • There may be confusion and difficulty in recalling recent events
A stroke is also known as a BRAIN ATTACK. An individual having the symptoms of a brain attack should immediately go to the nearest hospital emergency room that is able to treat a brain attack or call 911. If seen in the emergency room within three hours, medication that dissolves the blood clot in the blocked artery can be given and the stroke reversed. Newer techniques, including breaking up the clot using special catheters and injecting the clot dissolving medication directly into the clotted artery, have extended the window to six hours or more in certain cases.

Tests

  • Doppler/Duplex Ultrasound- A sensor connected to a special computer and monitor is placed over the carotid artery in the neck and images the flow of blood in the artery. The presence and approximate degree of stenosis can be determined. (Figure 3A, 3B)
  • Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI)- Both these exams produce images of the brain which may demonstrate evidence of present or past strokes or evidence of a blood clot. (Figure 2 A, 2B)
  • CT or MR Angiography (CTA or MRA)- These are special types of CT and MRI that produce angiograms without having to pass a catheter into the body
    1. MRA is more accurate than Duplex Ultrasound but not as accurate as the standard angiogram
    2. CTA is closer but not quite as accurate as the standard angiogram
  •  

    Figure 3a - Normal Doppler/Duplex Ultrasound. Common, internal and external carotid arteries are labeled. Figure 3b - Ultrasound demonstrating a high grade (> 70%) stenosis if the internal carotid artery.
  • Angiography
    1. A catheter introduced into the femoral artery in the groin is passed upwards through the aorta and then under fluoroscopic control into each common carotid artery
    2. A dye that shows up on X-ray is injected through the catheter. Serial X-ray films or angiograms are then obtained of the carotid artery circulation Review of the films demonstrates whether a stenosis is present and the degree of the stenosis (Figure 4A)
    3. An ulcer in the wall of the artery may also be found (Figure 4B)
    4. Furthermore, examination of the remainder of the circulation may show a second point of narrowing or the occlusion of a vessel in the brain
    5. Angiography is frequently combined with PTA
Figure 4a - Carotid angiogram demonstrating a 70% stenosis of the internal carotid artery. Figure 4b - Carotid angiogram demonstrating a 50% carotid stenosis along with an ulceration in the plaque.

Indications

  • PTA is most appropriate when carotid endarterectomy is not desirable or possible
  • A patient without symptoms should have a carotid artery stenosis greater than 70% and a patient with symptoms should have a stenosis greater than 60%
  • As with carotid endarterectomy, PTA is indicated if:
    1. The plaque is ulcerated
    2. The patient remains symptomatic on aspirin
    3. Serial studies demonstrate progressive narrowing of the carotid artery
    4. Evidence on CT or MRI of a small stroke that did not produce symptoms
  • PTA is not indicated when
    1. The stenosis is less than 50% in a symptomatic patient
    2. The stenosis is less than 60% in an asymptomatic patient
    3. The patient has a recent large area of dead brain on studies
  • PTA/PTS is not a substitute for carotid endarterectomy since the long-term results of these procedures are still unknown and, at this time, has a greater incidence of stroke as a complication. The chance of stroke is decreasing as this technique continues to improve. Furthermore, the patient must be kept on blood thinners after PTA/PTS, which is not necessary following carotid endarterectomy
  • Indications for PTA/PTS are probably best limited to the following patients:
    1. A symptomatic patient who is relatively young or in extreme age and a prohibitive surgical risk
    2. The stenosis is caused by previous radiation (X-ray) therapy to the neck
    3. The patient has a recurrent stenosis after previous carotid endarterectomy
    4. The stenosis is high in the neck and not reachable with open surgery
    5. The patient is very ill with a stroke in progress and who may also need thrombolytic therapy (infusion of a drug that dissolves small clots)

Procedure of PTA with or without Stent (PAS)

  • The technique is similar to that used in coronary artery therapy (see Coronary Catheterization)
  • The patient is placed on a special flat X-ray table that is used with a fluoroscope (an X-ray unit that allows immediate viewing of the catheter and balloon in the blood vessels)
  • The procedure is carried out under sedation given through a vein (intravenous -IV) and local anesthesia (see Anesthesia) at the site of needle puncture where the catheter is placed, usually in the groin
  • Blood thinner medication (anticoagulant) is given through the IV during the procedure
  • The interventionalist (doctor doing the PTA or PTS) introduces a catheter into the femoral artery in the groin that is manipulated up through the aorta and into the involved artery under fluoroscopic control (Figure 5A)
  • Frequently a special 'umbrella' on a wire (distal-protection device or DPD) is first placed above the plaque to catch any debris that may be loosed from plaque and go to the brain
  • The next step is to position a catheter with a small balloon at its tip within the narrowed segment of the artery. The balloon is inflated, causing the plaque to be pushed against the vessel wall and opening the vessel to blood flow. This alone is called a transluminal angioplasty. (Figure 5B) Debris from the plaque is caught by the DPD
  • Frequently the balloon catheter is removed and replaced with a catheter carrying a collapsed stent (Figure 5C). The purpose of the stent is to keep the plaque from expanding again
  • The catheter is removed leaving the cylindrical mesh in place opposite the plaque (Figure 5D)
  • A second balloon catheter is inserted and the balloon expanded against the stent and plaque to expand the stent and keep the vessel open (Figure 5E). Again any debris is caught by the DPD
  • The balloon catheter is then removed leaving the stent in place. The vessel is then flushed to remove any loose pieces of plaque or clot and the DPD is removed (Figure 6F)
  • At various times during the procedure the X-ray dye is injected under fluoroscopic view to follow the progress of the procedure
  • The catheter is removed from the groin after the procedure and pressure held over the femoral artery to reduce bleeding, or a special small 'plug' may be placed in the puncture opening in the femoral artery before removing the catheter
Figure 5A - Carotid artery stenosis. DPD deployed. (Courtesy Michigan Stroke Network, © T. Graves) Figure 5B - Balloon inflated. (Courtesy Michigan Stroke Network, © T. Graves)
Figure 5C - Catheter with collapsed stent in place. (Courtesy Michigan Stroke Network, © T. Graves) Figure 5D - Stent left in place. (Courtesy Michigan Stroke Network, © T. Graves)
Figure 5E - Balloon expands stent. (Courtesy Michigan Stroke Network, © T. Graves) Figure 5F - Vessel open with stent in place. (Courtesy Michigan Stroke Network, © T. Graves)

 

Risks and Complications

  • Exposure to radiation - the amount of radiation is very small and the risk is difficult to measure. It is important to let the interventionalist know if the patient is pregnant
  • A major complication of this procedure is a stroke, just the medical problem that the patient is trying to avoid by having the surgery. Small amounts of debris or clots may be left behind and travel to the brain causing the stroke. The stroke may be minor or major and can lead to death. Stroke could result in paralysis, loss of feeling, blindness, loss of speech and other physical disabilities. This may be as high as 5-6%
  • Because the artery is diseased, it is fragile and may be further damages by the procedure causing hemorrhage or further obstruction that can lead to stroke or death
  • Rarely the procedure may lead to hemorrhage in the neck or brain that can lead to stroke or death
  • Allergic reaction to the dye which contains iodine. The interventionalist should be told if the patient has an iodine or shellfish allergy. Severe allergic reactions may cause shock or death
  • Infection or discomfort at the skin catheter entrance site
  • Persistent bleeding underneath the skin at the puncture site that may require surgical repair
  • Spasm in the vessels going to the brain or other organs during the procedure that can result in stroke or death
  • There may be no improvement in the condition
  • There is the possibility that emergency surgery may be required at any time during or after the procedure to decrease any of the above complications
  • The procedure may present risks, which are currently unknown and may vary from person to person or the location of the blockage

Postoperative Care

  • After surgery, the patient is placed in the Intensive Care Unit or other unit in which the patient can be closely monitored
  • In the unit the patient is closely monitored for any change in level of consciousness, excessively high or low blood pressure or bleeding
  • The patient may be discharged on the first post-operative day if there are no medical or surgical problems

After Care

  • The patient is placed on blood thinners for at least several months to prevent clotting at the stenosis site
  • A change in life style reduces the risk of further problems in the arteries
    1. Stop smoking
    2. Begin a low fat diet
    3. Check blood cholesterol at least twice per year
    4. Control diabetes and high blood pressure
    5. Have a regular exercise program
    6. Follow up with your doctor at regular intervals