Cardiovascular

Carotid artery stents: Opening the way to safer stroke prevention

Every 45 seconds, someone in the United States suffers a stroke.

About 80% are ischemic strokes, which result from carotid stenosis caused by thrombi and emboli. The most common location is the bifurcation of the common carotid artery into the internal and external carotid arteries. The external carotid artery doesn’t supply the brain, but the internal carotid artery does. It travels up the neck and supplies the middle cerebral and anterior cerebral arteries. Thus, an occlusion can trigger a significant stroke.

Why use a stent? 

The two options for preventing an ischemic stroke are carotid endarterectomy and stent placement. For years, endarterectomy has been standard procedure. But because of improvements in safety—especially the introduction of a distal embolic protection device—more stents are being inserted. Carotid stent placement is less invasive, causes less blood loss, requires shorter hospital stays and recovery time, and poses fewer complications.

Currently, stents can be used for symptomatic patients with greater than 50% carotid stenosis and asymptomatic patients with greater than 80% stenosis. The ideal patients include those who have

• restenosis following carotid endarterectomy
• scar tissue in the neck from surgery or radiation
• a tracheostomy
• lesions that are difficult to reach surgically—for example, high cervical lesions behind the jaw and common carotid lesions below the clavicle line
• serious conditions, such as severe heart failure and a recent myocardial infarction (MI).
Common contraindications include severe vessel tortuosity, heavy calcification at the lesion site, and significant visible thrombus.


Inserting the stent
A physician may perform the procedure in a radiology suite or cardiac catheterization laboratory. Typically, it’s a same-day procedure, though it may require an overnight stay.
During the procedure, a plastic squeaky toy is frequently placed in the patient’s contralateral hand, and the patient is asked to squeeze it during critical steps of the procedure. This duck squeezing test helps evaluate the patient’s neurologic responses. The test is a highly sensitive, specific way to identify neurologic complications. The patient does not receive a sedative, so the physician can evaluate neurologic status before and after every step—the initial angiogram, the placement of the protective device, the first balloon inflation, the stent placement, the second balloon inflation, the removal of the protective device, and the last angiogram. Neurologic evaluations continue after the procedure, as well.

The physician begins the procedure by making a percutaneous puncture in the femoral artery and, using fluoroscopic guidance, advancing catheters to the carotid artery level. Using fluoroscopy and a contrast agent, the physician obtains angiograms of the lesion and the baseline cerebral circulation.

The patient receives heparin to ensure that blood clots don’t form on the wires and at the lesion during the procedure. The dosage is titrated to a target activated clotting time of 250 to 299 seconds.

Then, the physician advances a distal embolic protection device beyond the lesion. This device is either a filter or balloon that prevents emboli from traveling into the intracerebral circulation during the procedure. The physician then determines the size and length of the lesion, so he can select the appropriate-size balloon catheter and stent.

Before placing the stent, the physician will use a balloon catheter to push plaque against the arterial wall. Because the carotid sinus baroreceptor is close to the carotid bifurcation, inflating the balloon can trigger a vasovagal reaction. Thus, to prevent hypotension and bradycardia, the physician may order atropine before inflating the balloon.

After dilating the balloon, the physician places a self-expanding, nitinol stent across the lesion. Then, another balloon is inflated to make sure the stent is fully expanded against the arterial walls. Next, the physician removes the protective device. Postprocedure angiograms are obtained to evaluate vessel patency and intracerebral blood flow.

The entire procedure takes less than an hour.

Checking for complications
At regular intervals after the procedure, monitor the patient’s neurologic status, hemodynamic status, puncture site, and peripheral pulses. Unstable blood pressure is fairly common, but sustained hypotension or hypertension can be serious.

Hypotension
Hypotension may result from the continued pressure on the carotid artery sinus, especially if the lesion is calcified. Women, elderly patients, and patients with a history of MI may be prone to postprocedure hypotension. Administer I.V. fluid or a vasopressor infusion, as ordered, to prevent cerebral hypoperfusion. Also, assess the femoral access site for bleeding or a hematoma, which may be causing the hypotension.

Cerebral hyperperfusion
Cerebral hyperperfusion can develop in a patient with postprocedure hypertension. That’s because the stent suddenly makes patent a previously stenotic artery. And suddenly, the cerebral circulation is subjected to higher vascular pressures, which can lead to an intracranial hemorrhage.Symptoms of cerebral hyperperfusion include ipsilateral headache, confusion, nausea, and vomiting. Postprocedure hyperperfusion isn’t common, but if these symptoms appear with hypertension, the patient must be evaluated. Closely monitor the blood pressure of any postprocedure patient and keep systolic pressure between 100 and 160 mm Hg.

Neurologic status
The protective device used in the stent procedure has dramatically decreased the number of neurologic complications. Elderly patients, patients who undergo longer procedures, and patients with symptomatic carotid artery stenosis, contralateral carotid disease, or severe coronary artery disease have an increased risk of periprocedural stroke.

Monitor the neurologic status of all postprocedure patients to detect signs of cerebral ischemia caused by embolism. A complete neurologic evaluation incorporating the National Institute of Health Stroke Scale should be performed before and after the procedure to identify any neurologic deficit as soon as possible. Report any change in the patient’s neurologic status, so the physician can determine the cause and order treatment to prevent a permanent disability.Discharge teaching

Most complications occur within 24 hours, but some do occur later, so teach your patient the signs and symptoms of neurologic, cardiovascular, and access-site complications. And make sure the patient understands that complications require emergency medical attention. Also, make sure the patient understands the need for antiplatelet therapy, as prescribed. Dual antiplatelet therapy with aspirin and clopidogrel (Plavix) is usually prescribed because it significantly reduces neurologic complications. Teach the patient, too, about vascular risk factors and reinforce the need for lifestyle changes to prevent disease.

Innovation and improvement
Today, carotid stents are used more and more to prevent death and disability from ischemic strokes. And chances are the trend will continue, and stents will get even better. The next innovation will likely be drug-eluting stents.

As a nurse, you should keep on top of such trends, no matter where you work. And, of course, you should understand the nurse’s role in this life-saving procedure.

Selected references
Barr J, Connors J, Sacks D, Wojak J, Becker G, et al. Quality improvement guidelines for the performance of cervical carotid angioplasty and stent placement. J Vasc Interv Radiol. 2003;14:S321-S335.

Gomez C, Roubin G, Dean L, Iyer S, Vitek J, et al. Neurological monitoring during carotid artery stenting: the duck squeezing test. J Endovasc Surg. 1999;6(4):332-336.

Kastrup A, Groschel K, Krapf H, et al. Early outcome of carotid angioplasty and stenting with and without cerebral protection devices: a systematic review of the literature. Stroke. 2003;34:813-819.

Tan K, Cleveland T, Berczi V, McKevitt F, Venables G, et al. Timing and frequency of complications after carotid artery stenting: what is the optimal period of observation? J Vasc Surg. 2003;38:236-243.

Yadav JS, Wholey MH, Kuntz RE, Fayad P, Katzen BT, et al. Protected carotid-artery stenting versus endarterectomy in high-risk patients. N Engl J Med. 2004;351(15):1493-1501.

For a complete list of selected references, visit www.AmericanNurseToday.com.

Carolyn L. Strimike, MSN, RN, CCRN, APRN, BC, is a Cardiac Nurse Practitioner at St. Joseph’s Regional Medical Center in Paterson, New Jersey.

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