Watch for warning signs to reduce risk.
- Approximately 87% of all strokes are ischemic, with 30% directly attributed to atherosclerosis of the internal carotid artery.
- Within the first 3 months after a transient ischemic attack (TIA), 10% to 15% of patients will have a stroke, half of which occur within 48 hours of the initial TIA.
- Modifiable risk factors associated with stroke include diabetes, obesity, lack of exercise, and smoking.
JAMES SMITH*, a 65-year-old white man, presents to his primary care provider (PCP) with symptoms consistent with a transient ischemic attack (TIA). He has had three transient episodes of left-eye blindness in the past 2 weeks and today experienced a fourth episode accompanied by right-arm numbness that lasted 30 minutes. Mr. Smith’s past medical history includes coronary artery disease, diabetes mellitus, tobacco use, and hypertension.
The PCP tells Mr. Smith that he may have had several TIAs and is at risk for a stroke. Mr. Smith is sent to the emergency department (ED), where the ED physician orders a carotid ultrasound (to evaluate for carotid stenosis), magnetic resonance imaging (MRI) of the brain (to assess for ischemia or infarct), electrocardiogram (to assess for cardiac arrhythmia), and lab work. The ED physician reviews Mr. Smith’s medication list, ensuring that he’s currently taking anti-platelet and statin therapy. The MRI is negative for a stroke, but Mr. Smith’s carotid duplex reveals velocities consistent with a critical carotid stenosis. Mr. Smith’s TIA symptoms are attributed to the stenosis, and he’s referred to a vascular surgeon who initiates dual anti-platelet therapy. The American Heart Association/American Stroke Association (AHA/ASA) recommends starting dual anti platelet therapy within 24 to 48 hours after a TIA and continuing these medications for 21 days. After 21 days, clopidogrel is continued for 90 days for secondary . prevention. As Mr. Smith has both carotid and coronary artery disease, he’ll continue lifelong antiplatelet therapy.
*Name is fictitious
Carotid stenosis research
In an 8-year study on the prevalence and risk factors of asymptomatic carotid artery stenosis, Kaul and colleagues determined that carotid artery atherosclerosis is a major risk factor for stroke. Hypertension and diabetes also were noted as significant risk factors; 56% of participants with hypertension had a 2.5 times increased risk of ICA stenosis, and 55% of those with diabetes for 15 years or longer had a 6.2 times increased risk.
Baradaran and colleagues studied silent brain infarctions in patients with asymptomatic carotid artery atherosclerotic disease who had unilateral ICA stenosis of 50% or more. Their retrospective analysis of MRI or computed tomography images found that one-third of participants had evidence of silent brain infarctions on the same side as the ICA stenosis. The researchers state that their findings suggest atherosclerotic ICA stenosis is associated with an increased incidence of embolic occlusion in the anterior cerebral circulation. In addition, patients may report lack of carotid stenosis symptoms, but may have suffered at least one small, silent brain infarction. The researchers recommended examining the current treatment guidelines to evaluate if targeted therapy can decrease the risk of stroke. The results of this study indicate the importance of treating patients with carotid stenosis whether or not they have symptoms.
A review by Rubin and colleagues of several randomized controlled trials of carotid stenosis and stroke risk demonstrated that surgical intervention (carotid endarterectomy) provided effective secondary prevention in patients with more than 50% stenosis. However, the same report found that in asymptomatic patients with severe stenosis, endarterectomy effectiveness was significantly less than in symptomatic patients.
TIA as warning sign
A TIA is a brief episode of neurologic deficit resulting from cerebral or retinal ischemia without evidence of cerebral infarction. The ASA calls a TIA a “warning stroke.” Within the first 3 months after a TIA, 10% to 15% of patients will have a stroke, half of which occur within 48 hours after the initial TIA, according to Khare and colleagues.
Because TIA symptoms typically resolve quickly, they’re frequently ignored, but this early warning sign of stroke should be taken seriously. An online AHA/ASA survey revealed that up to one-third of adults in the United States had experienced a TIA symptom but only 3% sought medical assistance. Public knowledge of TIA symptoms and recommended treatments may help reduce the financial burden and physical impairment from stroke caused by ICA stenosis.
Typical symptoms of a TIA or stroke resulting from carotid disease include amaurosis fugax (temporary monocular blindness caused by an embolus in the retinal artery), arm or leg weakness or paralysis, facial paralysis, or speech difficulties (slurred words or an inability to speak). Retinal examination can reveal Hollenhorst plaque (atherosclerotic embolus from the carotid arteries or the aorta). Dizziness, vertigo, and syncope are not caused by carotid stenosis and aren’t considered carotid occlusive disease symptoms. Patients with TIA symptoms should seek evaluation in the ED to help identify the cause of the TIA so that risk factors can be addressed and appropriate treatment initiated.
Mr. Smith’s vascular surgeon reviews his ultrasound and recommends a computed tomography angiography (CTA) to confirm the findings and prepare for surgery. The CTA confirms the critical left ICA stenosis, and the surgeon recommends a left carotid endarterectomy to decrease future stroke risk.
Carotid endarterectomy is recommended for patients who have symptoms of a TIA or stroke and ultrasound or CTA evidence of carotid stenosis in the 70% to 99% range and for patients with asymptomatic carotid stenosis that’s 80% or more. The guidelines for carotid endarterectomy for symptomatic patients are endorsed by the AHA/ASA when the risk of mortality or perioperative stroke is less than 6% and for asymptomatic patients when stroke risk and perioperative mortality is less than 3%. The degree of internal carotid artery stenosis that a surgeon uses when deciding to perform a carotid endarterectomy may vary from one institution to another.
Mr. Smith undergoes the left carotid endarterectomy and is transferred to the intensive care unit (ICU) for postoperative care, which includes monitoring for complications.
After surgery, patients are at risk for several conditions and require close monitoring. Because the carotid baroreceptors are located near the carotid sinus (superior to the carotid bifurcation and site of a carotid endarterectomy), hypertension or hypotension may occur i the early postoperative period. Patients also may be at risk for intraoperative or postoperative stroke caused by embolization from disrupted plaque or a blood clot traveling to the brain from the carotid artery. Neurovascular assessment and vital signs are monitored to prevent hypertension (systolic blood pressure > 180 mmHg) and hypotension (systolic blood pressure < 90 mmHg or mean arterial pressure < 65 mmHg) according to guidelines from the Society for Vascular Nursing.
Other complications associated with carotid endarterectomy include neck hematoma, suture disruption, cerebral reperfusion syndrome, airway compromise, and cranial nerve injuries. Adequate control of hypertension can reduce the risk of neck hematoma, suture disruption, cerebral reperfusion syndrome, and airway compromise (caused by an expanding hematoma).
Although cerebral reperfusion syndrome is rare, it’s the most common cause of intracranial hemorrhage and seizure activity in the first 2 weeks after carotid endarterectomy. Nurses should be aware of carotid reperfusion symptoms to ensure prompt treatment. Symptoms include severe ipsilateral (same side as the carotid endarterectomy) headache, focal contralateral (opposite side) neurologic symptoms, hypertension, or seizure. The nurse should notify the patient’s provider and administer medication to control hypertension, headache, and/or seizure activity as ordered. Rigorous blood pressure control also is required, and a neurologist may be consulted to assist with management.
Cranial nerve injuries associated with carotid endarterectomy include the facial (VII), vagus (X), accessory (XI), glossopharyngeal (IX), and hypoglossal (XII) nerves, with vagus and hypoglossal the most common. Signs of vagus nerve injury are dysphagia or hoarseness; signs of hypoglossal nerve injury include tongue deviation to the operative side. Neurologic and cranial nerve assessments should be performed according to the organization’s protocol.
Medical management for stroke prevention
Medical management for stroke prevention targets both surgical and nonsurgical candidates who have stroke risk factors. Outpatient carotid stenosis management focuses on reducing stroke risk with antiplatelet/antithrombotic, antihypertensive, and hypercholesterolemia (statin) therapy; smoking cessation; diabetes management; and exercise. (See Modifiable risk factors.)
Single antiplatelet therapy with aspirin is recommended to prevent coronary events in patients with ICA stenosis who are asymptomatic and don’t have a history of stroke. For patients with non-cardioembolic acute ischemic stroke, aspirin and extended-release dipyridamole and clopidogrel have shown efficacy. Early antiplatelet therapy with aspirin (81 to 325 mg) should be started within the first 48 hours of symptom presentation, before surgical intervention, and continued after surgery.
Good blood pressure control is essential to stroke prevention. In patients who are neurologically stable, a blood pressure goal of < 140/90 mmHg is considered safe and reasonable to maintain for long-term control.
Hypercholesterolemia (statin) therapy
Statin therapy is recommended for primary and secondary prevention of atherosclerotic cardiovascular disease (ASCVD). According to the 2018 American College of Cardiology (ACC)/AHA guidelines for treating blood cholesterol, high-intensity statin therapy is recommended to reduce ASCVD in adults younger than 75 years old. The AHA/ASA also recommends assessing the coronary artery calcium (CAC) score (with a noninvasive heart scan) in patients over 40 years old with uncertain risk status. CAC scores range from 0 (low risk) to >100 (an indication to start statin therapy).
After surgery, Mr. Smith is neurologically intact and has stable vital signs. He’s discharged 24 hours after his ICU stay. Because Mr. Smith has known atherosclerosis, a statin medication and aspirin are prescribed at discharge. He also receives education about smoking cessation and the various pharmacologic therapies available.
Currently, the United States Preventive Services Task Force recommends against screening for asymptomatic carotid stenosis. However, ACC/AHA guidelines recommend cardiovascular risk assessments (age, cholesterol, gender, ethnicity, blood pressure screening, diabetes, and tobacco use) in all adults to help reduce cardiovascular events and stroke risk associated with ICA stenosis.
Pamela Anderson is an adult nurse practitioner in vascular surgery at St. Vincent Medical Group in Indianapolis, Indiana. Terri Townsend is a staff educator for cardiovascular and outpatient services at Community Hospital in Anderson, Indiana. Jennifer Schneider Davis is an adult nurse practitioner at the Ball State University Student Health Center in Muncie, Indiana.
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