Practical Considerations for Vascular Screening
Practical Considerations for Vascular Screening
Author: J. Crayton Pruitt, MD, FACS, Founder and Director Emeritus of the Vascular Institute of Florida, St. Petersburg, Fla.
Peer Reviewers: William M. Blackshear, Jr., MD, Director and Surgeon-in-Chief, Vascular Institute of Florida, St. Petersburg, Fla., and George S. Lavenson, Jr., MD, RVT, Editorial Board, Vascular Ultrasound Today.
Editor’s Note—Appropriately targeted screening programs are one of the most cost-effective modalities we have in preventing disease or detecting disease at an early, treatable stage. Because cardiovascular disease (CVD) remains the number one cause of death and morbidity in this country, it would seem reasonable that screening for CVD would be a productive exercise. We already routinely screen for high blood pressure, cholesterol, and diabetes. The conundrum for clinicicans is that screening procedures are often insufficiently reimbursed or not reimbursed at all. The current article describes the rationale for expanding the role of CV screening in selected populations and discusses some of the methodological challenges.
It has become increasingly apparent that the most efficient method of diagnosing some medical problems involves screening those persons most at risk for the condition. Screening can be defined as "a mass examination of the population to detect the existence of a particular disease."1 (See Table 1.)
| Table 1. Common Medical Conditions for Which Screening Tests are Frequently Recommended |
| • PAP smear for carcinoma of the cervix.2 |
| • Mammography for carcinoma of the breast.3 |
| • Chest x-ray for carcinoma of the lung.4 |
| • Bone density for osteoporosis.5 |
| • EKG rhythm strip for atrial fibrillation.6 |
This paper deals with vascular screening only and includes a discussion of recording of pertinent medical history, risks, patient education, notification of results, sensitivity, specificity and predictive value. (See Table 2.)
| Table 2. Vascular Conditions for Which Screening may be Helpful |
| • Hypercholesterolemia or lipidemia |
| • Carotid stenosis |
| • Abdominal aortic aneurysms |
| • Peripheral arterial insufficiency |
| • Atrial fibrillation |
| • Hypertension |
Obtaining History
The necessary history to be obtained and recorded when screening for vascular conditions should include questions providing information concerning risk factors and symptoms suggestive of the conditions. (See Table 3.)
| Table 3. Obtaining History |
| Screening for vascular conditions should include the following questions: |
| 1. Have you ever had a stroke or have you ever had a sudden temporary weakness or numbness of the face, arms, or legs? |
| 2. Have you had a sudden loss of speech or trouble understanding speech? |
| 3. Have you had a sudden transient memory loss? |
| 4. Have you had a sudden loss or shading of your vision, either temporary or permanent? |
| 5. Have you had severe dizzy spells? |
| 6. Have you had a recent change in personality? |
| 7. Have you ever been told that you had carotid artery disease? |
| 8. Have you been told that you have atherosclerosis or hardening of the arteries? |
| 9. Have you ever had a ministroke? |
| 10. Have you had an aortic ultrasound test in the past? |
| 11. Has anyone in your family had a stroke? |
| 12. Has anyone in your family had heart disease? |
| 13. Has anyone in your family had diabetes mellitus? |
| 14. Has anyone in your family had an abdominal aortic aneurysm? |
| 15. Have you ever been told that you have a high cholesterol level in your blood? What was your cholesterol when last tested? |
| 16. Have you ever been told that you have a high triglyceride level? |
| 17. Are you currently taking medication for high cholesterol? If yes, what is the name of the medication? |
| 18. Do you have leg pain during exercise, which is relieved by rest? |
| 19. Do you have constant leg pain? |
| 20. Do you have numbness or loss of sensation in your feet? |
| 21. Do you have hair loss from your toes and feet? |
| 22. Do minor scratches and injuries heal properly? |
| 23. Do your legs and feet feel cold all the time? |
| 24. Have you ever had an ultrasound test of your abdominal aorta? If so, when? Results? |
| 25. Have you ever had a carotid ultrasound test? When? Results? |
| 26. Do you smoke? |
| 27. Have you ever smoked? How long? How many packs per day? When did you quit smoking? |
| 28. How far can you walk without leg pain? |
| 29. Have you ever been told that your blood pressure was elevated? |
Risk Factors for Carotid Stenosis, Abdominal Aortic Aneurysms, and Peripheral Arterial Insufficiency
The most common cause of carotid stenosis, abdominal aortic aneurysm, and peripheral arterial insufficiency is atherosclerotic vascular disease. So risk factors for these three conditions are similar. Those risk factors include:
• Family history. Relatives who have suffered strokes or had peripheral arterial insufficiency or abdominal aortic aneurysms may mean increased risk.
• Age. The risk of vascular problem increases with advancing age.
• Gender. Males are more likely to develop carotid stenosis, abdominal aortic aneurysms, and peripheral arterial insufficiency than females although all three conditions also occur in females.
• Hypertension. High blood pressure damages the wall of the arteries and causes an acceleration of the atherosclerotic process.
• Previous symptoms. Transient neurologic deficits or intermittent claudication may indicate carotid stenosis or peripheral arterial insufficiency.
• Previous stroke. A previous stroke increases the likelihood that the problem will recur.
• Ulcerated plaque. Ulcerated plaque in the carotid artery increases the danger of emboli or thrombosis.
• Diabetes mellitus. Predisposes to early atherosclerotic disease.
• Myocardial infarction. Previous history of myocardial infarction is a warning sign that the patient has an increased likelihood of developing carotid stenosis or peripheral arterial insufficiency.
• Hyperlipidemia. The elevation of serum cholesterol or triglycerides increases the risk of the atherosclerotic process and intermittent claudication. Pain in the legs often indicates arterial insufficiency and patients with arterial insufficiency in the legs also frequently get abdominal aortic aneurysms or carotid stenosis.
Vascular Conditions for Which Screening may be Helpful Hyperlipidemia
To screen for hypercholesterolemia or hyperlipidemia a lipid profile is ordered, which is a series of blood tests involving measurement of fatty material in the blood. Two types of lipids are measured, cholesterol and triglycerides. They are measured in milligrams per deciliter (mg/dL). The total cholesterol represents the total number of cholesterol particles in your blood. Total cholesterol should be 200 mg/dL or less. The total cholesterol is made up of high-density lipoprotein (HDL), which is considered a good type of cholesterol, and low-density lipoprotein (LDL), which is considered a bad type of cholesterol. The HDL value should be 35 mg/dL or more. The total cholesterol/HDL ratio compares the amount of good cholesterol to your total cholesterol level. A TC/HDL ratio of 4.5 or less is desirable.7
LDL cholesterol is considered undesirable cholesterol. An LDL value of 130 mg/dL or less is normal.
Triglycerides in the blood should measure 250 mg/dL or less.
Blood glucose levels help to determine if one needs to be evaluated for diabetes mellitus. A glucose value of less than 120 mg/dL is normal and more than 120 mg/dL is abnormal.
Carotid Stenosis
Although there are at least 20 different conditions that can lead to stroke, almost 90% of strokes are caused by carotid stenosis, atrial fibrillation with emboli to the brain, and hypertension with hemorrhage into the brain. It should be possible to screen for the three conditions to find those most at risk and, with treatment, significantly reduce the incidence of stroke. This should be done because in spite of our current knowledge of the causes of stroke, it is estimated that in 1998 there were 730,000 strokes in the United States alone.8 More than 4 million persons die each year worldwide of strokes.
The primary cause of stroke is carotid stenosis. About 50% of people who have a stroke do not have any symptoms before they have the stroke, so in order to identify the asymptomatic patients at risk for stroke screening is the most efficient way. National and international cooperative studies, which were double-blind carefully monitored studies, have now provided information on which groups of patients with carotid stenosis should be treated medically and which groups should be treated by carotid endarterectomy. Those national and international cooperative studies include:
• The North American Symptomatic Carotid Endarterectomy Trial (NASCET). The NASCET study reported February 21, 1991, and indicated that carotid endarterectomy was highly beneficial for patients with recent hemispheric transient ischemic attacks with ipsilateral 70-99% stenosis.9
• The European Carotid Surgery Trial (ECST) was reported also in 1991, confirming surgery was better than medical management for patients with 70-99% unilateral carotid stenosis who were symptomatic.10
• The VA Symptomatic Carotid Endarterectomy Trial reported also in 1991 that surgery was better than medical management for patients with 70% stenosis in one carotid artery who were symptomatic.11
• The Asymptomatic Carotid Atherosclerosis Study (ACAS) was a study of asymptomatic patients with 60% stenosis of one carotid artery. Results were reported on May 10, 1995. Results indicated that when carotid endarterectomy in these patients was performed in medical centers with documented combined perioperative morbidity mortality rates of less than 3%, surgery was better than medical management.12
In order to significantly reduce the 730,000 strokes that occur in the United States each year it will be necessary to screen those patients at risk for carotid stenosis in order for them to be treated before the actual stroke occurs. At the present time it is probably wise to recommend carotid endarterectomy for prevention of stroke in patients who have 60% or greater stenosis if there are no serious medical contraindications.
Risk Factors for Stroke Identified in the NASCET Study and the European Carotid Surgery Trial
• Age older than 80 years.
• Male gender.
• Systolic blood pressure above 160 mm Hg.
• Diastolic blood pressure above 90 mm Hg.
• Transient ischemic attacks occurring within the previous 31 days.
• Previous completed stroke.
• Greater than 80% carotid stenosis.
• Plaque ulcer.
• History of smoking.
• Myocardial infarction.
• Congestive heart failure.
• Diabetes.
• Hyperlipidemia.
• Intermittent claudication.
• High blood pressure.
The odds of having a stroke within two years in the medically treated patients increased with the number of risk factors.
Screening for Carotid Stenosis
If everyone who were going to have a stroke had a symptom first, then there would not be a problem in diagnosing this condition before the stroke occurred. It is true, however, that at least half of the people who have a stroke do not have any prior transient ischemic attacks. The stroke is the first event. Therefore, it is necessary to perform some type of screening test to determine which patients are at risk. Many patients with significant carotid stenosis have a bruit but a large number of patients with significant carotid stenosis do not have a bruit. Some of those patients have more than 90% stenosis and still do not have a bruit. Therefore, listening with a stethoscope or even a handheld Doppler device is not adequate. It is necessary to do an ultrasound screening test to rule out asymptomatic carotid stenosis. The test is painless, harmless, and inexpensive. The National Stroke Association has recommended a program for screening for carotid artery stenosis, atrial fibrillation, and hypertension in all persons older than 50 years of age.13 Organizations, which recommend screening of the carotid artery, have recommended screening methods varying from simply listening to the carotid artery with a stethoscope or listening to the carotid artery with a handheld Doppler to performing an abbreviated color flow duplex ultrasound test.14 The most accurate method of screening is an abbreviated color flow duplex ultrasound test. If a person is screened and found to have no atherosclerotic plaques in the carotid arteries, another screening test is not necessary for about three years. If he or she is found to have a mild amount of atherosclerotic plaque, another test should be done in two years. If a mild to moderate amount of plaque is reported, another test should be done in one year and if a moderate to severe amount of plaque or a severe amount of plaque is reported, instructions should be included with the report advising that an appointment be made with his or her personal physician. Usually at that time the physician will suggest ordering a more complete ultrasound test at an accredited vascular laboratory. Whether treatment is necessary will depend on the confirmation of significant stenosis by the more complete test. Some physicians will prefer to have a digital carotid arteriogram rather than another ultrasound test, and some will recommend a magnetic resonance angiogram.
Cost-Effectiveness of Screening
There are many screening organizations in the United States that do abbreviated ultrasound screening of the carotid arteries for carotid stenosis. Most charge about $35 for a screening test. Those patients who have moderately severe or severe stenosis on the screening test are sent certified letters advising them to see their physician to be considered for further diagnostic testing. Several articles have appeared in the literature recently recommending screening for asymptomatic carotid stenosis.15-20 "Cost-Effectiveness of Screening for Asymptomatic Carotid Stenosis" was addressed and confirmed by several authors.21-24 Patients older than 65 were 4.1 times more likely to have significant stenosis than those younger than 65.
Abdominal Aortic Aneurysm
Abdominal aortic aneurysm is a fairly common condition, which is a major cause of sudden death if not diagnosed before rupture occurs.25 Abdominal aortic aneurysms increase in incidence with advancing age. They usually occur just below the renal arteries, although aneurysms can also involve the renal artery segment and also the thoracic aorta. Most abdominal aortic aneurysms are secondary to atherosclerosis. Surgical removal of the aneurysm with insertion of a Dacron or gortex graft is the conventional method of treating abdominal aortic aneurysms. At least 95% of abdominal aortic aneurysms can be successfully treated if operated on electively. It is for that reason that it is extremely important to detect the aneurysm before rupture. Risk factors include age, smoking, elevated serum cholesterol levels, hypertension, and coronary artery disease. Family history is important and some aneurysms are thought to have a hereditary component. Often an abdominal aortic aneurysm can be suspected or diagnosed by physical exam. A pulsating mass is sometimes palpable.26 If not diagnosed and treated by grafting, 33% will rupture within one year and 81% will rupture within five years. Most aneurysms are asymptomatic until rupture.
Screening for abdominal aneurysms is usually accomplished by duplex ultrasound, which is noninvasive and painless and inexpensive.27 Most screening facilities charge approximately $35 for an aortic ultrasound screen to discover the presence of an abdominal aortic aneurysm. Recent statistics from a leading screening organization revealed that 1.84% of all patients screened were positive for abdominal aortic aneurysms. The prevalence of abdominal aortic aneurysms in older adults (age 65-80 years) varies from 4-7%.28,29 An abdominal aorta is considered to be aneurysmal if its diameter is greater than 3.0 cm.30 Some aneurysms can be repaired by endovascular stent grafts.31-34 Additional papers concerning aortic aneurysm screening are given.35-37 One group thought screening was a bad idea.38
Peripheral Arterial Insufficiency
Peripheral arterial insufficiency is most often caused by atherosclerotic vascular disease, and risk factors include hyper-cholesterolemia, smoking, hypertension, diabetes mellitus, age, and heredity. These are essentially the same risk factors as those causing atherosclerosis in the coronary vessels and the extracranial vessels, so if a patient is found to have peripheral arterial insufficiency a physician should suspect that the patient might also have coexisting atherosclerosis in the coronary arteries or extracranial vessels. Some of these risk factors are treatable to slow down the formation of the atherosclerotic process. Those include hypercholesterol or lipidemia, hypertension, smoking, and diabetes mellitus. Screening for arterial insufficiency involves obtaining Doppler blood pressures in the upper arm and in the ankles bilaterally. An ankle/brachial index is calculated and if the ankle/brachial index is less than 0.90 the person is considered to have a positive screening test and is advised to have further evaluation by his or her physician. The calculation of the ankle/brachial index is easy to do and it is a reliable test for peripheral arterial insufficiency.39-41 Diabetic patients frequently have increased arterial wall stiffness and the vessels are not easily compressible, resulting in high-pressure readings. In cases of high-pressure readings because of non-compressibility, diabetes mellitus needs to be ruled out. Lifeline screening recently reported an incidence of 5.74% of patients screened who were found to have abnormal ankle/brachial indices.42 The usual charge for screening for peripheral arterial insufficiency is about $35.
Atrial Fibrillation
Atrial fibrillation is a condition occurring when the two upper chambers of the heart contract in a rapid but irregular and inefficient manner. The rhythm is not capable of pumping the blood in a meaningful way so blood remains static in the upper heart chambers long enough to form thrombi. Some of the thrombi may break loose from the left atrium and travel through the blood vessels to the brain, causing stroke, or they may travel to other organs, causing sudden ischemia to the kidney or legs depending upon their ultimate resting place. More than 2 million adults in the United States have atrial fibrillation and the incidence increases with increasing age.43
Risk Factors for Atrial Fibrillation
Risk factors include history of rheumatic fever, history of hypertension, and history of ischemic heart disease. When any of those conditions cause congestive heart failure the risk of atrial fibrillation is increased.
Structural heart disease is present in 85-90% of patients with atrial fibrillation. Atrial fibrillation affects approximately 4% of the population older than age 60 and 10% of persons older than age 80.44
Large cooperative trials performed in a prospective manner have definitively demonstrated that long-term anticoagulant use can safely reduce the risk of stroke due to atrial fibrillation for those patients who cannot be cardioverted successfully and monitored in a normal sinus rhythm. The anticoagulant treatment helps to prevent the formation of blood clots and therefore reduces emboli to the brain. At the present time, fewer than half of the appropriate patients with atrial fibrillation are actually on long-term anticoagulation treatment.45,46
Atrial fibrillation is not difficult to diagnose. It can usually be discovered with a screening test using a rhythm strip obtained from an electrocardiograph machine and interpreted by a physician. (See Figure 1.)
Approximately 15% of strokes are caused by atrial fibrillation with thrombi formation and emboli to the brain.47 If efficient screening methods were used and those patients with atrial fibrillation were diagnosed and cardioverted or placed on anticoagulant therapy most of these strokes could be prevented.48,49
Hypertension
Hypertension or abnormal high blood pressure over time injures key organs and blood vessels in many parts of the body. Damage to these blood vessels often leads to atherosclerosis, increasing the risk of heart disease and stroke. More than 62 million Americans are hypertensive and nearly half of them do not realize they are hypertensive and are not controlling the problem.50 Usually hypertension causes no symptoms and people may be hypertensive for many years without realizing it. Screening for hypertension is easy, requiring only a blood pressure measurement on several occasions to confirm consistent elevation of the pressure above 140/90 mm Hg. If a screening test reveals hypertension, the patient should be referred to his or her physician in order that additional testing may be performed to determine that the blood pressure persistently remains above 140/90 mm Hg and so additional testing can be performed to determine why the patient has hypertension. The hypertension most often is essential hypertension but sometimes it is due to kidney disease or renal artery stenosis or coartation of the aorta or an adrenal tumor. Risk factors include:
1. Age. Hypertension increases with increasing age.
2. Race. African Americans, Asians, Puerto Ricans, Cuban Americans, and Hispanics are more often hypertensive than other groups.
3. Pregnancy. Pregnant women are at greater risk of becoming hypertensive than other women.
If a person is diagnosed as having hypertension it is extremely important that the hypertension is treated to prevent the complications of persistent hypertension.
Education
The screening event for all the above conditions should be considered an opportunity to better educate potential candidates about the conditions for which they are being screened. Literature pointing out the prevalence of the conditions, the risk factors, and the symptoms of the conditions should be provided and the likely outcome with and without treatment should be discussed. The group being screened should be made aware of the accuracy of the screen and when or if another screen should be done at a later time and, if so, at what time interval. Companies providing screening tests need to be aware that recommendations for screening too often and screening persons who are not at risk open the companies to criticism for overuse.
Notification of Results
It should be made clear to the person being screened how soon results will be available and how he or she will receive those results. Results should be available within two weeks and preferably results should be mailed to each individual. If the screening test is positive, it is preferable to send the results by certified mail. The individual should be advised in writing to take the written result to their physician so their physician may decide if any further testing or treatment is necessary. Positive screening tests usually require additional testing for confirmation before a definitive diagnosis can be established.
Sensitivity, Specificity, and Predictive Value Sensitivity
The specificity, sensitivity, and predictive value of the test performed should be calculated and provided to all interested parties. There is a trade-off between sensitivity and specificity with any screening tests. To avoid missing those who are "true positive" and increase the specificity, one must allow for a decrease in the sensitivity.
The sensitivity of a screening test equals the probability that if the screening test is positive, the diagnostic test is also positive. The ratio is sensitivity = screening test +/diagnostic test +.
In other words, in the case of carotid stenosis when we desire to locate all the persons with a carotid stenosis of 60% or greater the screening tests would be reported positive at 60% stenosis, meaning that person should have an additional diagnostic test to confirm. We need to know what is the probability that the diagnostic test (either a complete ultrasound study in a certified vascular laboratory or a carotid angiogram) will actually confirm the 60% stenosis seen on the screening test.
Specificity
The specificity of the test equals probability that if the screening test is negative, the diagnostic test would also be negative. In the case of carotid screening, the screening ultrasound test reported less than 60% stenosis and on the report the category sent out was "does not need follow-up testing." If one performed a diagnostic test anyway on that person (either a complete carotid ultrasound test in an accredited vascular laboratory or a carotid angiogram), what is the probability that the diagnostic test would also be negative? This would only be done at some expense because insurance companies and Medicare could not be expected to pay for these expensive tests to confirm negative screening tests.
By increasing the threshold velocity in the internal carotid required to call a stenosis significant we can increase the likelihood of the diagnostic tests confirming a positive screening test (sensitivity). However, we at the same time would be increasing the possibility of missing some individuals who actually had a 60% stenosis but were classified as "does not need follow-up diagnostic test." (Specificity.)
Predictive Values
The predictive value of a positive test is equal to probability of the diagnostic test being positive divided by the screening test being positive.
The predictive value of a positive test is the percentage of persons reported positive on a diagnostic test divided by the percentage of persons reported positive on a screening test.
The predictive value of a negative screening test equals the probability of diagnostic tests being negative divided by the screening test being negative.
References
1. Dorlands Illustrated Medical Dictionary. 24th ed. Philadelphia, Pa; London, England: W.B. Saunders and Company; 1968.
2. Eady DM. Primary Care Reports. 123.
3. Hayward RP. Primary Care Reports. 123.
4. National Cancer Institute PDQ Website. htt://cancernet.NCI.NIHgov/cancer/inks. 01/2000.
5. Osteoporosis. http://www.crha-health.ab.ca/hlthconn/items.osteo.htm
6. Patient Outcomes Research Team. "Secondary and Tortuary Prevention of Stroke." Agency for Healthcare and Policy Research publication no. 950051 (Sept. 1995).
7. Caplan LR, et al. American Heart Association Family Guide to Stroke: Treatment, Recovery, and Prevention. New York: Times Books; 1994:69.
8. National Stroke Association Home Page: www.stroke.org (1998).
9. North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med 1991;325:445-453.
10. European Carotid Surgery Trialists’ Collaborative Group. MRC European Carotid Surgery Trial: Interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) carotid stenosis. Lancet 1991;337:1235-1243.
11. Mayberg MR, et al. Carotid endarterectomy and prevention of cerebral ischemia in symptomatic carotid stenosis. JAMA 1991; 266:3289-3294.
12. ACAS. Endarterectomy for asymptomatic carotid artery stenosis. JAMA 1995;273:1421-1428.
13. Be Stroke Smart. National Stroke Association Newsletter 11, no. 2 (1994): 3.
14. Lavenson GS Jr. Carotid screening: Preparing for the future. Vasc US Today 1997;2:61-72.
15. Bluth EL, et al. A screening test for carotid stenosis: A preliminary feasibility study. RSNA: Session 1706: November 28, 1997.
16. Lavenson GS Jr. Carotid screening: Preparing for the future. Vasc US Today 1997;2:61-72.
17. Smith JK, et al. Assessment of new criteria for the duplex Doppler ultrasound detection of clinically significant carotid artery stenosis. RSNA: Session 1703; Nov. 28, 1997.
18. Brown JJ, Pruitt JC. The efficiency of screening for carotid artery stenosis in the asymptomatic population: A historical and clinical perspective. Educational pamphlet for Lifeline Screening, Inc. 1998.
19. Obuchowski NA, et al. Assessment of the efficacy of noninvasive screening for patients with asymptomatic neck bruits. Stroke 1997;28:1330-1339.
20. Fujitani RM, Kafie F. Screening and preoperative imaging of candidates for carotid endarterectomy. Semin Vasc Surg 1999; 12(4):261-274.
21. Yin D, Carpenter JP. Cost-effectiveness of screening for asymptomatic carotid stenosis. J Vasc Surg 1998;27:245-255.
22. Carsten CG III, et al. Use of limited color-flow duplex for a carotid screening project. Am J Surg 1999;178:173-176.
23. Lavenson GS Jr, Sharma D. Cost savings of carotid endarterectomy: Value of one vascular surgeon in one year. Perspectives in Vascular Surgery 1994;7.
24. Brown JJ, Pruitt JC. The efficiency of screening for carotid artery stenosis in the asymptomatic population: A historical and clinical perspective. Educational pamphlet for Lifeline Screening, Inc. (1998).
25. Estes JE, Jr. Abdominal aortic aneurysm: A study of one hundred and two cases. Circulation 1950;2:258.
26. Pysklywec M, Evans MF. Diagnosing abdominal aortic aneurysm. How good is the physical examination? Can Fam Physician 1999;45:2069-2070.
27. Wong JG. Appropriate abdominal aortic aneurysm screening. Postgrad Med 2000;107(3):21-22.
28. Lifeline Screening, Inc; Personal communication, 4-1-00.
29. Kyriakides C, et al. Screening of abdominal aortic aneurysm: A pragmatic approach. Ann R Coll Surg Engl 2000;82(1):59-63.
30. Vardulaki KA, et al. Incidence among men of asymptomatic abdominal aortic aneurysms: Estimates from 500 screen detected cases. J Med Screen 1999;6(1):50-54.
31. Allen RC, et al. What are the characteristics of the ideal endovascular graft for abdominal aortic aneurysm exclusion? J Endovasc Surg 1997;4(2):195-202.
32. Moore WS. The EVT tube and bifurcated endograft systems: Technical considerations and clinical summary. J Endovasc Surg 1997;4(2):182-194.
33. Thompson MM, et al. Aortomonoiliac endovascular grafting: Difficult solutions to difficult aneurysms. J Endovasc Surg 1997;4(2):174-181.
34. Manord JD, et al. Endovascular treatment of abdominal aortic aneurysm: Case report and review of literature. J La State Med Soc 1997;149:334-337.
35. Beebe HG, Kritpracha B. Screening and preoperative imaging of candidates for conventional repair of abdominal aortic aneurysm. Semin Vasc Surg 1999;12(4):300-305.
36. Lindholt JS, et al. Mass or high-risk screening for abdominal aortic aneurysm. Br J Surg 1997;84(1):40-42.
37. Cole CW. Prospects for screening for abdominal aortic aneurysms. Lancet 1997;349(9064):1490-1491.
38. Shiralkar S, et al. The case against a national screening programme for aortic aneurysms. Ann R Coll Surg Engl 1997;79(5):385-386.
39. Ray SA, et al. Reliability of ankle: Brachial pressure index measurement by junior doctors. Br J Surg 1994;81:181-190.
40. Stoffers HE. Peripheral arterial occlusive disease in general practice: The reproducibility of ankle:arm systolic pressure ratio. Scand J Primary Health Care 1991;9:109-114.
41. Fowkes FGR, et al. Variability of ankle and brachial systolic pressures in the measurement of atherosclerotic peripheral arterial disease. J Epidemiol Commun Health 1988;42:128-133.
42. Lifeline Screening, Inc., personal communication, April 1, 2000.
43. Wiener DH. Atrial fibrillation: Comprehensive management in the primary care setting. Monograph from the Temple University School of Medicine, pp. 1-11. 1995.
44. Wolf PA, et al. Atrial fibrillation as an independent risk factor for stroke: The Framingham Study. Stroke 1991;22:983-988.
45. Albers GW, et al. Status of antithrombotic therapy for patients with atrial fibrillation in university hospitals. Arch Intern Med 1996;156:2311-2316.
46. Stafford RS, Singer DE. National patterns of warfarin use in atrial fibrillation. Arch Intern Med 1996;156:2537-2541.
47. Kannel WB, et al. Epidemiologic features of chronic atrial fibrillation: The Framingham Study. N Engl J Med 1982;306: 1018-1022.
48. Patient Outcomes Research Team. Secondary and tertiary prevention of stroke. Agency for Healthcare and Policy Research publication no. 95-0091 (Sept 1995).
49. Stafford RS, Singer DE. National patterns of warfarin use in atrial fibrillation. Arch Intern Med 1996;156:2537-2541.
50. Caplan LR, et al. American Heart Association Family Guide to Stroke, Treatment, Recovery and Prevention. New York: Times Books; 1994: 54-55, 58-59.
Physician CME Questions
38. The relationship of carotid bruit with significant carotid stenosis can best be characterized as:
a. Carotid bruit is always present in patients with significant carotid stenosis.
b. Carotid bruit may be present but frequently is not present in patients with significant carotid stenosis.
c. Carotid bruit has no relationship to carotid stenosis.
d. All patients with carotid bruits have significant carotid stenosis.
e. Listening for bruit over the carotid artery is the best screening test available.
39. The asymptomatic carotid artery study ACAS reported in May 1995 concerned asymptomatic patients with:
a. 50% stenosis in one carotid artery.
b. 60% stenosis in one carotid artery.
c. 70% stenosis in one carotid artery.
d. 80% stenosis in one carotid artery.
e. 90% stenosis in one carotid artery.
40. The results of the ACAS study indicated that:
a. carotid endarterectomy when performed in medical centers with morbidity/mortality rates of less than 3% is better than medical management.
b. carotid endarterectomy is as good as medical management.
c. medical management is superior to surgical management with carotid endarterectomy.
d. angioplasty for carotid stenosis is equally as good as endarterectomy.
e. angioplasty with stent insertion is an office procedure.
41. The abdominal aorta is considered to be aneurysmal when the diameter of the aorta is more than:
a. 2 cm.
b. 3 cm.
c. 4 cm.
d 5 cm.
e. 6 cm.
42. The prevalence of abdominal aortic aneurysms in older adults age 65-80 years varies from:
a. 1-2%.
b. 2-4%.
c. 4-7%.
d. 5-8%.
e. 6-9%.
43. Atrial fibrillation with emboli to the brain causes:
a. approximately 10% of all strokes.
b. approximately 15% of all strokes.
c. approximately 20% of all strokes.
d. approximately 25% of all strokes.
e. approximately 30% of all strokes.
44. Which of the following statements is false?
a. More than 62 million Americans are hypertensive.
b. Nearly half of hypertensive patients do not realize they are hypertensive and are not controlling the problem.
c. Hypertension increases with increasing age.
d. African Americans, Asians, Puerto Ricans, Cuban Americans, and Hispanics are more often hypertensive than other groups.
e. Most hypertension is secondary to renal artery stenosis.
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