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* From the Advocate Christ Medical Center (Dr. Zelinger), Oak Lawn, IL; and the University of Illinois at Chicago (Dr. Wayhs), Chicago, IL; Harvard Medical School (Dr. Graboys), Lown Cardiovascular Center, Brigham and Women’s Hospital, Boston, MA; and Editor of Clinical Problems in Cardiopulmonary Disease (Dr. Tavel).
Correspondence to: Allan Zelinger, MD, Assistant Clinical Professor of Medicine, Director, Echocardiography Laboratory, Advocate Christ Medical Center, 4400 W 95th St, Suite 407, Oak Lawn, IL 60453
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Introduction |
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 TOP Introduction Questions for ConsultantsComments by Allan Zelinger,...Comments by Thomas B....Follow-up Information and...References |
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The physical examination disclosed a BP of 126/66 mm Hg with a pulse rate of 60 beats/min. The results of a cardiac examination were normal, the chest was clear, and the results of the abdominal examination were normal. The arterial pulses were all present and normal.
Pertinent laboratory values included the following: hematocrit, 41 (normal); BUN level, 26 mg/dL; creatinine level, 1.1 m/dL; fasting blood sugar level, 85 mg/dL; total cholesterol level, 171 mg/dL; LDL, 103 mg/dL; HDL, 45 mg/dL; and triglycerides, 185 mg/dL.
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Questions for Consultants |
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TOPIntroductionQuestions for ConsultantsComments by Allan Zelinger,...Comments by Thomas B....Follow-up Information and...References |
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Comments by Allan Zelinger, MD, and Roberto Wayhs, MD |
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TOPIntroductionQuestions for ConsultantsComments by Allan Zelinger,...Comments by Thomas B....Follow-up Information and...References |
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This case raises several interesting issues. Was the initial EBCT scan justified? Should the abnormal findings of the EBCT scan have dictated a course of treatment that proceeded directly to coronary angiography without the stress test? What treatment should be prescribed for his asymptomatic coronary disease? Occult coronary disease is a major public health concern in our country and is increasingly so in other regions. Coronary artery disease (CAD) remains the number one cause of death in the United States and by 2020 is projected to become a leading killer worldwide. Estimates indicate that at least 50% of the 1,000,000 myocardial infarctions (MIs) that occur annually are a first event for persons without known coronary disease. In many of these cases, death occurs early due to ventricular fibrillation even before the opportunity to benefit from current interventional or thrombolytic therapy. Identifying at-risk individuals is made difficult since 25 to 50% of persons experiencing MIs lack the conventional Framingham risk factors. Newer insights into the pathobiology of MI have indicated that two of three culprit plaques are < 50% stenotic. Inflammation has been suggested to weaken the protective fibrous cap and injure the overlying endothelium, predisposing the patient to plaque rupture or surface erosion with subsequent thrombosis. How do we detect persons at risk when we know that clinical risk factor analysis frequently is inadequate and that stress testing, either by echocardiography or a nuclear technique, will likely yield negative results if nonobstructive plaque is present? In fact, stress testing is not generally advocated to screen for asymptomatic occult CAD.1 More recently, EBCT scanning has gained interest as a coronary screening modality since it can identify persons with both obstructive and nonobstructive plaque. An EBCT scan is able to quantify coronary calcium, which is typically found on pathologic analysis of atherosclerotic lesions. While only 20 to 25% of all plaque is calcified enough to be seen by EBCT scanning, it is unusual to have only "soft," uncalcified, lipid-laden plaque in the absence of any calcified plaque that can be detected by EBCT scan. Moreover, the total CS correlates with the pathologic and angiographic quantity of atherosclerosis allowing EBCT to noninvasively estimate total plaque burden. Because the relationship between the severity of coronary stenosis and the CS is not a direct one, a high CS may occur in the absence of severe angiographic narrowing.2 In addition to its capacity for the detection of occult CAD, the EBCT scan-derived CS is related to coronary prognosis. A 3.6-year study of 1,172 asymptomatic persons demonstrated an odds ratio for coronary events of 14.3 with a CS of > 80, and an odds ratio for coronary events of 19.7 with a CS of > 160. Importantly, EBCT scanning added independently to the prognostic information obtained from clinical risk factors.3 The consideration of the age-related and sex-related percentiles might be a better way to categorize individuals in relation to coronary risk than the absolute CS. The risk to a 45-year-old woman with a score of 100 is greater than that for a 45-year-old man with a CS of 100, and both have a greater risk than a 65-year-old person with a similar CS. A recent study4 demonstrated that 96% of persons who experience a first MI have coronary calcium present. The risk of MI was related to the age and sex percentiles of the CS. About 90% of individuals who experienced an MI had a CS in > 50th percentile and 70% had a CS in > 75th percentile. Surprisingly, one third of those experiencing MIs had a relatively low CS of < 100.4 Very few such individuals would be expected to have severe stenosis, and they would almost certainly have escaped detection by conventional stress testing. Because inflammation may be a factor in plaque destabilization, it is possible that concomitant high-sensitivity C-reactive protein values would aid in risk stratifying subgroups with low-to-moderate levels of coronary calcium. However, a prospective study combining coronary CS and C-reactive protein values has yet to be reported.
Getting back to our case, a CS of 100 at the age of 62 years places the patient in the 50th percentile for age and sex. Stress testing to exclude ischemia has been suggested for a CS of > 100 to 400 since coronary stenosis of > 50% is more likely to be present in those individuals with moderate-to-heavy coronary calcium levels. In our practice, there is no score for which we directly proceed to angiography before functional testing, and a stress test is usually obtained for those with a CS of > 100 to 150.
What treatment is recommended when occult CAD is identified by EBCT scanning? Certainly, standard risk factor modification always should be prescribed and an LDL goal should be set, as recommended by the National Cholesterol Education Program guidelines.5 However, when an accelerated atherosclerotic process is identified by EBCT scanning as indicated by a higher percentile score for age and sex, a more aggressive approach should be undertaken to slow plaque growth and to "pacify" any inflammatory process.6 In such cases, the LDL level should be lowered to < 100 mg/dL, the HDL should be increased to > 40 mg/dL, and the triglyceride level should be brought to < 150 mg/dL. Serial EBCT studies have detected the slowing of and even the reversal of plaque growth by using statin treatment to lower LDL levels.7 Aspirin also should be considered as therapy in the absence of contraindication. Since our patient had an excellent functional capacity on the treadmill test and would be expected to have a good prognosis with medical therapy alone, coronary angiography would not be necessary. Medical management with ß-blocker, statin, and aspirin therapy should suffice. Perhaps, in view of the recently completed Heart Outcomes Prevention Evaluation trial, therapy with an angiotensin-converting enzyme inhibitor might be added as well. While even with these measures there cannot be 100% assurance of not having a future coronary event, the preventive approach for this individual will have been optimized. Only the results of further prospective studies will dictate whether EBCT scanning becomes a more widely utilized means of coronary screening to help stem the epidemic of coronary atherosclerosis we presently confront.
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Comments by Thomas B. Graboys, MD |
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TOPIntroductionQuestions for ConsultantsComments by Allan Zelinger,...Comments by Thomas B....Follow-up Information and...References |
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Our experience published nearly 20 years ago and recently updated underscored the notion that exercise duration as an indicator of intact ventricular function determined outcome and that profound ST-segment depression per se was not a predictor of outcome.8 9 10 11 12 Furthermore, according to the results of this patient’s imaging study, the only area suggestive of ischemia was in the distribution of the right coronary artery. Our enthusiasm for intervening can be tempered, knowing that single-vessel coronary disease in the distribution of the right or circumflex coronary arteries is associated with an extremely low risk for future cardiac events and that the vast majority of such patients can have their condition managed by medical therapy.
At this juncture, I see no role for coronary angiography. I do not believe that subjecting the patient to this procedure would alter the management of his condition. Nonetheless, had typical angina that was refractory to medical treatment or unstable angina emerged, coronary angiography might, of course, be indicated.
The current management of this patient’s condition would include the following:
In the absence of defined outcome data, urging individuals to undergo EBCT scanning as a routine means for disclosing coronary disease raises legitimate concerns regarding not only false-positive results but subjecting patients unnecessarily to both noninvasive and invasive evaluations.
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Follow-up Information and Editorial Comments |
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TOPIntroductionQuestions for ConsultantsComments by Allan Zelinger,...Comments by Thomas B....Follow-up Information and...References |
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This case exemplifies the following two important problems confronting the contemporary clinician: (1) in what ways, if any, should we screen for the presence of coronary artery disease in the asymptomatic individual?; and (2) if such disease is discovered, how far should one proceed in precisely defining its anatomy, and when can treatment modify the subsequent outcome?
Regarding the first question above, a simple analysis of risk factors, such as BP, smoking, and lipid values, has traditionally been used to assess the likelihood of coronary disease. While this information can provide valuable assistance in identifying high-risk populations for more aggressive testing, it does not provide definitive evidence of disease. Stress testing in such high-risk groups may be employed but remains controversial.1 If one tests in this fashion, probably the symptom-limited maximal test with electrocardiography is the method of choice.13 If an individual can display good effort tolerance combined with the absence of symptoms or ECG changes, this generally assures a good prognosis even if coronary disease is known to be present. Under such circumstances, a conservative approach with medical therapy is generally warranted. Inasmuch as stress testing can only detect flow-restricting arterial lesions, tests that can detect lesser levels of disease should assist in a better selection of patients requiring stress testing and/or treatment. As pointed out by Dr. Zelinger, there is mounting evidence that CT scanning of the heart can help to identify actual disease and to provide an assessment of risk for subsequent cardiac events. The test might prove especially useful when applied to groups of patients with multiple risk factors wherein the test results may aid in additional stratification of subsequent risk. As pointed out by Dr. Graboys, however, the indiscriminate use of such testing may result in excessive testing and anxiety to patients.
What should one do after a CT scan detects coronary arterial calcification? In asymptomatic individuals, our approach has been to proceed with stress testing with ECG, although some would recommend combining this with nuclear or echocardiographic imaging. If ischemia is detected, management can then proceed in the usual fashion. In the case above, we agree with both consultants that coronary cineangiography did not provide information that was necessary for subsequent management of the patient’s condition. Even if stress testing shows no evidence of ischemia, however, coronary calcification can lead one to confidently conclude that CAD is present and that vigorous measures to control risk factors and lipid levels are warranted. This would include lipid management for secondary prevention of cardiac events according to the most recent National Cholesterol Education Program guidelines.5
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Footnotes |
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Received for publication September 21, 2001. Accepted for publication October 16, 2001.
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References |
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TOPIntroductionQuestions for ConsultantsComments by Allan Zelinger,...Comments by Thomas B....Follow-up Information and...References |
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