(Circulation. 2003;108:1772.)
© 2003 American Heart Association, Inc.
Review: Current Perspective |
From The Center for Vulnerable Plaque Research, University of TexasHouston, The Texas Heart Institute, and President Bush Center for Cardiovascular Health, Memorial Hermann Hospital, Houston (M. Naghavi, S.W.C., S.L., M.M., A.Z., J.T.W.); The Leducq Center for Cardiovascular Research, Department of Medicine, Brigham and Womens Hospital, Harvard Medical School, Boston, Mass (P.L., M.A.); Department of Cardiology and Institute of Experimental Clinical Research, Aarhus University, Aarhus, Denmark (E.F.); Experimental Cardiology Laboratory, Vascular Biology of the University Medical Center in Utrecht, the Netherlands (G.P.); Ohio State University (J.R.); the Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai Medical Center, New York, NY (Z.F.); Cardiac Catheterization Laboratory at the VA Medical Center, University of Kentucky, Lexington (P.M.); Cardiovascular Division, Department of Medicine, Brigham and Womens Hospital, Harvard Medical School, Boston, Mass (P.H.S.); Division of Cardiology, New England Medical Center, Boston, Mass (S.W.); Department of Medicine, Section of Cardiology, Tulane University School of Medicine, New Orleans, La (P.R.); Department of Cardiovascular Pathology, Armed Forces Institute of Pathology, Washington, DC (A.B., A.F., R.V.); Department of Radiology, University of Washington, Seattle (C.Y.); Stanford University Medical Center Stanford, Calif (P.J.F.); Cardiovascular Health Research Unit, University of Washington, Seattle (D.S.S.); Department of Cardiology, Athens Medical School, Athens, Greece (C.S.); Catheterization Laboratory, Thorax Center, Erasmus University, Rotterdam, the Netherlands (C.L.d.K.); Division of Cardiology, Department of Medicine, University of Turku, Finland (K.E.J.A.); Institute of Arteriosclerosis Research and the Institute of Clinical Chemistry and Laboratory Medicine, Central Laboratory, Hospital of the University of Münster, Munich, Germany (G.A.); Department of Clinical Radiology, University of Münster, Munich, Germany (C.R.B.); Mayo Clinic Medical School, Jacksonville, Fla (J.H.C.); Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Ga (Z.S.G.); Bristol Heart Institute, Bristol University, Bristol, United Kingdom (C.J.); Cardiology Division, Massachusetts General Hospital and Harvard Medical School, Boston, Mass (I.-K.J.); Department of Internal Medicine II, Cardiology, University of Ulm, Ulm, Germany (W.K.); University of Kentucky, Lexington, Ky (R.A.L.); R.L. Roudebush VA Medical Center, Indianapolis, Ind (K.M.); School of Public Health, University of TexasHouston, Houston, Texas (J.D.); Division of Cardiology, University of California Los Angeles, Los Angeles, Calif (M. Navab); Fondazione Salvatore Maugeri, University of Pavia, Pavia, Italy (S.G.P.); Department of Cardiovascular Therapeutics, Pfizer Global Research and Development, Ann Arbor Laboratories, Ann Arbor, Mich (M.D.R.); Paul Dudley White Coronary Care System at St. Agnes HealthCare, Baltimore, Md (R.B.); Center for Human Nutrition, University of Texas Health Science Center, Dallas (S.M.G.); Lenox Hill Hospital, New York, NY (R.M.); Catheterization Laboratories, Ospedale San Raffaele and Emo Centro Cuore Columbus, Milan, Italy (A.C.); Human Genetics Center, Institute of Molecular Medicine, Houston, Tex (E.B.); Department of Medicine, Baylor College of Medicine, Houston, Tex (C.B., W.I.); Minneapolis Heart Institute and Foundation, Minneapolis, Minn (R.S.S.); Division of Cardiology, University of Maryland School of Medicine, Baltimore, Md (R.V.); Karolinska Institute, Center for Molecular Medicine, Karolinska Hospital, Stockholm, Sweden (G.K.H.); Section of Cardiology, University of Chicago, Ill (D.P.F.); Vascular Physiology and Thrombosis Research Laboratory of the Atherosclerosis Research Center, Cedars-Sinai Medical Center, Los Angeles, California (S.K.); Cardiology Department, Hannover University, Hannover, Germany (H.D.); Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Ill (P.G.); UCLA School of Medicine and Cedars-Sinai Medical Center, Los Angeles, Calif (P.K.S.); Massachusetts General Hospital, Harvard Medical School and CIMIT (Center for Integration of Medicine and Innovative Technology), Boston, Mass (J.E.M.); Cardiovascular Division, Division of Preventive Medicine, Brigham and Womens Hospital, Boston, Mass (P.M.R.); and Indiana University School of Medicine, Krannert Institute of Cardiology, Indianapolis (D.P.Z.).
Correspondence to Morteza Naghavi, MD, Association for Eradication of Heart Attack, P.O. Box 20345, Houston, TX 77225-0345. E-mail mn{at}vp.org
| Abstract |
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Key Words: coronary disease plaque myocardial infarction atherosclerosis death, sudden
| Introduction |
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| Vulnerable (Thrombogenic) Blood |
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Circulating interleukin-6 levels, which are elevated in patients with acute coronary syndromes, also predict the risk of future coronary events in such patients.6 Recently, investigators have shown that high plasma concentrations of soluble CD40 ligand may indicate an increased vascular risk in apparently healthy women.7 Likewise, Hwang et al8 showed in a large population-based sample of individuals that circulating levels of soluble intracellular adhesion molecule were predictive of future acute coronary events.
Markers of systemic inflammation, such as soluble adhesion molecules, circulating bacterial endotoxin, soluble human heat-shock protein 60, and antibodies to mycobacterial heat-shock protein 65, may predict an increased risk of atherosclerosis.9 Pregnancy-associated plasma protein A (PAPP-A) is present in unstable plaques, and its circulating levels are elevated in patients with acute coronary syndromes.10 Increased serum levels of PAPP-A may reflect instability of atherosclerotic plaques.11
With major advances in high-throughput genomics and proteomics research, future studies will undoubtedly identify new risk and protective factors and biomarkers that can be used for screening purposes. A recent study suggested an association between several genetic polymorphisms and clinical outcomes, some of which can be possibly related to plaque, blood, and myocardial vulnerability.12 The tools and knowledge base made possible by the Human Genome Project allow the field to move beyond one or a few single-nucleotide polymorphisms in a priori candidate genes. Genome-wide linkage analyses have been carried out for coronary artery calcification,13 and genome-wide association studies for myocardial infarction are already a reality.14 Further studies are needed to address the relationship between single-nucleotide polymorphisms in components of each of the plaque, blood, and myocardial vulnerabilities and future outcomes (acute coronary syndromes and sudden cardiac death). However, ongoing proteomic research on serum samples of vulnerable patients collected from prospective studies before the onset of symptoms is most promising.
| Coagulation/Anticoagulation System |
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Some platelet polymorphisms, such as glycoprotein IIIa P1(A2),17 Ib
gene-5T/C Kozak,18 high factor V and factor VII clotting,19 have been reported as independent risk factors for myocardial infarction. Reiner et al20 recently reviewed the associations of known and potential genetic susceptibility markers for intermediate hemostatic phenotypes with arterial thrombotic disease.
Other conditions that lead to a hypercoagulable state are diabetes mellitus, hypercholesterolemia, and cigarette smoking. High levels of circulating tissue factor may be the mechanism of action responsible for the increased thrombotic complications associated with the presence of these cardiovascular risk factors.21 Acute coronary syndromes are associated with proinflammatory and prothrombotic conditions that involve a prolonged increase in the levels of fibrinogen, CRP, and plasminogen activator inhibitor.22,23
A number of blood abnormalities, including antithrombin III deficiency, protein C or S deficiency, and resistance to activated protein C (also known as factor V Leiden), have been implicated as causes of venous thrombosis. The risk of arterial thrombosis is only modestly increased in these conditions, but these abnormalities are thought to interact with traditional risk factors for arterial thrombosis.
Venous and arterial thromboses are prominent features of the antiphospholipid syndrome.24,25 The main antibodies of this syndrome are the anticardiolipin antibody, the lupus anticoagulant, and the IgG antibodies against prothrombin and ß2-glycoprotein.24,25
In the nephrotic syndrome, proteinuria results in abnormal concentration and activity of coagulation factors. Moreover, the associated hypoalbuminemia, thrombocytosis, and hypercholesterolemia may induce arterial and venous thrombosis.26
The importance of the coagulation/fibrinolytic system is highlighted by several autopsy studies that have shown a high prevalence of old plaque disruptions without infarctions. Therefore, an active fibrinolytic system may be able to prevent luminal thrombosis in some cases of plaque disruption.27,28
A transient shift in the coagulation and anticoagulation balance is likely to be an important factor in plaque-blood interaction, resulting in an acute event. "Triggers" such as exercise and smoking, which are associated with catecholamine release, may increase the risk of plaque thrombosis.29 Similarly, metabolic factors, such as postprandial metabolic changes, are associated with increased blood coagulability.30 Likewise, estrogen replacement therapy can lead to a hypercoagulable state.31
Finally, plasma viscosity, as well as fibrinogen and white blood cell counts, is positively associated with CHD events as shown by Koenig et al.32 Furthermore, Junker et al33 showed a positive relationship between plasma viscosity and the severity of coronary heart disease (CHD).
| Vulnerable Myocardium |
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There seems to be a wide interindividual variation in the type and severity of autonomic reactions during the early phase of abrupt coronary occlusion, a critical period for out-of-hospital cardiac arrest. The pre-existing severity of a coronary stenosis, adaptation or preconditioning to myocardial ischemia, habitual physical exercise, ß-blockade, and gender seem to affect autonomic reactions and the risk of fatal ventricular arrhythmias.38,40,41 Recent studies have documented a hereditary component for autonomic function, and genetic factors may also modify the clinical presentation of acute coronary occlusion.42,43 Table 3 depicts conditions and markers associated with myocardial vulnerability.
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Ischemic Vulnerable Myocardium With Prior Atherosclerosis-Derived Myocardial Damage (Chronic Myocardial Damage)
Any type of atherosclerosis-related myocardial injury, such as ischemia, an old or new myocardial infarction, inflammation, and/or fibrosis, potentially increases the patients vulnerability to arrhythmia and sudden death. In the past few decades, a number of diagnostic methods have been developed for imaging cardiac ischemia and for assessing the risk of developing a life-threatening cardiac arrhythmia. In patients with a history of ischemic heart disease, ischemic cardiomyopathy is the ultimate form of myocardial damage. With the advent of new, effective treatments for hypertension and more efficient management of acute myocardial infarction, deaths resulting from stroke and acute myocardial infarction have steadily decreased.44 More patients are now surviving acute events, but some develop heart failure or ischemic cardiomyopathy later with the potential for fatal arrhythmias. It is also important to remember that in a significant number of patients, sudden cardiac death is the first manifestation of underlying heart disease, and it is still responsible for >450 000 deaths annually in the United States.
Nonischemic Vulnerable Myocardium
A smaller subset of patients experience fatal arrhythmia as a result of diseases other than coronary atherosclerosis. The various forms of cardiomyopathy (dilated, hypertrophic, restrictive, and right ventricular) account for most noncoronary cardiac deaths. Other underlying pathological processes include valvular heart disease, such as aortic stenosis and primary electrical disturbances (long-QT syndromes, Brugada syndrome, Wolff-Parkinson-White syndrome, sinus and atrioventricular conduction disturbances, catecholaminergic polymorphic ventricular tachycardia, and congenital and drug-induced long QT syndromes with torsades de pointes), and, infrequently, commotio cordis from chest trauma. Less common pathological conditions include anomalous origin of a coronary artery, myocarditis, and myocardial bridging (Table 3). Circulating nonesterified fatty acids are another risk factor for sudden death in middle-aged men, as is elevated serum concentration of CRP; serum measurements may help screening for vulnerable myocardium.45
Recently, the Task Force on Sudden Cardiac Death, organized by the European Society of Cardiology, issued a report that includes detailed diagnostic and therapeutic recommendations for a large number of cardiomyopathic conditions capable of causing sudden cardiac death.46
Table 4 provides electrophysiological diagnostic criteria and techniques for detection of myocardial vulnerability.
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| Risk Assessment for Vulnerable Patients |
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The traditional risk assessment has been shown to predict long-term outcome in large populations. However, they fall short in predicting near-future events particularly in individual clinical practice. For example, a high Framingham Risk Score, although capable of forecasting an adverse cardiovascular event in 10 years, clearly falls short in accurately predicting events in individual patients and cannot provide a clear clinical route for cardiologists to identify and treat, to prevent near future victims of acute coronary syndromes and sudden death. The same is true for coronary evaluations using electrocardiography, myocardial perfusion tests, and coronary angiography. A positive test for coronary stenosis or reversible perfusion defect (ischemia), although considered as a major risk factor, must be coupled in the future with emerging methods of risk assessment for detection of vulnerable patients to predict more accurately the near-future outcome and prognosis. Those who have no indication of coronary stenosis or myocardial ischemia and who may even lack traditional risk factors may benefit from the techniques now under development that evaluate plaque biology and inflammation.
| New Risk Assessment Strategies |
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This proposal is by no means intended to disregard the predictive value of traditional risk assessment strategies that have been proven in predicting long-term outcome but instead to strengthen their value in providing higher accuracy, especially for near-term outcomes.
Atherosclerosis is a diffuse and multisystem, chronic inflammatory disorder involving vascular, metabolic, and immune systems with various local and systemic manifestations. Therefore, it is essential to assess total vulnerability burden and not just search for a single, unstable coronary plaque. A composite risk score (eg, a vulnerability index), that comprises the total burden of atherosclerosis and vulnerable plaque in the coronaries (and aorta and carotid, femoral, etc, arteries), and that includes blood and myocardial vulnerability factors, should be a more accurate method of risk stratification. Such a vulnerability index would indicate the likelihood that a patient with certain factors would have a clinical event in the coming year. Use of the state-of-the-art bioinformatics tools such as neural networks may provide substantial improvement for risk calculations.61
The information used for developing such risk stratification in the future is likely to come from a combination of smaller prospective studies (eg, from new imaging techniques) and retrospective cohort studies (eg, for serum factors) in which the risks for near future cardiovascular events can be quantitatively calculated. A few such studies have been conducted or are underway.2,62
In Search of the Vulnerable Patient
The ideal method for screening vulnerable patients should be (1) inexpensive, (2) relatively noninvasive, (3) widely reproducible, (4) readily applicable to an asymptomatic population, and (5) capable of adding predicted value to measurements of established risk factors. Such a method should provide a cost-effective, stepwise approach designed to further stratify risk and provide reliable diagnosis and pathways for monitoring therapy. Obviously, these goals are hard to achieve with todays tools. However, it is well within our reach, if academia and industry in the field of cardiovascular medicine undertake a coordinated effort to embark on developing new screening and diagnostic techniques to identify vulnerable patients (Figure).
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| Acknowledgments |
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| Footnotes |
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This article is Part II of a 2-part article. Part I appeared in the October 7, 2003 issue of Circulation (Circulation. 2003;108:16641672).
Guest editor for this article was Eugene Braunwald, MD, Brigham and Womens Hospital, Boston, Mass.
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A transition, and factor V Leiden in coronary artery disease: high factor V clotting activity is an independent risk factor for myocardial infarction. Arterioscler Thromb Vasc Biol. 1999; 19: 10201025.This article has been cited by other articles:
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