Risk Stratification and Prognostic Factors in the Post-Myocardial Infarction Patient

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Among the 5 million patients presenting to emergency departments with chest pain each year in the United States, approximately 1 million are diagnosed with myocardial infarction (MI). Physicians have the difficult task of making decisions regarding admission and treatment and identifying patients at high risk for adverse outcomes, such as early mortality, left ventricular dysfunction (LVD), and heart failure. Several measures can be implemented in the process of risk assessment, including clinical judgment, electrocardiographic and echocardiographic findings, and the presence of biomarkers. Biomarkers—which can be classified as antecedent, screening, diagnostic, staging, or prognostic—may help identify the subset of patients who need early intervention and/or intensive therapy. Using a multimarker strategy that combines a marker of hemodynamic stress (brain natriuretic peptide) or of inflammation (C-reactive protein) with a marker of necrosis (cardiac troponin) may help to risk-stratify patients, guide treatment, and optimize admission and discharge decisions. This article discusses the potential benefits of risk assessment tools in the management of post-MI patients with LVD.

Section snippets

Risk Stratification Methods for Acute Coronary Syndrome

The approach to the 5 million patients arriving in the emergency department with chest pain each year requires careful risk stratification, which involves 2 steps: (1) establishing the diagnosis of ACS (as opposed to noncardiac chest pain), and (2) identifying high- versus low-risk patients.2, 10 The early diagnosis and stratification of ST-segment elevation MI (STEMI), non-STEMI, and unstable angina is essential for assessing risk, guiding therapy, and improving outcomes. Despite improvements

Use of Biomarkers for Risk Stratification

A better understanding of the pathophysiology of ACS has led to substantial advances in the treatment of acute MI over the past several years, which, in turn, have greatly increased the likelihood of survival. Several studies have shown the significant benefit of immediate reperfusion therapy with fibrinolysis or percutaneous coronary intervention.18, 19, 20 The improved treatment strategies have resulted in fewer patients developing post-MI LVD; however, patients with LVD remain a high-risk

Risk Stratification Can Guide the Use of Targeted Therapies

Cardiac markers not only can predict the risk of mortality and morbidity, but they also can guide decision making and choice of therapy in the emergency department. A major challenge for physicians is to identify patients with ACS who may benefit from treatment with various reperfusion strategies (pharmacologic or invasive). Early reperfusion of patients with STEMI results in the reduction in infarct size, an improved LVEF, and the reduction of in-hospital mortality.20 Patients with non-STEMI

Risk Stratification Can Be Used to Monitor Therapy

Landmark clinical trials have established angiotensin-converting enzyme inhibitors and β-blockers as the standard of care in post-MI and HF patients.39, 40, 41 However, even with intensive treatment, morbidity and mortality remain high. Current treatment strategies ignore plasma neurohormone concentrations, yet they are independent markers of cardiac status and prognosis in cardiac disease and could help monitor the effect of therapies, such as β-blockers.

Concentrations of BNP and NT-proBNP are

Practical Use of Biomarkers at the Bedside

The practicality of using many biomarkers in the emergency department or at the bedside for rapid assessment has been questioned. The TIMI HF risk score, a tool involving assessment of basic clinical findings as well as a biomarker, is particularly useful because none of its components requires difficult or intensive measurements. The TIMI risk score is a relatively new risk assessment tool focused on the risk of developing post-ACS HF leading to hospitalization.52 In multivariate analysis,

Distinguishing Between Markers of Disease Versus Pathogenesis

Biomarkers may indicate the severity of disease and/or underlying pathology. An ideal marker for the underlying pathology should be specific to myocardial injury, be sensitive to small injuries, be rapidly released after injury, last long enough in the blood to permit delayed diagnosis, produce blood levels that are proportionate to infarct size, permit risk assessment, and be technically easy to measure. CRP, for example, is a marker indicating inflammation that appears to play a role in the

Conclusion

The potential for finding new and useful biomarkers is great, and as this technology continues to advance, these biomarkers may be incorporated into a single bedside assessment tool that can rapidly and conveniently obtain much more information about the pathologic processes in a patient than we currently are able to surmise by clinical presentation, signs, and symptoms. The next generation of cardiac markers should have a high sensitivity for ischemia (unstable angina and silent ischemia). The

Author Disclosures

The authors who contributed to this article have disclosed the following industry relationships.

Christopher P. Cannon, MD, receives research grants/support from Accumetrics, AstraZeneca, Bristol Myers Squibb, GlaxoSmithKline, Merck Schering Plough Partnership, and sanofi-aventis.

Barry H. Greenberg, MD, has served as a member of the advisory committee for GlaxoSmithKline, NitroMed, and Novartis; and served as a member of the Speakers' Bureau for AstraZeneca, GlaxoSmithKline, Merck, NitroMed, and

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    Statement of author disclosure: Please see the Author Disclosures section at the end of this article.

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