eMedicine Specialties > Cardiology > Coronary Artery Disease

Myocardial Infarction: Differential Diagnoses & Workup

Author: Samer Garas, MD, FACC, Chief of Cardiology, Department of Interventional Cardiology, St Vincent's Hospital
Coauthor(s): A Maziar Zafari, MD, PhD, FACC, Associate Professor, Department of Medicine, Emory University School of Medicine; Chief, Section of Cardiology, Atlanta Veterans Affairs Medical Center
Contributor Information and Disclosures

Updated: Oct 5, 2009

Differential Diagnoses

Anxiety Disorders
Gastritis, Acute
Aortic Dissection
Gastroesophageal Reflux Disease
Aortic Stenosis
Myocarditis
Cholecystitis
Pericarditis, Acute
Esophageal Spasm
Pneumothorax
Esophagitis
Pulmonary Embolism

Other Problems to Be Considered

Pneumonia
Pancreatitis

Workup

Laboratory Studies

Lab studies for patients with myocardial infarction include the following:

  • Cardiac enzymes: In patients with suspected myocardial infarction, obtain cardiac enzymes at regular intervals, starting upon admission and serially for as long as 24 hours.
  • Troponin levels
    • Troponin levels are now considered the criterion standard in defining and diagnosing myocardial infarction, according to the American College of Cardiology (ACC)/American Heart Association (AHA) consensus statement on myocardial infarction.1,2
    • Cardiac troponin levels (troponin-T and troponin-I) have a greater sensitivity and specificity than CK-MB levels in detecting myocardial infarction. They have important diagnostic and prognostic roles. Positive troponin levels are considered virtually diagnostic of myocardial infarction in the most recent ACC/AHA revisions, as they are without equal in combined specificity and sensitivity in this diagnosis.
    • Serum levels increase within 3-12 hours from the onset of chest pain, peak at 24-48 hours, and return to baseline over 5-14 days.
    • According to a 2009 study published in the New England Journal new sensitive cardiac troponin assays have greater diagnostic accuracy than the standard assays, especially for early diagnosis. These assays can substantially improve the early diagnosis of acute myocardial infarction, particularly in patients with a recent onset of chest pain.32  
  • Creatine kinase level
    • Creatine kinase comprises 3 isoenzymes, including creatine kinase with muscle subunits (CK-MM), which is found mainly in skeletal muscle; creatine kinase with brain subunits (CK-BB), predominantly found in the brain; and myocardial muscle creatine kinase (CK-MB), which is found mainly in the heart.
    • Serial measurements of CK-MB isoenzyme levels were previously the standard criterion for diagnosis of myocardial infarction. CK-MB levels increase within 3-12 hours of onset of chest pain, reach peak values within 24 hours, and return to baseline after 48-72 hours. levels peak earlier (wash out) if reperfusion occurs. Sensitivity is approximately 95%, with high specificity. However, sensitivity and specificity are not as high as for troponin levels, and the trend has favored using troponins for the diagnosis of myocardial infarction.
    • Myoglobin levels
      • Urine myoglobin levels rise within 1-4 hours from the onset of chest pain.
      • Myoglobin levels are highly sensitive but not specific, and they may be useful within the context of other studies and in early detection of myocardial infarction in the emergency department.
    • Complete blood cell count
      • Obtain a CBC count if myocardial infarction is suspected to rule out anemia as a cause of decreased oxygen supply and prior to giving thrombolytics.
      • Leukocytosis is also common, but not universal, in the setting of acute myocardial infarction.
      • A platelet count is necessary if a IIb/IIIa agent is considered; furthermore, the patient's WBC count may be elevated modestly in the setting of myocardial infarction, signifying an acute inflammatory state.
    • Chemistry profile
      • In the setting of myocardial infarction, closely monitor potassium and magnesium levels.
      • Creatinine level is also needed prior to initiating treatment with an angiotensin-converting enzyme (ACE) inhibitor.
    • Lipid level profile: This may be helpful if obtained upon presentation because levels can change after 12-24 hours of an acute illness.
    • C-reactive protein (CRP) levels: Consider measuring CRP levels and other markers of inflammation upon presentation if an acute coronary syndrome is suspected.

Imaging Studies

  • Chest radiography
    • Upon presentation, obtain a chest radiograph to assess the patient's heart size and the presence or absence of decompensated congestive heart failure with or without pulmonary edema.
    • A chest radiograph may also assist in diagnosing concomitant disease, such as pneumonia in an elderly patient, as a precipitating cause for myocardial infarction.
    • A chest radiograph may be helpful in evaluation for aortic dissection.
  • Echocardiography
    • An echocardiogram may play an important role in the setting of myocardial infarction.
    • Regional wall motion abnormalities can be identified, which are especially helpful if the diagnosis is questionable.
    • An echocardiogram can also define the extent of the infarction and assess overall left ventricle (LV) and right ventricle (RV) function. In addition, an echocardiogram can identify complications, such as acute mitral regurgitation, LV rupture, or pericardial effusion.
  • Myocardial perfusion imaging
    • Prior to discharge, obtain myocardial perfusion imaging to assess the extent of residual ischemia if the patient has not undergone cardiac catheterization. The extent of ischemia can guide further therapy as to whether to proceed with catheterization or to continue conservative therapy.
    • Myocardial perfusion has been shown to be a valuable method for triage of patients with chest pain in the emergency department. Significant variability exists among centers, and the results of the trials can be applied only to those centers with proven reliability and experience.
  • Cardiac angiography
    • Cardiac catheterization defines the patient's coronary anatomy and the extent of the disease. Most investigators recommend that all patients with myocardial infarction should undergo cardiac catheterization, if it is available.
    • Patients with cardiogenic shock, intractable angina despite medications, or severe pulmonary congestion should undergo cardiac catheterization immediately.

Other Tests

  • The electrocardiogram (ECG) is the most important tool in the initial evaluation and triage of patients in whom an ACS is suspected (see Media files 1-3). It is confirmatory of the diagnosis in approximately 80% of cases.
    • Obtain an ECG immediately if myocardial infarction is considered or suspected.
    • In patients with inferior myocardial infarction, record a right-sided ECG to rule out RV infarct.
    • Qualified personnel should review the ECG as soon as possible.
    • Perform ECGs serially upon presentation to evaluate progression and assess changes with and without pain.
    • Obtain daily serial ECGs for the first 2-3 days and additionally as needed.
    • Convex ST-segment elevation with upright or inverted T waves is generally indicative of myocardial infarction in the appropriate clinical setting.
    • ST depression and T-wave changes may also indicate evolution of NSTEMI.

Acute anterior myocardial infarction.

Acute anterior myocardial infarction.

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Acute anterior myocardial infarction.

Acute anterior myocardial infarction.


Acute inferior myocardial infarction.

Acute inferior myocardial infarction.

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Acute inferior myocardial infarction.

Acute inferior myocardial infarction.


Posterolateral myocardial infarction.

Posterolateral myocardial infarction.

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Posterolateral myocardial infarction.

Posterolateral myocardial infarction.


More on Myocardial Infarction

Overview: Myocardial Infarction
Differential Diagnoses & Workup: Myocardial Infarction
Treatment & Medication: Myocardial Infarction
Follow-up: Myocardial Infarction
Multimedia: Myocardial Infarction
References
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References

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  2. [Guideline] Braunwald E, Antman EM, Beasley JW, Califf RM, Cheitlin MD, Hochman JS, et al. ACC/AHA guidelines for the management of patients with unstable angina and non-ST-segment elevation myocardial infarction: executive summary and recommendations. A report of the American College of Cardiology/American Heart Association task force on practice guidelines (committee on the management of patients with unstable angina). Circulation. Sep 5 2000;102(10):1193-209. [Medline].

  3. Sabatine. Clopidogrel Shines in STEMI Reperfusion: CLARITY-TIMI 28. Paper presented at: American College of Cardiology Annual Scientific Session Late-Breaking Clinical Trials. March 9, 2005;Orlando, FL.

  4. [Best Evidence] Chen ZM, Jiang LX, Chen YP, Xie JX, Pan HC, Peto R, et al. Addition of clopidogrel to aspirin in 45,852 patients with acute myocardial infarction: randomised placebo-controlled trial. Lancet. Nov 5 2005;366(9497):1607-21. [Medline].

  5. Antman EM, Giugliano RP, Gibson CM, McCabe CH, Coussement P, Kleiman NS, et al. Abciximab facilitates the rate and extent of thrombolysis: results of the thrombolysis in myocardial infarction (TIMI) 14 trial. The TIMI 14 Investigators. Circulation. Jun 1 1999;99(21):2720-32. [Medline].

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  7. [Best Evidence] Chen ZM, Pan HC, Chen YP, Peto R, Collins R, Jiang LX, et al. Early intravenous then oral metoprolol in 45,852 patients with acute myocardial infarction: randomised placebo-controlled trial. Lancet. Nov 5 2005;366(9497):1622-32. [Medline].

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  11. Schwartz GG, Olsson AG, Ezekowitz MD, et al. Effects of atorvastatin on early recurrent ischemic events in acute coronary syndromes: the MIRACL study: a randomized controlled trial. JAMA. Apr 4 2001;285(13):1711-8. [Medline].

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  13. Antman EM, Anbe DT, Armstrong PW, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction; A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1999 Guidelines for the Manage. J Am Coll Cardiol. Aug 4 2004;44(3):E1-E211. [Medline].

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  17. Antman EM, McCabe CH, Gurfinkel EP, et al. Enoxaparin prevents death and cardiac ischemic events in unstable angina/non-Q-wave myocardial infarction. Results of the thrombolysis in myocardial infarction (TIMI) 11B trial. Circulation. Oct 12 1999;100(15):1593-601. [Medline].

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  25. Ryan TJ, Antman EM, Brooks NH, et al. 1999 update: ACC/AHA guidelines for the management of patients with acute myocardial infarction. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Acute Myocardial Infa. J Am Coll Cardiol. Sep 1999;34(3):890-911. [Medline].

  26. Tavazzi L. Clinical epidemiology of acute myocardial infarction. Am Heart J. Aug 1999;138(2 Pt 2):S48-54. [Medline].

  27. The SOLVD Investigattors. Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions. N Engl J Med. Sep 3 1992;327(10):685-91. [Medline].

  28. Yusuf S, Sleight P, Pogue J, et al. Effects of an angiotensin-converting-enzyme inhibitor, ramipril, on cardiovascular events in high-risk patients. The Heart Outcomes Prevention Evaluation Study Investigators. N Engl J Med. Jan 20 2000;342(3):145-53. [Medline].

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  31. Zafari AM, Wenger NK. Secondary prevention of coronary heart disease. Arch Phys Med Rehabil. Aug 1998;79(8):1006-17. [Medline].

  32. [Best Evidence] Reichlin T, Hochholzer W, Bassetti S, Steuer S, Stelzig C, Hartwiger S, et al. Early diagnosis of myocardial infarction with sensitive cardiac troponin assays. N Engl J Med. Aug 27 2009;361(9):858-67. [Medline].

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Further Reading

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Keywords

myocardial infarction, heart attack, acute coronary syndromes, ACS, MI, unstable angina, non–ST-elevation MI, NSTEMI, coronary artery disease, CAD, ischemic heart disease, chest pain, impaired systolic function, impaired diastolic function, myocardial necrosis, atherosclerosis, coronary thrombus, plaque rupture, coronary emboli, infected cardiac valve, coronary occlusion secondary to vasculitis, primary coronary vasospasm, variant angina

cardiovascular disease, congestive heart failure, CHF, coronary heart disease, smoking, diabetes mellitus, hypertension, dyslipidemia, obesity, elevated homocysteine levels, male pattern baldness, sedentary lifestyle, psychosocial stress, peripheral vascular disease, poor oral hygiene

vasculitis, congenital coronary anomalies, coronary trauma, coronary spasm, necrosis of heart muscle, coronary thrombosis, pulmonary rales, lower extremity edema, elevated jugularvenous pressure, cocaine use, heavy exertion, hyperthyroidism, severe anemia

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Contributor Information and Disclosures

Author

Samer Garas, MD, FACC, Chief of Cardiology, Department of Interventional Cardiology, St Vincent's Hospital
Samer Garas, MD, FACC is a member of the following medical societies: Alpha Omega Alpha, American College of Cardiology, and American Medical Association
Disclosure: Nothing to disclose.

Coauthor(s)

A Maziar Zafari, MD, PhD, FACC, Associate Professor, Department of Medicine, Emory University School of Medicine; Chief, Section of Cardiology, Atlanta Veterans Affairs Medical Center
A Maziar Zafari, MD, PhD, FACC is a member of the following medical societies: American Association for the Advancement of Science, American College of Cardiology, American Heart Association, American Society of Echocardiography, and Association of Professors of Medicine
Disclosure: Nothing to disclose.

Medical Editor

Eric Vanderbush, MD, FACC, MD, Chief, Department of Internal Medicine, Division of Cardiology, Clinical Assistant Professor, Harlem Hospital Center and Columbia University
Eric Vanderbush, MD, FACC, MD is a member of the following medical societies: American College of Cardiology and American Heart Association
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Marschall S Runge, MD, PhD, Charles and Anne Sanders Distinguished Professor of Medicine, Chairman, Department of Medicine, Vice Dean for Clinical Affairs, University of North Carolina at Chapel Hill School of Medicine
Marschall S Runge, MD, PhD is a member of the following medical societies: American Association for the Advancement of Science, American College of Cardiology, American College of Physicians-American Society of Internal Medicine, American Federation for Clinical Research, American Federation for Medical Research, American Heart Association, American Physiological Society, American Society for Clinical Investigation, American Society for Investigative Pathology, Association of American Physicians, Association of Professors of Cardiology, Association of Professors of Medicine, Southern Society for Clinical Investigation, and Texas Medical Association
Disclosure: Pfizer Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; Orthoclinica Diagnostica Consulting fee Consulting

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Eric H Yang, MD, Assistant Professor of Medicine, Director of Coronary Care Unit, University of North Carolina at Chapel Hill School of Medicine
Eric H Yang, MD is a member of the following medical societies: Alpha Omega Alpha
Disclosure: Up to Date Royalty Review panel membership

 
 
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