Myocardial Infarction in Childhood Workup

Updated: May 23, 2014
  • Author: Louis I Bezold, MD; Chief Editor: Stuart Berger, MD  more...
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Workup

Laboratory Studies

A number of laboratory studies are indicated in pediatric patients with myocardial infarction (MI).

Testing of cardiac enzymes is the standard for identification of myocardial cell death. The following levels are measured:

  • Aspartate transaminase (AST)
  • Lactate dehydrogenase (LDH) and isoenzymes
  • Creatine kinase (CK)
  • CK-MB isoforms
  • Troponin I and troponin T

Levels of acute-phase reactants are elevated in the early stages of Kawasaki disease. Studies of the following are indicated:

  • White blood cell (WBC) count
  • C-reactive protein (CRP)
  • Erythrocyte sedimentation rate (ESR)
  • Thrombocytosis
  • Alpha 1 -antitrypsin (A1AT)

Evaluation for heritable forms of thrombophilia (eg, prothrombin G20210 and C677T MTHFR gene mutations) and protein C deficiencies should be considered in young patients with myocardial ischemia. [10]

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Radiography

Chest radiography is indicated to reveal cardiomegaly, with or without pulmonary venous congestion.

Angiographic evaluation of the coronary artery system is indicated on an urgent basis but should be performed with caution because of the inherent instability of the diseased myocardium.

Definitive diagnosis of an anomalous left coronary artery (LCA) from the pulmonary artery is made. Aortography demonstrates an enlarged right coronary artery (RCA) system with collateralization to the LCA and reflux of contrast into the pulmonary arterial system (ie, anomalous origin of the LCA from the pulmonary artery [ALCAPA]). Patients with Kawasaki disease frequently have coronary aneurysm, ectasia, or both.

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Echocardiography

Two-dimensional echocardiography may be used to identify the following:

  • The abnormal origin of the LCA from the main pulmonary artery
  • Chamber enlargement
  • Systolic and diastolic dysfunction
  • Coronary artery ectasia or aneurysm
  • A flail mitral valve leaflet and ruptured papillary muscle
  • Segmental wall motion abnormality
  • Mural or intraventricular thrombi

In experienced hands, color-flow Doppler mapping can have the following uses:

  • Diagnosing ALCAPA by demonstrating retrograde flow from the anomalous LCA into the pulmonary trunk
  • Demonstrating the direction of coronary artery flow
  • Quantifying mitral insufficiency
  • Quantifying pulmonary hypertension, in conjunction with spectral Doppler

Tissue Doppler imaging (TDI) is an echocardiographic technique that can noninvasively evaluate myocardial contraction and relaxation. Data suggest that TDI may have a role in early detection of graft failure due to coronary vasculopathy in orthotopic transplant recipients. [18]

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CT and MRI

Multislice computed tomography (CT) angiography has been shown to be useful in identifying coronary ostial or arterial stenoses in pediatric patients after an arterial switch operation for dextro-transposition of the great arteries (D-TGA). [19]

Magnetic resonance imaging (MRI) can reveal coronary origins, anatomy, and abnormalities, as well as infarction, in patients with Kawasaki disease. [20, 21, 22] Cardiac MRI has been used to determine myocardial viability and prognosis in a case of MI in utero. [23] Cardiac MRI has also been very useful in distinguishing between MI and myocarditis in pediatric patients with chest pain and elevated troponin. [24]

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Electrocardiography

Classic electrocardiographic (ECG) findings for diagnosing ischemia or infarction in adults have been described as follows:

  • Deep Q waves in a completed transmural infarct over the involved areas
  • Peaked T waves hyperacutely
  • ST elevation in the acute phase
  • ST depression when ischemia is present or in the latter stages of acute injury
  • Various dysrhythmias and ectopy secondary to ischemia and irritable myocardium or conductive tissue (see the image below)
    Electrocardiogram in an infant with anomalous orig Electrocardiogram in an infant with anomalous origin of the left coronary artery from the pulmonary artery, demonstrating pathologic q waves in leads I and aVL and diffuse ST-T wave changes consistent with an anterolateral infarction.

An anterolateral infarct is demonstrated with abnormal deep (> 3 mm) and wide (> 30 ms) Q waves in leads I, aVL, V5, and V6, with absent Q waves in leads II, III, and aVF. The QRS axis is typically normal, though a left superior axis is observed in some patients.

ST-segment changes diagnostic of transmural infarction in adults may be seen in pediatric patients in the absence of coronary occlusion. [25] Additional criteria for diagnosing pediatric ischemia have been described, as follows [26] :

  • Wide Q waves (>35 ms) with or without Q-wave notching
  • ST-segment elevation (>2 mm)
  • Prolonged QTc (>440 ms) with accompanying Q-wave abnormalities

Exercise myocardial perfusion stress testing has been shown to be safe and useful for assessment of myocardial perfusion and for risk stratification in children with Kawasaki disease. [27]

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Other Studies

Myocardial perfusion imaging may be useful in evaluating myocardial ischemia and infarction in various disease states. [28]

Hemodynamic (oximetric) measurements may demonstrate the following:

  • Decreased systemic venous oxygen content is consistent with low cardiac output
  • A small left-to-right shunt may be demonstrated by oximetry in the main pulmonary artery if ALCAPA is the diagnosis
  • Elevated left atrial pressures are secondary to reduced left ventricular compliance, significant mitral valve insufficiency, or both
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