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EXPERIENCE & REASON |
Division of Pediatric Cardiology, Washington University School of Medicine–St Louis Children's Hospital, St Louis, Missouri
ABSTRACT
Electrocardiographic criteria for the diagnosis of cardiac ischemia in adults are well defined; however, analogous criteria for the diagnosis of cardiac ischemia in infants and children remain ambiguous. The difficulty in defining electrocardiographic criteria in pediatrics relates to age-dependent differences in the pediatric electrocardiogram, the presence or absence of congenital heart disease, and multiple and diverse etiologies of myocardial injury that lead to an ischemic pattern on the electrocardiogram. In this report, we illustrate 3 pediatric cases in which the electrocardiogram met adult diagnostic criteria for acute transmural myocardial infarction, without coronary artery abnormalities in 2 cases and with a transient coronary abnormality in the third. In conclusion, ST-segment changes diagnostic of transmural myocardial infarction in adults may be seen in pediatric patients in the absence of coronary artery occlusion.
Key Words: pediatric • ischemia • electrocardiogram • infarction
Abbreviations: ECG, electrocardiogram • MI, myocardial infarction
"In Medicine one must pay attention not to plausible theorizing but to experience and reason together.... I agree that theorizing is to be approved, provided that it is based on facts, and systematically makes its deductions from what is observed.... But conclusions drawn from unaided reason can hardly be serviceable; only those drawn from observed fact."
—Hippocrates, Precepts
Although rare, cardiac ischemia can occur in children. The diagnosis of cardiac ischemia in children is also complicated by the indeterminate sensitivity and specificity of common diagnostic tests such as routine electrocardiography and serum biomarkers in this generally low-risk population. In this report we describe 3 cases in which the electrocardiogram (ECG) was diagnostic for transmural acute myocardial infarction (MI); however, coronary artery abnormalities were present in only 1 case. This retrospective chart review was approved by our institutional review board.
CASE REPORTS
Patient1.
A 2-year-old black boy status post–orthotopic heart transplant in infancy for complex heterotaxy syndrome with unbalanced atrioventricular canal and aortic atresia (functional hypoplastic left heart syndrome) was admitted to the cardiac ICU with severe respiratory distress. On physical examination, a gallop rhythm was noted. The chest radiograph demonstrated pan-lobar infiltrates (most prominent in the right middle lobe) and new-onset cardiomegaly. An echocardiogram performed at the time of admission was significant for severely decreased global left ventricular systolic dysfunction with an ejection fraction of 20% and a lateral segmental wall-motion abnormality. The 12-lead ECG was diagnostic for acute lateral MI (Fig 1). His serum troponin level (tested in response to the ECG results) was mildly elevated at 0.9 ng/mL (reference: <0.1 ng/mL). Additional ischemic biomarkers were not tested. Coronary angiography was normal, and ventricular myocardial biopsy revealed grade 1B, mild cellular rejection. After a 5-day course of plasmapheresis and OKT3 lytic therapy for presumed humoral rejection, there was marked improvement in his symptoms and left ventricular systolic function and normalization of his ECG without progression to Q-wave infarction.
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Patient3.
A previously healthy 6-year-old black boy presented with chest pain and syncope. While playing the next day, he had a similar episode with documented ventricular tachycardia. These events were followed by multiple episodes of hypotension with widespread ischemic ST-segment elevation in the left main coronary artery distribution (Fig 3) with subsequent polymorphic ventricular tachycardia and ventricular fibrillation that required multiple external defibrillations, mechanical ventilatory support, and high-dose inotropic support. He was transferred to our hospital for extracorporeal membrane oxygenator support and consideration for cardiac transplantation.
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DISCUSSION
Acute coronary syndrome, including unstable angina, ST-segment elevation MI (STEMI), and non-STEMI, is rare in the pediatric population. The most important risk factor for myocardial ischemia in neonates and infants is congenital heart disease. Anomalous left coronary artery origin from the main pulmonary artery is the most common significant coronary artery anomaly (Bland-White-Garland syndrome).1,2 Infants with transposition of the great vessels undergoing an arterial switch procedure and children with aortic valve disease requiring a Ross procedure3 are also at risk for developing myocardial ischemia associated with reimplantation of the coronary arteries. Neonates with pulmonary atresia and intact ventricular septum may have right ventricular–dependent coronary perfusion via fistulas between the right ventricle and the coronary arteries. A decrease in the right ventricular pressure can produce postnatal MI. Delineation of the coronary arteries and the degree of right ventricular dependency is essential and should be performed in the cardiac catheterization laboratory before surgical intervention.
A risk factor for subendocardial ischemia in older children and adolescents is left ventricular hypertrophy either because of hypertrophic cardiomyopathy or as the result of increased afterload caused by left ventricular outflow obstruction or systemic hypertension. Another important etiology for acquired coronary occlusion in children is Kawasaki disease.4 Rapidly expanding coronary aneurysms in Kawasaki disease significantly increase the risk of coronary occlusion. Other rare causes of neonatal MI include endocardial fibroelastosis and mediocalcinosis of the coronary arteries.5–7 Finally, congenital anomalies of the origins of the coronary arteries have been associated with myocardial ischemia and sudden death, especially during athletic competition.8
The differential diagnosis of electrocardiographic ischemia in children is broad and should include the following etiologies: (1) infections (acute viral myocarditis, bacterial and fungal endocarditis) and protozoal diseases (Chagas disease); (2) neoplasms and paraneoplastic syndromes (Loeffler endocarditis); (3) inflammatory vascular diseases (including systemic lupus erythematosus, Takayasu arteritis, and periarteritis nodosa); (4) inborn errors of metabolism/genetic disorders; (5) trauma/iatrogenesis/substance abuse; and (6) miscellaneous (post–heart transplant coronary vasculopathy).
As seen in this report, myocardial injury that mimics transmural infarction in children can be seen in various diverse disease processes. The history and physical examination in children with myocardial ischemia or MI is significantly different from adults with MI. In neonates and nonverbal children, the history depends on the primary caregivers. They usually describe general symptoms of illness including irritability, loss of appetite/poor feeding, vomiting, diarrhea, pallor, cool extremities, and tachypnea. Fever or hypothermia may be reported. Verbal children will describe the location and radiation of their chest pain with reproducibility but have difficulty describing its character; they will invariably describe the pain as "sharp."9 On physical examination, neonates and children with myocardial ischemia/MI look sick; they are pale and not interactive. They may be tachypneic or dyspneic. Vital signs may reveal evidence of cardiogenic shock with tachycardia and hypotension. Cardiovascular examination may reveal an irregular rhythm, and a gallop may be appreciated. The extremities may be cool, and pulses may be either decreased or bounding. Bounding pulses may be misleading and falsely point toward a diagnosis of sepsis, although acute endocarditis involving the aortic valve with severe aortic regurgitation may be the culprit. The child might present with ventricular arrhythmias or heart block.
Therefore, in children, appropriate triage and swift, accurate clinical evaluation is of utmost importance. The pediatrician should have a high index of suspicion for cardiac involvement in a child who presents with the above-mentioned clinical signs and should proceed quickly with diagnostic studies for evaluation of potential myocardial ischemia or MI. Laboratory studies in the acutely ill child should encompass the main differential diagnoses and include cardiac troponin levels. Unfortunately, there exists little evidence regarding the positive and negative predictive value of these studies in evaluating pediatric myocardial ischemia/MI.10,11 However, as the cases discussed above demonstrate, troponin levels may be a useful adjunct to diagnosis; they were elevated in all 3 of our cases but were extremely elevated in the patient with true coronary artery ischemia. It is interesting to note that in each of our 3 cases, the troponin level was obtained subsequent to finding the ECG abnormality and not as part of the initial screening studies. Therefore, a 12-lead ECG should be obtained routinely, and there should be a low threshold for performing an echocardiogram given the indeterminate specificity of a troponin level that is within the reference range in excluding myocarditis without overt myocardial necrosis.
As mentioned above, electrocardiographic criteria for diagnosing MI in adults are well established (Table 1), but no general criteria exist for children. Towbin et al11 reported 37 autopsy-proven pediatric cases of transmural MI with ECG evidence of MI in 30 of these cases. On the basis of their findings, they developed electrocardiographic criteria for diagnosing MI in children (Table 2). Using these criteria, Towbin et al were able to diagnose 3 more patients prospectively and confirm the diagnosis at autopsy.
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CONCLUSIONS
Patients 1 and 2 in this report clearly demonstrate that ST-segment changes diagnostic of transmural MI in adults may be seen in pediatric patients in the absence of any coronary ischemia. These children were diagnosed with acute rejection after orthotopic heart transplantation and viral myocarditis, respectively. Patient 3 did have involvement of his coronary arteries as a result of coronary artery spasm that was not evident on his initial evaluation. On the basis of our experience and the cases described, the clinical approach to children who present with significant hemodynamic compromise, global or segmental decrease in systolic ventricular function on echocardiography, and ST-segment changes with elevated cardiac enzyme levels should not be interpreted on the basis of the adult criteria for acute coronary syndrome.12,13 The pediatric acute care physician and pediatric cardiologist should be aware of Towbin's criteria11 for pediatric ischemia, as well as the broad range of etiologies that are capable of producing an ischemic ECG pattern. In view of the third patient and another child with Prinzmetal angina encountered by our group,14 a high index of suspicion for coronary artery involvement is important in the evaluation of anginal symptoms associated with ischemic ECG changes; however, this evaluation should not delay workup for other more common pediatric etiologies.
FOOTNOTES
Accepted Mar 22, 2007.
Address correspondence to Edward K. Rhee, MD, One Children's Place, Campus Box 8116-NWT, St Louis, MO 63110. E-mail: rhee_e{at}kids.wustl.edu
The authors have indicated they have no financial relationships relevant to this article to disclose.
Short communications of factual material are published here. Comments and criticisms appear as Commentaries or Letters to the Editor.
REFERENCES
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