HISTORY OF PRESENT ILLNESS
A 9-year-old girl was well until 6 days prior to admission when she developed vomiting, abdominal pain, and lethargy. Four days prior to admission she was noted to have a fever to 102°F and cough. She received amoxicillin for a presumed lower lobe pneumonia with referred abdominal pain; chest radiograph was not performed. Over the next 2 days she had worsening of her abdominal pain and increased listlessness. Her mother reported that the whites of her eyes had looked yellow for the past 3 weeks.
The patient had no major illnesses or hospitalizations. She had four episodes of dizziness during the past 5 months that had been evaluated with an EEG and an ECG which were both normal. She was on no medication except for the amoxicillin for her diagnosis of pneumonia. Family history was significant only for several family members with diabetes mellitus. The mother required a splenectomy after blunt abdominal trauma.
T 37.4°C; HR 118 bpm; RR 30 bpm; BP 91/50 mmHg; Oxygen saturation 94% on room air
Weight 27.9 kg (25th percentile)
The patient was responsive but withdrawn. There were mildly icteric sclera, no oral lesions, and no pharyngeal injection. The neck was supple with shotty lymphadenopathy. The lung examination was clear with equal breath sounds bilaterally. Cardiac examination revealed a normal precordium, mild tachycardia, normal S1 and S2, no gallop, and no murmur. The abdomen was soft and nontender with normal bowel sounds, and the liver was palpated 4 cm below the right costal margin and the spleen tip was palpable. The extremities were warm, but there were diminished pulses in both the upper and lower extremities. The neurologic examination was normal and the skin revealed no rash.
Complete blood count revealed a white blood count of 9600/mm3 with 72% segmented neutrophils and 23% lymphocytes. The hemoglobin and platelets were normal. Prothrombin time, partial thromboplastin time, electrolytes, blood urea nitrogen, and creatinine were all normal. A hepatic function panel revealed a bilirubin of 3.2 mg/dL; with an unconjugated bilirubin of 1.8 mg/dL; albumin, 3.8 gm/dL; alkaline phosphatase, 78 U/L; AST, 54 U/L; LDH, 237 U/L; and uric acid, 7.3 mg/dL. Lipase was 168 U/L and amylase 63 U/L. ECG revealed a sinus rhythm at 129 bpm, PR interval of 0.144 seconds, right axis deviation, normal voltage, and no ST segment changes. The chest radiograph was abnormal (Figure 7-4).
FIGURE 7-4. Chest radiograph.
COURSE OF ILLNESS
The patient had an ECHO which revealed a markedly dilated left ventricle to 5.4 cm, moderate to severe mitral regurgitation, and a markedly decreased shortening fraction of 10%-18%. The patient was started on furosemide and milrinone. Despite increasing doses, by the fourth hospital day the patient had distended neck veins, increasing dyspnea, cough, and lethargy. Repeat ECHO showed a decrease in the shortening fraction to less than 10% with a dilated and thin walled left ventricle, persistent severe mitral regurgitation, and moderate tricuspid regurgitation with a right ventricular pressure 30 mm greater than the right atrium.
DISCUSSION CASE 7-4
Myocarditis and other forms of heart disease are listed as possible etiologies for abdominal pain. Cardiomegaly on this patient’s chest radiograph gave the first indication of heart disease and heart failure. Possible etiologies of this heart failure include congenital heart disease, particularly septal lesions, which must be ruled out in the pediatric population at any age. There are several possible causes of heart failure that include dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy, arrhythmogenic right ventricular dysplasia, obliterative cardiomyopathy, inflammatory cardiomyopathy (myocarditis), and giant cell myocarditis. In pediatrics, it is most helpful to make the more broad distinction between cardiomyopathy and myocarditis.
Chest radiograph revealed dramatic cardiomegaly and prominence of the pulmonary vasculature (Figure 7-4). Cardiac catheterization with endomyocardial biopsy was done and the patient was noted to have a decreased cardiac index of 1.47 mm/m2, a left ventricular end diastolic pressure of 35, and an increased pulmonary wedge pressure of 38 and a right atrial pressure of 18. Biopsy revealed no inflammatory cells. The patient was diagnosed with idiopathic dilated cardiomyopathy and listed for cardiac transplant. The diagnosis is idiopathic dilated cardiomyopathy.
INCIDENCE AND EPIDEMIOLOGY OF DILATED CARDIOMYOPATHY
While heart failure represents a major problem in adult medicine, it is far less common in pediatrics. Excluding infancy when congenital heart disease is the most common indication for heart transplant, dilated cardiomyopathy is the primary indication for pediatric heart transplants throughout the world. The majority of cases of dilated cardiomyopathy have no definitive cause. Several genetic and molecular lesions have been identified, including mutations in the cytoskeleton, troponin, and other sarcomere protein genes. Autosomal dominant, autosomal recessive, and x-linked are some of the modes of inheritance of these genes that have been identified thus far. A relative with dilated cardiomyopathy is one of the diagnostic criteria for familial dilated cardiomyopathy. While it has long been known that the skeletal muscular dystrophies have skeletal involvement, familial dilated cardiomyopathy, although poorly understood, has been recognized more frequently.
The structural changes that occur in dilated cardiomyopathy include increased left ventricular mass, normal or reduced left ventricular wall thickness, and increased left ventricular cavity size. Histologic samples can show anything from focal myocyte death, increase in interstitial macrophage, and interstitial fibrosis.
Some new onset cardiomyopathy can be attributed to myocarditis. Survival rates can be as high as 80% and the infections can be either fulminant (usually with a better prognosis) or insidious. Arguably, insidious cases may be missed and later contribute to cases of idiopathic cardiomyopathy. Infectious agents (bacterial, spirochetal, fungal, protozoal, parasitic, rickettsial, and viral) have all been implicated. Worldwide, infections with Trypanosoma cruzi(Chagas disease) and Corynebacterium diphtheriae (diphtheria) are the most common causes of myocarditis while in the United States, viruses are more common. The two major viral etiologies are coxsackievirus B and adenovirus. Infections with hepatitis C, HIV, EBV, and CMV have also been implicated. Other causative etiologies of myocarditis include immune-mediated mechanisms, and toxins such as medications and heavy metals.
CLINICAL PRESENTATION OF DILATED CARDIOMYOPATHY
The clinical presentation of dilated cardiomyopathy encompasses that of clinical heart failure including fatigue, shortness of breath, cough, and abdominal pain. However, the clinical features are varied and can range from asymptomatic patients to those with fulminant cardiac failure. In myocarditis, there is frequently a history of a recent flu-like syndrome and sometimes arrhythmias secondary to the rapid ventricular dilatation.
The distinction between dilated cardiomyopathy and myocarditis is important, as it may alter the management that the child receives. Although clinical symptoms (clinical heart failure, recent flu-like syndrome accompanied by fever) and laboratory tests (leukocytosis, eosinophilia, elevated creatinine kinase, or troponin) can be helpful in supporting a diagnosis of myocarditis, they are not sufficient.
Echocardiogram. All patients should have an echocardiogram to rule out structural anomalies.
Myocardial biopsy. Although there are other non-invasive modalities that are important, myocardial biopsy is still the gold standard for diagnosis of myocarditis.
Other studies. Testing for infectious (e.g., coxsackie, adenovirus, echoviruses, RSV, CMV, EBV, HIV) and any other possible etiologies including autoimmune diseases (e.g., systemic lupus erythematosus) and mitochondrial diseases is warranted in all new cases of pediatric heart failure.
Symptom counseling and management as well as supportive therapy are the mainstays of treatment. Although there is less evidence to support specific treatment of heart disease in the pediatric population, the therapy mirrors that of adult medicine and includes ACE inhibitors. Less frequently, beta blockers and digoxin are used. Although there is not strong literature and controversies persist, the standard is to treat cases of biopsy-proven myocarditis with immunomodulators (ranging from immunoglobulin therapy and steroids to cyclosporine and cytoxan) in an attempt to suppress the inflammation. Patients with progressively worsening heart failure may be candidates for mechanical-assist devices (i.e., LVAD or ECMO) which may provide stabilization until cardiac transplant can be achieved.
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