Case 2: The perspiring infant

A previously healthy five-month-old Caucasian boy presented to the emergency department during the summer with three days of cough and clear rhinorrhea, and one day of tactile fever. He was seen by his paediatrician the day before presentation and diagnosed with a viral upper respiratory infection. He had no documented fever at that time. The night before presentation, his mother noted that he felt ‘very warm’. No temperature was measured.

On review of systems, the patient was noted to be a ‘sweaty baby’ since birth; the diaphoresis was exacerbated by feedings. A family member also had an upper respiratory infection. The patient had had decreased feeding and decreased urine output for three days. The child had not lost any weight and had been growing normally. The remainder of the history was unremarkable.

He was born at 34 weeks’ gestation via vaginal delivery without any complications and had been developing well. The family history was remarkable only for an unspecified heart condition recently diagnosed in the child’s mother. The mother was not familiar with the specific diagnosis, but reported that she was not symptomatic.

On physical examination, the boy’s temperature was 37.9°C, pulse was 144 beats/min and blood pressure was 98 mmHg (palpated). His respiratory rate was 28 breaths/min with mild subcostal retractions. The child’s weight was 6.70 kg. Generally, he was interactive and in no acute distress. A soft, holosystolic murmur was heard intermittently at the apex. However, the heart had a regular rate and rhythm, with no rubs or gallops. The lungs were clear to auscultation bilaterally without wheezes or crackles. Femoral and radial pulses were 2+ (normal) and equal bilaterally. There was no jugular venous distention. The abdomen was soft and nontender. There was no hepatosplenomegaly. He had no rash. The remainder of the physical examination was unremarkable.

One further test led to the diagnosis.

CASE 2 DIAGNOSIS: HEART FAILURE SECONDARY TO ANOMALOUS ORIGIN OF THE LEFT MAIN CORONARY ARTERY FROM THE PULMONARY ARTERY

The patient’s chest x-ray is shown in Figure 1. It demonstrated cardiomegaly, which in this setting, was consistent with heart failure. In one’s differential diagnosis of an infant with fever, viral symptoms and heart failure, a diagnosis of myocarditis should be considered. However, an electrocardiogram (ECG) and subsequent echocardiogram in the present case revealed the underlying etiology to be an anomalous origin of the left main coronary artery (LCA) from the pulmonary artery (ALCAPA). The echocardiogram was also significant for mitral regurgitation, which is common in patients with ALCAPA.

Figure 1).

Chest x-ray demonstrating cardiomegaly

Heart failure is a condition that occurs when cardiac output is insufficient to meet the metabolic needs of the body. There are two main pathophysiological conditions that lead to the clinical syndrome of heart failure in children: volume overload lesions and those causing myocardial dysfunction. Ventricular septal defect and patent ductus arteriosus are examples of volume overload lesions, meaning these conditions result in increased pulmonary blood flow and relative preservation of myocardial function. Conversely, myocarditis, dilated cardiomyopathy and ALCAPA result in myocardial dysfunction. Collectively, these two pathophysiological categories account for the multiple etiologies of heart failure in infants, children and adolescents. (Refer to Table 1 for a list of common etiologies.)

TABLE 1.

Etiology of heart failure

Premature neonate	Full-term neonate
Patent ductus arteriosus Ventricular septal defect Cor pulmonale Genetic cardiomyopathy	Arteriovenous malformation Coarctation of the aorta Myocarditis Asphyxial cardiomyopathy
Infant-toddler	Child-adolescents
Ventricular septal defect Arteriovenous malformation ALCAPA Hemolytic-uremic syndrome Kawasaki’s disease	Rheumatic fever Thyrotoxicosis Sickle cell anemia Endocarditis Cystic fibrosis

Adapted from reference 3. ALCAPA Anomalous origin of the left main coronary artery from the pulmonary artery

The presentation of heart failure is extremely variable depending on the degree of cardiac compromise. Children who have not yet exhausted compensatory control mechanisms may be asymptomatic, even during times of moderate activity. Symptoms of heart failure can include the usual dyspnea, fatigue, cough, anorexia and exercise intolerance, as is seen in adults. Adolescents may present with isolated abdominal pain as their only complaint. Infants with heart failure usually present with tachypnea, subcostal retractions, nasal flaring, feeding difficulty, poor weight gain, hepatomegaly and excessive sweating.

The initial workup of a child with suspected heart failure includes an ECG, echocardiogram, arterial blood gas (ABG), electrolytes and brain natriuretic peptide (BNP) testing. The ECG may reveal ventricular ischemia, low-voltage QRS complexes or ST-T wave abnormalities. While this diagnostic modality is most useful for detecting an underlying rhythm disorder, the ECG of a child with ALCAPA syndrome may demonstrate pathological Q waves characteristic of anterolateral infarction, which in addition to clinical signs, can be used to arouse suspicion for ALCAPA even before the echocardiogram is obtained (Figure 2). The echocardiogram is considered to be the most useful test for assessing ventricular function. In children with heart failure, it can demonstrate the degree of left ventricular systolic dysfunction. In patients with ALCAPA, the echocardiogram will reveal not only the anomalous origin of the LCA, but also may demonstrate mitral regurgitation, an enlarged right main coronary artery and retrograde flow through the LCA into the pulmonary trunk. An ABG is obtained to evaluate for ventilation-perfusion abnormalities that may occur as a result of pulmonary edema. ABG values may also indicate metabolic or respiratory acidosis, which suggests severely decompensated cardiac function. Electrolyte levels can be measured to test for hyponatremia, which is a common finding in children with heart failure, secondary to renal water retention. Troponin T and troponin I may also be used as both diagnostic and prognostic markers in patients with suspected heart failure. Elevation of these cardiac bio-markers in patients with heart failure can indicate poorer prognosis. BNP is a cardiac neurohormone whose elevation parallels increases in ventricular wall tension. Therefore, an elevated BNP level in children can help to confirm cardiomyopathy or volume overload. Additionally, testing for an elevated BNP level may be a useful screen for heart disease in paediatric patients (1).

Figure 2).

Electrocardiogram of a child with anomalous origin of the left main coronary artery from the pulmonary artery

The successful treatment of paediatric heart failure is based on the correction of any underlying structural deficit and the use of pharmacological intervention to help improve cardiac function. The primary goal of treating heart failure pharmacologically is to reduce afterload, often by way of diuretics. The primary role of diuretics in heart failure is to control pulmonary insufficiency and peripheral venous congestion. Positive inotropic agents such as digoxin are typically initiated as well. These agents serve to increase the force of myocardial contraction. Beta-blockers and aldosterone blockers are also commonly used. Indications for the use of the aforementioned medications are severe cardiac dysfunction and evidence of dilated cardiomyopathy, respectively.

ALCAPA is a rare congenital coronary artery anomaly with an estimated mortality of 90% if the condition is left untreated (2). The lesion is not symptomatic in the fetus because of high pulmonary pressures. As pulmonary arterial pressure declines in the first few hours of life, flow through the LCA decreases and eventually reverses. Consequently, this retrograde flow results in ischemia, angina and, potentially, myocardial infarction. This results in dilated cardiomyopathy and, eventually, congestive heart failure. Children with ALCAPA usually present after two months of age in heart failure with profuse sweating, dyspnea, pallor and failure to thrive. These symptoms will be more prominent during periods of increased cardiac demand, such as when the child is feeding or crying. Diagnosis is primarily by echocardiography or computed tomography/magnetic resonance angiography. ALCAPA requires immediate surgical correction. Following surgical reimplantation of the LCA to the aorta, the left ventricle will usually recover function over several months.

CLINICAL PEARLS

• Presentation of heart failure in infancy can, on occasion, be very subtle (as in the present case). Heart failure should be considered in any infant presenting with respiratory distress who has a history of excessive sweating, particularly with feeding. An intercurrent illness may precipitate the infant’s clinical presentation.

• Chest x-rays, ECGs and cardiac enzymes may be useful diagnostic tests for infants in whom heart failure is a consideration.