Etiology And Presentation

The heart is a pump. It may fail as a pump either from the inability to generate enough contractile force or from structural anomalies that prevent or inappropriately direct blood to the tissues. Examples of the former include myocarditis, an infection of heart muscle cells (myocytes), or a cardiomyopathy, a primary structural or metabolic abnormality of the microscopic elements of a myocyte. Examples of structural anomalies that might lead to heart failure include left-to-right shunt lesions such as ventricular septal defect; patent ductus arteriosus, and, rarely, atrial septal defect, or valvar regurgitation because of the increased volume load on the heart; and severe valvar stenosis because of the increased pressure load. When the heart is no longer able to compensate, the state of heart failure exists.

When the heart fails to adequately pump blood forward for any reason, venous congestion occurs. On the right side, the liver in particular becomes distended and engorged with blood. This leads to abdominal discomfort or vomiting initially, but in certain prolonged cases, it may lead to liver dysfunction and distension of venous collaterals, some of which may be visible under the skin (Figure 46-1). The signs of peripheral edema and jugular venous distension (Figure 46-2, left), classically seen in adults are not typically seen in infants or young children. On the left side, pulmonary venous congestion leads to fluid extravasation within the lungs, typically interstitial in infants and intraalveolar in older children and adults (Figure 46-2, right). This leads to shortness of breath, tachypnea, and dyspnea and can present on chest radiography similar to pneumonia. Indeed, in some cases, a secondary infection may develop superimposed on these wet and stiff lungs.

Figure 46-1 Liver in heart failure.

Figure 46-2 Clinical presentation of heart failure in a teenager and infant.

As the heart begins to fail in the volume of blood it can pump, the sympathetic nervous system seeks to compensate by increasing the heart rate. In these cases, an ECG may be useful in differentiating a sinus tachycardia in response to a failing heart (P-wave axis between 0 and 90 with a one-to-one relationship to the QRS complexes) versus a primary arrhythmia. If prolonged and untreated, some nonsinus heart rhythms can be the cause of heart failure. Finally, upregulation of the sympathetic nervous system may also cause vasoconstriction and diaphoresis, and the child may present as cold, pale, and diaphoretic.

The apex beat may be displaced downward and laterally and may be full and bounding or weak depending on both the cause of the heart failure and how successful the child is compensating. In newborns, anything more than a slight pulsation felt with two fingers placed beneath the xiphisternum is concerning for cardiac involvement. Auscultation may reveal a number of clues as to the cause. Difficult-to-hear heart sounds may signify a pericardial effusion with fluid between the heart and the pericardium that does not permit adequate filling of blood into the heart but more often is caused by poor contraction from a primary cardiomyopathy. A gallop is frequently heard in failing hearts and refers to an extra (third or fourth) heart sound. Third heart sounds may be normal in some children and are thought to be caused by rapid diastolic filling. A fourth heart sound is never normal and is indicative of a poorly compliant ventricle reflecting a high-pressure wave back toward the atrium.

Murmurs may be heard in the setting of heart failure caused by a primary structural abnormality (discussed elsewhere). Some murmurs represent turbulence across an incompetent valve caused by severe left ventricular dilatation seen in some failing hearts.

Case Example

Myocarditis occurs when there is inflammation of the myocardium with cell damage or death leading to decreased ventricular function and cardiac output. In the United States and Europe, most cases are of viral origin. Although the suspected causative agents have changed over recent decades, today when a successful diagnosis is made, adenovirus and enterovirus are the most frequently isolated viral species. Myocarditis may however arise from a host of other agents, including bacteria, protozoa, pharmaceuticals, and even rheumatologic and autoimmune processes.

There are wildly differing estimations as to the incidence of this disease, but it is likely that many cases remain subclinical and are never discovered. Catheter-based biopsy-proven diagnosis in this disease is often fraught with difficulty. Taking a heart muscle biopsy from an acutely ill child has its dangers, and the result of such a biopsy may not lead to any changes in the acute course of treatment. When biopsy is possible, samples consistent with viral myocarditis will show a lymphocytic infiltrate and cell necrosis. Magnetic resonance imaging may come to play an important role in future diagnoses with tissue characterization suggestive of inflammation, edema, and possibly myocardial scarring.

The decrease in myocardial function caused by myocarditis may present either suddenly or indolently. Paradoxically, patients who present most suddenly (and often in cardiogenic shock, or “fulminant myocarditis”) tend to recover most readily if the initial course is supported; more than 90% of these patients survive transplant free 11 years later. But patients in whom function limps along with little recovery rarely regain full function and either develop chronic although stable dilated cardiomyopathy or end-stage heart failure. Of these, fewer than half of patients are alive and transplant free after 11 years. Myocarditis may present at any age.

Infants and children present in varying degrees of heart failure as detailed above, and primary complaints may revolve around chest pain (pericarditis), respiratory distress, or abdominal distress and decreased appetite from increasing venous stasis. There may be a fever or a history thereof from the primary infection; a history of a flulike illness may precede the presentation by 1 to 4 weeks. A resting tachycardia with or without a gallop will be present along with tachypnea or cough. More severe cases may have a signs of cardiogenic shock (hypotension, cool and pale extremities). There may be a systolic murmur of mitral regurgitation, a finding seen when significant left ventricular dilation has occurred. Atrial and ventricular fibrillation along with atrioventricular nodal block are sometimes seen and may lead to sudden death.

The ECG tends to show low-voltage and often markedly widened QRS complexes. There may be inversion of the T waves along with Q waves indicative of myocardial infarction. Cardiomegaly may be present on chest radiography, but its absence does not rule out the disease, particularly in the very beginning of fulminant myocarditis. Echocardiography, the most sensitive of these tests, demonstrates left ventricular dilatation and decreased ventricular function. Global and uniform hypokinesis is the norm, although segmental wall motion abnormality (dyskinesia) may also be present. With increasing left ventricular volume and worsening valve leaflet apposition, color-Doppler ultrasonography will demonstrate mitral regurgitation. Cardiac troponin T will be elevated in patients with myocarditis and is often a useful test in distinguishing myocarditis from cardiomyopathy, in which it is not elevated.

Because of the rapidity with which cardiovascular collapse may ensue, prompt consultation is recommended. Inotropic support with milrinone or dopamine (or both), arterial monitoring, 24-hour telemetry to monitor for ectopy, and ECMO are often needed in the acute fulminant phase of this disease. Lidocaine infusions and magnesium may be necessary if ventricular ectopy develops. Treatment is therefore primarily supportive. Immunosuppressive regimens are controversial, with many studies showing no improvement with combinations of steroids and medications, including cyclosporine and azathioprine. Some evidence has been emerging that IV immune globulin with the possible addition of vitamin C may have a beneficial effect on some forms of myocarditis.

Future Directions

One area of rapid improvement in pediatric heart failure is the continuing development of pediatric ventricular assist devices (VADs). Unlike nonpulsatile ECMO, with which a child’s heart may be supported for weeks in the hope that it may recover from whatever insult it has sustained, VADs allow much longer support periods and can be used until a child is listed for and receives a heart transplant. Many devices use extrathoracic pneumatic pumps that circulate blood through cannulae introduced through the abdominal wall into the child’s circulation. One such device that has found frequent use is the Berlin Heart EXCOR, which just supported its 500th child.