CHAPTER 104

Congestive Heart Failure

Robin Winkler Doroshow, MD, MMS, MEd, FAAP, and Deepa Mokshagundam, MD, FAAP

Congestive heart failure (CHF) is the most common symptomatic presentation of serious heart disease in infants. Although this condition also occurs in older children, an estimated 90% of cases of CHF in the pediatric population begin in the first year after birth. In infants and young children, CHF is most often caused by structural congenital heart disease (CHD); in older children, acquired cardiomyopathy and myocarditis are more prevalent. Compensatory mechanisms are fewer and less successful in small infants. Other causes of CHF are included in Box 104.1.

Epidemiology

The prevalence of CHF in children is approximately 0.1%. Most cases result from CHD, which occurs in 0.8% of live births. Each year, approximately 14,000 pediatric patients are hospitalized for management of CHF in the United States. The prevalence of CHD varies little by geography, ethnic group, or sex, but it is much more common in children with recognizable genetic syndromes (eg, Down syndrome, Turner syndrome). Rheumatic fever, which is far more prevalent in developing countries, is a rare cause of CHF in the United States.

Clinical Presentation

Most commonly, initial symptoms of CHF in an infant take the form of parental concerns about feeding. Comments are often vague (eg, “My baby is not a good eater”) but may be more precise (eg, “He is taking less formula with each feeding”; “He is taking longer to nurse”). The parent or caregiver may also describe rapid breathing, excessive sweating, or decreased activity, but usually only on specific questioning. The older child with CHF may report subjective symptoms, such as shortness of breath.

Congestive heart failure may also be detected on examination during routine infant checkups or evaluations for non-cardiac symptoms. In the child with CHF, careful assessment of the physical findings, including vital signs, reveals tachypnea, tachycardia, and hepatomegaly and often signs of underlying structural heart defects, such as a murmur (Box 104.2).

Pathophysiology

High cardiac output may result in CHF in the infant with a large left-to-right shunt. Myocardial contractility is relatively normal, and the child remains on the “normal” line of the Starling curve, which relates cardiac output to diastolic volume (also called preload) or pressure (Figure 104.1). The shunt requires a very large volume of output, primarily to the pulmonary bed. Although the heart may be able to meet this demand, preload is high, resulting in “congestive” signs and symptoms (eg, tachypnea, hepatomegaly). In more severe cases, systemic output may be compromised, resulting in hypotension, decreased systemic perfusion, renal failure, and metabolic acidosis.

Left-sided failure resulting in elevated pulmonary venous pressure produces increased lung water. Initially, this fluid is interstitial, and it does not interfere with gas exchange but does trigger reflex tachypnea. Minute volume is kept normal by decreasing tidal (ie, breath-to-breath) volume, resulting in shallow, rapid breathing (sometimes called “happy tachypnea” because of the absence of dyspnea). Only when the ability of the pulmonary lymphatics to drain this fluid is overcome by large volume does fluid accumulate in the alveoli; rales and respiratory distress, or dyspnea, result and gas exchange may be compromised.

Right-sided failure caused by an elevated systemic venous load usually produces more volume than pressure load on this system, possibly as a result of the greater venous compliance in infants compared with adults. The liver becomes quite distended and is easily palpated. As long as the liver can absorb the increased venous volume, the portal pressure does not rise, and splenomegaly does not occur. Because the venous pressure rises very little, jugular distention, which is always difficult to detect in the young infant, rarely occurs; edema is also rare.

Figure 104.1. Relationship of cardiac output to preload. The solid curve represents normal myocardial contractility, and the dotted curves represent impaired function (shifted downward) and the positive inotropic state (shifted upward). A, Normal range (no heart disease). B, Left-to-right shunt with congestive heart failure (CHF). Note that overall output is high, but most of it is shunted. C, Same situation as B but after treatment for CHF. Cardiac output is the same or better, but preload is now out of the range that results in congestive symptoms.

The left and right (ie, systemic and pulmonary, respectively) circulations are more interdependent in infants and younger children than in older children and adults. As a result, in infants and younger children bilateral heart failure is much more common than right-sided or left-sided failure alone. Although this means that recognition of CHF may be easier in younger patients, determination of the underlying condition may be more difficult because the clues are less specific. For example, in an adult with left-sided failure, the differential diagnosis includes mitral, but not tricuspid, valve disease.

Differential Diagnosis

In the presence of tachycardia, tachypnea without dyspnea, and hepatomegaly, the diagnosis of CHF is straightforward. Congestive heart failure is most commonly confused with major respiratory infections, such as bronchiolitis and pneumonia. Pulmonary infections frequently are associated with dyspnea as well as tachypnea, impaired gas exchange, and other respiratory findings. Rhinorrhea, cough, fever, or wheezing may also be present. Rales may accompany pneumonia but are rare in CHF of infancy or early childhood. Hyperinflation caused by lung disease may result in a false impression of hepatomegaly. In some children, CHD, CHF, and respiratory infections coexist and compound one another to increase morbidity and mortality, as is seen with respiratory syncytial virus.

Signs of structural heart disease, such as a murmur or absent femoral pulses, may support the diagnosis of CHF. Severe CHF, with low cardiac output or even shock, has a broader differential diagnosis. In addition to cardiac causes, sepsis, hypovolemia, and disorders associated with inborn errors of metabolism should be considered.

Evaluation

History

The history should include specific questions about feeding and growth (Box 104.3). Poor feeding, which is often a nonspecific symptom in infants with chronic or subacute illness, results from tachypnea and fatigability in infants with heart disease. Growth failure may result from poor feeding and increased cardiopulmonary work. The physician should specifically query the parent or caregiver about possible excessive sweating or rapid breathing in infants, because that information may not be volunteered.

Physical Examination

The diagnosis of CHF is primarily based on clinical findings, and physical examination is essential. The resting respiratory rate must be precisely counted, because the infant with CHF most often exhibits tachypnea without dyspnea. The liver edge is palpable more than 1 cm below the right costal margin in the midclavicular line, and the extent of enlargement mirrors the severity of the CHF.

The physical examination may also provide clues about the underlying cause of CHF, such as a heart murmur or gallop, or pulses that are weaker in the lower extremities than the upper extremities.

In the older child or adolescent, physical findings are more similar to those of the adult with CHF. Additional findings that may be present in the older child or adolescent include jugular venous distention, basilar rales, and peripheral pitting edema.

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