Chapter 40: Congestive Heart Failure

• A directed history and physical examination can provide clues to the presence and possible etiologies of heart failure.

• Abnormal vital signs with normal temperature may suggest cardiac disease.

• Tachycardia of heart failure is often “monotonous” or incessant, and does not typically respond to treatment (i.e., volume, antipyretics, pain medications, etc.).

• Tachypnea, failure to thrive, or diaphoresis with feeding, accompanied by abnormal lung sounds, tachycardia, gallop, and hepatomegaly suggest CHF in an infant.

• New-onset heart failure may be less overtly symptomatic in older children. Symptoms of abdominal pain and nausea and anorexia can be present, sometimes diverting attention from the real cause.

• Management is directed at the cause. Medications to consider include diuretics, vasodilators, inotropes, and neurohumoral modulators.

Heart failure is a clinical condition that results from impairment of the ventricle to fill with or eject blood. Heart failure is caused by ventricular pump dysfunction, or by overload of volume (preload) or pressure (afterload).^1–3 Heart failure in children has many etiologies (Table 40-1). In the younger infant, congestive heart failure (CHF) is most likely related to structural heart disease, yet respiratory illnesses, anemia, and infection must be considered and appropriately managed. In an older child, the etiology may have a structural, metabolic, infectious, and/or environmental origin.^1–3

Cardiac output is determined by four factors: preload, afterload, contractility, and rate. Preload, or filling volume, is increased in left-to-right shunts. Afterload, or the resistance the ventricles face upon ejection of blood, has an important role in outlet obstruction or systemic hypertension. Contractility is altered in cardiomyopathy. Rate can either be too slow, resulting in inadequate output, or too fast, decreasing diastolic filling.^2,3

In acute CHF, end-organ hypoperfusion explains most clinical features. Decreased flow to the kidney results in renin/angiotensin-based salt and water retention, and an increased circulating volume. Angiotensin II, a potent vasoconstrictor, increases vascular resistance resulting in a rise in blood pressure. Sympathetic discharge, as a result of decreased oxygen delivery, results in improved contractility. Redistribution of blood from skin and skeletal muscle to heart, brain, and kidney improves vital function. As the disease process worsens, physiologic mechanisms are unable to keep up. Overcompensation results in symptoms. Salt and water retention produces edema. Increased adrenergic response and tachycardia cause inadequate diastolic filling. Diaphoresis during feeding is secondary to catecholamine release. Decreased skin perfusion results in mottling and pallor. Increased systemic vascular resistance increases myocardial demand, causing hypertrophy or dilation. Valve insufficiency or myocardial ischemia can cause further decrease in cardiac output.^1–4

In chronic CHF, myocardial cells die from energy starvation, from cytotoxic mechanisms leading to necrosis, or from the acceleration of apoptosis. This loss of myocytes leads to cardiac dilation, increased afterload, wall tension, and further systolic dysfunction.^5,6

The presentation of acute heart failure syndrome (AHFS) can be classified into four presentations which will assist the emergency physician in providing care for these children.^7,8

1. Warm and Dry: Represents asymptomatic ventricular dysfunction (normal filling pressures and adequate perfusion). The primary focus is prevention of disease progression.

2. Warm and Wet: The most common presentation characterized by elevated filling pressures and pulmonary edema with adequate perfusion.

3. Cold and Wet: Characterized by elevated filling pressures and poor perfusion requiring intensive care management.

4. Cold and Dry: A dire condition best described as the presence of normal filling pressures with poor perfusion requiring aggressive treatment.

History

Signs of CHF vary with the age of the child. In an infant, questions related to feeding and nutritional status are extremely important (Table 40-2). Poor weight gain, cachexia, and malnutrition may be a sign of a flailing heart and failure to thrive may suggest uncompensated CHF.^7,9

In an older child, questions regarding exercise ability, fatigability, and shortness of breath, weight gain, or weight loss are important. An adolescent may complain of fatigue, cool extremities, exercise intolerance, dizziness, or syncope.

Older children may complain of abdominal pain, nausea and anorexia, sometimes diverting attention from the real cause. The modified Ross classification for heart failure aids the physician in assessing the severity of disease in infants and children (Table 40-3).^7,9

Past Medical/Surgical History

The past medical and surgical history can assist in identifying causes of CHF and should include any history of recent viral illness, heart disease, rheumatic heart disease, Kawasaki's disease, hypothyroidism, cancer/chemotherapy, and any surgical procedures, especially related to the heart. Check for family medical history of cardiomyopathy, sudden death, and/or syncope.⁹

Physical Examination

The severity of CHF is based upon the clinical appearance and behavior, including alertness, respiratory effort, and ability to take oral fluids/nutrition. The first manifestation of CHF is usually “tachycardia.” This is especially important in the infant with suspected heart failure. An infant's myocardium is “stiffer” and less distensible, and hence the infant is unable to increase the stroke volume as an older child does. An infant compensates primarily by raising heart rate. Abnormal vital signs such as unexplained tachycardia or tachypnea with normal temperature may suggest cardiac disease. The tachycardia of heart failure is often “monotonous” or incessant, and does not respond to treatment (i.e., volume, antipyretics, and pain medications). Left-sided heart failure is associated with pulmonary venous congestion, whereas right-sided heart failure is associated with signs of systemic venous congestion (Table 40-4).^1,4

Physical examination should evaluate for resting tachycardia, tachypnea, hepatomegaly, ascites, edema, and diminished perfusion. Facial edema and anasarca are late signs. Pedal edema and neck vein distention is rare. Cardiac examination should focus on heart rate, presence of gallops, new murmurs, displaced PMI, an RV impulse, and perfusion deficits. A pathologic murmur or gallop rhythm is characteristic for CHF.⁴

Initial laboratory testing includes arterial or venous blood gas, complete blood cell count with hemoglobin concentration, electrolytes, calcium, BUN, creatinine, lactic acid, liver function tests, and urinalysis. A metabolic and respiratory acidemia is generally present due to pulmonary congestion and poor tissue perfusion; hyponatremia and hypochloremia are secondary to free water retention and elevated creatinine levels due to poor renal perfusion and compromised renal function. Elevated lactic acid is present with significant tissue hypoxia. The hemoglobin and hematocrit should be checked since severe anemia can precipitate high-output cardiac failure. It is critical to know the calcium level in the infant as they rely on circulating calcium. If it is low, it will be more difficult to manage the CHF. Cortisol level may be drawn and if low, consider giving corticosteroids.^1,7

Laboratory tests assessing neurohormonal markers in heart failure have evolved. Elevated norepinephrine, aldosterone, angiotensin II, and vasopressin levels have all been linked to worse outcomes in patients with chronic CHF. One laboratory test in particular, as β-type natriuretic peptide (BNP), is being used to diagnose and manage CHF. The measurement of serum BNP is useful in differentiating a pulmonary cause of dyspnea from a cardiac cause of dyspnea.^1,7,10,11

An elevated BNP level correlates positively with heart failure and negatively with ejection fraction. A BNP >100 pg/mL is considered abnormal; between 100 and 500, the test is inconclusive; and a level >500 pg/mL is indicative for heart failure in children.¹¹

Additional biomarkers for myocardial injury include troponin and CK-MB. An elevated troponin suggests myocarditis rather than dilated cardiomyopathy. CK-MB is elevated in patients with myocardial ischemia and/or myocarditis and is elevated earlier than troponin.¹²

Finally, inflammatory markers such as ESR and CRP may differentiate myocarditis from dilated cardiomyopathy. Genetic, rheumatologic, thyroid, carnitine, urine organic acid, serum amino acids, and viral cultures may be obtained when evaluating a child with newly diagnosed cardiomyopathy which can be obtained in the inpatient setting.^1,7

Ancillary tests include a chest radiograph, electrocardiogram and echocardiogram.^1,7,13

Chest Radiograph

The chest radiograph (CXR) helps assess heart size and pulmonary congestion. It is a reliable tool for measuring volume overload.¹³ Cardiomegaly is present if the cardiothoracic ratio is greater than 0.55 in infants and greater than 0.5 in children. Remember, a normal CXR does not rule out heart failure (Figs. 40-1 and 40-2).

Electrocardiogram

The electrocardiogram (ECG) may show nonspecific findings of atrial enlargement, ventricular hypertrophy, strain, and changes in ST segment or T-wave morphology. The ECG shows sinus tachycardia with low-voltage QRS complexes, with or without low-voltage or inverted T waves. As failure worsens, managing brady- and tachyarrhythmias may be necessary. Wide Q waves and ST-segment changes, indicating myocardial infarction, can be seen (Fig. 40-3).

Echocardiography

The quickest way to assess cardiac function is with two-dimensional echocardiography (ECHO). It is utilized to assess cardiac anatomy in congenital heart disease, and to estimate gradients, shunting, and cardiac output. ECHO evaluates for myocardial disease, such as hypertrophic, restrictive, and dilated cardiomyopathies and typically reveals a dilated, dysfunctional left ventricle. A pericardial effusion is frequently present.⁴

Management of heart failure is multidimensional and requires a stepwise approach. A pediatric cardiologist should be involved early on in the child's care. In the emergency department setting, the goal is to recognize the child in acute CHF and begin management, remembering always the ABCs. Current therapy for acute heart failure focuses on improving myocardial performance with inotropic agents, adjustments to afterload and preload, and on correcting the underlying cause. When the cause is known, correctable tasks must be undertaken. Examples include interventional techniques for obstructive lesions, exchange transfusion for profound anemia, β-blocker for thyroid storm, or pericardiocentesis for cardiac tamponade. When the cause is unknown, empiric therapy is initiated based on the need to control rate, decrease preload, and improve afterload and/or contractility (Fig. 40-4 and Table 40-5).

Treatment of CHF

Pharmacologic therapy is directed at the specific cause of CHF when dealing with known cardiac disease. Treatment involves the use of diuretics, digoxin, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARB), aldosterone antagonists, and β-blockers.^14–16 (See Tables 40-6A 40-6B for specific drug classes and dosing guidelines.)

Fluid overload is initially treated with diuretics to reduce increased work of breathing, peripheral edema, and ascites.^17,18 Digoxin has a positive inotropic effect, negative chronotropic effect, and a vagotonic effect. Years ago, digoxin was the drug of choice in the management of children in heart failure. It is no longer the first-line agent and reserved for patients with ventricular dysfunction with symptoms consistent with Class III heart failure.¹⁵

Afterload reduction is obtained by ACE inhibitors. They are vasodilators, but they affect neurohormonal mechanisms. In the setting of low output with increased systemic resistance, such as in hypertensive cardiomyopathy, afterload reduction with ACE inhibitors may be helpful. Captopril and enalapril are used most frequently. Contraindications include patients with renal insufficiency and those with right-to-left shunts. In right-to-left shunt, the systemic circulation may improve at the expense of the pulmonary circulation.¹⁹

Contractility can be supported with intravenous agents (dopamine) or mixed agents (dobutamine, milrinone). Milrinone, a phosphodiesterase inhibitor has gained popularity in many institutions as a first-line agent. Milrinone is shown to increase cardiac muscle contractility, vascular smooth muscle relaxation, and cardiac output without increasing myocardial oxygen consumption or ventricular afterload. Dobutamine has fallen out of favor because of increased mortality in adult heart failure patients.^20,21

β-blockers may have a role in chronic CHF. They “upregulate” cell wall receptors, increasing contractility.^5,6,22 The decision to begin long-term agents, digoxin, ACE inhibitors, or β-blockers is best made in consultation with a pediatric cardiologist or intensivist. An algorithmic approach to CHF is presented in Figures 40-4 and 40-5.

The child in moderate-to-severe CHF will require the intensive care unit or transfer to a tertiary care facility. Intubation may be necessary to improve oxygenation and provide positive end-expiratory pressure (PEEP), useful in pulmonary edema. Inotropic support includes milrinone to increase cardiac muscle contractility, vascular smooth muscle relaxation, and cardiac output without increasing myocardial oxygen consumption or ventricular afterload, dopamine to increase contractility and blood pressure, and epinephrine to improve blood pressure.^14–16

In severe cases, such as myocarditis with cardiogenic shock, the weakened myocardium ineffectively pumps against increased afterload. Vasodilators such as sodium nitroprusside may be helpful. It has venodilator and arteriolar dilator effects and is easily titratable.^14–16

β₂-Blockers are being used more frequently in the pediatric patient. Carvedilol, a β-adrenergic blocker with vasodilating action, appears to be beneficial in chronic CHF in adults. In recent multicenter pediatric clinical trial, Carvedilol, as an adjunct to standard therapy for pediatric heart failure, improved symptoms and left ventricular function. Because of its potential side effects of hypotension and its negative inotropic action, Carvedilol should be started at a low dose and only after the patient has been stabilized with diuretics, digoxin, and ACE inhibitors. Carvedilol most likely will be beneficial in children with CHF due to dilated cardiomyopathy.^22–24

Nesiritide (BNP) is a newer therapy in the treatment of decompensated CHF in adults. It possesses vasodilatory, natriuretic, diuretic, and neurohormonal effects. However, it has significant side effects. Pediatric cardiologists have reported on small numbers of pediatric patients in the last 5 years with similar results. The pediatric patients diuresed and had symptomatic improvement with only dose-related hypotension and asymptomatic hyponatremia as recognized side effects. Nesiritide infusion, alone or in combination, may be an alternative for decompensated heart failure in children.^25–28

Spironolactone/Aldactone (aldosterone antagonist) is used in the management of chronic heart failure in adults. The RALES (Randomized Aldactone Evaluation Study) demonstrated a decrease in morbidity and mortality when incorporated into the treatment regimen of adults with significant symptomatic CHF. It is not known if these benefits apply to children but is being used more often by pediatric cardiologists in treating CHF in children.²⁸

Levosimendan, a calcium sensitizer, is a promising new agent in a new class of medications. Levosimendan increases both inotropic and vasodilation without increasing calcium levels or myocardial oxygen demand.^21,28

Other options are extracorporeal membrane oxygenation (ECMO) and ventricular assist devices (VADs), which are being utilized in children with CHF who are not responding to medical management. The hope is to extend the child's life while awaiting cardiac transplantation or recovery from the infection.^8,29–31 Consider early transfer to centers with ECMO and VAD capabilities.

In all age groups, a directed history and physical examination can provide valuable clues to the presence and possible etiologies of impending decompensated heart failure. Remember that tachycardia may be the only sign. Abdominal pain can be a chief complaint or presenting symptom for a great number of children with heart failure. Current therapy for acute heart failure focuses on improving myocardial performance with inotropic agents, adjustments to afterload and preload, and on correcting the underlying cause. In addition, with technologic advances in mechanical devices, infants and children who are not responding to medical management have hope awaiting cardiac transplantation or recovery from infection.