Cardiac emergencies in children are rare, especially if compared to the adult population. While 0.8% to 1% of infants have congenital heart disease, the vast majority are stable and present no acute problems in management for the primary pediatrician. Nevertheless, it is important to identify patients who present with an acute illness related to congenital heart disease. The symptoms of cardiovascular disease in children may be nonspecific, resembling those of more common disorders such as neonatal sepsis or overwhelming pneumonia. However, the management and stabilization of these patients may require different strategies. This article discusses the more frequent pediatric cardiac emergencies and gives practical guidelines in their initial management.
OBSTRUCTIVE LEFT-SIDED CARDIAC LESIONS
Critical coarctation of the aorta, critical aortic stenosis, and hypoplastic left heart typically present in the newborn period. Frequently, patients are severely ill and present with the rather rapid onset and progression of symptoms. Due to the patient's age and clinical appearance, shock due to sepsis is often the presumed initial diagnosis. If the physician fails to consider the possibility of a left-sided obstructive cardiac lesion, the clinical course is usually fatal.
In critical aortic stenosis and coarctation of the aorta, left ventricular output is decreased severely, leading to left atrial dilatation and pulmonary venous congestion. Increased left atrial pressure and size also lead to left-to-right shunting via the foramen ovale and thereby increase the amount of blood being pumped toward the lungs. Systemic perfusion is maintained via the ductus arteriosus with the shunting of blood from right to left (pulmonary artery across the ductus arteriosus to the aorta).1 The ductus arteriosus not only provides the blood flow to the body, but also decreases the volume overload on the lungs. As soon as the ductus arteriosus begins to close, the infant develops symptoms of cardiogenic shock. Additionally, in coarctation of the aorta, the pressure grathent over the narrowed aortic segment may increase because of the close proximity of ductal tissue to the stenosed area.2 Systemic perfusion is impaired severely and pulmonary congestion increases. Signs of respiratory failure develop with tachypnea, rales, and retractions, as well as hepatomegaly and early shock with tachycardia. The femoral pulses are weak or absent. Auscultation of a murmur may not be easy due to the respiratory noise. Arterial blood gas analysis reveals a metabolic acidosis (lactic acidosis) due to hypoperfusion of the systemic circulation.
Hypoplastic left heart syndrome presents in a similar manner. Atrial left-to-right shunting is always present due to the left ventricular hypoplasia, causing increased blood flow to the lungs. Systemic perfusion is dependent on a patent ductus arteriosus, similar to coarctation and aortic stenosis. Blood supply to the brachiocephalic vessels and the coronary arteries is retrograde because the aortic arch is hypoplastic. Closure of the ductus arteriosus leads to shock and circulatory collapse as described above. In addition, coronary blood flow is compromised, which may further compromise cardiovascular function.
The initial management of patients with left-sided obstruction of the heart should follow the basic ABC's of resuscitation. Establishing a reliable airway by endotracheal intubation and adequate ventilation are the first steps. Rapid venous access is achieved via peripheral IV, intraosseous line, or umbilical vein catheterization (if still possible). To reestablish circulatory stability, closure of the ductus arteriosus needs to be reversed and reclosure prevented with prostaglandin E via a continuous infusion.3 Prostaglandin E should be started immediately after suspecting the diagnosis; without it circulatory failure cannot be treated successfully. Prostaglandin E should be started if the diagnosis is suspected even before it is confirmed by echocardiography or catheterization. Adverse effects of prostaglandin E include apnea, fever, hypotension, and seizures.4
Once prostaglandin E is started and the ductus is reopened, the balance between systemic and pulmonary circulation is determined by the difference in the vascular resistance of the two vascular beds. Oxygen is a potent pulmonary vasodilator, and ventilation with a high E-Oj actually may decrease pulmonary vascular resistance and worsen pulmonary congestion with a decreased blood flow to the systemic circulation.5 An oxygen saturation of 100% does not mean that the patient is doing well - it means that there is overcirculation of the pulmonary vascular bed with decreased systemic perfusion. It may be necessary to ventilate these patients with room air to achieve the desired saturation of 75% to 80% that occurs with a pulmonary to systemic flow of 1:1. Similarly, overperfusion of the pulmonary circulation may occur with hyperventilation and lowering of the arterial CO2. Therefore, attention needs to be paid not to overventilate those patients and to keep oxygen administration limited.6 Metabolic acidosis should be corrected carefully with sodium bicarbonate to achieve a pH of 7.25 to 7.3. The inotropic function of the right ventricle may be improved with dopamine. After initial stabilization, the patient should be transported immediately to the closest pediatric cardiac center for further treatment.
CYANOTIC HEART DISEASE
Cyanotic heart disease is a fairly stable condition most of the time. Emergencies usually occur in the newborn period and involve the most severe forms of cyanotic disorders in which pulmonary blood flow is dependent on the patency of the ductus arteriosus. All lesions have right-to-left shunting on the cardiac level, and the administration of 100% oxygen does not improve the systemic arterial saturation. Any of the cyanotic lesions may present in infancy including truncus arteriosus, tetralogy of Fallot, transposition of the great vessels, total anomalous pulmonary venous return, and tricuspid atresia (the five T's).
In the classic form of truncus arteriosus, the pulmonary artery and aorta fail to separate during the embryologie development. They form a single large artery originating from both ventricles overriding a ventricular septal defect. Severe congestive heart failure is the major complication.
With tricuspid atresia, the entire systemic venous return is directed via an atrial septal defect or persistent foramen ovale to the left atrium and subsequently the left ventricle. If a ventricular septal defect is present, blood will enter the right ventricle and supply the lungs via the pulmonary artery. Unless there is pulmonary stenosis or restriction of blood flow via the ventricular septal defect, patients will develop congestive heart failure. If there is no ventricular septal defect, or if there is severe right ventricular outflow tract obstruction, sufficient pulmonary blood flow only occurs via the persistent ductus arteriosus (leftto-right shunting from the aorta to the pulmonary artery). If the persistent ductus arteriosus closes, severe hypoxemia and death are imminent. These patients require pharmacologic reopening of the ductus with prostaglandin E.
Transposition of the Great Vessels
Transposition of the great vessels is characterized by complete separation of the pulmonary and systemic circulation. The right heart receives blood from the superior and inferior vena cava and pumps blood back to the systemic circulation. The left heart receives blood from the pulmonary veins and returns blood back to the lungs. Unless there are septal defects (atrial or ventricular), the ductus arteriosus and the foramen ovale are the only ways of mixing blood between these circuits. Patients are cyanotic at birth and often are tachypneic, without acute distress. Administration of oxygen does not improve arterial saturation. This should alert the physician and enable a differentiation from respiratory distress syndrome in the newborn. Again, closure of the ductus arteriosus leads to acute decompensation. On the other hand, if a ventricular septal defect is present, blood mixture is good. Congestive heart failure is uncommon within the first few weeks of life, unless there is additional ventricular outflow obstruction. Congestive failure develops later in the first month of life as the pulmonary vascular resistance drops and left-to-right shunting increases.
Total Anomalous Pulmonary Venous Return
In total anomalous pulmonary venous return, the pulmonary veins empty into the systemic venous circulation instead of the left atrium. The only blood supply to the left heart arrives from right-to-left shunting via the foramen ovale or an atrial septal defect. The anomalous venous return may be above the diaphragm to a venous confluence that empties into the right atrium or below the diaphragm to the inferior vena cava. With the latter condition, symptoms generally develop early since the venous return generally is partially obstructed, leading to pulmonary venous congestion and respiratory distress. These patients present in the immediate newborn period, and differentiation from severe respiratory distress syndrome or persistent fetal circulation may be difficult. Frequently, high ventilatory pressures are needed, but symptoms can be relieved only by surgical correction of the pulmonary venous obstruction and connection of the pulmonary veins to the left atrium. Congestive heart failure due to pulmonary volume overload also may occur from the large left-to-right shunt.
Tetralogy of Fallot
Tetralogy of Fallot includes a large ventricular septal defect with an overriding aorta, pulmonary stenosis (valvular and infundibular), and right ventricular hypertrophy. The symptoms in the newborn period vary from none to severe hypoxemia depending on the degree of pulmonary stenosis. If there is severe pulmonary stenosis or even pulmonary atresia, an open ductus arteriosus is essential to provide pulmonary blood flow. Closure of the ductus arteriosus leads to severe hypoxemia and cardiovascular collapse. The infundibular component of the pulmonary stenosis usually worsens during infancy and childhood with increasing right-to-left shunting and progressive cyanosis.
With exertion, agitation, and even without apparent reason, patients with tetralogy of Fallot may have acute hypoxemic episodes, also called "Tet spells." These are caused by constriction of the subpulmonic muscular infundibulum, which leads to a sudden increase in the right ventricular outflow obstruction, increased right-to-left shunting, and severe cyanosis. The ratio of pulmonary to systemic flow is determined by the difference in the vascular resistance of the pulmonary and systemic beds. Factors that increase pulmonary vascular resistance/infundibular spasm or decrease systemic vascular resistance can increase right-to-left shunting and thereby increase hypoxemia. Older patients may assume a squatting kneechest position, which increases systemic vascular resistance. The increased systemic vascular resistance decreases right-to-left shunting and increases blood flow to the lungs. Other simple modes of treatment for cyanotic spells include having the parents calm the child while pressing the knees against the chest and administering oxygen.
Most spells are self-limited and last only minutes. If simple management fails, 0.1 to 0.2 mg/kg morphine sq or IV should be administered as an anxiolytic agent. If IV access is available, either phenylephrine (2 to 4pg/kg) or a beta-adrenergic blocking agent such as propranolol (0.01 to 0.03 mg/kg) should be given intravenously to relax the infundibular spasm. While the majority of experience in the pharmacologic management of Tet spells is with the betaadrenergic blocking agent propranolol, esmolol is an additional agent with beta-adrenergic blocking properties that offers the advantage of a short halflife/duration of action (9 minutes versus 2 hours for propranolol). Therefore, its effects dissipate rapidly if adverse hemodynamic effects are noted. Dosing includes an initial intravenous bolus of 0.5 mg/kg followed by an infusion of 0.1 to 0.3 mg/kg/minute.
Metabolic acidosis should be corrected with sodium bicarbonate. Extremely severe spells may require endotracheal intubation and assisted ventilation, in which case heavy sedation/analgesia with opioids is needed to avoid ongoing spells, brought on by patient discomfort. Hypoxic spells are always an indication for surgical correction in the near future.
Frequently Used Medications
As in left-sided obstructive lesions, patients with congenital cyanotic heart disease may depend on patency of the ductus arteriosus. If the ductus arteriosus closes, pulmonary blood flow is markedly decreased and severe hypoxemia develops. Ductal dependent patients may present in the newborn period. These patients deteriorate rapidly from a seemingly stable state to a shock-like picture. Even though a patient has cyanotic heart disease, the cyanosis may have been subclinical in the initial neonatal period,7 and acute decompensation can be the first sign that something is wrong with the patient. Cardiomegaly on chest radiograph or a murmur are sometimes present and may lead to the correct diagnosis.
After airway stabilization and establishing vascular access, prostoglandin E infusion (Table 1 ) needs to be started immediately to enable effective resuscitation.3 Unlike obstructive left-sided lesions, the reopened ductus arteriosus increases blood flow to the lungs by shunting left- to-right in cyanotic heart disease. This explains why starting prostaglandin E may lead to pulmonary congestion and may worsen the respiratory distress. Therefore, fluid resuscitation should be conservative. Endotracheal intubation and mechanical ventilation frequently is required to stabilize the patient prior to transport to a pediatric cardiac center for the same reason.
CONGESTIVE HEART FAILURE
Congestive heart failure in infancy or childhood may be due to decompensated congenital heart disease, myocarditis, or cardiac arrhythmias (Table 2). In most congenital heart diseases, increased blood flow to the lungs is required for the development of congestive heart failure. This increased blood flow causes volume overload on the pulmonary capillary bed and leads to pulmonary congestion. Usually, it is a "high-output" failure with normal cardiac contractility. Typical examples of congenital heart diseases leading to congestive heart failure are large ventricular septal defects and truncus arteriosus. Because pulmonary vascular resistance remains elevated immediately after birth and gradually drops in the first several weeks of life, patients are initially in no acute distress since there is not a significant amount of blood shunting from left-to-right. A murmur is often the only sign of cardiac disease.
Between the first and second months of life, the pulmonary vascular resistance drops enough for the infant to become symptomatic. Poor feeding, increased sweating, slow weight gain, and mild respiratory problems are the typical symptoms. These symptoms often are misdiagnosed as primary pulmonary diseases such as pneumonia or bronchiolitis. On physical examination, hepatomegaly may be present due to systemic venous congestion from volume overload on the right heart. Chest radiograph reveals increased pulmonary vascular markings, pulmonary edema, and possibly cardiomegaly. Most of the patients are relatively stable, and assisted ventilation for respiratory failure rarely is required. After obtaining intravenous access, furosemide ( 1 mg/kg) should be administered intravenously. Aggressive fluid resuscitation should be avoided so as not to cause further fluid overload of the lungs.8
Many cases of myocarditis are mild and lead to only minimal respiratory distress. However, severe congestive heart failure due to myocarditis can present at any age. Most cases are related to viral infections, with Coxsackie B virus being the most common agent. In contrast to congestive heart failure from congenital heart disease, the onset and progression of symptoms are more rapid. Patients often have been completely healthy except for an upper respiratory infection over the last few days. The cardiac failure typically is global, involving both sides of the heart. It is a "low-output" heart failure with decreased cardiac contractility. Right-sided failure leads to hepatomegaly, jugular venous distention, and occasionally, peripheral edema. Left ventricular failure is characterized by pulmonary congestion with rhonchi and rales, poor peripheral perfusion with prolonged capillary refill, cold extremities, tachycardia, and possibly borderline low blood pressure. In addition to the tachycardia, a gallop rhythm frequently can be auscultated. Severe arrhythmias are possible and may further decrease the already low cardiac output or result in sudden death.
Evaluation of serum electrolytes, especially calcium, potassium, and magnesium, should be performed immediately and imbalances should be corrected. Both hypokalemia and hypomagnesemia can precipitate severe ventricular arrhythmias, especially in the setting of myocarditis. Hypomagnesemia is corrected by the administration of magnesium sulfate (50 mg/kg up to 2 g) over 1 hour. Hypokalemia should be corrected gradually because the risks of hyperkalemia are far greater than hypokalemia. Potassium should be administered in small doses (0.25 mEq/kg up to 10 mEq) over 30 to 60 minutes with a repeat serum potassium checked prior to a second bolus. Hypocalcemia is corrected by the administration of either calcium chloride or calcium gluconate (0.1 to 0.2 mL/kg of 10% calcium chloride or 0.2 to 0.5 mL/kg of 10% calcium gluconate). Because the onset of symptoms can be so fast, patients may present to the emergency department with impending respiratory failure and in cardiogenic shock. A chest radiograph in this setting shows cardiomegaly, increased vascularity, and pulmonary edema. It is not always easy to separate these findings from overwhelming pneumonia. Stabilization of the respiratory status is the first step in the management of congestive heart failure. One hundred percent oxygen via face mask should always be administered to improve tissue oxygenation, which is already impaired by the decreased cardiac output. If respiratory distress is severe, endotracheal intubation and mechanical ventilation may be necessary.
Because cardiac output is decreased, measures should be undertaken to minimize the workload on the heart and avoid unnecessary demands for increased cardiac output. This includes aggressive control of fever with acetaminophen or Ibuprofen and effective sedation for agitated patients. Fluid restriction together with intravenous fiirosemide (0.5 to 1 mg/kg) is useful in decreasing cardiac preload. While most patients are hypervolemic, some patients may have decreased intravascular volume, and one fluid bolus of 5 cc/kg normal saline given over 20 to 30 minutes is appropriate and may improve the hemodynamic status in fluid-depleted patients.9
Common Ciusa of Conqntlv. Hart Failure In Childhood
Inotropic cardiac support frequently is required. Because it takes a long time for digoxin to reach therapeutic levels, it is not very useful in the emergency room setting. If used at all, tiie physician should be aware that myocarditis causes increased cardiac irritability, and therefore the total digitalizing dose should be decreased and administered over an 18- to 24-hour period. Dopamine and dobutamine are more helpful and safer in the immediate management of congestive heart failure. Dobutamine is preferred over dopamine because in addition to its inotropic effects, dobutamine acts as a vasodilator and thereby reduces afterload. Additionally, the arrythmogenic effects of dopamine are greater. Both drugs are used as continuous intravenous infusions at 5 to 20 pg/kg/minute.
Angiotensin-Converting enzyme inhibitors and other afterload reducing agents can be used, but are not a first-line treatment and may precipitate hypotension in the initial setting. After the initial stabilization, the patient should be transported to a pediatric intensive care unit for further management.
Cardiac arrhythmias in children occur less commonly than in the adult population. Often, they are caused by an underlying congenital heart defect, especially after cardiac surgery. If a previously healthy child presents to the emergency department with a symptomatic arrhythmia, the physician should consider the possibility of a drug ingestion, even if mental status changes are not present. Myocarditis is also a frequent cause of new-onset arrhythmias, even if other symptoms are not noticeable on the physical examination. Evaluation of serum electrolytes (potassium, calcium, and magnesium) is always indicated especially in patients with ventricular arrhythmias.
Supraventricular tachycardia is the most common pediatric arrhythmia. It is characterized by a fixed heart rate >200 beats per minute (frequently even above 220 beats/minute) and narrow QRS complexes. In contrast to sinus tachycardia, the heart rate does not fluctuate with agitation. Most infants and children can have supraventricular tachycardia for several hours or days without developing clinical symptoms. In those patients, vagal maneuvers (unilateral carotid massage, Valsalva's maneuver, or inducing a cough) may be used in an attempt to convert the rhythm. Crushed ice in a plastic bag or rubber glove can be applied to the face for up to 30 seconds ("diving reflex"). Gagging the patient or carotid massage may be attempted. If unsuccessful, pharmacologic conversion may be indicated. Adenosine (0.05 mg/kg up to 4 mg) should be administered as a rapid intravenous bolus.10 Because the half-life of adenosine is only several seconds, it is ineffective if given too slowly. Patients should be placed on a cardiac monitor during the above procedures. The adenosine dose can be increased in 0.05 mg/kg increments up to 0.25 mg/kg with each dose given 1 to 2 minutes apart.
Adenosine is indicated immediately if a patient presents in unstable supraventricular tachycardia with poor capillary refill, weak pulses, diaphoresis, and hepatomegaly. Vagal maneuvers may be attempted while obtaining intravenous access. If adenosine is not readily available or unsuccessful in the hemodynamically unstable patient or if intravenous access is delayed, synchronized cardioversion with 0.5 to 1 J/kg is the next step.
Because of its short half-life time, adenosine may not prevent recurrence of supraventricular tachycardia. After successfully reestablishing sinus rhythm, a pediatric cardiologist should be consulted to arrange for further management and evaluation.
Pediatric cardiac emergencies require very specific treatment in the emergency room setting. Considering the possibility of a cardiac problem as the cause for the presenting symptoms is the initial step in successful management. Many patients present with what is initially considered a primary pulmonary disorder such as pneumonia, asthma, or bronchiolitis. Airway stabilization and ventilatory support, if needed, remain the first steps in stabilizing the patient. Many neonates with acutely decompensating heart disease may require the patency of the ductus arteriosus for survival. Prostaglandin E given as continuous infusion is the treatment of choice.
Congestive heart failure can present at any age. In older patients, it is often due to myocarditis and is characterized by low cardiac output. Supportive measures, fluid restriction, and inotropic support are the basic concepts for initial treatment. Supraventricular tachycardia is a frequent arrhythmia, especially in young children. If the patient is unstable, immediate intravenous administration of adenosine or synchronized cardioversion are the initial interventions. In stable patients, vagal maneuvers may be attempted to abort the arrhythmia.
1. Broderick TW, Higgins CB, Guthaner DF, et al. Critical aortic stenosis in neonates. Radiology. 1978;129:393-399.
2. van Son JA, Lacquet LK, Smedts F. Patterns of ductal tissue in coarctation of the aorta in early infancy. ] Thorac Cardiovasc Surg. 1993;105:368-369.
3. Freed MD, Heymann MA, Lewis AB, et al Prostaglandin Ej m infants with ductus dependent congenital heart disease. Circulation. 1981;64:899-905.
4. Lewis AB, Freed MD, Heymann MA, et a). Side effects of therapy with Prostaglandin Ej in infants with critical congenital heart disease. Circulation. 1981;64:893-898.
5. Fineman JR, Soifer SJ1 Heymann MA, Regulation of pulmonary vascular tone In the perinatal period. Atmu Rev Physiol. 1995:57:1 15-134.
6. Jobes DR1 Nicolson SC, Steven JM, et al. Carbon dioxide prevents pulmonary overcirculation in hypoplastic left heart syndrome. Ann Thorac Surg. 1992:54:150-151.
7. Lacy D, Watkinson M. Lack of cyanosis in cyanotic heart disease. BMJ. 1991;302:1403-1410.
8. Kaplan S. New drug approaches to the treatment ot heart failure in infants and children. Drugs. i990:39:388-393.
9. Battiti RM- Congestive heart failure in children. J Emerg Med. 1986:4:379-382.
10. Green AP, Giattina KH. Adenosine administration for neonatal SVT. Neonatal Network. 1993:12:15-18.
11. DeGroff CG, Sitka MJ. Bronchospasm after intravenous administration of adenosine in a patient with asthma. ] Pediatr. 1994;125:822-823.
12. Tomcsanyi J, Tenczer J, Horvath L Unusual effect of adenosine, inter ] Cardtoi. 1995;49:89-91.
Frequently Used Medications
Common Ciusa of Conqntlv. Hart Failure In Childhood