PEDIATRIC EMERGENCY MEDICINE
0031-3955/92 $0.00
+
.20
CARDIAC ISSUES IN THE PEDIATRIC EMERGENCY ROOM Patrick A. Flynn, MO, Mary Allen Engle, MO, and Kathryn H. Ehlers, MO
In this article we discuss many of the pediatric cardiology issues that come to light in the emergency room, from the initial presentation of the infant with congenital heart disease, to the medical management of these patients on subsequent emergency visits, to miscellaneous topics such as chest pain, Kawasaki disease, and syncope, which may have cardiac implications. Our focus is on the recognition of the patient with a cardiac diagnosis and the acute management of that patient in the emergency room setting. Interventions that extend beyond the patient's tenure in the emergency room can best be left to the cardiologist, intensivist, or inpatient pediatric staff and thus are not pursued here. EMERGENCY PRESENTATION OF THE INFANT WITH HEART DISEASE
There are few more terrifying prospects for the front-line pediatrician than the presentation of an infant with previously undiagnosed congenital heart disease. Whether profound cyanosis, congestive heart failure, or circulatory shock is the mode of presentation, fast recognition and early intervention are vital to a good outcome. The role of the primary care physician should be to realize the type of presentation (cyanosis, shock, failure) and act accordingly to stabilize the situation until the cardiologist or intensive care personnel can assume responsiFrom the Division of Pediatric Cardiology, The New York Hospital-Cornell University Medical College, New York, New York
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bility or until the patient can be transferred to an institution that has those resources in place. Age of presentation is the first key piece of information that can help to direct diagnostic and therapeutic decision-making at the outset. Lesions that depend on a patent ductus arteriosus, whether cyanotic lesions (i.e., tetralogy of Fallot) or shock-producing lesions (severe coarctation of the aorta) are most likely to have a sudden onset and occur in the first week of life. Lesions that produce congestive heart failure are more likely to have a gradual onset later in the neonatal period or early infancy. Therefore, the crashing l-week-old infant is likely to benefit from prompt prostaglandin therapy, whereas the dwindling older infant will likely improve with diuresis. Presentation of Cyanotic Congenital Heart Disease
The most important task on arrival of the cyanotic infant lies in clearly defining the problem as stemming from a cardiac lesion and not some other systemic or pulmonary derangement (Table 1). This can be done quickly by answering a few questions. Is the Cyanosis Central or Peripheral?
At a quick glance, the infant with peripheral cyanosis appears just as blue as does the infant with central cyanosis. This infant's cyanosis is caused by poor perfusion of the skin, however, rather than circulation of poorly oxygenated blood. The extremities are cool, capillary refill is poor and, most importantly, the mucous membranes are pink. Pigmentary variations can make evaluation of the lips fruitless, but a quick peek at the tongue and conjunctivae reveal them to be pink. Arterial blood gases show a normal Pa0 2 • Transcutaneous oximetry may be unreliable because of the poor perfusion. Causes of peripheral cyanosis include environmental cold, sepsis, and other causes of shock. Therapy is aimed at the particular cause. The infant with central cyanosis generally is warm and well perfused but is blue, including the mucous membranes. Arterial Pa0 2 and transcutaneous saturation are low. This infant leads us to ask the next question. Is This Cyanosis Secondary to a Pulmonary or Cardiac Etiology?
Simple observation of the infant may give a clue. The cyanotic cardiac infant may be comfortably blue at rest but becomes exceedingly agitated and more deeply cyanotic at any provocation. The pulmonary patient, on the other hand, has some degree of respiratory distress even at rest, but because this infant's problem is one of inadequate ventilation, crying may actually lessen the cyanosis. The presence of a hyperdynamic precordium or a cardiac murmur
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Table 1. ALGORITHM FOR THE CYANOTIC INFANT Cyanosis
PERIPHERAL Tongue, conjunctivae pink Pa02 normal Extremities cool, refill poor Dx; sepsis, cold, shock Treatment directed at cause
CENTRAL Cyanotic, including tongue, conjunctivae Pa0 2, saturation low Warm, well-perfused
CARDIAC Worsens with crying Comfortable at rest ± Abnormal ECG ± Cardiomegaly or other radiographic abnormality Normal pC0 2 No response to 100% oxygen Murmur ± hyperdynamic precordium Rx; prostaglandin at 0.1 mcg/kg/min, cardiac consult
INCREASED PULMONARY FLOW Transposition of the great arteries Total anomalous pulmonary return Truncus arteriosus Single ventricle Other complex lesions
PULMONARY May improve with crying Respiratory distress Normal ECG Normal cardiac silhouette CO2 retention Response to 100% oxygen Normal cardiac examination Oxygen, other specific treatments directed at lungs
DECREASED PULMONARY FLOW Tetralogy of Fallot Pulmonary atresia Tricuspid atresia Complex lesions with associated pulmonary stenosis/atresia
should point to a cardiac cause. Absence of a murmur is inconclusive, however, because some of the lesions themselves create little or no audible turbulence, and the ductus arteriosus, if essentially closed or if wide open (naturally or after prostaglandin therapy), also generates insufficient turbulence to be heard. The 100% oxygen challenge further helps to separate cardiac from pulmonary causes. Administration of oxygen to the infant with true cyanotic heart disease leaves him or her just as cyanotic as before, whereas the infant with pulmonary disease should improve not only by clinical observation but also by measurement of transcutaneous saturation or arterial blood gas. Absolute standards for the degree of improvement necessary for definition of pulmonary cyanosis are difficult to establish for many reasons, including the possibility that some pulmonary disease may be superimposed on the cyanotic cardiac patient, but in general, any Pa02 more than 10042 makes true cyanotic congenital heart disease unlikely.
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Additionally, when arterial blood gas measurement is obtained, PCO z can be revealing, because the cardiac infant should, in the absence of coincident lung pathologic conditions, have normal values, whereas the infant with enough lung disease to become cyanotic also should be retaining CO 2 • Further data can be obtained from the electrocardiogram (ECG), which is often, although not always, abnormal in the infant with cardiac disease and normal in the infant without. Recall that the normal neonate has right axis deviation; that a dominant R wave in the right chest leads is normal, although voltages should not be excessive; and that, although a positive T wave in lead VI may be normal in the first week of life, persistence of this sign beyond the fourth day or so should prompt careful interrogation for other signs of right ventricular hypertrophy. The chest radiograph should show a normal cardiac silhouette with or without abnormality in the lung fields in the infant with a pulmonary problem. The cyanotic cardiac infant's radiograph may be normal, may show generalized cardiomegaly, or may reveal one of the peculiar shapes signifying a specific lesion (the "boot-shaped heart" of tetralogy of Fallot, the "egg-on-side" heart of transposition of the great arteries). One should also remember to look below the diaphragm for the position of the stomach bubble and the liver, because abnormal abdominal situs suggests complex cardiac disease. It is important to remember that all of these signs must be considered in concert to arrive at a diagnosis. A normal ECG, absence of a murmur, or a normal cardiac silhouette should not cause one to rule out congenital heart disease if the other signs point to it. At this point if the diagnosis of cyanotic congenital heart disease is still being courted (an infant with reasonably sudden onset of central cyanosis, with little or no response to 100% oxygen and no evidence of overwhelming lung disease), the course of action of the primary care physician is clear: begin infusion of prostaglandin El and arrange consultation with the pediatric cardiologist and admission to the neonatal or pediatric intensive care unit. Prostaglandin E should be administered at a dose of 0.1 J-l-g/kgl min to start, decreasing to half that amount after cyanosis has been relieved, with increase in saturation to the 80% to 90% range in most infants, but approaching 100% in others. The newly pink infant should not inspire a false sense of security, however. The major, and not uncommon, side effects of prostaglandin are apnea and systemic hypotension. 52 Also, central nervous system effects such as fever and jitteriness are common. Materials for emergent airway management and volume resuscitation should be on hand at all times; in fact, if the patient is to be transported to another institution, it is good practice to electively intubate the infant to avoid the prospect of an airway emergency en route. Now that the problem has been delineated and effectively palliated for the time being, it is fair to consider the specific diagnosis at hand. This process begins with another question. j
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Is Pulmonary Blood Flow Increased or Decreased?
Dark lung fields with small pulmonary artery segments indicate obstruction to pulmonary blood flow as the cause of cyanosis (tricuspid atresia, severe tetralogy of Fallot). Overperfused lungs with full pulmonary arteries suggest lesions such as transposed great arteries or anomalous venous return. Specifics of some of the more common lesions include the following conditions. Transposition of the great arteries is the most COmmon cyanotic lesion to present suddenly in the neonatal period. Cyanosis is caused by delivery of systemic venous blood directly to the aorta. Pulmonary blood flow is increased because of lower resistance in the pulmonary circuit than in the systemic side, so chest radiographs reveal increased pulmonary vascular markings in addition to cardiomegaly and the typical narrow basel! (the so-called "egg on side") (Fig. 1). Physical examination is remarkable for a loud second sound because the aortic valve is just beneath the sternum, and there may not be a murmur. 50 ECG is usually normal for a newborn, but there may be high, peaked P waves of right atrial enlargement. Tetralogy of Fallot is the next most common lesion, but it may present in a variety of ways depending on severity of obstruction to pulmonary flow. The most severe form, tetralogy with pulmonary atresia (or "pseudotruncus arteriosus"), is a ductal-dependent lesion that manifests itself as soon as the ductus begins to close. Patients with less severe degrees of obstruction may present with gradually increasing cyanosis or may remain acyanotic at baseline but with episodes of
Figure 1. Radiograph of newborn with cyanosis with complete transpOSition of the great ;lrteries. Note the enlarged heart with concave pulmonary artery segment, abnormally narrow base, and heavy hilar pulmonary vasculature.
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cyanosis during crying or in association with hypercyanotic spells. Physical examination reveals a loud second sound and usually a systolic murmur associated with flow through the stenosed pulmonary outflow region. Chest radiographs show decreased pulmonary markings, an average-sized heart, and absence of the pulmonary artery contour contributing to the classic "boot-shaped" configuration (Fig. 2). Twentyfive percent have a right-sided aortic arch. ECG reveals right axis deviation and right ventricular hypertrophy, which of course are normal in the first month of life. Pulmonary atresia with intact septum accounts for about 25% of newborn cyanotic heart disease. The second heart sound is single and of normal intensity. Commonly there is no murmur, or there may be the systolic murmur of tricuspid regurgitation. ECG reveals right atrial enlargement and left ventricular hypertrophy, but right ventricular forces are discernible and may also be increased. Observations on chest radiographs vary from an average-sized to a tremendously enlarged heart. Tricuspid atresia may be difficult to distinguish from pulmonary atresia, but subtle clues can reveal the difference. The second heart sound is single, and palpation of the precordium reveals a left ventricular thrust. The ECG makes the diagnosis when it shows right atrial enlargement, left axis deviation, and left ventricular dominance in the absence of right ventricular forces . Chest radiographs reveal nonspecific cardiomegaly and decreased pulmonary markings. Total anomalous pulmonary venous return can present in a variety of ways. This variability is based on the degree of obstruction to pulmo-
Figure 2. Radiograph of infant with cyanosis with tetralogy of Fallot. The heart is small, with a concave pulmonary segment, wide base, and excessively clear lung fields.
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nary venous return to the heart. Cases with little or no obstruction may be asymptomatic in infancy or may present with nonspecific signs like failure to thrive. Obstructed pulmonary return, however, can present as early as the first few days of life, usually with mixed signs of both cyanosis and congestive failure as all pulmonary and systemic venous blood returns to the right side of the heart. Symptoms of cyanosis and dyspnea may progress rapidly, signifying a true medical emergency. Absence of a murmur and the mixed picture of symptoms may allow the cardiac diagnosis to escape detection at first. Chest radiographs are unique in revealing pulmonary overcirculation and pulmonary venous congestion with a small heart. 53 The results of the ECG are normal or show right ventricular hypertrophy. This lesion is also unique in this category because infusion of prostaglandin does not alter the course. Only aggressive medical management with inotropic support, diuresis, and usually ventilatory support with an eye toward prompt (if not immediate!) surgical intervention can secure a positive outcome.
Lesions Presenting with Congestive Heart Failure
This category includes those defects that produce overcirculation of the pulmonary vascular bed via left-to-right shunting. These lesions are usually inapparent at birth because the relatively high pulmonary vascular resistance of the neonate restricts the amount of left-to-right shunting. A murmur may not appear until 2 weeks to 2 months 55 of age, and symptoms may not become apparent until pulmonary resistance drops to sufficiently low levels to permit a large left-to-right shunt. This usually happens at 6 to 8 weeks of age. The signs and symptoms of congestive heart failure usually evolve slowly and often are overlooked in the mild to moderate stage. Fatigue during feedings, diaphoresis, and poor weight gain are symptoms that often precede by days to weeks the tachypnea and fussiness that usually bring the infant to medical attention. Often intercurrent infection is the precipitating factor that pushes the previously tenuously balanced infant over the brink into symptomatology. Vital signs reveal tachypnea and tachycardia. The tachypnea may be remarkable, but the infant usually looks more comfortable than his or her actual respiratory rate would suggest. Look for nasal flaring, subcostal and intercostal retractions, and the use of accessory muscles of respiration. Rales are unusual in the infant in failure, and peripheral edema is virtually never seen until late. A hyperactive precordium with a visibly prominent precordial bulge of the left chest may be evident. Likewise, a thrill may be palpable. Cardiac murmurs are invariably present, corresponding to the nature of the specific lesion. Cardiomegaly-both on physical examination and via chest radiographs-and hepatomegaly are very sensitive physical signs of congestive heart failure. In addition to the cardiomegaly, the chest radiograph reveals pulmonary arterial and often venous congestion (Fig. 3).
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Figure 3. Chest radiograph of 6-week-old infant in congestive cardiac failure because of a large left-to-right shunt that causes cardiomegaly and increased pulmonary arterial markings.
Infants who present to the emergency room with signs, symptoms, and radiographic evidence of failure as described previously require urgent evaluation by the cardiologist, with hospitalization likely unless symptoms are mild. Furosemide administered intravenously at a dose of 1 mg/kg should provide prompt diuresis and clinical improvement as the infant awaits admission. Digitalization is carried out under the supervision of the cardiologist. Infants with new murmurs but no tachypnea, tachycardia, organomegaly, or other signs and symptoms of congestive heart failure do not require treatment or hospitalization, but they should be referred for prompt outpatient evaluation by the pediatric cardiologist. Lesions in this category are quite common. They include the following conditions. Ventricular septal defect, the most common congenital heart defect,24 is the hallmark of this group. A holosystolic murmur, maximal at the left lower sternal border and often radiating over the entire precordium and to the lung fields, is the calling card of this lesion. The precordium may be hyperactive in a sizable defect. A palpable thrill may be present. EeG may show left or combined ventricular hypertrophy. Patent ductus arteriosus is also common but is an unusual cause of symptoms unless it is a huge duct. In the first month or so, the left upper sternal border murmur may be systolic only, rather than the familiar continuous, machine-like murmur of later infancy and childhood. Atrioventricular septal defect, sometimes called atrioventricular canal or endocardial cushion defect, involves defects in the atrial and ven-
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tricular septa as well as abnormality in the atrioventricular valves, which can range from mild leaflet defects to a common valve for both sides of the heart. This anomaly frequently occurs in infants with Down syndrome,72 but it also occurs not infrequently in the rest of the population. Symptoms depend on the size of the defect(s) and thus on the magnitude of left-to-right shunt as well as on the degree of atrioventricular valve regurgitation. Murmurs vary from the holosystolic left lower sternal border murmur of the ventricular septal defect, to the long systolic murmur radiating to the apex and axilla from atrioventricular valve regurgitation, to the left upper sternal border systolic ejection murmur of relative pulmonic stenosis (i.e., excessive blood flow through a normal-sized pulmonic valve). If pulmonary artery pressure is as high as aortic pressure (pulmonary hypertension), the second sound is single and quite loud. The ECG shows a superior axis, a prolonged P-R interval,20 and evidence of atrial enlargement and left or biventricular hypertrophy. Supraventricular tachycardia is another entity that can cause the infant to present in the emergency setting with signs of congestive heart failure or, if the rapid heart rate of more than 200 beats per minute is left long enough, in shock. Another, much rarer entity that does not qualify as a congenital heart defect but can present as congestive heart failure or shock in the neonatal period or later is myocarditis. Myocarditis typically begins with a prodrome of fever, rhinorrhea, or diarrhea, with sometimes dramatic progression to lethargy, ashen pallor, tachycardia, and respiratory distress. Cardiomegaly and hepatomegaly are common but may take some time to evolve. The ECG shows ST and T-wave abnormalities along with conduction disturbances and dysrhythmias, but no hypertrophy. The diagnosis is often confusing because signs and symptoms may be confused with those of some of the congenital defects, but the presentation (usually later than the ductal-dependent lesions and with more acute onset than the failure lesions) aids in the diagnosis. The cause is usually viral. The infant with myocarditis needs hospitalization for supportive therapy.
Cardiac Disease in the Infant in Shock
The previously healthy infant who presents with circulatory collapse may have sepsis, may suffer from another metabolic or other systemic problem, or may have a cardiac diagnosis that may be immediately life threatening. These babies are apt to present with severe left ventricular outflow obstruction. Severe coarctation of the aorta is different from the other ductaldependent lesions described earlier because the infant depends on the ductus for right-to-Ieft flow into the descending aorta (rather than leftto-right flow into the pulmonary artery) to sustain life. The infant usually has been discharged from the nursery with no suspicion of
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heart disease because the patent ductus had allowed for perfectly normal femoral pulses and was likely so widely patent as to cause insufficient turbulence to produce an audible murmur. Usually late in the first week of life the ductus closes, causing impairment of flow to the lower body. The infant then develops fussiness that fairly rapidly progresses to respiratory distress and shock. The infant usually arrives pale, clammy, and lethargic, but the discrepancy between the color of the upper body (precoarctation, pink) and lower body (postductal, blue) often goes unnoticed, especially if there is an associated large ventricular septal defect that allows mixing of arterial and venous blood at the ventricular level, which is common. The discrepancy between the pulses in the lower extremities and the right arm (the left arm being variably supplied because the left subclavian artery may originate proximal or distal to the coarctation) is not easy to miss if interrogated, however. The precordium is hyperactive and a cardiac murmur is absent unless an associated abnormality such as a ventricular septal defect or atrioventricular valve abnormality is present. Blood pressure discrepancy (signifying that the ductus is essentially closed) or difference in saturation (meaning that the ductus is still somewhat patent and supplying the lower body with unoxygenated right ventricular blood) between the right arm and the foot seals the diagnosis. Chest radiographs reveal cardiomegaly, and the ECG usually shows right ventricular hypertrophy. Prostaglandin infusion, with dosage and monitoring as described earlier maintains ductal patency and is a life-saving measure. Often inotropic support is also necessary in preparation for transfer to the intensive care unit where definitive diagnosis by echocardiogram and further management by the cardiologist and cardiac surgeon await. Hypoplastic left heart syndrome provides a radical extreme of the previously mentioned situation, with some vital exceptions. The mitral valve, aortic valve, or proximal aortic arch all failed to form, and the left ventricle is hypoplastic. The patent ductus arteriosus thus provides for all systemic blood supply, so all pulses are diminished when the infant finally presents with a closing ductus. Marked pallor and cyanosis, poor perfusion, and a hyperdynamic precordium with a single S2 are evident on examination. Chest radiographs show cardiomegaly and increased pulmonary vascular markings, and ECG reveals right ventricular hypertrophy and paucity of left-sided forces. Sometimes there are striking ST and T-wave changes, indicating myocardial damage from poor myocardial perfusion. Prostaglandin infusion, inotropic support, and treatment of respiratory distress and metabolic acidosis usually stabilize the infant for transfer to the critical care unit for further diagnosis and management. MEDICAL MANAGEMENT OF THE PEDIATRIC CARDIOLOGY PATIENT
Next, our focus shifts to the patient who has already been diagnosed with heart disease and who presents to the pediatric emergency
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room for a complaint that mayor may not be. associated with the primary cardiac diagnosis. Some situations are peculiar to the cardiac patient (bacterial endocarditis, hypercyanotic spells), whereas others pertain to common pediatric issues that just take on a different meaning in the cardiac patient (respiratory syncytial virus, dehydration, and, in the cyanotic child, fever). Adverse Reactions to Cardiac Medications
Digoxin is the major weapon in the artillery of the pediatric cardiologist in the war against congestive heart failure and some dysrhythmias. Its ubiquitous use necessitates a clear understanding of its adverse effects and somewhat peculiar signs of toxicity (Table 2). Symptoms of digoxin toxicity include nausea, vomiting, diarrhea, anorexia, and visual disturbance. The most dangerous effects are cardiac, with rhythm and conduction disturbances leading the way. In therapeutic amounts, digoxin affects the ECG by prolonging the P-R interval, shortening the Q-T interval, and promoting S-T segment and T-wave abnormalities in comparison with the patient's pre-digitalization baseline tracing (Fig. 4). These effects signify therapeutic changes and not toxicity. Digoxin toxicity, on the other hand, is manifest by secondor even third-degree atrioventricular block, excessive sinus slowing, exaggerated depression of S-T segments, or supraventricular or ventricular arrhythmias. Slowing of the sinus rate is a sign of good therapeutic effect (in fact, the well-digitalized patient often exhibits truncated Table 2. DIGOXIN THERAPY AND TOXICITY Therapeutic Effects Decreased heart rate from predigitalization baseline Blunted tachycardic response to fever, stimulus ECG: prolonged P-R, shortened Q-T, S-T and T wave changes Toxic Effects Nausea, anorexia, vomiting, diarrhea Visual disturbances ECG: second degree atrioventricular block, prolonged QRS, ventricular dysrhythmias, bradycardia, supraventricular tachycardias Contributors to Toxicity Renal impairment Hypokalemia Hypercalcemia, intravenous calcium infusion Treatment of Toxicity (Severe): Digoxin Immune Fab (DIGIBIND) Each vial binds approximately 0.6 mg (600 mcg) Toxicity during chronic therapy Children
0031-3955/92 $0.00
+
.20
CARDIAC ISSUES IN THE PEDIATRIC EMERGENCY ROOM Patrick A. Flynn, MO, Mary Allen Engle, MO, and Kathryn H. Ehlers, MO
In this article we discuss many of the pediatric cardiology issues that come to light in the emergency room, from the initial presentation of the infant with congenital heart disease, to the medical management of these patients on subsequent emergency visits, to miscellaneous topics such as chest pain, Kawasaki disease, and syncope, which may have cardiac implications. Our focus is on the recognition of the patient with a cardiac diagnosis and the acute management of that patient in the emergency room setting. Interventions that extend beyond the patient's tenure in the emergency room can best be left to the cardiologist, intensivist, or inpatient pediatric staff and thus are not pursued here. EMERGENCY PRESENTATION OF THE INFANT WITH HEART DISEASE
There are few more terrifying prospects for the front-line pediatrician than the presentation of an infant with previously undiagnosed congenital heart disease. Whether profound cyanosis, congestive heart failure, or circulatory shock is the mode of presentation, fast recognition and early intervention are vital to a good outcome. The role of the primary care physician should be to realize the type of presentation (cyanosis, shock, failure) and act accordingly to stabilize the situation until the cardiologist or intensive care personnel can assume responsiFrom the Division of Pediatric Cardiology, The New York Hospital-Cornell University Medical College, New York, New York
PEDIATRIC CLINICS OF NORTH AMERICA VOLUME 39 • NUMBER 5 • OCTOBER 1992
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bility or until the patient can be transferred to an institution that has those resources in place. Age of presentation is the first key piece of information that can help to direct diagnostic and therapeutic decision-making at the outset. Lesions that depend on a patent ductus arteriosus, whether cyanotic lesions (i.e., tetralogy of Fallot) or shock-producing lesions (severe coarctation of the aorta) are most likely to have a sudden onset and occur in the first week of life. Lesions that produce congestive heart failure are more likely to have a gradual onset later in the neonatal period or early infancy. Therefore, the crashing l-week-old infant is likely to benefit from prompt prostaglandin therapy, whereas the dwindling older infant will likely improve with diuresis. Presentation of Cyanotic Congenital Heart Disease
The most important task on arrival of the cyanotic infant lies in clearly defining the problem as stemming from a cardiac lesion and not some other systemic or pulmonary derangement (Table 1). This can be done quickly by answering a few questions. Is the Cyanosis Central or Peripheral?
At a quick glance, the infant with peripheral cyanosis appears just as blue as does the infant with central cyanosis. This infant's cyanosis is caused by poor perfusion of the skin, however, rather than circulation of poorly oxygenated blood. The extremities are cool, capillary refill is poor and, most importantly, the mucous membranes are pink. Pigmentary variations can make evaluation of the lips fruitless, but a quick peek at the tongue and conjunctivae reveal them to be pink. Arterial blood gases show a normal Pa0 2 • Transcutaneous oximetry may be unreliable because of the poor perfusion. Causes of peripheral cyanosis include environmental cold, sepsis, and other causes of shock. Therapy is aimed at the particular cause. The infant with central cyanosis generally is warm and well perfused but is blue, including the mucous membranes. Arterial Pa0 2 and transcutaneous saturation are low. This infant leads us to ask the next question. Is This Cyanosis Secondary to a Pulmonary or Cardiac Etiology?
Simple observation of the infant may give a clue. The cyanotic cardiac infant may be comfortably blue at rest but becomes exceedingly agitated and more deeply cyanotic at any provocation. The pulmonary patient, on the other hand, has some degree of respiratory distress even at rest, but because this infant's problem is one of inadequate ventilation, crying may actually lessen the cyanosis. The presence of a hyperdynamic precordium or a cardiac murmur
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Table 1. ALGORITHM FOR THE CYANOTIC INFANT Cyanosis
PERIPHERAL Tongue, conjunctivae pink Pa02 normal Extremities cool, refill poor Dx; sepsis, cold, shock Treatment directed at cause
CENTRAL Cyanotic, including tongue, conjunctivae Pa0 2, saturation low Warm, well-perfused
CARDIAC Worsens with crying Comfortable at rest ± Abnormal ECG ± Cardiomegaly or other radiographic abnormality Normal pC0 2 No response to 100% oxygen Murmur ± hyperdynamic precordium Rx; prostaglandin at 0.1 mcg/kg/min, cardiac consult
INCREASED PULMONARY FLOW Transposition of the great arteries Total anomalous pulmonary return Truncus arteriosus Single ventricle Other complex lesions
PULMONARY May improve with crying Respiratory distress Normal ECG Normal cardiac silhouette CO2 retention Response to 100% oxygen Normal cardiac examination Oxygen, other specific treatments directed at lungs
DECREASED PULMONARY FLOW Tetralogy of Fallot Pulmonary atresia Tricuspid atresia Complex lesions with associated pulmonary stenosis/atresia
should point to a cardiac cause. Absence of a murmur is inconclusive, however, because some of the lesions themselves create little or no audible turbulence, and the ductus arteriosus, if essentially closed or if wide open (naturally or after prostaglandin therapy), also generates insufficient turbulence to be heard. The 100% oxygen challenge further helps to separate cardiac from pulmonary causes. Administration of oxygen to the infant with true cyanotic heart disease leaves him or her just as cyanotic as before, whereas the infant with pulmonary disease should improve not only by clinical observation but also by measurement of transcutaneous saturation or arterial blood gas. Absolute standards for the degree of improvement necessary for definition of pulmonary cyanosis are difficult to establish for many reasons, including the possibility that some pulmonary disease may be superimposed on the cyanotic cardiac patient, but in general, any Pa02 more than 10042 makes true cyanotic congenital heart disease unlikely.
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Additionally, when arterial blood gas measurement is obtained, PCO z can be revealing, because the cardiac infant should, in the absence of coincident lung pathologic conditions, have normal values, whereas the infant with enough lung disease to become cyanotic also should be retaining CO 2 • Further data can be obtained from the electrocardiogram (ECG), which is often, although not always, abnormal in the infant with cardiac disease and normal in the infant without. Recall that the normal neonate has right axis deviation; that a dominant R wave in the right chest leads is normal, although voltages should not be excessive; and that, although a positive T wave in lead VI may be normal in the first week of life, persistence of this sign beyond the fourth day or so should prompt careful interrogation for other signs of right ventricular hypertrophy. The chest radiograph should show a normal cardiac silhouette with or without abnormality in the lung fields in the infant with a pulmonary problem. The cyanotic cardiac infant's radiograph may be normal, may show generalized cardiomegaly, or may reveal one of the peculiar shapes signifying a specific lesion (the "boot-shaped heart" of tetralogy of Fallot, the "egg-on-side" heart of transposition of the great arteries). One should also remember to look below the diaphragm for the position of the stomach bubble and the liver, because abnormal abdominal situs suggests complex cardiac disease. It is important to remember that all of these signs must be considered in concert to arrive at a diagnosis. A normal ECG, absence of a murmur, or a normal cardiac silhouette should not cause one to rule out congenital heart disease if the other signs point to it. At this point if the diagnosis of cyanotic congenital heart disease is still being courted (an infant with reasonably sudden onset of central cyanosis, with little or no response to 100% oxygen and no evidence of overwhelming lung disease), the course of action of the primary care physician is clear: begin infusion of prostaglandin El and arrange consultation with the pediatric cardiologist and admission to the neonatal or pediatric intensive care unit. Prostaglandin E should be administered at a dose of 0.1 J-l-g/kgl min to start, decreasing to half that amount after cyanosis has been relieved, with increase in saturation to the 80% to 90% range in most infants, but approaching 100% in others. The newly pink infant should not inspire a false sense of security, however. The major, and not uncommon, side effects of prostaglandin are apnea and systemic hypotension. 52 Also, central nervous system effects such as fever and jitteriness are common. Materials for emergent airway management and volume resuscitation should be on hand at all times; in fact, if the patient is to be transported to another institution, it is good practice to electively intubate the infant to avoid the prospect of an airway emergency en route. Now that the problem has been delineated and effectively palliated for the time being, it is fair to consider the specific diagnosis at hand. This process begins with another question. j
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Is Pulmonary Blood Flow Increased or Decreased?
Dark lung fields with small pulmonary artery segments indicate obstruction to pulmonary blood flow as the cause of cyanosis (tricuspid atresia, severe tetralogy of Fallot). Overperfused lungs with full pulmonary arteries suggest lesions such as transposed great arteries or anomalous venous return. Specifics of some of the more common lesions include the following conditions. Transposition of the great arteries is the most COmmon cyanotic lesion to present suddenly in the neonatal period. Cyanosis is caused by delivery of systemic venous blood directly to the aorta. Pulmonary blood flow is increased because of lower resistance in the pulmonary circuit than in the systemic side, so chest radiographs reveal increased pulmonary vascular markings in addition to cardiomegaly and the typical narrow basel! (the so-called "egg on side") (Fig. 1). Physical examination is remarkable for a loud second sound because the aortic valve is just beneath the sternum, and there may not be a murmur. 50 ECG is usually normal for a newborn, but there may be high, peaked P waves of right atrial enlargement. Tetralogy of Fallot is the next most common lesion, but it may present in a variety of ways depending on severity of obstruction to pulmonary flow. The most severe form, tetralogy with pulmonary atresia (or "pseudotruncus arteriosus"), is a ductal-dependent lesion that manifests itself as soon as the ductus begins to close. Patients with less severe degrees of obstruction may present with gradually increasing cyanosis or may remain acyanotic at baseline but with episodes of
Figure 1. Radiograph of newborn with cyanosis with complete transpOSition of the great ;lrteries. Note the enlarged heart with concave pulmonary artery segment, abnormally narrow base, and heavy hilar pulmonary vasculature.
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cyanosis during crying or in association with hypercyanotic spells. Physical examination reveals a loud second sound and usually a systolic murmur associated with flow through the stenosed pulmonary outflow region. Chest radiographs show decreased pulmonary markings, an average-sized heart, and absence of the pulmonary artery contour contributing to the classic "boot-shaped" configuration (Fig. 2). Twentyfive percent have a right-sided aortic arch. ECG reveals right axis deviation and right ventricular hypertrophy, which of course are normal in the first month of life. Pulmonary atresia with intact septum accounts for about 25% of newborn cyanotic heart disease. The second heart sound is single and of normal intensity. Commonly there is no murmur, or there may be the systolic murmur of tricuspid regurgitation. ECG reveals right atrial enlargement and left ventricular hypertrophy, but right ventricular forces are discernible and may also be increased. Observations on chest radiographs vary from an average-sized to a tremendously enlarged heart. Tricuspid atresia may be difficult to distinguish from pulmonary atresia, but subtle clues can reveal the difference. The second heart sound is single, and palpation of the precordium reveals a left ventricular thrust. The ECG makes the diagnosis when it shows right atrial enlargement, left axis deviation, and left ventricular dominance in the absence of right ventricular forces . Chest radiographs reveal nonspecific cardiomegaly and decreased pulmonary markings. Total anomalous pulmonary venous return can present in a variety of ways. This variability is based on the degree of obstruction to pulmo-
Figure 2. Radiograph of infant with cyanosis with tetralogy of Fallot. The heart is small, with a concave pulmonary segment, wide base, and excessively clear lung fields.
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nary venous return to the heart. Cases with little or no obstruction may be asymptomatic in infancy or may present with nonspecific signs like failure to thrive. Obstructed pulmonary return, however, can present as early as the first few days of life, usually with mixed signs of both cyanosis and congestive failure as all pulmonary and systemic venous blood returns to the right side of the heart. Symptoms of cyanosis and dyspnea may progress rapidly, signifying a true medical emergency. Absence of a murmur and the mixed picture of symptoms may allow the cardiac diagnosis to escape detection at first. Chest radiographs are unique in revealing pulmonary overcirculation and pulmonary venous congestion with a small heart. 53 The results of the ECG are normal or show right ventricular hypertrophy. This lesion is also unique in this category because infusion of prostaglandin does not alter the course. Only aggressive medical management with inotropic support, diuresis, and usually ventilatory support with an eye toward prompt (if not immediate!) surgical intervention can secure a positive outcome.
Lesions Presenting with Congestive Heart Failure
This category includes those defects that produce overcirculation of the pulmonary vascular bed via left-to-right shunting. These lesions are usually inapparent at birth because the relatively high pulmonary vascular resistance of the neonate restricts the amount of left-to-right shunting. A murmur may not appear until 2 weeks to 2 months 55 of age, and symptoms may not become apparent until pulmonary resistance drops to sufficiently low levels to permit a large left-to-right shunt. This usually happens at 6 to 8 weeks of age. The signs and symptoms of congestive heart failure usually evolve slowly and often are overlooked in the mild to moderate stage. Fatigue during feedings, diaphoresis, and poor weight gain are symptoms that often precede by days to weeks the tachypnea and fussiness that usually bring the infant to medical attention. Often intercurrent infection is the precipitating factor that pushes the previously tenuously balanced infant over the brink into symptomatology. Vital signs reveal tachypnea and tachycardia. The tachypnea may be remarkable, but the infant usually looks more comfortable than his or her actual respiratory rate would suggest. Look for nasal flaring, subcostal and intercostal retractions, and the use of accessory muscles of respiration. Rales are unusual in the infant in failure, and peripheral edema is virtually never seen until late. A hyperactive precordium with a visibly prominent precordial bulge of the left chest may be evident. Likewise, a thrill may be palpable. Cardiac murmurs are invariably present, corresponding to the nature of the specific lesion. Cardiomegaly-both on physical examination and via chest radiographs-and hepatomegaly are very sensitive physical signs of congestive heart failure. In addition to the cardiomegaly, the chest radiograph reveals pulmonary arterial and often venous congestion (Fig. 3).
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Figure 3. Chest radiograph of 6-week-old infant in congestive cardiac failure because of a large left-to-right shunt that causes cardiomegaly and increased pulmonary arterial markings.
Infants who present to the emergency room with signs, symptoms, and radiographic evidence of failure as described previously require urgent evaluation by the cardiologist, with hospitalization likely unless symptoms are mild. Furosemide administered intravenously at a dose of 1 mg/kg should provide prompt diuresis and clinical improvement as the infant awaits admission. Digitalization is carried out under the supervision of the cardiologist. Infants with new murmurs but no tachypnea, tachycardia, organomegaly, or other signs and symptoms of congestive heart failure do not require treatment or hospitalization, but they should be referred for prompt outpatient evaluation by the pediatric cardiologist. Lesions in this category are quite common. They include the following conditions. Ventricular septal defect, the most common congenital heart defect,24 is the hallmark of this group. A holosystolic murmur, maximal at the left lower sternal border and often radiating over the entire precordium and to the lung fields, is the calling card of this lesion. The precordium may be hyperactive in a sizable defect. A palpable thrill may be present. EeG may show left or combined ventricular hypertrophy. Patent ductus arteriosus is also common but is an unusual cause of symptoms unless it is a huge duct. In the first month or so, the left upper sternal border murmur may be systolic only, rather than the familiar continuous, machine-like murmur of later infancy and childhood. Atrioventricular septal defect, sometimes called atrioventricular canal or endocardial cushion defect, involves defects in the atrial and ven-
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tricular septa as well as abnormality in the atrioventricular valves, which can range from mild leaflet defects to a common valve for both sides of the heart. This anomaly frequently occurs in infants with Down syndrome,72 but it also occurs not infrequently in the rest of the population. Symptoms depend on the size of the defect(s) and thus on the magnitude of left-to-right shunt as well as on the degree of atrioventricular valve regurgitation. Murmurs vary from the holosystolic left lower sternal border murmur of the ventricular septal defect, to the long systolic murmur radiating to the apex and axilla from atrioventricular valve regurgitation, to the left upper sternal border systolic ejection murmur of relative pulmonic stenosis (i.e., excessive blood flow through a normal-sized pulmonic valve). If pulmonary artery pressure is as high as aortic pressure (pulmonary hypertension), the second sound is single and quite loud. The ECG shows a superior axis, a prolonged P-R interval,20 and evidence of atrial enlargement and left or biventricular hypertrophy. Supraventricular tachycardia is another entity that can cause the infant to present in the emergency setting with signs of congestive heart failure or, if the rapid heart rate of more than 200 beats per minute is left long enough, in shock. Another, much rarer entity that does not qualify as a congenital heart defect but can present as congestive heart failure or shock in the neonatal period or later is myocarditis. Myocarditis typically begins with a prodrome of fever, rhinorrhea, or diarrhea, with sometimes dramatic progression to lethargy, ashen pallor, tachycardia, and respiratory distress. Cardiomegaly and hepatomegaly are common but may take some time to evolve. The ECG shows ST and T-wave abnormalities along with conduction disturbances and dysrhythmias, but no hypertrophy. The diagnosis is often confusing because signs and symptoms may be confused with those of some of the congenital defects, but the presentation (usually later than the ductal-dependent lesions and with more acute onset than the failure lesions) aids in the diagnosis. The cause is usually viral. The infant with myocarditis needs hospitalization for supportive therapy.
Cardiac Disease in the Infant in Shock
The previously healthy infant who presents with circulatory collapse may have sepsis, may suffer from another metabolic or other systemic problem, or may have a cardiac diagnosis that may be immediately life threatening. These babies are apt to present with severe left ventricular outflow obstruction. Severe coarctation of the aorta is different from the other ductaldependent lesions described earlier because the infant depends on the ductus for right-to-Ieft flow into the descending aorta (rather than leftto-right flow into the pulmonary artery) to sustain life. The infant usually has been discharged from the nursery with no suspicion of
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heart disease because the patent ductus had allowed for perfectly normal femoral pulses and was likely so widely patent as to cause insufficient turbulence to produce an audible murmur. Usually late in the first week of life the ductus closes, causing impairment of flow to the lower body. The infant then develops fussiness that fairly rapidly progresses to respiratory distress and shock. The infant usually arrives pale, clammy, and lethargic, but the discrepancy between the color of the upper body (precoarctation, pink) and lower body (postductal, blue) often goes unnoticed, especially if there is an associated large ventricular septal defect that allows mixing of arterial and venous blood at the ventricular level, which is common. The discrepancy between the pulses in the lower extremities and the right arm (the left arm being variably supplied because the left subclavian artery may originate proximal or distal to the coarctation) is not easy to miss if interrogated, however. The precordium is hyperactive and a cardiac murmur is absent unless an associated abnormality such as a ventricular septal defect or atrioventricular valve abnormality is present. Blood pressure discrepancy (signifying that the ductus is essentially closed) or difference in saturation (meaning that the ductus is still somewhat patent and supplying the lower body with unoxygenated right ventricular blood) between the right arm and the foot seals the diagnosis. Chest radiographs reveal cardiomegaly, and the ECG usually shows right ventricular hypertrophy. Prostaglandin infusion, with dosage and monitoring as described earlier maintains ductal patency and is a life-saving measure. Often inotropic support is also necessary in preparation for transfer to the intensive care unit where definitive diagnosis by echocardiogram and further management by the cardiologist and cardiac surgeon await. Hypoplastic left heart syndrome provides a radical extreme of the previously mentioned situation, with some vital exceptions. The mitral valve, aortic valve, or proximal aortic arch all failed to form, and the left ventricle is hypoplastic. The patent ductus arteriosus thus provides for all systemic blood supply, so all pulses are diminished when the infant finally presents with a closing ductus. Marked pallor and cyanosis, poor perfusion, and a hyperdynamic precordium with a single S2 are evident on examination. Chest radiographs show cardiomegaly and increased pulmonary vascular markings, and ECG reveals right ventricular hypertrophy and paucity of left-sided forces. Sometimes there are striking ST and T-wave changes, indicating myocardial damage from poor myocardial perfusion. Prostaglandin infusion, inotropic support, and treatment of respiratory distress and metabolic acidosis usually stabilize the infant for transfer to the critical care unit for further diagnosis and management. MEDICAL MANAGEMENT OF THE PEDIATRIC CARDIOLOGY PATIENT
Next, our focus shifts to the patient who has already been diagnosed with heart disease and who presents to the pediatric emergency
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room for a complaint that mayor may not be. associated with the primary cardiac diagnosis. Some situations are peculiar to the cardiac patient (bacterial endocarditis, hypercyanotic spells), whereas others pertain to common pediatric issues that just take on a different meaning in the cardiac patient (respiratory syncytial virus, dehydration, and, in the cyanotic child, fever). Adverse Reactions to Cardiac Medications
Digoxin is the major weapon in the artillery of the pediatric cardiologist in the war against congestive heart failure and some dysrhythmias. Its ubiquitous use necessitates a clear understanding of its adverse effects and somewhat peculiar signs of toxicity (Table 2). Symptoms of digoxin toxicity include nausea, vomiting, diarrhea, anorexia, and visual disturbance. The most dangerous effects are cardiac, with rhythm and conduction disturbances leading the way. In therapeutic amounts, digoxin affects the ECG by prolonging the P-R interval, shortening the Q-T interval, and promoting S-T segment and T-wave abnormalities in comparison with the patient's pre-digitalization baseline tracing (Fig. 4). These effects signify therapeutic changes and not toxicity. Digoxin toxicity, on the other hand, is manifest by secondor even third-degree atrioventricular block, excessive sinus slowing, exaggerated depression of S-T segments, or supraventricular or ventricular arrhythmias. Slowing of the sinus rate is a sign of good therapeutic effect (in fact, the well-digitalized patient often exhibits truncated Table 2. DIGOXIN THERAPY AND TOXICITY Therapeutic Effects Decreased heart rate from predigitalization baseline Blunted tachycardic response to fever, stimulus ECG: prolonged P-R, shortened Q-T, S-T and T wave changes Toxic Effects Nausea, anorexia, vomiting, diarrhea Visual disturbances ECG: second degree atrioventricular block, prolonged QRS, ventricular dysrhythmias, bradycardia, supraventricular tachycardias Contributors to Toxicity Renal impairment Hypokalemia Hypercalcemia, intravenous calcium infusion Treatment of Toxicity (Severe): Digoxin Immune Fab (DIGIBIND) Each vial binds approximately 0.6 mg (600 mcg) Toxicity during chronic therapy Children
