Evaluation of the Cyanotic Newborn

Congenital Heart Disease

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Evaluation of the Cyanotic Newborn

David]. Driscoll, MD*

PATHOPHYSIOLOGY Cyanosis is a physical sign characterized by a slate-blue color of the mucous membranes, nail beds, and skin. It results from the presence of deoxygenated hemoglobin in the blood at a concentration of at least 5 gm per dL. At 5 gm per dL or slightly less, deoxygenated hemoglobin may not be associated with cyanosis or may produce a ruddy appearance. Cyanosis is less likely to occur in a patient with severe anemia because the hemoglobin levels may be too low to produce the color. In contrast, patients with polycythemia may exhibit a ruddy appearance or cyanosis despite a normal arterial partial pressure of oxygen (Pa02)' Because cyanosis is a physical sign, detecting it depends on the observer's acuity. It may be more difficult to appreciate the presence of cyanosis in patients who have heavily pigmented skin. Hypoxemia is a state of abnormally decreased arterial blood oxygen concentration. It is recognized by measurement ofPa02 or arterial blood oxygen saturation (Sa02)' The degree of hypoxemia mayor may not correlate with the physical sign of cyanosis, depending on the blood hemoglobin concentration and the ability of the examiner to detect cyanosis. A polycythemic newborn may appear plethoric or cyanotic despite a normal Pa02 and absence of cardiac or pulmonary disease. The relationship between Pa02 and Sa02 is important in understanding the determinants of cyanosis, hypoxemia, and tissue oxygenation. An Sa02 of 88 per cent (a level at which cyanosis is apparent to most observers) can be achieved with Pa02 ranging from 30 to 85 mm Hg, depending on the fetal hemoglobin concentration, pH, temperature, and level of 2,3-diphosphoglycerate (2,3-DPG). It is apparent from Figure 1 why a polycythemic normal newborn with increased fetal hemoglobin and increased 2,3-DPG can appear cyanotic

* Head, Section of Pediatric Cardiology, Mayo Clinic and ~1ayo Foundation; and Professor of Pediatrics, Mayo Medical School, Rochester, Minnesota Pediatric Clinics of North America-Vol. 37, No.1, February 1990

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with a normal Pa02. it also is clear that above 80 mm Hg the Pa02 will have little effect on Sa02. From Figure 1, the equation for tissue oxygenation (Table 1), and the systemic arterial blood oxygen content, it is apparent that tissue oxygenation is dependent on systemic Sa02, which in turn depends on Pa02, the amount of fetal hemoglobin, and the level of2,3-DPG. Normally, all of the systemic venous return flows from the right atrium to the right ventricle to the pulmonary artery. The volume of blood flowing into the pulmonary artery, "Op" is the same as the volume of blood that travels through the lungs to the left atrium to the left ventricle and into the aorta. The volume of blood flowing into the aorta is systemic blood flow or "Os". The terms "Os" and "cardiac output" are frequently used interchangeably. Effective pulmonary blood flow, Oep, is the volume of systemic venous return that travels through the pulmonary vascular bed and becomes oxygenated-that is, the volume of pulmonary blood flow that is effective in participating in gas exchange in the lung. In the normal situation, systemic, pulmonary, and effective pulmonary blood flows are equal: Os =

Op = Oep.

.

The formulae for calculating these volumes are listed in Table 1. The denominator of each of these equations merely describes oxygen 100

80

?fl. c

0

60

t t t t

.~ ::J

1a en

40

C\I

0

... H+conc PC02

temp 2,3-DPG

20

20

40

60

P02,

mm Hg

80

Figure 1. Oxyhemoglobin dissociation curve.

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Table 1. Tissue Oxygenation and Blood Oxygen Content 1. Tissue oxygenation = systemic arterial blood oxygen content x cardiac tissue. 2. Systemic arterial blood oxygen content = (Hb in gm/dL x 1.36 in ml 02/gm per Hb x Hb O 2 saturation in per cent) + (Pa02 in mm Hg x 0.003 ml 02/dL per mm Hg). The second term, Pa02 x 0.003, represents oxygen dissolved in the blood, unattached to hemoglobin. Systemic .

(0,),

Pulmonary

(Op), and Effective Pulmonary (Oep) Blood Flow V'02

Q,=---------------------------------------------------[(Hb x 1.36 x Sao02) + (Pa02 x 0.003)] - [(Hb x 1.36 x Smv02) + (Pmv02 x 0.003)]

.

V'02

Qp=--------------------------------------------~------

[(Hb x 1.36 x SpV02) + (PpV02 x 0.003)] - [(Hb x 1.36 x Spa02)] + (Ppa02 x 0.003)]

.

V'02

Qep=---------------------------------------------------[(Hb x 1.36 x SpV02) + (PpV02 x 0.003)] - [(Hb x 1.36 x Smv02) + (Pmv02 x 0.003)]

Where:

V'02 = oxygen uptake, liter/min Hb = hemoglobin, gm/dL 1.36 = ml O 2/ gm Hb 0.003 = ml 02/dL per mm Hg

mv = mixed venous pa = pulmonary artery pv = pulmonary vein Sa02 = O 2 saturation in aorta

extraction or oxygen addition to blood as it passes through either the systemic or the pulmonary vascular bed. In c~mtr.ast to ~ormal, for patients with cyanotic congenital heart disease, Qp, Qs, and Qep usually are not equal, and the physiologic consequences of,the.specific. defect can be understood and described by the values of Qp, Qs, and Qep and the relationships among them. In addition, the concept of left-to-right and right-to-Ieft shunts is useful in understanding and describing the physiologic consequences of cyanotic forms of congenital heart defects. A left-to-right shunt exists when oxygenated blood from the lungs returns to a systemic vein, the right atrium, the right ventricle, or the pulmonary artery rather than going to the aorta via the left ventricle and left atrium. A right-to-Ieft shunt exists when a volume of deoxygenated blood (systemic venous return) travels directly to the left atrium, left ventricle, or aorta instead of traveling through the lungs and becoming oxygenated. An important concept in understanding the physiologic consequences of cyanotic forms of congenital heart defects is the relationship between the volume of pulmonary blood flow and the degree of hypoxemia. Tetralogy of Fallot, pulmonary atresia with ventricular septal defect, truncus arteriosus, and tricuspid atresia are four defects in which the volume of pulmonary blood flow may be abnormally low and there is a communication between the two ventricles. In these instances, tl:te lower the Qp the more cyanotic the patient will be; the higher the Qp the less cyanotic the patient will be. Why is this? Consider tetralogy of Fallot. Sa02 in the ascending aorta will depend on the relative volumes of deoxygenated blood reaching the aorta from

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the right ventricle and of oxygenated blood reaching the aorta from the left ventricle. The volume of oxygenated blood in the right ventricle is relatively fixed and depends on systemic venous return to the right atrium. However, the volume of oxygenated blood in the left ventricle represents the volume of oxygenated blood it receives from the left atrium, which in turn depends on the volume of pulmonary blood flow. In tetralogy of Fallot, the volume of pulmonary blood flow depends on the degree of restriction of blood flow into the pulmonary artery from the right ventricle. A second important concept is the anatomic relationship of the systemic veins (inferior and superior venae cavae and coronary sinus) and the pulmonary veins to the aorta and the pulmonary artery. Normally, the inferior and superior venae cavae are connected with the pulmonary artery via the right atrium and ventricle, and the pulmonary veins are connected with the aorta via the left atrium and ventricle (Fig. 2). Thus, deoxygenated blood is directed to the lungs, and OXygenated blood is directed to the body. In transposition of the great arteries, these relationships are unusual and the inferior and superior venae cavae are connected with the aorta via the right atrium and ventricle, and the pulmonary veins connect with the pulmonary artery via the left atrium and ventricle. Thus, deoxygenated blood is directed to the aorta, and oxygenated blood is directed to the pulmonary artery. Obviously, a communication must exist between these two circuits or survival would be impossible. In these instances, it is the size of the communication and the degree of blood mixing through the communication that determines the degree of cyanosis and hypoxemia, much more so than the volume of pulmonary blood flow. Indeed, in patients with transposition of the great arteries without a ventricular septal defect, pulmonary blood flow characteristically is greater than normal but cyanosis is intense. Total anomalous pulmonary venous return is another example of a cyanotic form of congenital heart disease that results from an inappropriate relationship of the pulmonary venous drainage to the pulmonary artery rather than to the aorta (see Fig. 2). In this case, both systemic and pulmonary venous drainages connect with the pulmonary artery via the right atrium and ventricle. With these concepts in mind, there are two questions that must be answered to understand the anatomy and physiology of cyanotic forms of congenital heart disease: (1) What are the sources, reliability, and volume of pulmonary blood flow? (2) What is the relationship between the venous drainage to the heart and the arterial exit from the heart? The answers to these questions are critical in clinical management of these patients. Cardiac, pulmonary, metabolic, and hematologic diseases can produce cyanosis in the newborn. Any condition that causes cardiac shock can produce cyanosis, even in a patient with a structurally normal heart. When evaluating a cyanotic newborn, the first consideration is whether the problem causing the cyanosis is cardiac, pulmonary, metabolic, or hematologic (although methemoglobinemia also is in-

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Dark blood with low oxygen content


.... Dark blood with ~ low oxygen content

<) Pink blood oxygenated by the lungs C

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.... Dark blood with ~ low oxygen content


Figure 2. Anatomic relationships. A, Normal. B, Transposition of the great arteries. C, Total anomalous pulmonary venous return. (Courtesy of the late Mr. Americo SimmonellL)

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eluded in the differential diagnosis of cyanosis in the infant, it rarely is encountered). The most common causes of cyanosis in newborns are cardiac disease and pulmonary disease, and these two must be distinguished. The history is important in making this distinction. If the baby was born prematurely, respiratory distress syndrome of the newborn may be the cause of the cyanosis. If me coni urn aspiration occurred before or during delivery, pneumonia may be the cause. In general, cyanotic infants with pulmonary disease are more tachypneic and appear to have greater respiratory distress than babies with cyanotic congenital heart disease, particularly in the first 24 to 48 hours of life. Newborn babies with cyanotic congenital heart disease are tachypneic but to a lesser extent than those with pulmonary disease. An important caveat is that significant pulmonary edema associated with a congenital cardiac defect can be misinterpreted as primary pulmonary disease. Many pulmonary causes of cyanosis are readily apparent from the chest radiograph; this film should be obtained early in the evaluation of the cyanotic infant (Table 2). The use of echocardiography greatly simplifies the distinction of pulmonary from cardiac disease in infants. However, if echocardiography is not available, the "hyperoxia test" is useful in this regard. In an infant breathing room air, Pa02 may be depressed to a similar level by pulmonary disease and by congenital heart disease. In cyanotic congenital heart disease, the Pa02 is decreased because of a right-toleft shunt of blood, that is, systemic venous return (blood that is low in oxygen) travels to the left side of the heart and into the aorta without going through the lungs to participate in gas transfer. Regardless of the effectiveness of ventilation and the amount of oxygen delivered to each alveolus, the blood that is shunting right to left cannot participate

Table 2. Pulmonary Causes of Cyanosis Respiratory distress syndrome of the newborn Pneumonia Meconium aspiration Pulmonary hypoplasia Pneumothorax Chylothorax Diaphragmatic hernia Hemothorax Anatomic airway obstruction Pulmonary telangiectasis Bronchogenic cyst Labor emphysema Pleural effusion

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in gas transfer and cyanosis will persist. In pulmonary disease, all of the systemic venous return passes through the lung but, because of the pulmonary disease, not all the alveoli are being ventilated appropriately. Blood passing nonventilated alveoli cannot participate in gas exchange. However, if the F j 0 2 is increased and the patient is ventilated optimally, the ventilation of these alveoli will be improved, gas exchange with the pulmonary blood flow will be improved, and Pa02 will increase. Thus, as a rule of thumb, if the Pa02 increases above 150 mm Hg when the F j 0 2 is 0.9 to 1 and the baby is adequately ventilated, cyanotic cardiac disease is unlikely. If the Pa02 fails to increase above 100 mm Hg, however, cyanotic congenital heart disease probably is the cause of the cyanosis. If the Pa02 is between 100 and 150 mm Hg, cardiac disease is likely to be the cause but the diagnosis is not certain.

APPROACH TO DIAGNOSIS The goal of the primary-care physician is to recognize the presence of significant heart disease in the infant. Utilizing history, physical findings, chest radiography, and electrocardiography, one can make a reasonable assessment of the physiologic manifestations of the underlying congenital heart defect (increased or decreased pulmonary blood flow; presence or absence of a shunt). However, it is difficult to determine the underlying anatomic defect without the aid of echocardiography, cardiac catheterization, angiography, or a combination of these. History The family history and the pregnancy and delivery history may be helpful in some cases. If there is a strong family history of congenital heart disease, one may be more likely to suspect this in the infant. Maternal diabetes or parental congenital heart disease is associated with a higher-than-normal prevalence of congenital heart disease in offspring. Perinatal problems such as meconium staining or aspiration may make pulmonary disease a more likely explanation than cardiac disease for cyanosis in the newborn. Physical Examination The respiratory pattern and frequency are helpful in distinguishing pulmonary from cardiac disease in cyanotic newborns. With cyanotic congenital heart disease, the baby usually will be tachypneic but will not have significant respiratory distress or retraction. The exception to this is when the baby has a totally obstructed anomalous pulmonary venous return with significant pulmonary edema. Careful palpation of the carotid, brachial, and femoral pulses is important to exclude associated coarctation of the aorta or interruption of the aortic arch. The quality of the precordial activity should be noted. Most forms of cyanotic congenital heart disease are associated

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EVALUATION OF THE CYANOTIC NEWBORN

with pressure or volume overload of the right ventricle, and a prominent impulse at the lower left sternal border will be apparent. The first heart sound usually is normal. The second heart sound usually is single in newborns with cyanotic congenital heart disease but, if it is widely split, Ebstein's anomaly should be considered as a likely diagnostic possibility. The absence of a cardiac murmur does not exclude the presence of significant cyanotic congenital heart disease. A systolic pulmonary ejection murmur may suggest tetralogy of Fallot; a harsh to-and-fro murmur would suggest absent pulmonary valve syndrome. A systolic murmur of tricuspid insufficiency and a tricuspid diastolic murmur may suggest Ebstein's anomaly. Chest Radiograph The chest radiograph is important in evaluating a cyanotic newborn. It is most helpful in excluding noncardiac causes of cyanosis (see Table 2). Except for certain classical appearances, the chest radiograph has limited use in defining the exact nature of a congenital cardiac defect. Clinically, babies with transposition of the great arteries have cardiomegaly and increased pulmonary vascular markings, but this is quite variable (Fig. 3). The so-called egg on a string appearance of the cardiac silhouette is not very useful in the diagnosis of transposition of the great arteries. A chest radiograph showing a normal heart size and paucity of pulmonary vascular markings suggests tetralogy of Fallot or

Figure 3. Chest radiograph from six patients with transposition of the great arteries. Note spectrum of cardiac size and pulmonary vascularity.

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pulmonary artery atresia with ventricular septal defect especially if there also is a right-sided aortic arch. Marked cardiomegaly and decreased pulmonary vascular markings suggest Ebstein's anomaly or pulmonaIY atresia with intact ventricular septum. Electrocardiogram The electrocardiogram of a normal newborn is characterized by right ventricular dominance. Left axis deviation and an initial counterclockwise frontal plane loop are abnormal and, in a cyanotic infant, are consistent with tricuspid atresia or complete atrioventricular canal with associated pulmonary stenosis. SPECIFIC CONGENITAL CARDIAC MALFORMATIONS D-Transposition of the Great Arteries D-transposition of the great arteries (d-TGA) is the most common formof congenital heart disease that presents with cyanosis in a new c born; it constitutes 3.8 per cent of all congenital cardiac defects.l D-TGA results from abnormal conotruncal septation such that the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. Forty per cent of patients with d-TGA have an associated ventricular septal defect. Among patients WIth d-TGA, 6 per cent of those with intact ventricular septum and 31 per cent of those with ventricular septal defect have associated pulmonary stenosis. 2 In d -TGA systemic venous return (blood with low oxygen content) returnsto the right ventricle and then is pumped to the body via the aorta without passing through the lungs for gas exchange. Pulmonary venous return (oxygenated blood) returns to the left ventricle and then is pumped back to the lungs. The effective pulmonary blood flow (the volume of deoxygenated blood that participates in gas exchange in the lungs) is low, albeit total pulmonary blood flow is increased. This is incompatible with life unless a communication exists between the two circuits to allow mixture of the oxygenated and deoxygenated blood. This mixture occurs at the patent foramen ovale (or atrial septal defect), the ductus arteriosus if patent, and the ventricular septal defect (if present). This is a tenuous situation for a patient with an intact ventricular septum and no true atrial septal defect because mixing of the two circuits will decrease as the patent ductus arteriosus closes and the patent foramen ovale becomes sealed. Cyanosis, a prominent precordial impulse at the lower left sternal border ("right ventricular impulse"), and a single second heart sound that is increased in intensity are common findings in babies with d-TGA. There are no physical findings that are pathognomonic of d-TGA. There may be no cardiac murmur or there may be a systolic ejection murmur audible along the left sternal border resulting from relative dynamic left ventricular outflow obstruction or pulmonary valve stenosis. Physical examination is important for excluding the presence of associated anomalies such as coarctation of the aorta.

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The chest radiograph reveals cardiomegaly with increased pulmonary vascular markings in most patients with d-TGA and intact ventricular septum. However, the variability of thesefeatures is apparent from Figure 3. Patients with d-TGA, ventricular septal defect, and pulmonary stenosis may have decreased pulmonary vascular markings. A newborn with d-TGA represents a medical emergency. It is critical to establish or to exclude this diagnosis and to document and insure adequate sites for mixing between the systemic and pulmonary circuits which, in d-TGA, are in parallel rather than in series. The diagnosis of d-TGA and most associated malformations can be established noninvasively with two-dimensional echocardiography. The presence of a patent ductus arteriosus can be determined, but the ductus arteriosus cannot be relied on as a stable source of mixing because it likely will close. The ductus arteriosus can be maintained patent by infusion of prostaglandin El and this should be done if the baby is extremely hypoxemic (Pa02 < 25 mm Hg), is acidotic, or is to be transferred to another institution. Management of D-TGA with Intact Ventricular Septum

Arterial Switch (Jatene) Procedure. Although still slightly controversial, this procedure is the best management for infants with d-TGA, intact ventricular septum, and a normal pulmonary valve.3-5 In this operation, the aorta and pulmonary artery are transected cephalad to their respective valves. The ostia of the coronary arteries are removed from the stump of the aorta and sewed to the stump of the pulmonary artery. The distal portion of the aorta is anastomosed to the proximal stump of the pulmonary artery, and the distal portion of the pulmonary artery is anastomosed to the stump of the aorta (Fig. 4). The mortality after this procedure is lO per cent or less and the 'midterm results are quite good. This procedure must be done early (at < 3 weeks of age), before the thickened left ventricular walls involute as pulmonary arterial resistance decreases. In many institutions, the operation is performed without preoperative cardiac catheterization if an experienced echocardiographer is available. Prostaglandin El is infused preoperatively to maintain patency of the ductus arteriosus and the acid-base stability of the patient. Atrial Switch (Senning or Mustard) Procedure. This is an alternative to the arterial switch procedure.6-9 These procedures reroute the systemic and pulmonary venous return in the atria such that systemic venous return from the superior and inferior venae cavae is routed through the mitral valve and into the left ventricle (and subsequently from the left ventricle to the pulmonary artery). The pulmonary venous return is routed through the tricuspid valve (and subsequently from the right ventricle to the aorta). This is accomplished by sewing a baffle in the atrium (Fig. 5). The Senning and Mustard operations usually are performed in patients 6 months to 1 year of age. If one of these methods of operation is to be utilized, an adequate interatrial communication must be estab-

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Figure 4. A and B, Diagram of the arterial switch procedure for TGA.

Figure 5. Diagram of the (Mustard) atrial switch operation for transposition of the great arteries.

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lished in the newborn period. This is accomplished by the Rashkind balloon septostomy technique.]() A chatheter with an inflatable balloon at its tip is advanced from the femoral or umbilical vein to the right atrium through the patent foramen ovale and into the left atrium. The balloon is inflated in the left: atrium, and the catheter is withdrawn rapidly into the right atrium, producing a rent in the atrial septum. The Senning and Mustard operations have a low operative mortality but significant intermediate and long-term problems. These include obstruction of systemic and pulmonary venous return by the baffle, atrial arrhythmias, tricuspid insufficiency, and right ventricular failure. Management of D-TGA with Ventricular Septal Defect But No Pulmonary Stenosis When a significant ventricular septal defect coexists with d-TGA, the systemic and pulmonary venous returns can mix through the ventricular septal defect. In general, babies with associated ventricular septal defect but no pulmonary stenosis are less hypoxemic than those with intact ventricular septum. D-TGA and ventricular septal defect with no pulmonary stenosis canbe managed by an arterial switch procedure (Jatene) plus ventricular septal defect closure or by a Rastelli procedure. The arterial switch procedure usually is performed at age 1 to 2 months. In contrast to d-TGA with intact ventricular septum, the operation can be delayed because the ventricular septal defect allows maintenance of left ventricular hypertension and left ventricular wall thickness. The Rastelli procedure ll involves closure of the ventricular septal defect so that the blood exits from the left ventricle through the ventricular septal defect and enters the aorta. The pulmonary artery is divided, the proximal stump is oversewn, and a conduit is placed from the right ventricle to a distal portion of the main pulmonary artery. This operation has the disadvantage of using a prosthetic extracardiac conduit which eventually will fail and need to be replaced. Because of this, and to allow placement of a reasonably large conduit, the operation usually is delayed until age 4 to 6 years. Because of this delay, a pulmonary artery band must be placed during early infancy to prevent pulmonary vascular obstructive disease. Management of D-TGA with Ventricular Septal Defect and Pulmonary Stenosis or Atresia The physiology of d-TGA with ventricular septal defect and pulmonary stenosis is different from that of d-TGA without pulmonary stenosis because the pulmonary blood flow is limited by the stenosis. The degree of hypoxemia in these patients will be determined by the extent of mixing of the systemic and pulmonary venous returns and by the volume of pulmonary blood flow. In these patients, the sources and adequacy of the pulmonary blood flow must be assessed. With severe pulmonary stenosis or pulmonary artery atresia, the ductus arteriosus may be contributing significantly to the pulmonary blood flow. When

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the ductus arteriosus closes, severe hypoxemia and acidosis may ensue. Although the diagnosis of d-TGA, ventricular septal defect, and pulmonary stenosis can be madewith echocardiography, cardiac catheterization may be necessary to document the sources and reliability of the pulmonary blood flow. Because of the abnormal pulmonary valve, these patients are not candidates for an arterial switch (Jatene) procedure. Eventually, repair is best accomplished by the Rastelli procedure as described above. Prior to 4 to 6 years age, it may be necessary to establish a systemic-to-pulmonary artery shunt to augment pulmonary blood flow. Tetralogy of Fallot Tetralogy of Fallot consists of (1) ventricular septal defect, (2) pulmonary stenosis (this may be valvular or subvalvular and/or supravalvular), (3) an aorta that "overrides" the ventricular septal defect, and (4) right ventricular hypertrophy (Fig. 6). Tetralogy of Fallot represents 4 to 8 per cent of congenital cardiac defects. 1 Presumably, it results from unequal conotruncal septation. These babies are cyanotic because of the right-to-Ieft shunt through the ventricular septal defect and the decreased pulmonary blood flow. The degree of hypoxemia will be proportional to the volume of pulmonary blood flow which will be related to the severity of the right ventricular outflow tract obstruction and the sources of additional pulmonary blood flow such as a patent ductus arteriosus and systemic-to-pulmonary artery collateral vessels. If the degree of right ventricular outflow obstruction is mild, cyanosis may not be apparent (so-called pink tetralogy of Fallot). Also, if a significant portion of the pulmonary blood flow results from pa-

Figure 6. Angiogram of tetralogy of Fallot.

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tency of the ductus arteriosus, cyanosis and hypoxemia will increase when the ductus arteriosus closes. In most patients with tetralogy of Fallot, cyanosis is apparent soon after birth. There is an increased right ventricular impulse at the lower left sternal border. Usually, there is a systolic ejection murmur along the left sternal border. In the classic case, the chest radiograph will reveal a normal heart size and decreased pulmonary vascular markings. In approximately 25 per cent of these patients, a right aortic arch will be apparent on the chest radiograph. There may be a diminished main pulmonary artery segment. Hypoplasia of the main pulmonary artery and right ventricular hypertrophy may produce the "coeur en sabot" configuration of the cardiac silhouette, but this is not a particularly helpful sign in an infant. Because of normal right ventricular dominance in newborns, the electrocardiogram usually is not distinctly abnormal. The diagnosis of tetralogy ofFallot, the presence and size of the patent ductus arteriosus, and the size of the main and central right and left pulmonary arteries all can be established by using twodimensional echocardiography. Angiography is necessary to ascertain the size and distribution of the peripheral pulmonary arteries, the presence or absence of peripheral pulmonary stenosis, and the presence of additional ventricular septal defects. The initial management involves establishing important details of the anatomic diagnosis and treating the hypoxemia and acidosis if they are significant. Severely hypoxemic infants should be treated with an infusion of prostaglandin E1 to reopen the ductus arteriosus or to maintain its patency. If pulmonary blood flow is inadequate, a systemic-to-pulmonary artery anastomosis should be established surgically. A Blalock-Taussig (subclavian artery to pulmonary artery anastomosis) or modified Blalock-Taussig (interposition of a Gore-Tex tube from the subclavian artery to the pulmonary artery) is the procedure of choice. Intracardiac repair of tetralogy of Fallot is normally performed between ages 6 and 18 months, depending on the size and distribution of the pulmonary arteries and the presence or absence of associated anomalies such as anomalous origin of the left anterior descending coronary artery from the right coronary artery and multiple ventricular septal defects. Intracardiac repair involves closure of the ventricular septal defect and relief of the pulmonary stenosis .12-15 The latter may necessitate patch enlargement of the right ventricular outflow tract or the pulmonary annulus or both. Hypercyanotic or "tetralogy" spells can occur in forms of congenital heart disease in which there is obstruction to pulmonary blood flow and a communication between the subpulmonary and subaortic ventricles. These spells initially were associated with tetralogy of Fallot; hence, the name. Hypercyanotic spells consist of the abrupt onset of increased cyanosis, hypoxemia, dyspnea, and agitation. If left untreated, they can lead to profound hypoxemia, acidosis, seizures, and death. They rarely occur before the age of 2 months. Hypercyanotic spells tend to occur more frequently in the morning, within several hours after the patient awakens, but can occur at any time. The

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cause of hyper cyanotic spells is multifactorial. Physiologically, there is an increased right-to-Ieft shunt and decreased pulmonary blood How. Restlessness and agitation may lead to crying which increases pulmonary vascular resistance, further decreasing pulmonary blood How and accentuating the hypoxemia. The hypoxemia may produce acidosis which causes further pulmonary vasoconstriction, further decrease in pulmonary blood How, and increased hypoxemia. The vicious cycle is obvious. Hypercyanotic spells are treated in a stepwise fashion as outlined in Table 3. Once the spell resolves, further steps in treatment of the acute spell are unnecessary, but surgical repair of the cardiac abnormality or establishment of a systemic-to-pulmonary anastomosis should be performed without delay. Pulmonary Artery Atresia with Ventricular Septal Defect Although pulmonary atresia with ventricular septal defect has been described by some as "severe tetralogy of Fallot" or "tetralogy of Fallot with pulmonary atresia," the management of these problems and the morbid anatomy of the pulmonary artery tree can be considerably different from that in tetralogy of Fallot. In contrast to tetralogy of Fallot, with pulmonary atresia/ventricular septal defect, there is no systolic ejection murmur. There may be a continuous murmur resulting from blood How through the ductus arteriosus or systemic-topulmonary artery collateral vessels. As in tetralogy of Fallot, it is important to establish the sources and reliability of the pulmonary blood How. If its sources are insufficient or considered to be unreliable, a systemic-to-pulmonary artery anastomosis should be created. It is important to determine, as accurately as possible (usually by angiography), the anatomic features of the pulmonary artery tree before surgery because the entire pulmonary tree may not be in continuity. Eventual repair of pulmonary artery atresia/ventricular septal defect involves closure of the ventricular septal defect and establishing Table 3. Stepwise Treatment of Hypercyanotic Spells 1. Comfort child and place in knee-chest position. 2. Administer O 2 by face mask. 3. Give morphine, 0.01-0.1 mg/kg, sq. 4. Begin intravenous fluid replacement and volume expansion (if child is anemic, administer blood). 5. Treat acidosis with sodium bicarbonate. 6. Repeat morphine, 0.01-0.1 mg/kg, intravenously. 7. Increase systemic vascular resistance by intravenous administration of phenylephrine. Titrate dose to increase systemic systolic blood pressure by 20 per cent. 8. Administer propranolol, 0.1 mg/kg, intravenously. 9. Administer general anesthesia. 10. Operate to repair defect or to establish systemic-to-pulmonary artery anastomosis.

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continuity between the right ventricle and the pulmonary artery. The feasibility of accomplishing this depends on the size, distribution, and confluence or nonconfluence of the pulmonary artery tree. 16-18 Truncus Arteriosus Truncus arteriosus consists of a ventricular septal defect and only one great artery ("the truncus") arising from the heart (Fig. 7). This great artery is positioned above the ventricular septal defect and gives rise to the coronary arteries, the pulmonary arteries, and the aortic arch. There are three types of truncus arteriosus: (1) both pulmonary arteries arise as a single vessel from the truncus arteriosus; (2) the right and left pulmonary arteries arise from separate orifices but from the same side of the truncus arteriosus; and (3) the right and left pulmonary arteries arise from separate orifices on opposite sides of the truncus arteriosus. Significant associated anomalies include truncal valve insufficiency and interrupted aortic arch. Truncus arteriosus constitutes approximately 0.7 per cent of all congenital heart defects. I9 It results from abnormal conotruncal septation. Babies with truncus arteriosus may present with cyanosis or severe congestive heart failure. Cyanosis occurs because of a right-to-Ieft shunt at the level of the ventricular septal defect and is dependent upon the volume of pulmonary blood flow. This volume is related to the pulmonary arteriolar vascular resistance, the absence or presence

Figure 7. Diagram of truncus arteriosus. (Courtesy of the late Mr. Americo Simmonelli.)

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of proximal pulmonary artery stenosis, and the severity of this stenosis. These patients have a prominent right ventricular impulse at the lower left sternal border. Usually there is a systolic ejection murmur at the left sternal border. There may be an apical aortic ejection click and an increased pulse pressure. If there is associated interruption of the aortic arch, the femoral pulses may be decreased or absent. The chest radiograph is not particularly distinctive, usually revealing cardiomegaly and increased pulmonary vascular markings. The electrocardiogram reveals the usual right ventricular predominance of infancy. The diagnosis can be made by echocardiography. As pulmonary arteriolar resistance decreases in these babies, significant congestive heart failure develops. The initial management consists of medical treatment of the congestive heart failure (digitalis, diuretics, and, perhaps, afterload-reducing agents). Surgery td correct truncus arteriosus is necessary and should be performed before age 6 months, and in many cases between ages 3 and 6 months. Surgical correction involves closure of the ventricular septal defect, removal of the pulmonary arteries from the truncus, and the establishment of continuity between the right ventricle and pulmonary arteries with a conduit. Early surgical correction is necessary to prevent the development of pulmonary vascular obstructive disease and to treat the congestive heart failure. 20- 22 Because correction of this defect is necessary in infancy and requires use of an extracardiac conduit, reoperation will be necessary when the patient outgrows the relatively small conduit. Tricuspid Atresia In tricuspid atresia, there is no direct communication between the right atrium and the right ventricle. The initial survival of infants with tricuspid atresia depends on the presence of an interatrial communication to allow egress of blood from the right atrium to the left atrium. Tricuspid atresia occurs in combination with normally related or transposed great arteries and with or without pulmonary stenosis or atresia. The clinical presentation, physiologic manifestations, and treatment can depend, to some extent, on the relationship of the great arteries (normal or transposed) and the presence or absence of pulmonary stenosis or atresia. 23, 24 Tricuspid atresia constitutes 2.7 per cent of all forms of congenital heart disease. 25 Infants with tricuspid atresia usually present with cyanosis and frequently have an associated murmur. The apical impulse may be overactive. The presence of a systolic ejection murmur can result from associated pulmonary stenosis or a restrictive ventricular septal defect. The second heart sound may be single or split. A mid-diastolic apical cardiac murmur may be present, particularly if there is increased pulmonary blood flow and congestive heart failure. The chest radiograph reveals cardiomegaly, and the pulmonary vascular markings may be normal, increased, or decreased, depending on the degree of pulmonary stenosis. The right atrium (right heart border) may be prominent on a chest radiograph. The electrocardiogram is quite helpful in suggesting this diagno-

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EVALUATION OF THE CYANOTIC NEWBORN

sis. It is characterized by left axis deviation and an initial counterclockwise frontal plane loop. There may be left ventricular hypertrophy. The diagnosis of tricuspid atresia and delineation of most of the associated anomalies can be accomplished by echocardiography. Because tricuspid atresia can be associated with pulmonary stenosis and pulmonary atresia, it is important to establish the sources and reliability of the pulmonary blood flow. If these are not readily apparent by echocardiography, cardiac catheterization and angiography may be necessary. Rarely, the interatrial communication is too small for adequate egress of blood from the right atrium, and balloon atrial septosto my is necessary to enlarge this communication. Initial Management. This involves treatment of the congestive heart failure, if present, with digitalis and diuretics and establishment of a reliable source of pulmonary blood flow if the pulmonary blood flow is insufficient and severe hypoxemia and acidosis are present. This can be accomplished with an infusion of prostaglandin E 1 in the period before establishment of a systemic-to-pulmonary artery communication.

Subsequent Management. Tricuspid Atresia with Normally Related Great Arteries. Almost invariably, tricuspid atresia with normally related great arteries is associated with pulmonary stenosis or a restrictive ventricular septal defect that frequently becomes even more restrictive. Thus, the course of these patients is characterized by a progressive decrease in pulmonary blood flow and an increase in cyanosis. Many of these patients eventually will require surgical placement of a systemic-to-pulmonary artery anastomosis to augment pulmonary blood flow. Rarely, a patient with tricuspid atresia and normally related great arteries will not have subpulmonary stenosis or a restrictive ventricular septal defect. These patients will have increased pulmonary blood flow, pulmonary hypertension, and congestive heart failure; eventually, pulmonary vascular obstructive disease will develop unless a pulmonary artery band is placed to decrease pulmonary blood flow and pulmonary hypertension. Tricuspid Atresia with Pulmonary Artery Atresia. As in all forms of congenital heart disease associated with pulmonary atresia, the sources and reliability of pulmonary blood flow must be established (usually by cardiac catheterization and angiography). Surgical creation of a systemic-to-pulmonary artery shunt frequently is necessary to augment pulmonary blood flow for these patients. Tricuspid Atresia with Transposed Great Arteries. Usually, this condition is not associated with pulmonary stenosis. Pulmonary blood flow is increased, pulmonary hypertension is present, and congestive heart failure is striking. Surgical banding of the pulmonary artery is necessary to decrease the volume of pulmonary flow, to decrease the pulmonary hypertension, and to control the symptoms of congestive heart failure. A disadvantage of pulmonary artery banding is the possible acceleration of ventricular septal defect closure which can result in subaortic stenosis.

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Eventual Management. Eventual definitive palliation of tricus~id atresia is accomplished by the modified Fontan procedure (Fig. 8).2 ,27 In this operation, the atrial septal defect is closed, the main pulmonary artery is ligated and divided, and the right atrium is connected to the pulmonary artery. This separates systemic and pulmonary venous returns and decreases ventricular volume overload. Univentricular Heart In essence, tricuspid atresia is one form of univentricular heart, and the principles outlined above for the management of tricuspid atresia can be applied to the management of other forms of univentricular heart. One must establish an anatomic diagnosis (usually with echocardiography), define the status of pulmonary perfusion (too much or too little), and determine the sources and reliability of pulmonary blood How (usually with cardiac catheterization and angiography). If pulmonary blood How is insufficient, a systemic-to-pulmonary artery shunt is needed. If pulmonary blood How is excessive, a pulmonary artery band is placed. Eventual definitive palliation is accomplished by the modified Fontan procedure. 27 Total Anomalous Pulmonary Venous Return Total anomalous pulmonary venous return can be divided into four anatomic groups: (1) supracardiac, (2) cardiac, (3) infracardiac, and (4) mixed. Also, it can be divided into two physiologic types: nonobstructed and obstructed. Instead of connecting to the left atrium, the

Figure 8. Diagram of the modified Fontan operation for tricuspid atresia. The intra-atrial communication is closed, the main pulmonary artery is transected, and the right atrium is connected to the pulmonary artery.

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EVALUATION OF TilE CYANOTIC NEWBORN

pulmonary veins connect to the systemic venous system. 2H Consequently, pulmonary venous blood returns to the right atrium instead of to the left atrium. The locations of the connection of the pulmonary veins to the systemic veins (in order of frequency) are: the left vertical vein, innominate vein, coronary sinus, right atrium, umbilicovitalline system (portal vein, ductus venosus, inferior vena cava, hepatic vein), and superior vena cava. 29 In "mixed" total anomalous pulmonary venous return, a combination of the above might occur. For example, the left pulmonary veins may connect to the left vertical vein and the right pulmonary veins directly to the right atrium. Because there is no direct communication between the pulmonary veins and the left atrium, a communication must exist between the right atrium and left atrium to allow blood to reach the left atrium and the left ventricle. Relatively complete mixing of the systemic and pulmonary venous returns occurs in the right atrium such that Sa02 values in the right atrium, left atrium, right ventricle, pulmonary artery, left ventricle, and aorta are similar. If there is an adequate interatrial communication and no significant obstruction to pulmonary venous return, the baby has mild cyanosis and evidence of increased pulmonary blood flow. Examination reveals an increased right ventricle impulse at the lower left sternal border and a systolic ejection murmur. The chest radiography may reveal mild to moderate cardiomegaly and increased pulmonary vascular markings. The electrocardiogram is not particularly revealing. The diagnosis can be established by echocardiography but may need to be confirmed by cardiac catheterization and angiography. The clinical picture is completely different if there is an obstruction to pulmonary venous return. 30 Characteristically, obstruction to pulmonary venous return occurs with infradiaphragmatic forms of total anomalous pulmonary venous return. In this case, there is pulmonary edema and respiratory stress. This is a surgical emergency, and immediate repair is indicated on diagnosis. The clinical picture and chest radiographic findings can be confused with those of the respiratory distress syndrome of the newborn. In the infant with atypical respiratory distress syndrome, obstructed total anomalous pulmonary venous return should be suspected, and the possibility oflack of connection of the pulmonary veins to the left atrium should be investigated. The Hypoplastic Left Heart Syndrome The hypoplastic left heart syndrome includes aortic valve atresia, mitral valve atresia with intact ventricular septum, and hypoplasia of the mitral and aortic valves and left ventricle. Neonates with hypoplastic left heart syndrome may appear normal for several hours after birth or may display mild cyanosis. Several hours after birth, a systolic murmur may become apparent, and the signs and symptoms of congestive heart failure occur. There is an increased right ventricular impulse at the lower left sternal border. If the patent ductus arteriosus is closing, the peripheral pulses will be diminished or absent. The presence of normally palpable pulses does not exclude the diagnosis of hypo-

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plastic left heart syndrome because the pulses can be normal as long as the ductus arteriosus is relatively patent. The diagnosis of hypoplastic left heart syndrome is made by echocardiography. There is a relatively common association between coarctation of the aorta and hypoplastic left heart syndrome. Hypoplastic left heart syndrome is a lethal malformation. Norwood developed a palliative procedure that allows survival of some of these infants. 31 Babies who survive the Norwood procedure are candidates for a modified Fontan operation or cardiac transplantation. Neonatal cardiac transplantation has been successful as initial surgical treatment in a limited number of babies with hypoplastic left heart syndrome. Ebstein's Anomaly Ebstein's anomaly is a malformation of the tricuspid valve in which the anterior leaflet is abnormally attached to the endocardial surface of the right ventricle. The valve usually is incompetent or rarely can be stenotic. Thirty to 78 per cent of patients with Ebstein's anomaly have an associated atrial septal defect32, 33 and are cyanotic because of a right-to-left shunt through the atrial septal defect. The findings on physical examination are characterized by an easily recognizable split-second heart sound. The chest radiograph reveals a large heart with a prominent right-side border and decreased pulmonary blood flow. The electrocardiogram is characterized by tall P waves in limb lead II, indicating right atrial enlargement and a right bundle branch block pattern. The diagnosis of Ebstein' s anomaly can be confirmed by echocardiography. Patients with Ebstein's anomaly, normal pulmonary arteries, and no pulmonary stenosis usually do well during the newborn period without treatment. As pulmonary vascular resistance decreases, pulmonary blood flow increases and cyanosis lessens. Prostaglandin El infusion can be used if necessary to augment pulmonary blood flow until pulmonary resistance decreases. Infants with Ebstein's anomaly and right ventricular outflow tract obstruction are difficult to manage, and it never has been clear whether the establishment of a systemic-topulmonary artery shunt is helpful or harmful in these patients. Certainly, if complete pulmonary atresia exists a systemic-to-pulmonary artery shunt must be established surgically. Pulmonary Atresia with Intact Ventricular Septum Pulmonary atresia with intact ventricular septum is completely different from pulmonary atresia with ventricular septal defect and is less common. There is nothing particularly characteristic about the physical findings, but the chest radiograph reveals marked cardiomegaly with a prominent right atrium, similar to the appearance with Ebstein's anomaly. The electrocardiogram reveals tall P waves in limb lead II, indicative of the right atrial enlargement. The diagnosis can be confirmed by echocardiography. An unrestrictive atrial septal defect is

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EVALUATION OF THE CYANOTIC NEWBORN

necessary for survival. If the atrial septal defect appears to be restrictive, cardiac catheterization and balloon atrial septostomy will be necessary. The patent ductus arteriosus is the only source of pulmonary blood flow, and patency of the ductus arteriosus should be maintained with prostaglandin EI infusion until the systemic-topulmonary artery shunt can be established. 34 , 35 Cardiovascular Shock Cardiovascular collapse or shock from any cause can be associated with cyanosis. The cyanosis in shock is the result of two mechanisms: (1) increased transit time of blood through the skin vasculature, resulting in increased extraction of oxygen, and (2) right-to-left intrapulmonary shunting of the blood. Treatment should be directed at the underlying cause of shock and appropriate support of the cardiovascular system with pharmacologic agents. 36 REFERENCES 1. Hoffmann J: Incidence, mortality, and natural history. In Anderson R, Macartney F,

2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

Shinebourne E, et al (eds): Pediatric Cardiology. London, Churchill Livingston, 1987, pp 3-14 Kidd BSL: Complete transposition of the great arteries. In Keith J, Rowe R, Vlad P (eds): Heart Disease in Infancy and Childhood, ed 3. New York, Macmillan Publishing Co, 1978, pp 590-611 Jatene A, Fontes V, Paulista P, et al: Successful anatomic correction of transposition of the great vessels: A preliminary report. Arq Bras CardioI28:461-464, 1975 Quaegebeur J, Rohmer J, Ottenkamp J, et al: The arterial switch operation: An eight-year experience. J Thorac Cardiovasc Surg 92:361-384, 1986 Idriss F, Ilbawi M, DeLeon S, et al: Arterial switch in simple and complex transposition of the great arteries. J Thorac Cardiovasc Surg 95:29-36, 1988 Gutgesell H, McNamara D: Transposition of the great arteries: Results of treatment with early palliation and late intracardiac repair. Circulation 51:32-38, 1975 Mahony L, Turley K, Ebert P, et al: Long-term results after atrial repair of trans position of the great arteries in early infancy. Circulation 60:253-258, 1982 Okuda H, Nakazawa M, Yasuharu I, et al: Comparison of ventricular function after Senning and Jatene procedures for complete transposition of the great arteries. Am J Cardiol 55:530-534, 1985 Castaneda A, Trusler G, Paul M, et al: The early results of treatment of simple transposition in the current era. J Thorac Cardiovasc Surg 95:14-28,1988 Rashkind W, Miller W: Creation of an atrial septal defect without thoracotomy: A palliative approach to complete transposition of the great arteries. JAM A 196:991992, 1966 Rastelli G, McGoon D, Wallace R: Anatomic correction of transposition of the great arteries with ventricular septal defect and subpulmonary stenosis. J Thorac Cardiovasc Surg 58:545-552, 1969 Tucker W, Turley K, Ullyot D, et al: Management of symptomatic tetralogy of Fallot in the first year of life. J Thorac Cardiovasc Surg 78:494-501,1979 Kirklin J, Blackstone E, Pacifico A: Routine primary vs. two-stage repair of tetralogy of Fallot. Circulation 60:373-386, 1979 Garson A, Nihill M, McNamara D, et al: Status of the adult and adolescent after repair of tetralogy of Fallot. Circulation 59: 1232-1240, 1979 Fuster V, McGoon D, Kennedy M, et al: Long-term evaluation (12 to 22 years) of open heart surgery for tetralogy of Fallot. Am J Cardiol 46:635-642, 1980 Puga F, McGoon D, Julsrud P, et al: Complete repair of pulmonary atresia with nonconHuent pulmonary arteries. Ann Thorac Surg 35:36-44, 1983

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17. McGood D, Danielson G, Puga F, et al: Late results after extra cardiac conduit repair for congenital cardiac defects. Am J CardioI49:1741-1749, 1982 18. Millikan J, Puga F, Danielson G, et al: Staged surgical repair of pulmonary atresia, ventricular septal defect, and hypoplastic, confluent pulmonary arteries. J Thorac Cardiovasc Surg 91:818-825, 1986 19. Kidd BSL: Persistent truncus arteriosus. In Keith J, Rowe R, Vlad P (eds): Heart Disease in Infancy and Childhood, ed 3. New York, Macmillan Publishing Co, 1978, pp 457-469 20. McGoon D, Rastelli G, Ongly P: An operation for the correction of truncus arteriosus. J Am Med Assoc 205:59-63, 1968 21. Marcelletti C, McGoon D, Mair D: The natural history of truncus arteriosus. Circulation 54:108-111,1976 22. DiDonato R, Fyfe D, Puga F, et al: Fifteen-year experience with surgical repair of truncus arteriosus. J Thorac Cardiovasc Surg 89:414-422, 1985 23. Williams W, Rubis L, Fowler R, et al: Tricuspid atresia: Results of treatment in 160 children. Am J CardioI38:235-240, 1976 24. Dick M, Fyler D, Nadas A: Tricuspid atresia: Clinical course in 101 patients. Am J CardioI36:327-337,1975 25. Rosenthal A: Tricuspid atresia. In Moss A, Adams F, Emmanovilides G (eds): Heart Disease in Infants, Children, and Adolescents, ed 2. Baltimore, Williams and Wilkins, 1977, pp 289-301 26. Fontan F, Baudet E: Surgical repair of tricuspid atresia. Thorax 26:240-248, 1971 27. Humes R, Porter C, Mair D, et al: Intermediate follow-up and predicted survival after the modified Fontan procedure for tricuspid atresia and double-inlet ventricle. Circulation 76(suppl IV):67-71, 1987 28. Gathman G, Nadas A: Total anomalous pulmonary venous connection: Clinical and physiologic observations of75 pediatric patients. Circulation XLII: 143-154, 1970 29. Lucas R, Schmidt R: Anomalous venous connections, pulmonary and systemic. In Moss A, Adams F, Emmanovilides G (eds): Heart Disease in Infants, Children, and Adolescents, ed 2. Baltimore, Williams and Wilkins, 1977, pp 437-470 30. Duff D, Nihill M, McNamara D: Infradiaphragmatic total anomalous pulmonary venous return: Review of clinical and pathological findings and results of operation in 28 cases. Br Heart J 39:619-626, 1977 31. Norwood W, Lang P, Hansen D: Physiologic repair of aortic atresia-hypoplastic left heart syndrome. N Engl J Med 308:23-26, 1983 32. Anderson K, Zuberbuhler J, Anderson R, et al: Morphologic spectrum of Ebstein's anomaly of the heart: A review. Mayo Clin Proc 54:174-180,1979 33. Danielson G, Fuster V: Surgical repair ofEbstein's anomaly. Ann Surg 196:499-503, 1982 34. DeLeval M, Bull C, Hopkins R, et al: Decision-making in the definitive repair of the heart with a small right ventricle. Circulation 72(suppl II):52-60, 1985 35. Alboliras E, Julsruds P, Danielson G, et al: Definitive operation for pulmonary atresia with intact ventricular septum. J Thorac Cardiovasc Surg 93:454-464, 1987 36. Driscoll D: Use of inotropic and chronotropic agents in newborns. Clin Perinatol 14:931-949, 1987 Mayo Clinic 200 First Street S.W. Rochester, MN 55905