Cyanosis in the newborn is defined as an arterial saturation less than 90% and a PO2 less than 60 torr.1 The most common causes include intrinsic pulmonary disease, congenital heart disease, and central nervous system depression with hypoventilation. Differentiating among these causes is the first step toward diagnosis and treatment. A careful history should be obtained from the parents with particular attention to any problems with feeding, breathing, or diaphoresis. A thorough physical examination should then be performed. Dysmorphic features may suggest a genetic syndrome with associated congenital heart lesions. The character of the infant's respirations should be noted. Tachypnea is usually associated with the presence of pulmonary edema and increased pulmonary flow. Auscultation of the lung fields and precordium may reveal rales or murmurs, and abdominal examination may reveal hepatomegaly. Peripheral perfusion, pulses, and coloration should be assessed. Pulse oximetry and an arterial blood gas determinations should be performed immediately if cyanosis is present or suspected.
These measurements should be performed initially on room air to serve as a baseline. Subsequent measurements should be obtained on 100% oxygen and may help to differentiate between cardiogenic and non-cardiogenic causes of neonatal cyanosis. Infants with neurogenic or primary pulmonary causes of cyanosis will demonstrate substantial increases in arterial blood saturation on 100% oxygen while infants with congenital heart disease show minimal elevation. In general, patients with a PO2 greater than 250 torr on 100% oxygen will have a non-cardiac problem; conversely, those with PO2 less than 100 torr will likely have congenital heart disease.1
A chest radiograph should also be performed. Aberrancy of the cardiothymic silhouette may suggest the presence of structural heart disease, and abnormalities of the lung fields may be helpful in distinguishing a primary pulmonary problem such as meconium aspiration from a congenital heart lesion as the cause for cyanosis. Pulmonary vascular markings will be decreased in congenital heart lesions with obstructed pulmonary blood flow such as tetralogy of Fallot, severe pulmonary stenosis or atresia, and tricuspid atresia. In contrast, pulmonary vascular markings may be increased in admixture lesions with cyanosis like transposition of the great arteries, total anomalous pulmonary venous connection, and truncus arteriosus.
If cyanotic congenital heart disease is suspected, a pediatric
cardiology consult should be obtained prior to performing further
diagnostic tests. This approach has been shown to improve
diagnostic accuracy and reduce costs2. In cases of
congenital heart disease, an accurate diagnosis can be made
non-invasively using echocardiography combined with color
Doppler flow mapping and continuous or pulsed wave Doppler
studies. A preoperative echo is all that may be necessary prior
to surgical intervention for some cyanotic congenital heart
defects, but in most cases a cardiac catheterization is also
performed to enhance diagnostic accuracy, measure intracardiac
pressures, calculate intracardiac shunts, and quantitate
pulmonary and systemic flow ratios. In certain cases,
catheter-based techniques can dramatically improve the patients
condition prior to surgical intervention or provide an
alternative to surgery in some cases (i.e. balloon dilatation of
severe stenotic pulmonary valve, or balloon atrial septostomy to
increase interatrial mixing in transposition of the great
arteries).
There are three general sources of arterial desaturation in neonates with structural heart disease: 1) lesions with decreased pulmonary blood flow (tetralogy of Fallot, severe pulmonary stenosis/atresia, and tricuspid atresia); 2) admixture lesions, in which desaturated systemic venous blood mixes with intracardiac blood, and then enters the aorta (transposition of great vessels, partial anomalous pulmonary venous drainage); and 3) lesions with increased pulmonary blood flow and pulmonary edema, in which diffusion barriers and intrapulmonary shunting prevent proper oxygenation (truncus arteriosus).
Immediate treatment of cyanosis may be necessary, especially if saturations are poor and acidosis is present. For cyanotic heart defects with reduced pulmonary blood flow, the most rapid and effective first-line therapy is intravenous administration of prostaglandin E1 (PGE1). PGE1 serves to reopen the ductus arteriosus or prevent it from closing. This allows partially desaturated systemic arterial blood to enter the pulmonary artery and be oxygenated. The widespread use of this agent has profoundly decreased early morbidity and mortality in patients with cyanotic heart defects. Patients can be stabilized more easily, allowing for safe transport to a tertiary care center. More time is also available for thorough diagnostic evaluation and patients can be brought to surgery in a more stable condition. The initial dose of PGE1 is 0.1 mg/kg/min, which can be reduced to 0.02 - 0.05 mg/kg/min when the patient is stable. Adverse effects are relatively uncommon and include apnea, hypotension, edema, and low grade fever.
Various invasive catheterization procedures, already mentioned, may also be utilized early to stabilize patients with congenital heart disease. The most common procedure involves tearing the interatrial septum with a balloon catheter to enhance intracardiac mixing of saturated and desaturated blood (Rashkind balloon septostomy). This technique is particularly useful in improving the arterial saturation of patients with transposition of the great arteries.
Many infants with cyanotic heart disease will only survive with early surgical intervention. This is best approached by an experienced, multidisciplinary team which includes pediatric cardiac surgeons, cardiologists, anesthesiologists, intensivists, and skilled nursing personnel in a tertiary care setting. The timing and nature of each surgical procedure must be individualized to the specific cardiac malformation diagnosed, while taking the patient's overall condition into account. While some cyanotic heart defects can be repaired in infancy (e.g. transposition of the great arteries), other defects must be palliated to allow for stabilization and improvement of the patient, while also allowing for further growth which makes subsequent surgical repair much less risky.
The most common palliative procedure performed in cyanotic neonates is a systemic to pulmonary arterial shunt. This allows partially desaturated systemic blood to enter the pulmonary artery, thus increasing pulmonary blood flow, and hence, oxygenation. The first successful attempt to create such a shunt was in 1944 when the subclavian artery was anastomosed to the pulmonary artery. Known as the Blalock-Taussig shunt, this procedure is still an important part of surgical therapy for cyanotic heart disease. The procedure can be performed on either side of the chest, depending on surgical anatomy, utilizing small Gore-Tex® tube grafts which link the subclavian artery to the right or left branch pulmonary artery. Alternatively, a graft may be placed between the aorta and the main or branch pulmonary artery (central shunt).
In the past, early shunting was routinely performed on cyanotic patients with decreased pulmonary blood flow to improve oxygen saturation so that growth and development could occur. The "shunt now, fix later" philosophy offered the surgical convenience of a larger heart (and patient) to work with as well as a lower morbidity and mortality when the patient ultimately underwent complete repair. The disadvantage is that two operations are required, each with its own attendant morbidity and mortality. With improvements in surgical skill, cardiopulmonary bypass techniques, and perioperative intensive care, more patients are being completely corrected at an earlier age. Data indicate that primary repair in early infancy carries a comparable morbidity and mortality than early palliation followed by delayed repair.3-5
The most common cyanotic heart conditions presenting in the neonatal period are referred to as "the five T's": Tetralogy of Fallot; Transposition of the Great Arteries; Truncus Arteriosus; Tricuspid Atresia; and Total Anomalous Pulmonary Venous Connection. In addition, pulmonary atresia with and without a ventrical septal defect is a complex condition which often requires early surgical intervention. Each is briefly described below with its preferred therapeutic approach.
Tetralogy of Fallot is perhaps the best known of the cyanotic heart lesions. Of the four anomalies (overriding aorta, right ventricular hypertrophy, ventricular septal defect, and right ventricular outflow tract obstruction) only the latter two are of major physiologic consequence. The outflow obstruction usually occurs in the subvalvar region (infundibulum), but may be at the level of the valve or in the pulmonary arteries. Cyanosis varies with the degree of outflow tract obstruction and the size of the ventricular septal defect. This lesion is often accompanied by hypercyanotic episodes (Tet spells) which occur when systemic vascular resistance drops or right ventricular outflow obstruction increases. Right to left shunting through the ventricular septal defect causes cyanosis. Infundibular spasm is thought to play a role in initiation of Tet spells. Early repair is favored over palliation unless birth weight is low or if the patient's condition is suboptimal. At surgery, the ventricular septal defect is closed with a patch, and any obstructing right ventricular muscle is removed. All other sites of outflow tract obstruction, including the valve and pulmonary arteries must also be addressed.
Transposition of the Great Arteries is the most common cyanotic condition that requires hospitalization in the first two weeks of life.4 Anatomically, the aorta arises from the right ventricle and carriers deoxygenated blood to the systemic vasculature. The pulmonary artery arises from the left ventricular and carries oxygenated blood to the lungs. The only possibility for survival is to allow the two parallel circuits to mix. This is accomplished initially by augmenting ductal flow with PGE1. The interatrial septum may be opened by balloon septostomy to further improve intracardiac mixing, and the patient is allowed to stabilize for a short period of time prior to definitive surgical correction. Although a number of repairs have been utilized for transposition, the most effective one is the arterial switch procedure. At surgery, the aorta and pulmonary artery are removed from their respective ventricles, and reattached to the correct ventricles. The coronary arteries are transferred separately to the newly reconstructed aorta. The procedure is technically challenging, but the results are gratifying. Experienced centers enjoy a 90-95% survival rate.4
Truncus arteriosus is a condition in which only one artery (the truncus) originates from the heart, supplying both the aorta and pulmonary artery. A ventricular septal defect is present just below the truncal valve which allows mixing of right and left ventricular blood. The degree of cyanosis is variable and depends on the pulmonary vascular resistance; and signs of progressive heart failure are prominent. Despite early medical management for heart failure (digoxin, diuretics), most patients require surgical repair at 2 to 3 months of age. At surgery, the ventricular septal defect is closed, and the pulmonary artery trunk is separated from the truncus. Continuity is then established between the right ventricle and the pulmonary artery utilizing a valved homograft conduit. This procedure restores the normal cardiac anatomy with greater than 90% survival.5 However, late complications can occur. The homograft valve may degenerate and calcify, becoming partially obstructive. The conduit may also become obstructed. The patient may outgrow the repair, thus requiring one or more repeat operations later in life.5
Tricuspid atresia occurs when the tricuspid valve fails to develop and there is no connection between right atrium and right ventricle. Desaturated venous blood returning to the right atrium must therefore cross though the patent foramen ovale to the left atrium and ventricle. The right ventricle is often hypoplastic, and therefore unusable in any subsequent repair. The philosophy of repairing tricuspid atresia and other "functional single ventricle" defects is to utilize the developed ventricle solely for systemic arterial flow, allowing venous return to flow passively to the lungs without the aid of a pumping chamber. The superior and inferior vena cavae are connected directly to the pulmonary arteries. Pulmonary blood flow is dependent upon very low pulmonary vascular resistance and is driven by elevated central venous pressure. Thus, these procedures cannot be performed in the neonatal period because the pulmonary vascular resistance is elevated. Initially, a systemic to pulmonary arterial shunt is required to increase pulmonary blood flow. Several months later, a superior caval to pulmonary artery connection (Glenn shunt) is performed and the initial shunt is ligated. The inferior caval connection may be done 12 to 18 months later (completion Fontan). Staging has helped to reduce morbidity and mortality in high-risk patients.6
With total anomalous pulmonary venous return the pulmonary veins are not attached to the left atrium, but converge in a common confluence just posterior to that atrium. This confluence drains into a systemic vein, or veins which may be obstructed. Obstruction to pulmonary venous flow causes pulmonary edema and decreased pulmonary arterial flow, resulting in cyanosis. These children are often extremely ill, with profound desaturation and acidosis. PGE1 administration does not improve oxygenation in this case because elevated pulmonary pressures in the right side of the heart (due to obstructed pulmonary outflow) will result in right to left shunting across an open ductus further decreasing arterial saturation. The only treatment for this condition is expeditious surgery. A surgical connection is made between the pulmonary venous confluence and the left atrium. The anomalous connection to the systemic venous circulation is then ligated. Mortality rates can be as high as 20% because of the critical condition of the children, but most patients do well.7
Pulmonary atresia is among the least common of the cyanotic congenital heart defects. Anatomically, there is no communication between the right ventricle and the pulmonary arteries, and abnormalities of the right ventricle and coronary arteries are common. Infants born with pulmonary atresia are dependent on the ductal arteriosus for pulmonary blood flow and therefore ductal patency must be maintained by PGE1. Right ventricular pressures may be systemic if a large VSD is present, or supra-systemic with severe tricuspid regurgitation if no VSD is present. In some of these latter cases, right ventricular to coronary artery fistulae develop.
Early surgical intervention in neonates with pulmonary atresia is indicated in all cases. The goals of surgical intervention are to enhance pulmonary blood flow and promote right ventricular growth in cases of relative hypoplasia. The initial approach is palliative. In patients with a large ventricular septal defect and well-developed right ventricle, a systemic to pulmonary arterial shunt is usually sufficient. For those patients with a poorly developed right ventricle (and small or absent septal defect), restoring the pulmonary artery connection can decompress the high-pressure right ventricle, enhance its development, and minimize coronary fistulae. A shunt is also performed to further improve pulmonary blood flow. In these conditions, further reconstruction is usually required later in infancy. Survival is variable in this morphologically diverse group and depends largely on the favorability of the anatomy.
Cyanotic heart disease commonly presents in the neonatal period. Rapid diagnosis and referral are mandatory because patients can become unstable very quickly. Prostaglandin E1 promotes blood flow through the ductus arteriosus and is a useful stabilizing maneuver in many, but not all, of these conditions. Echocardiography and cardiac catheterization are the diagnostic tools of choice and early surgical intervention is often required, either for palliation or for definitive correction. Current surgical therapy for most lesions has evolved from early palliation and delayed repair to complete correction in early infancy with improved morbidity and mortality.
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