Congenital cardiovascular disease occurs in about 1% of live births (excluding bicuspid aortic valve and hemodynamically insignificant lesions, such as very small secundum atrial and muscular ventricular septal defects). Congenital cardiovascular disease is considered to be critical if it will predictably result in death or severe morbidity if unrecognized and not treated in early infancy. These conditions often depend on patency of the ductus arteriosus to maintain either pulmonary or systemic blood flow. Signs of severe cyanosis or progressive heart failure leading to cardiovascular collapse develop as the ductus arteriosus constricts during the first few days or weeks after birth. It is important to recognize that a newborn with critical congenital cardiovascular disease may show little evidence of cardiovascular compromise on physical examination in the first 24 to 48 hours of life. Cardiovascular instability may not occur until after the infant is discharged from the hospital. The recent addition of routine pulse oximetry screening in many hospitals should greatly enhance our ability to diagnose such infants before discharge and thus decrease the number who present critically ill in the days and weeks after discharge.
The National Vital Statistic Report reported 3,932,181 registered births in the United States in 2013, which means that about 40,000 infants were born with heart defects. Of the 25% to 30% of infants with heart defects, at least 10,000 are predicted to have critical disease. Diagnosis before the onset of cardiovascular decompensation is essential for optimal outcome. In the absence of detection during fetal life by ultrasound examination or pulse oximetry screening after birth, about 70% of infants with critical congenital cardiovascular disease are not diagnosed before 2 days of age. This leads to severe morbidity and mortality in many hundreds of newborns each year in the United States alone, at a large social and economic cost. Thus, it is incumbent on all physicians and other health care professionals who care for newborns to rigorously evaluate every newborn for the possibility of critical cardiovascular disease. Furthermore, if there is any indication that such disease might exist, the infant must be referred for further evaluation without delay.
The evaluation of the infant for critical cardiovascular disease should focus on the three cardinal signs of neonatal cardiovascular distress: cyanosis, decreased systemic perfusion, and tachypnea. Cyanosis may be appreciated by careful visual inspection and pulse oximetry, decreased systemic perfusion is identified by examination of the extremities, and tachypnea is noted by observing the respiratory rate and pattern. The presence of a congenital cardiovascular defect (or, less commonly, a cardiomyopathy or arrhythmia) must be considered in the differential diagnosis of any infant with one or more of these findings. A cyanotic infant most likely has underlying cardiovascular disease and almost certainly does in the absence of significant respiratory distress. An infant with decreased systemic perfusion may be septic or have a primary metabolic abnormality, but about one-half of such infants have symptomatic cardiovascular disease. An infant who has tachypnea without either cyanosis or decreased perfusion most often has primary parenchymal or extraparenchymal lung disease but could also have cardiovascular disease associated with excessive pulmonary blood flow. The respiratory symptoms are often subtle and develop slowly, and there may be only mild distress so that the most notable manifestation may not be the respiratory distress but, rather, poor weight gain, particularly after a few weeks of life. A thoughtful and rational approach to the differential diagnosis of all three of these signs is important for prompt recognition and appropriate management. Moreover, the clinician must be cognizant of the fact that the transition from a fetal to a mature postnatal circulation occurs not immediately but rather over the first several days or weeks of life so that serial evaluations are necessary, each as rigorous as the first.
Each cardinal sign of neonatal cardiovascular disease can be attributed to one of at least two pathophysiologic causes:
Cyanosis
Decreased pulmonary blood flow
Normal to increased pulmonary blood flow but with a transposed aorta; for example, d-transposition of the great arteries
Decreased systemic perfusion
Obstruction of the left heart (inflow or outflow)
Cardiac dysfunction without obstruction (primary cardiomyopathy or secondary dysfunction)
Tachypnea/poor weight gain (due to excessive pulmonary blood flow)
Exclusive left-to-right shunt
Dominant left-to-right shunt with a lesser right-to-left shunt
The cardiac defects in each hemodynamic category are discussed in Chapters 6 (cyanosis), 7 (excessive pulmonary blood flow), and 8 (decreased systemic perfusion). This chapter will describe the general approach to the cardiovascular evaluation of the newborn, including history, physical examination, and ancillary tests. The information obtained from each step of the evaluation should follow a logical progression, from recognizing the primary sign to defining the underlying pathophysiologic process and eventually to determining the specific diagnosis. The latter is rarely important at the initial evaluation. Understanding the pathophysiologic process allows effective initiation of therapy and stabilization of the patient. The specific diagnosis is usually important only to implement the definitive therapeutic plan.
From these considerations, a focused and rational approach to the newborn with symptomatic congenital cardiovascular disease can be developed. Admittedly, this approach is imperfect; some lesions are complex with overlapping manifestations (eg, an infant with hypoplastic left heart syndrome who has decreased systemic perfusion may also be tachypneic and mildly cyanotic). However, even in the most complex cases, one of the major signs usually predominates and provides a clue to the most likely category of disease. The concepts described in this and other chapters emphasize the importance of a simple, clear, logical, and stepwise approach to the evaluation and treatment of each infant with cardiovascular disease.
The prenatal evaluation of the newborn for congenital cardiovascular disease is reviewed in Chapter 4, including the evaluation of the fetus with a family history of congenital cardiovascular disease or a genetic syndrome that is associated with cardiovascular disease. If the perinatal history is completely benign (eg, no history of perinatal asphyxia), it is more likely that a problem causing symptoms in a neonate is cardiac in origin.
Cyanosis is caused by either congenital cardiovascular disease, pulmonary hypertension of the newborn, or intra- or extraparenchymal lung disease. The primary differential diagnosis of congenital cardiovascular disease is persistent pulmonary hypertension of the newborn. Persistent pulmonary hypertension must be excluded when a diagnosis of congenital heart disease is being considered. Infants with either of these conditions often have mild or moderate respiratory distress. In contrast, cyanotic infants with primary parenchymal lung disease usually have severe respiratory distress requiring mechanical ventilation and have a chest radiograph showing abnormal lung parenchyma. The infant with persistent pulmonary hypertension, however, often has a perinatal history of birth asphyxia, with or without meconium aspiration. Additionally, the infant may be small for gestational age, or the mother may have taken nonsteroidal anti-inflammatory medications over the weeks before birth, which can cause intrauterine constriction of the ductus arteriosus and subsequent pulmonary hypertension.
The infant with cyanotic cardiovascular disease typically has a benign birth history with a normal or nearly normal Apgar score. The ductus arteriosus usually maintains adequate blood flow and mixing immediately after birth, and cyanosis is not readily apparent. It may not be until hours or days after birth that the infant becomes cyanotic, frequently during feeding or crying. The increased physical effort associated with feeding or crying increases oxygen consumption and decreases pulmonary blood flow, accentuating the cyanosis. Despite the presence of cyanosis, respiratory distress is typically not part of the history. The chemoreceptor response to hypoxemia is intact so that mild tachypnea often occurs but respiratory distress (eg, retractions, nasal flaring, grunting) is usually absent because ventilation is normal. Use of pulse oximetry screening should allow recognition of nearly all infants with cyanotic cardiovascular disease who do not show visible cyanosis.
At times when a newborn infant cries, a transient increase in right atrial pressure occurs and results in a small right-to-left shunt through the foramen ovale, causing the infant to appear dusky. This transient desaturation must be distinguished from infants with cyanotic cardiovascular disease who may also appear dusky initially only with crying or feeding. Although not apparently cyanotic at rest, infants with cyanotic congenital cardiovascular disease show some degree of oxygen desaturation by pulse oximetry at all times, whereas the normal newborn infant has normal oxygen saturation at rest. This is important to appreciate during pulse oximetry screening, which should be repeated when an infant is quiet if an abnormal value is obtained when the infant is crying.
The differential diagnosis of decreased systemic perfusion includes obstructive cardiovascular lesions and myocardial dysfunction from sepsis, hematological abnormalities (anemia and polycythemia), or endocrine/metabolic disorders, such as hypocalcemia, hypoglycemia, and metabolic acidosis. Neonatal sepsis is common, especially in the setting of prolonged rupture of the membranes. Hematological abnormalities are associated with placenta abruptio, twin-to-twin transfusion, placental insufficiency, postterm delivery, or small-for-gestational age infants. A positive family history is often present in newborns with endocrine/metabolic diseases. Newborns with obstructive cardiovascular disease rarely have a positive perinatal history. These infants typically are stable during the first hours of life, but eventually develop poor feeding, pallor, diaphoresis, and tachypnea with respiratory distress. This may occur as late as 3 to 4 weeks after birth, so it is extremely important for every infant to be carefully assessed at the time of discharge and at subsequent visits during the first month of life. Subtle findings of irritability, pallor, poor feeding, or diaphoresis may reflect inadequate systemic perfusion. Particularly concerning is that many of these infants may “pass” the pulse oximetry screen, unless right-to-left shunting of desaturated blood to the lower body via the ductus arteriosus is present and lower body pulse oximetry is included a part of the screening. Tachypnea is often a subtle finding that develops over days or weeks, as pulmonary vascular resistance and hemoglobin concentration decline during the first 6 weeks of life. Although some patients show dramatic shunting and respiratory symptoms in the first few days of life (particularly those with trisomy 21), tachypnea during this time period, in the absence of signs of cyanosis or decreased systemic perfusion, often points to pulmonary disease rather than cardiovascular disease. Parents rarely appreciate that an infant is breathing more rapidly than normal. Poor feeding with associated failure to thrive and diaphoresis is common; murmurs may be absent. Thus, an infant with unexplained failure to thrive, particularly in association with tachypnea and diaphoresis, should be evaluated for possible congenital cardiovascular disease. Many of these infants “pass” pulse oximetry screening, supporting the approach that the clinician must evaluate every infant over the first weeks of life for congenital cardiovascular disease at each encounter and not rely on the newborn evaluation only.
A family history of congenital cardiovascular defects or cardiomyopathy is relevant to the outcome of the fetus, as a positive family history increases the risk for subsequent children. Genetic abnormalities are increasingly recognized to contribute to congenital cardiovascular disease and are discussed in Chapter 15.
Pulse oximetry screening for all newborn infants is accepted and has been implemented widely. In 2010, the US Health and Human Services Secretary’s Advisory Committee on Heritable Disorders in Newborns and Children recommended universal screening, and a working group selected from that committee as well as the American Academy of Pediatrics, the American College of Cardiology, and the American Heart Association published a joint document outlining how pulse oximetry screening should be performed. As of May 2016, only five states have neither active nor pending legislation or regulations mandating universal screening (Figure 5-1). Unfortunately, screening is not yet mandated in Canada, and only four European countries (Switzerland, Ireland, Poland, and Norway) have national recommendations to screen. Despite this, many hospitals in Canada and European countries have instituted screening, and a recent study has shown it to be nearly universal throughout the Nordic countries.
FIGURE 5-1.
Status of pulse oximetry screening for critical congenital heart disease in the United States. As of May 2, 2016 legislation has been fully enacted in 40 states and the District of Columbia, and in only three states has no action been taken. Image extracted from https://www.aap.org/en-us/ advocacy-and-policy/state-advocacy/Documents/2016%20CCHD%20Newborn%20Screening%20 Bills,%20Regulations,%20and%20Executive%20Orders%20-%20AAP%20Division%20of%20State%20Govt%20Affairs.pdf
The physical examination should be performed systematically (Ch5An1). Each step determines if the infant falls into a specific mode of presentation (cyanosis, decreased systemic perfusion, or excessive pulmonary blood flow) and, once defined, into a specific hemodynamic category. Ancillary tests assist in establishing specific diagnoses and defining the most appropriate therapy for each infant.
The general examination includes vital signs and observation of the unclothed and warm infant. The vital signs of temperature, heart rate, respiratory rate, and blood pressure are measured in conjunction with respiratory status, perfusion, and color. We consider that pulse oximetry is also a vital sign in the infant, not just to be performed as part of the initial screen but also to be included in any evaluation during the transitional circulatory period. Weight, length, and head circumference are measured and plotted on growth charts to aid in identifying growth impairment. Any postnatal decrease in weight percentiles compared to length and head circumference should raise the possibility of cardiovascular disease. This is of particular importance in lesions of excessive pulmonary blood flow—the other signs of cyanosis and hypoperfusion are not present, and there may be no murmurs or discernible respiratory distress.
The first sign to assess on general observation is cyanosis. Peripheral cyanosis (acrocyanosis) is common in newborn infants and reflects their normally unstable peripheral vasomotor tone. Central cyanosis, which is indicative of arterial oxygen desaturation, is the important sign to recognize. Thus, vascular beds with little vasoconstrictor tone, such as the tongue, gums, and the buccal mucosa, should be evaluated (not the hands, feet, or perioral region). It is also important to evaluate the patient during conditions such as feeding or crying, which are most likely to produce central cyanosis. Cyanosis is difficult to perceive until arterial oxygen saturation is less than about 85%, and the physiologic decrease in hemoglobin concentration in infants 4 to 12 weeks of age makes detecting cyanosis more difficult. Thus, oxygen saturation should be measured if there is any question of cyanosis. Measuring oxygen saturation simultaneously in the right hand and a lower extremity by use of two pulse oximeters is necessary to evaluate whether the upper and lower bodies are perfused, at least partially, by different ventricles. A difference in oxygen saturation of only 3% to 5% may be significant, but most oximeters are accurate only to within ±2% to 3%. For this reason, it may be helpful to reverse the probes to ensure that any difference (or absence of a difference) is real and not just related to inherent variations in the probes or oximeters. Less commonly, it may be necessary to measure the oxygen saturation in an earlobe if aortic arch and arch vessel anomalies are suspected (Chapter 6).
Next, the respiratory status should be carefully evaluated. Infants who have isolated cyanosis are usually tachypneic but do not otherwise exhibit increased work of breathing. In contrast, the increased pulmonary venous pressures and pulmonary edema seen in patients with hypoperfusion cause respiratory distress in addition to tachypnea. In that case, variable intercostal and/or subcostal retractions, nasal flaring, and grunting may be observed.
Signs of decreased systemic perfusion, including the temperature and color of the skin, blood pressure, peripheral pulses, and capillary refill in each extremity, should be assessed next. Lower extremity pulses are more easily palpated in the feet than in the inguinal area. If the infant has a normal dorsalis pedis or posterior tibial pulse, then pulsatile blood flow to the lower extremity is not impaired. Blood pressure should be measured in the upper and lower extremities; normally, the lower extremity blood pressure is slightly greater than that in the upper extremity. The left subclavian artery arises from the aortic isthmus and may be involved in a coarctation. Thus, the systolic pressures in the right arm and either leg should be measured simultaneously. If the pulses are decreased and no blood pressure differential is detected, the carotid arteries should be palpated. If they are increased, the infant may have a coarctation or interruption of the aorta in the presence of a right subclavian artery arising anomalously from the descending aorta.
The periphery, head, and neck should be examined for dysmorphic features of syndromes associated with cardiovascular disease, such as Down syndrome, 22q11 deletion (DiGeorge) syndrome, Turner syndrome, Noonan syndrome, Williams syndrome, and trisomy 21 (Chapter 15).
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