Congenital Heart Disease in the Pediatric Emergency Department: Part I
Congenital Heart Disease in the Pediatric Emergency Department
Part I: Pathophysiology and Clinical Characteristics
Authors: Dale P. Woolridge, MD, PhD, Department of Pediatrics/ Division of Emergency Medicine, Department of Surgery, University of Maryland Medicine, Baltimore; Jon C. Love, MD, Assistant Professor, Division of Pediatric Cardiology, Department of Pediatrics, University of Maryland Medicine, Baltimore.
Peer Reviewer: Perline Ramalanjaona, MD, MA, FAAP, Attending Physician, Department of Pediatrics, Wyckoff Hospital, Brooklyn, NY.
Patients with congenital heart disease (CHD) frequently are seen in the emergency department (ED). Most often these patients have exacerbations or complications related to previously diagnosed disease or from corrective surgeries. Chief complaints are varied and can be related to routine childhood illnesses or problems that stem directly from their specific heart defects. To adequately treat these patients, the emergency physician must have a basic understanding of each child’s specific cardiac lesion and pathophysiology.
In addition, despite improved technology and clinical awareness, there are still children who present to the ED with undiagnosed cardiac disease. The clinical presentation of these conditions will vary based on the physiology of the cardiac defect and the degree of decompensation. More often, infants present less emergently with a suspicious murmur, growth failure, feeding intolerance, or recurrent URIs. For these reasons, having a basic knowledge of the pathophysiology of CHD is necessary to recognize and initiate adequate treatment, prior to a critical decompensation. Obtaining a specific diagnosis is not always possible, and frankly, not necessary in the ED. Invariably, the definitive diagnosis is made after admission.
Congenital heart disease (and the issues surrounding it) is a rather extensive topic. For this reason, the topic will be presented in two parts. Part I will start by outlining the pathophysiology behind the more common congenital heart defects. The evaluation of these patients, including key points in the history, specific physical findings, and ancillary testing will be discussed. Part II will focus on likely presenting conditions and suggested methods of treatment. The focus of this article is to provide the ED physician with the adequate tools to correctly diagnosis and treat CHD in the ED.— The Editor
Introduction
As with any patient, the evaluation of children with CHD remains a stepwise process that requires an adequate understanding of the child’s underlying pathophysiology and a logical approach to the diagnostic evaluation based on clues from history, physical examination, imaging, and laboratory testing. Key diagnostic features may include the presence of cyanosis and its response to oxygen, the quality of peripheral perfusion, precordial auscultation, and palpation. Additional studies should include chest radiography to evaluate pulmonary markings and characteristics of the cardiac silhouette, electrocardiogram (ECG) features, and an upper/lower extremity blood pressure gradient.
In Part I, the fetal circulation will be reviewed, along with circulatory changes that occur after birth. The pathophysiology of common congenital cardiac defects will be discussed. Subsequent focus will be placed on key features of the history, physical, and ancillary tests used in the evaluation. Clinical findings common to each cardiac defect will be discussed, along with a stepwise approach that can be used to narrow the differential diagnosis.
Circulatory Changes in the Newborn
To adequately evaluate children with suspected CHD, emergency physicians must have an understanding of the changes in the circulatory system that take place after birth. This topic has been reviewed extensively in the literature and will be discussed only briefly here. The fundamental feature unique to the fetal circulation is that oxygenation takes place in the placenta, as opposed to the lungs. The circulatory changes that occur at birth culminate in the redirection of blood to the lungs for oxygenation and the elimination of shunting between the pulmonary and systemic circulations. There are three cardiovascular features unique to the fetal circulation that are involved in this circulation transition: the ductus venosus, ductus arteriosus, and the foramen ovale.
In the fetal circulation, oxygenated blood leaves the placenta by the umbilical vein. Most of this blood flow bypasses the liver through the ductus venosus and returns to the heart through the inferior vena cava. Blood returning from the inferior vena cava enters the right atrium and preferentially is shunted across the foramen ovale to the left atrium. From the left atrium, blood crosses the mitral valve and is pumped to the ascending aorta by the left ventricle. This blood, which has a relatively high oxygen saturation, is directed to the cerebral and coronary arteries. Conversely, desaturated blood that returns from the superior vena cava and enters the right atrium primarily is directed across the tricuspid valve into the right ventricle and out the pulmonary artery. Due to the absence of alveolar oxygen, the pulmonary vascular resistance (PVR) is high, which results in the majority of pulmonary artery flow being directed across the ductus arteriosus into the descending aorta. Thus, the fetal upper extremities (including the cerebral and coronary vessels) are perfused with blood that has a higher oxygen saturation than that of the fetal lower extremities. Blood from the descending aorta is then returned to the placenta via the umbilical arteries.
Passage through the birth canal and expansion of the lungs following delivery results in the expulsion of fluid from the lungs and aeration of the lungs. This, in turn, causes dilation of the pulmonary vasculature, decreased pulmonary resistance and improved pulmonary blood flow. With improved oxygenation, the umbilical arteries, vein, ductus arteriosus, and ductus venosus begin to contract within minutes. The combination of increased systemic resistance, by the removal of the placenta from the systemic circulation (resulting in an increased left atrial pressure), and decreased pulmonary artery resistance (causing decreased right atrial pressure), results in a switch in the flow and pressure gradient across the foramen ovale. This forces the foramen ovale to close by pressing the septum primum against the septum secundum. These changes culminate in the circulatory system adults have: two separate right and left circuits that work in series.
Following delivery, fetal ductal structures gradually will close completely. The foramen ovale usually becomes permanently closed as long as left atrial pressures are greater than right atrial pressures. Another feature of physiologic significance during this transition is the change in PVR. Typically there is a significant drop in PVR within the first 72 hours after delivery. Only a minor decrease occurs during the subsequent 2-3 weeks. In the presence of abnormal hemodynamics often found with CHD, PVR may decrease more gradually during the first 4-6 weeks of life.
Pathophysiology
Understanding CHD can be a difficult undertaking. To assist the reader, a list of abbreviations that are used throughout this article is shown in Table 1. Multiple organizational schemes have been used to make discussions on CHD easier. One commonly used scheme organizes each lesion based on its respective physiology. Initially, two broad categories exist: acyanotic and cyanotic lesions. Acyanotic lesions generally can be described as those that result in left-to-right shunts and those with left ventricular outflow obstruction. The classic mnemonic "the five Ts" is helpful in understanding cyanotic lesions. The five Ts are: tetralogy of Fallot (TOF), transposition of the great arteries (TGA), truncus arteriosus (TA), total anomalous pulmonary venous return (TAPVR), and tricuspid valve abnormalities. These cyanotic lesions can be divided further into lesions with increased pulmonary blood flow and lesions with decreased pulmonary blood flow. When learning these groupings, one must keep in mind that not all lesions will fit neatly into a single category. Some complex congenital heart defects have mixed effects.
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Acyanotic CHD
Left-to-Right Shunt Lesions. The most common isolated left-to-right shunt lesions include ventricular septal defects (VSD), atrial septal defects (ASD), patent ductus arteriosus (PDA), and endocardial cushion defects (ECD). These account for approximately 40-50% of all CHDs.1 As the name implies, these lesions result in blood shunting from the systemic circulation (left heart and aorta) into the pulmonary circulation. Thus, there is an excess of pulmonary blood flow and pressure. High PVR will limit the volume shunted during the newborn period. At 2-6 weeks of life, PVR drops sufficiently to permit further shunting. The size and type of the defect, as well as the amount of flow through it, also will cause a pressure overload in one or more chambers of the heart. Small defects often are inconsequential and will result in little hemodynamic change in the short term, whereas large defects result in increased pulmonary vascular flow, left or right heart enlargement, and elevated pulmonary artery pressures. Over time, the patient will develop progressive dyspnea and feeding problems as a precursor to the other signs or symptoms of congestive heart failure (CHF). If not corrected, the transmission of increased flow and pressure can result in chronic pulmonary vascular obstructive disease (Eisenmenger syndrome) later in life.2
Eisenmenger syndrome is a condition that can occur in any large left-to-right shunt lesion that is not corrected. Long-standing pulmonary hypertension results in a progressive and irreversible pulmonary vascular obstruction. As obstruction increases, PVR eventually will exceed systemic vascular resistance. When this occurs, the shunt will reverse, resulting in a right-to-left shunt. This will be manifested by the development of cyanosis. Other clinical features of patients who have developed Eisenmenger syndrome include chest pain, dyspnea on exertion, and hemoptysis.2
ASDs account for approximately 5-10% of CHDs.3 The different types of ASDs are categorized based on the portion of the atrial septum that is deficient. Simply stated, all of these lesions result in a communication between the left and right atria. Most of these defects are asymptomatic, and patients present for medical attention between 3 and 5 years of age as a suspicious murmur noted on routine physical exam.4 Fewer than 10% of these patients will develop complications in infancy.5 As with all isolated left-to-right shunt lesions, hemodynamic significance is based on the degree of shunting. Lesions that are more likely to present early are those in which the shunt volume is large, there is an associated defect such as in the atrioventricular valves or patients with a comorbid condition such as bronchopulmonary dysplasia. Presenting symptoms usually are those of pulmonary overcirculation: feeding intolerance, poor weight gain, and pulmonary edema. These patients also are more prone to lower respiratory tract infections (LRI). The ostium secundum type defect is the only type of ASD that may spontaneously close. Approximately 85% of these will close by the time the child is 4 years of age.6 For large defects that do not close or are not expected to close, recommended treatment is surgical closure at 2-4 years of age.7 If left untreated, large ASDs result in eventual right ventricular enlargement and the development of Eisenmenger syndrome.
VSDs are the most common type of CHD and account for approximately 20-25% of cases.8 Various forms exist and are categorized based on the component of the septum that is defective. All result in a functional communication between the ventricles that allows shunting to occur. Muscular and perimembranous VSDs may close spontaneously, with the former having the highest rate of spontaneous closure.9 Inlet and malalignment VSDs will not close spontaneously. The inlet form is located just inferior to the AV valves and is a type of ECD. Supracristal VSDs are located just inferior to the aortic valve and may be associated with aortic prolapse. These may close spontaneously, but closure typically is due to a prolapse of the aortic valve within the defect. This often leads to damage to the valve and progressive valvular insufficiency. The clinical manifestations of VSDs depend primarily on the size (and hence the degree of shunting) of the lesion. For patients with large VSDs, bi-ventricular hypertrophy and pulmonary hypertension will develop over time.
A PDA is due to a failed closure of the ductus arteriosus. This abnormality accounts for approximately 10% of CHDs.1 A PDA is much more prevalent in premature infants and also is more prevalent in children living at high altitudes. PDAs occur in 45% of infants weighing fewer than 1750 g at birth and in 80% of infants weighing fewer than 1200 g at birth.10 As with most other left-to-right shunts, the degree of symptoms is based on the amount of shunting. Preterm infants are much more likely to be symptomatic and present with symptoms of CHF. Full-term infants are less likely to be symptomatic, but those with large and/or short PDAs also may present with CHF.
ECDs are a category of defects that result from the abnormal development of the endocardial cushion. Collectively, these account for approximately 5% of CHDs.1 ECDs are divided into incomplete or complete defects. The complete defect is when there is abnormal development of the entire endocardial cushion. This results in a primum ASD contiguous with an inlet VSD and a single common AV valve that often has a cleft in one of the left-sided leaflets. The incomplete form of ECDs can result from isolated abnormalities in any of the areas noted above. As with all left-to-right shunt lesions, the clinical manifestations of these defects are dependent on the degree of shunting. Clinically, ECDs act very similar to large VSDs, where the patient develops progressive pulmonary hypertension and, eventually, CHF.
Left Heart Obstruction. Left heart obstructive lesions account for as many as 15% of CHD cases.11 These lesions result in impaired left ventricular output. The most common are coarctation of the aorta (CoA), aortic/subaortic stenosis (AS), and hypoplastic left heart syndrome (HLHS). Depending on the degree of outflow obstruction, patients may be asymptomatic at the time of diagnosis or present to the ED in shock.12
Coarctation of the Aorta. CoA is a congenital narrowing of the aorta and accounts for up to 8% of CHD cases.13 The most common site is at the insertion of the ductus arteriosus, but lesions proximal and distal to this also are seen. The severity of symptoms is based on the degree of narrowing, the length of narrowing, and the presence of associated cardiac defects. Patients with high degrees of obstruction tend to present as neonates (1-3 weeks of life).14 The delayed onset of symptoms is due to a temporizing effect of the PDA in its ability to alleviate obstructive effects of the coarctation and/or maintain flow to the body distal to the obstruction (in cases of pre-ductal narrowing). As the PDA closes, progressive pulmonary hypertension and pulmonary venous congestion ensues. These patients will develop symptoms of CHF, as well as tachypnea and poor feeding, which may progress to cardiogenic shock. If the obstruction is severe, symptoms secondary to hypoperfusion of the kidneys and GI tract may be present, along with a metabolic acidosis. Those with mild obstruction tend to be less severe and present later in childhood. Many CoA defects are asymptomatic and are diagnosed upon referral to a pediatric cardiologist. Causes for referral include evaluation of a heart murmur (50%), hypertension (16%), or to evaluate for CoA (4%).15 Adolescent patients are more likely to be diagnosed during an evaluation of hypertension.16
Aortic Stenosis. AS accounts for approximately 6% of children with CHD.11 The age at which these patients become symptomatic, as with coarctation, is dependent on the severity of obstruction. Those with more severe obstruction (~10-15%) may present in infancy with symptoms of CHF or a harsh systolic ejection murmur.17 Critical obstruction will present similar to patients with critical coarctation or HLHS. Older patients may be asymptomatic and present secondary to a suspicious murmur or have a progressive exercise intolerance or syncope.
Hypoplastic Left Heart Syndrome. HLHS is a severe form of CHD in which patients present early in the neonatal period with symptoms of cardiogenic shock. This defect is lethal, and without treatment, patients will die within the first month of life.18 In this form of CHD, the mitral valve, aortic valve, or proximal aortic arch partially or completely fail to form, resulting in a left ventricle that is hypoplastic. This leads to severely diminished left ventricular outflow. The systemic blood supply is, therefore, derived entirely from blood shunting across the ductus arteriosus, making this form of CHD absolutely ductal dependent. Since there is no forward flow beyond the left ventricle, an ASD is absolutely necessary to decompress the left atrium. In addition, a high PVR is needed to maintain adequate systemic perfusion. Most patients with this defect are diagnosed prenatally by fetal ultrasound. Following delivery, infants may appear normal during the first couple days of life.19 This is due to the patency of the ductus arteriosus and the high PVR at this stage in life. As PVR falls, increased pulmonary perfusion and decreased flow across the PDA results in respiratory distress, CHF, and metabolic acidosis. Likewise, the PDA naturally will begin to constrict, which also causes decreased systemic blood flow. Patients who present after two days of life owe their delayed symptoms solely to delayed closure of the PDA.
Cyanotic Congenital Heart Disease
The other major category of heart defects is cyanotic CHDs. These defects, due to the nature of the lesion, create a generalized (central) cyanosis in the patient. The cyanosis is either secondary to inadequate pulmonary blood flow to the lungs and/or desaturated blood shunting directly to the systemic circulation. Physiologically, these are best separated into those defects with decreased pulmonary blood flow and those with increased pulmonary blood flow. This distinction serves as a means to understand the pathophysiology of these disorders. Lesions with decreased pulmonary blood flow have in common an obstruction to right ventricular outflow: TOF, pulmonary atresia (PA) (with or without a VSD), and critical pulmonary valve stenosis. Lesions with increased pulmonary blood flow include: TGA, TA, and TAPVR. Tricuspid atresia (TriA) may present with either increased or decreased pulmonary blood flow depending on the presence and size of the VSD, which typically is associated with the defect. In the majority of these cyanotic lesions, the presence of an adequate atrial defect is critical in the stability of these patients.
Understanding the physiology of cyanosis is essential to adequately understanding cyanotic heart disease. Cyanosis is a clinical sign caused by the presence of desaturated blood in the capillary beds. On inspection, the skin, mucous membranes, conjunctiva, and/or nail beds appear blue. Oxyhemoglobin is seen as red, and deoxyhemoglobin is seen as blue. The blue coloration is evident when there is an increased amount of deoxygenated hemoglobin in the capillary beds. The presence of cyanosis usually means there is at least 4 mg/dL of deoxyhemoglobin in the blood. This typically correlates to an oxygen saturation of 80-85%.20 It should be understood that, since the presence of cyanosis is based on the absolute amount of deoxyhemoglobin, it is by no means directly reflective of the percent oxygen saturation of hemoglobin. For example, the polycythemic patient will attain 4 mg/dL of deoxyhemoglobin at a higher percent saturation (PaO2) than does the anemic patient. Therefore, cyanosis in an anemic patient is a more ominous finding. Fortunately, most newborns naturally are polycythemic. Another key point to keep in mind is that cyanosis is a relatively good indicator of low pO2, but its absence does not rule out a low pO2.
Tetralogy of Fallot. TOF is the most common congenital heart defect seen beyond infancy.21 It arises from a single morphologic abnormality where the subpulmonary conus fails to expand normally. The result is a tetrad of right ventricular outflow obstruction, right ventricular hypertrophy, overriding aorta, and an unrestrictive, malaligned VSD. Collectively this results in decreased pulmonary blood flow due to right-to-left shunting across the VSD. Presentation of this defect is highly variable secondary to the variable degree of right heart obstruction present at birth.22 Patients with mild right heart obstruction may be acyanotic and rarely may develop signs of pulmonary overcirculation.23 Since the right heart obstruction is muscular and often dynamic, these patients can have episodes of cyanosis that are brought on by stress, crying, or routine immunizations.24 Patients with severe right heart obstruction will demonstrate cyanosis immediately after birth.
Tricuspid Atresia. TriA results in absent flow from the right atrium to the right ventricle through the tricuspid valve. This mandates a right-to-left atrial shunt to decompress the right atrium. Shunting at this site serves as the point where deoxygenated blood mixes with oxygenated blood. The physiologic consequence of this lesion is highly dependent on the presence of a VSD and/or degree of pulmonary stenosis. In the absence of a large VSD, there is limited flow into the right ventricle, and it will be hypoplastic. If a VSD is present and of adequate size, there will be adequate pulmonary flow that will increase as PVR decreases. In the absence of an adequate VSD, these patients will have limited pulmonary blood flow and may require persistence of the PDA. In many cases, the VSD or pulmonary stenosis can become restrictive with time and will be manifested by worsening cyanosis.
Hypoplastic Right Heart Syndrome. Hypoplastic right heart syndrome (HRHS) is seen in pulmonary valve atresia without a VSD. This is very similar to TriA in the absence of a large VSD. As the name implies, in the absence of blood flow through the right ventricle, there is inadequate development of this chamber. The result is a small ventricular cavity with hypertrophied walls. The most severe cases can develop coronary artery fistulas, which can lead to sudden death if associated with coronary stenosis. Hemodynamically, these lesions are ductal dependent for pulmonary blood flow and require right-to-left shunting across an ASD. Pulmonary valve atresia in the presence of a VSD has a similar presentation, but due to the VSD, is dependent on the presence of a PDA but not an atrial communication. The size of the right ventricle is an important determinant in patients with PA or TriA for surgical correction.
Transposition of the Great Arteries. TGA is one of the cyanotic heart defects with increased pulmonary blood flow. This lesion accounts for approximately 5% of CHDs.25 In its simplest form, the aorta arises from the right ventricle. Multiple forms and confounding factors exist, but in all cases, a distinct feature is that oxygen saturation in the main pulmonary artery is greater than oxygen saturation in the aorta. The functional switching of these great vessels results in the two sides of the heart no longer operating in series but in parallel. This orientation is incompatible with life. A VSD, ASD, or PDA is necessary to sustain life. Following birth, these patients have a progressive acidosis in the absence of adequate mixing of oxygenated and deoxygenated blood. As the PDA begins to close, cyanosis becomes obvious. For those patients with large VSDs, cyanosis may not be apparent until days or weeks later.
Truncus Arteriosus. TA is a relatively rare form of CHD accounting for fewer than 3% of cases.25 During embryogenesis, the TA and bulbis cordis divides to form the two great arteries. When this separation is incomplete, a single great vessel arises from the heart and gives rise to the aorta, pulmonary arteries, and coronary arteries. At the origin of this vessel lies a single fused semilunar valve, the truncal valve. This valve is stenotic in about 30% of cases and regurgitant in about 50% of cases.26 Subtypes are categorized based on the origin of the pulmonary arteries. In addition, a large VSD always will be present. This allows for additional bidirectional mixing and equilibrates the pressure between the ventricles. After birth, PVR naturally falls and shunting increases, resulting in progressive pulmonary overcirculation and pulmonary vascular congestion.
Total Anomalous Pulmonary Venous Return. TAPVR is a cyanotic CHD with increased pulmonary blood flow. Here, some (partial) or all (total) of the blood returning from the lungs is directed to the right side of the heart instead of the left atrium. This defect occurs early in embryology and can result in the pulmonary veins attaching to the superior vena cava, coronary sinus, portal vein, or any combination of the above.27 Since all systemic and venous blood that returns to the heart is via the right ventricle, there is volume overload, resulting in significant right ventricular and atrial enlargement. Left-sided heart structures often are normal. In order for left-sided heart filling to occur, an ASD must be present. This mixed oxygenated and deoxygenated blood that shunts across the ASD subsequently is pumped systemically by the left ventricle. Factors that add to the hemodynamic instability of these patients include restriction across the ASD, stenosed anomalous pulmonary veins, and diminished PVR.
Evaluating Congenital Heart Disease
The next section will discuss key features of the history, physical examination, and ancillary tests that may assist in the diagnosis of CHD. It must be kept in mind that, although certain findings are suggestive of an underlying heart defect, none are specific. In fact, other pathologic conditions that present similarly tend to be more common. Therefore, the astute emergency clinician should maintain a broad differential early in the evaluation process so as not to miss a cardiac diagnosis. One good example is the neonate who presents in respiratory distress. Although, this child is far more likely to have a primary pulmonary cause (Group B streptococcus pneumonia, transient tachypnea in the newborn), airway obstruction (choanal atresia, reactive airway disease), or respiratory compensation of a metabolic acidosis, it is important not to miss subtle presenting signs of CHD. Early identification of an undiagnosed cardiac defect may prevent the development of severe disease. Often, patients with cardiac defects initially will demonstrate nonspecific signs, such as a feeding intolerance or failure to thrive (FTT). The following section will illustrate key features of the history and physical examination that may suggest an underlying diagnosis of CHD.
History
Obtaining a complete history from the patient’s caregiver is essential. Common presenting complaints often are nonspecific and may include fussiness, tachypnea, inadequate weight gain, or feeding intolerance. Feeding for the infant is equivalent to exercise in adults. Where adults with heart disease will express an exertional intolerance, parents of children with heart disease sometimes will give obvious and sometimes vague clues suggesting a feeding intolerance. Questions regarding length of feedings, sweating during feeds, taking frequent breaks, and even refusal of feedings often are helpful. Any child who takes longer than 30 minutes per feeding should warrant suspicion.28 In fact, feeding intolerance often precedes overt CHF.29
Central Cyanosis
Determining the presence of cyanosis is essential to the evaluation of CHD. Two forms of cyanosis exist: central and peripheral. Differentiating between these can be difficult. Central cyanosis is a characteristic feature of CHD and is seen in approximately 30% of cases.30 Peripheral cyanosis, on the other hand, is not characteristic of CHD. A list of the potential causes of central cyanosis is shown in Table 2. These include primary pulmonary, airway, metabolic, and cardiac disease. Guardians should be questioned regarding the location of the cyanosis to differentiate between central and peripheral cyanosis. Precipitating factors (such as crying during feedings) also are important. Transient cyanosis associated with crying may suggest pulmonary disease or a cardiac defect allowing right-to-left shunting. Cyanosis improved with crying is more likely to suggest choanal atresia or pulmonary disease.
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The birth history should include gestational age at delivery (preterm infants are more likely to have a PDA or respiratory distress syndrome), maternal history (diabetes, drug use, rubella), breech or cesarean section (transient tachypnea in the newborn), and whether the mother had obtained prenatal care. Routine prenatal ultrasound screening has been shown to detect up to 75% of CHD cases.31 Additional conditions or the appearance of a genetic abnormality should heighten suspicion since genetic abnormalities strongly are associated with CHD. For example, congenital heart lesions have been shown to be present in 90%, 50%, and 40% of patients with trisomy 18, trisomy 21, and Turner syndrome, respectively.32 Common genetic syndromes that are associated with CHD are summarized in Table 3. For a more thorough review, please refer to Marino et al.33
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The age when symptoms develop can serve as a valuable tool in discerning the underlying cardiac defect at hand. Unfortunately, a large amount of variation exists, but generalities still can be made. Patients who are symptomatic immediately following birth are those who have severe hemodynamic abnormalities. Such lesions include TGA, HLHS, TAPVR with associated pulmonary venous obstruction, PA without an associated VSD (HRHS), and TriA with a restrictive ASD. The next critical time for these patients is during closure of the PDA. This typically occurs anywhere from several hours to two weeks after birth.34 Patients who have cardiac defects that depend on shunting across the PDA (ductal dependent lesions) will deteriorate at this time. These include defects with critical left heart obstruction (critical CoA, severe AS, HLHS), severe right heart obstruction (TOF with significant PS, PA, critical PS, TriA without an adequate ventricular communication), and TGA. The next crucial time at which patients may present is marked by the fall in PVR and progressive left-to-right shunting (2-6 weeks of life). Patients that present at this time are those who have lesions that allow shunting in the face of unrestricted pulmonary blood flow. As PVR decreases, left-to-right shunting increases, which results in progressively increased pulmonary perfusion. This results in progressive pulmonary congestion and signs of CHF. These lesions include large ASDs, VSDs, large PDA, ECDs, and TA. Patients with TA typically present earliest, especially if there is significant truncal valve insufficiency. VSDs, PDAs, and ECDs also develop similar symptoms, with the major determining factor of time for presentation being the size of the VSD or shape and size of the PDA.
ASDs are a diastolic shunting phenomenon, which is unlike the shunting noted in the other defects. Therefore, it is not as dependent on the change in PVR for manifestation of clinical symptoms. In most cases, these patients will not present with signs of congestive failure as early and often will be diagnosed later in life. Lesions that present later in life tend to be the left-to-right shunt lesions where the shunting is somewhat restricted. These patients may develop an eventual chronic pulmonary vascular obstructive disease. Other lesions that present later in life include mild CoA that manifests as hypertension and mild pulmonary or aortic stenosis that worsens with time and leads to syncope or exercise intolerance.
Physical Exam
Patients with CHD should be approached in a systematic fashion. The general appearance of the patient will be the first indication of the severity. Activity can range from being consolable or irritable to lethargy. If the development of symptoms has progressed over days, there will be a degree of dehydration and/or muscle wasting due to inadequate oral intake. An increased work of breathing, although sometimes subtle, almost always is present. The respiratory rate and heart rate will be increased. Hypotension is a later and more ominous finding. Blood pressures should be measured in the upper and lower extremities to assess for a CoA or an interrupted aortic arch. This should be compared to pulse oximetry measurements both pre-ductal (right upper extremity) and post-ductal (lower extremity). Cyanosis may or may not be present by visual inspection. Therefore, arterial blood gases (ABG) should be analyzed to evaluate for hypoxemia.
Accurately detecting and distinguishing central cyanosis from peripheral cyanosis is critical in the evaluation of CHD. Some of the major causes of central cyanosis are listed in Table 2. Two distinct types of cyanosis exist: central and peripheral. Only central cyanosis is characteristic of cyanotic CHD, but peripheral cyanosis is by far more common. On initial evaluation, these two entities may appear the same. Fortunately, there are distinct differences. On initial evaluation, pulse oximetry will be low in both cases. Peripheral cyanosis is due to poor perfusion of the skin or changes in vascular tone. Cyanosis generally is confined to the perioral skin and nail beds, and the mucous membranes remain pink. Also, these patients usually have cool extremities and poor capillary refill. The ABG will reveal a normal pO2. In contrast, central cyanosis is due either to inadequate oxygenation or the mixing of deoxygenated blood with oxygenated blood. Patients with central cyanosis often will have warm extremities and normal capillary refill. In the absence of heart failure, these infants often are described as comfortably blue. The major distinguishing features are that patients with central cyanosis will have blue mucous membranes and a low pO2 value on ABG analysis.
The Lung Exam. The respiratory state of patients with CHD can vary. All patients with hemodynamically significant lesions will have some degree of an increased work of breathing. Tachypnea may be secondary to increased pulmonary perfusion, metabolic acidosis, hypoxia, pulmonary edema, or CHF. Findings may include retractions, nasal flaring, wheezing, and crackles on auscultation. In general, respiratory distress secondary to heart disease can be difficult to differentiate from that caused by pulmonary disease. To complicate matters, it is not uncommon for patients with CHD to have an underlying lower respiratory tract infection that contributes to their decompensation. Generally speaking, respirations from cardiac disease in the absence of pulmonary disease usually is not as labored.
The Precordial Exam. A thorough precordial exam is essential for the evaluation of a patient with suspected CHD. For a thorough review on the pediatric cardiac exam, please refer to Pelech, et al.35 Whether proficient in auscultation or not, specific rules can be used to facilitate identification of pathology. Features that should be scrutinized include the presence and location of a precordial thrill or impulse, nature of S1 and S2 heart sounds, the presence of associated clicks or gallops, and the characteristic and timing of audible murmurs. Murmurs are a common finding in pediatric patients. In addition, an ill or anxious child often will demonstrate a more pronounced murmur. Therefore, differentiating benign murmurs such as the Still’s murmur or a pulmonary flow murmur from a pathologic murmur can be difficult. Key indicators of a pathologic murmur are based on the harshness and/or character of the murmur,36 timing and the area of the precordium where it is loudest, and radiation of the murmur. In general, the ED physician should be highly critical of any murmur that is louder than a grade 3, associated with a thrill, or a hyperdynamic precordium. Continuous murmurs are consistent with either a venous hum or a PDA. Venous hums typically are not appreciated in the newborn or infant. Therefore, a continuous murmur at this age should be assumed to be due to a PDA. Venous hums are benign murmurs that change with position of the patient and with head maneuvers. Diastolic murmurs are always abnormal.35 Diastolic murmurs are due to insufficiency at the semilunar valves or, as in TA, a regurgitant truncal valve. They also are associated with atrioventricular valve stenosis, which typically is not seen in pediatrics. The most common murmurs are systolic. Holosystolic murmurs classically are related to VSD lesions, which include ECDs and TOF. Regurgitation of the AV valves will be heard as a holosystolic murmur and can be noted with Ebstein’s anomaly of the tricuspid valve or ECDs. These often can be differentiated based on the location where they are heard the loudest. Ebstein’s anomaly and VSDs tend to be loudest at the left lower sternal border, whereas ECDs (cleft mitral valve) are heard best at the apex. Systolic murmurs of a crescendo-decrescendo nature are associated with stenosis of the semilunar valves as seen in PS (left upper sternal border), AS (typically right upper sternal border), and TOF (left upper sternal border). Large ASDs will have a murmur similar to pulmonary stenosis associated with a fixed split of the S2 heart sound.
Abdominal Exam. Specific findings in the abdominal exam may include hepatomegaly, which is seen in cases of severe CHF or right heart failure and is indicative of increased right atrial pressures either due to volume or pressure overload. Right heart failure can be seen in severe right heart obstructive lesions in the absence of adequate atrial communication. Specific defects that frequently can produce such findings in the neonate include Ebstein’s anomaly and TAPVR.12
Extremity Pulses. Peripheral pulses should be assessed in all patients with CHD. The easiest pulses to assess in the small child are the brachial pulse and the femoral pulse. These are located along the medial aspect of the mid-shaft of the humerous (brachial pulse) and just superior to the inguinal crease (femoral pulse). The classic example CHD with abnormal peripheral pulse findings is that of diminished lower extremity pulse pressures with CoA. In general, any lesion with an interrupted aortic arch or stenosis along the aortic arch will cause a varied pulse pressure between upper and lower extremities. Keep in mind that, when evaluating an infant who is suspected of having a critical left heart obstruction, the classic findings of varying extremity blood pressures may not be present because the left ventricular function may be poor. In this case, pressures may be low in all extremities, thus masking the differing upper and lower extremity blood pressures that may be expected. Other peripheral pulse findings may include bounding pulses as seen with valvular insufficiency (aortic insufficiency or TA) or PDA. Diffusely weakened pulse pressures also can be seen in cases of left ventricular failure or severe left-to-right shunts. The typical child with an undiagnosed left-to-right shunt lesion who has had a gradual progression of symptoms often presents in the first year of life with heart failure.
Diagnostic Tests
Pulse Oximetry. Pulse oximetry is a rapid and noninvasive method of measuring oxygen saturation in the peripheral capillary bed. It is an indispensable tool in the evaluation of any patient in the pediatric ED. As with any diagnostic test, one must recognize its limitations. The technology used takes advantage of the fact that oxygenated and deoxygenated hemoglobin will absorb light at characteristic wavelengths. Therefore, anything that inhibits light (nail polish) or has additional absorbing properties (methemoglobinemia) will cause erroneous results. Also, one must recall that, due to the properties of the hemoglobin molecule, oxygen saturation is not linear with the partial pressure of oxygen in the blood. An acceptable correlation can be seen between saturations of 75% and 95%. Readings outside this range should not be strictly relied upon. Specific roles for pulse oximetry are in the initial patient evaluation, assessing the response to different therapies, and monitoring once the patient has been stabilized. Pulse oximetry may serve as the first indicator that an oxygenation problem exists, prompting the emergency physician to conduct further diagnostic tests. Obviously, pulse oximetry will assist in differentiating cyanotic from non-cyanotic heart defects. A specific diagnostic role for pulse oximetry is in testing pre- and post-ductal oxygen saturation. This is done by obtaining a reading from the right upper extremity and comparing it to the result obtained from the lower extremity. Lower oxygen saturations in the lower extremities suggest right-to-left shunting of deoxygenated blood across the PDA. This is seen in cases of severe pulmonary hypertension. If low oxygen saturation in the lower extremities is noted in conjunction with diminished lower extremity pulse pressures, one should consider CoA or an interrupted aortic arch. TGA is associated with a diffuse central cyanosis but can in some cases result in upper extremity oxygen saturations that are relatively lower than those in the lower extremity.37
The 100% Oxygen Test. The 100% oxygen test is used to assist in differentiating between pulmonary and cardiac forms of cyanosis. The test is performed by administering 100% oxygen and assessing the rise in arterial oxygenation. Hypoxia secondary to pulmonary disease or hypoventilation is more likely to be overcome with 100% oxygen. In these cases, pO2 values often will rise to more than 200 mmHg unless severe pulmonary disease is present. On the other hand, cyanotic cardiac defects have a central mixing of saturated and desaturated blood. Therefore, despite a total saturation of hemoglobin in the lungs (with 100% oxygen), there always will be further dilution upon mixing in the heart. This is manifested as a blunted response to 100% oxygen; pO2 values that do not exceed 100 mmHg despite 100% oxygen are highly suggestive of a cardiac etiology for cyanosis. The degree of blunting may suggest the type of heart defect. Low responses (pO2 < 100 mmHg) are more likely to be seen in cyanotic CHD with decreased pulmonary blood flow. Cyanotic lesions that result in high pulmonary blood flow have the added benefit of excess perfusion of the lungs. In these cases, the higher lung perfusion will add somewhat to the amount of oxygen solubilized. For these defects, pO2 values occasionally can be as high as 150 mmHg in response to 100% oxygen.
It should be mentioned that 100% oxygen technically can have a deleterious effect in the presence of some CHDs. High oxygen concentrations can promote PDA closure and, therefore, should be used with caution when stabilizing a child with critical left heart obstruction. In addition, oxygen causes vasodilation in the pulmonary vasculature and could exacerbate patients with pulmonary vascular congestion. Despite these technical cautions, as a general rule: if you can get a pO2 high enough to close the PDA, then you typically are not working with a ductal dependent cyanotic heart defect. Therefore, the administration of 100% oxygen should be used judiciously and limited to a brief diagnostic test when CHD is suspected.
Chest Radiography. Chest radiography is very valuable in the evaluation of a child with suspected CHD. Separate features of the chest radiograph that should be evaluated include: the size and shape of the cardiac silhouette, associated bony abnormalities, and the appearance of the pulmonary lung fields. Almost all CHDs, excluding TAPVR, will result in cardiomegaly, which can be detected on chest radiography. The overall shape of the cardiac silhouette may be suggestive of specific defects but very often is non-specific. Classic descriptions include a boot-shaped heart for TOF, an egg on a string for TGA, and a figure 8 for TAPVR. Additional features characteristic of specific lesions include a right-sided aortic arch in TOF and TGA. In a normal radiograph, the airway will deviate slightly to the right above the carina. In a right-sided aortic arch, the airway either will be straight or deviate to the left. The pulmonary lung fields should be evaluated for signs of effusions or infiltrates. This is important for the differentiation of cardiac and lung disease. Be aware of any findings suggestive of an infiltrate, since many patients with CHDs are more susceptible to LRIs that may have been the source of their initial decompensation. One also should identify the side of the stomach bubble since abnormal abdominal situs often is associated with complex heart defects.
Increased or decreased pulmonary vascular markings suggest the degree of pulmonary perfusion and may help differentiate between cardiac defects.39 Increased pulmonary vascular markings can be seen with large left-to-right shunt lesions and those cyanotic defects with increased pulmonary blood flow (TGA, TA). Decreased pulmonary vascular markings are seen with lesions that result in right heart obstruction (TOF, PS, PA, tricuspid stenosis/atresia). Pulmonary venous congestion can be seen with critical left heart outlet obstruction, TAPVR, and mitral stenosis. Evidence of rib notching also may be a helpful finding and may suggest increased collateral flow along the intercostal vessels. This can be seen with CoA and TAPVR with interrupted aortic arch. Rib notching is a late finding and often is seen in the adolescent who has been undiagnosed for years.
Electrocardiogram. The normal electrocardiographic findings in newborns and infants differ from those seen in the adult.38 Due to the hemodynamic influence of the fetal circulation, most infants are born with a rightward axis (~ 90-180°). This converts by approximately 3-4 weeks of life to the axis more often seen in adults (~ 0-90°). Deviation from this normal transition should be considered suspicious. For example, an upright T-wave in V1 is normal at birth but persistence beyond three days of age should prompt a careful cardiac evaluation/interrogation.38 Electrocardiographic findings suggestive of individual chamber hypertrophy are based on age. Most comprehensive pediatric handbooks will have reference tables listing population-based ECG findings in different age groups. Electrocardiographic evidence of CHD typically is noted by changes consistent with ventricular hypertrophy. ECG findings suggestive of chamber hypertrophy are summarized in Table 4. These changes can be a result of ventricular dilation, hypertrophy, or opposing hypoplasia. It also should be noted that axis deviation does not always correlate to chamber hypertrophy or hypoplasia and that these findings should be addressed individually. For example, HLHS taken at face value would suggest that right axis deviation invariably be present. On the contrary, these lesions often can have a normal (0-90°) axis.11 This is due to the fact that, although the left ventricular chamber is small, there still exists the left-sided myocardial mass that contributes to the overall polarity. Knowing the changes consistent with each cardiac defect will, therefore, assist in the diagnosis. For example, most lesions with left-to-right shunts (PDA, VSD, ECDs) of sufficient volume will result in left ventricular hypertrophy as a consequence of increased pulmonary venous return. If not repaired, PVR will increase over time, resulting in right ventricular hypertrophy. Lesions with left heart obstruction (AS, CoA) also will result in left ventricular hypertrophy. Cyanotic CHD with decreased pulmonary blood flow commonly have an RVOT obstruction that results in a right ventricular hypertrophy. These lesions also have right-to-left shunting, causing left-sided fluid overload and possible left ventricular hypertrophy. An additional feature to keep in mind is the finding of a superior QRS axis (0-90°) that typically is noted with ECDs or in patients with TriA. Other characteristics that may be helpful include a tall R-wave in II, III, or aVF that may reflect left ventricular pressure overload (AS, CoA), or in V5 or V6 that may reflect left ventricular volume overload (PDA or VSD). Lastly, an inverted T-wave in V6 is always abnormal and suggests left ventricular strain.39
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Arterial Blood Gases. Obtaining an ABG sample is essential for the evaluation of any critical patient who presents in respiratory distress or shock. Important values include pCO2, pO2, and pH. If used in conjunction with the rest of the exam, ABG may help in formulating a diagnosis. By no means is this test specific for determining the presence of a CHD. It is most helpful in influencing management decisions. As mentioned earlier, pO2 values are useful in distinguishing cyanotic from acyanotic lesions and central from peripheral cyanosis. The presence of acidosis suggests inadequate oxygenation in cyanotic lesions or inadequate perfusion in acyanotic lesions. pCO2 values are indicative of the patients ventilatory state. Patients with CHD in the absence of respiratory failure are unlikely to be hypercarbic (pCO2 > 40 mmHg). Most often these patients will have an increased ventilation at baseline demonstrated by a pCO2 of 25-40 mmHg.40
Focusing the Diagnosis
It should be stated clearly that the definitive diagnosis of CHD requires either echocardiography or cardiac catheterization. Fortunately, an exact diagnosis is not necessary for the emergency physician to make decisions regarding treatment and stabilization.
It is essential that the emergency physician use the tools discussed above to characterize the hemodynamics taking place. If done correctly, the diagnosis can be narrowed to a subset of defects. This is what will guide the physician in making critical care decisions. An algorithm for this decision process is shown in Figure 1. Here we demonstrate subgroups based on differing pulse oximetry, chest radiography, and ECG findings. The discussion on treatment will be the focus of part II of this series.
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Summary
CHD can be a very complex topic. Part I of this two-part series attempts to give the emergency physician an adequate background on the pathophysiology and differential diagnosis of various clinical presentations for CHD. A thorough history and physical exam are crucial both for a child with a known CHD or a child with an undiagnosed disease process. Patients can present at any time with only subtle findings or requiring emergent life-sustaining treatment. Early diagnosis dramatically can improve the patient’s outcome, and a missed diagnosis can have fatal outcomes.
Part II of this series will focus on the stabilization and management of CHD in the ED. Issues pertinent to the care of a child with CHD also will be discussed, such as the potential complications associated with corrective surgeries, and the risk for the development of arrhythmia, endocarditis, respiratory infections, and stroke.
References
1. Driscoll DJ. Left to right shunt lesions. Pediatr Clin N Am 1999;46: 355-368.
2. Niwa K, Perloff JK, Kaplan S, et al. Eisenmenger syndrome in adults: Ventricular septal defect, truncus arteriosus, univentricular heart. J Am Coll Cardiol 1999;34:223-232.
3. Mahoney LT, Truesdell SC, Krzmarzick TR, et al. Atrial septal defects that present in infancy. Am J Dis Child 1986;140:1115-1118.
4. Radzik D, Davignon A, van Doesburg N, et al. Predictive factors for spontaneous closure of atrial septal defects diagnosed in the first 3 months of life. J Am Coll Cardiol 1993;22:851-853.
5. Studer M, Blackstone E, Kirklin J, et al. Determinants of early and late results of repair of atrioventricular septal (conal) defects. J Thorac Cardiovasc Surg 1982;84:523-542.
6. Fukazawa M, Fukushige J, Ueda K. Atrial septal defects in neonates with reference to spontaneous closure. Am Heart J 1988;116: 123-127.
7. Murphy JG, Gersh BJ, McGoon MD, et al. Long-term outcome after surgical repair of isolated atrial septal defect. Follow-up at 27 to 32 years. N Eng J Med 1990;13:323:1645-1650.
8. Kidd L, Driscoll D, Gersony W, et al. Second natural history study of congenital heart defects: Results of treatment of patients with ventricular septal defects. Circulation 1993;87:38-51.
9. Spangler L, Feldt R, Danielson G. Secundum atrial septal defect encountered in infancy. J Thorac Cardiovasc Surg 1976;71:398-401.
10. Allan LD. Fetal cardiology. Curr Opin Obstet Gynecol 1996;8:142-147.
11. Fedderly RT. Left ventricular outflow obstruction. Pediatr Clin North Am 1999;46:369-384.
12. Burton DA, Cabalka AK. Cardiac evaluation of infants. The first year of life. Pediatr Clin N Am 1994;41:991-1015.
13. Demircin M, Arsan S, Pasaoglu I, et al. Coarctation of the aorta in infants and neonates: Results and assessment of prognostic variables. J Cardiovasc Surg 1995;36:459-464.
14. Pellegrino A, Deverall PB, Anderson RH, et al. Aortic coarctation in the first three months of life. J Thorac Cardiovasc Surg 1985; 89:121-127.
15. Ing FF, Starc TJ, Griffiths SP, et al. Early diagnosis of coarctation of the aorta in children: A continuing dilemma. Pediatrics 1996;98:378-382.
16. Hammon JW, Lupinetti FM, Maples MD. et al. Predictors of operative mortality in critical valvular aortic stenosis presenting in infancy. Ann Thorac Surg 1988;45:537-540.
17. Bando K, Turrentine MW, Sun K, et al. Surgical management of hypoplastic left heart syndrome. Ann Thorac Surg 1996;62:70-77.
18. Bailey LL, Gundry SR. Hypoplastic left heart syndrome. Pediatr Clin N Am 1990;37:137-159.
19. Lees MH, King DH: Cyanosis in the newborn. Pediatr Rev 1987;9:36-42.
20. DiDonato RM, Jonas RA, Lang P. et al. Neonatal repair of tetralogy of Fallot with and without pulmonary atresia. J Thorac Cardiovasc Surg 1991;101: 126-137.
21. Waldman JD, Wernly JA. Cyanotic congenital heart disease with decreased pulmonary blood flow in children. Pediatr Clin N Am 1999;46:385-404.
22. Pagani FD, Cheatham JP, Beekman RH, et al. The management of tetralogy of Fallot with pulmonary atresia and diminutive pulmonary arteries. J Thorac Cardiovasc Surg 1995;110:1521-1533.
23. Evans-Berro EA. How to defeat a tet spell.’ Am J Nurs 1991;91:46-48.
24. Grifka RG. Cyanotic congenital heart disease with increased pulmonary blood flow. Pediatr Clin N Am 1999;46:405-425.
25. Williams JM, de Leeuw M, Black MD, et al. Factors associated with outcomes of persistent truncus arteriosus. J Am Coll Cardiol 1999;34: 545-553.
26. Harris MA, Valmorida JN. Neonates with congenital heart disease. Part IV: Total anomalous pulmonary venous return. Neonatal Netw 1997;16:63-66.
27. Forchielli ML, McColl R, Walker WA, et al. Children with congenital heart disease: A nutrition challenge. Nutr Rev 1994;52:348-353.
28. Silove ED. Assessment and management of congenital heart disease in the newborn by the district pediatrician. Arch Dis Child Fetal Neonatal Ed 1994; 70:F71-74.
29. Link KM, Loehr SP, Martin EM, et al. Congenital heart disease. Coron Artery Dis 1993;4:340-344.
30. Allan LD. Fetal congenital heart disease: Diagnosis and management. Curr Opin Obstet Gynecol 1994;6:45-649.
31. Lin AE. Congenital heart defects in malformation syndromes. Clin Perinatol 1990;17:641-673.
32. Mahoney LT. Acyanotic congenital heart disease. Atrial and ventricular septal defects, atrioventricular canal, patent ductus arteriosus, pulmonic stenosis. Cardiol Clin 1993;11:603-616.
33. Marino B, Digilio MC. Congenital heart disease and genetic syndromes: Specific correlation between cardiac phenotypes and genotypes. Cardiovasc Pathol 2000;9:303-315.
34. Pelech AN. Evaluation of the pediatric patient with a cardiac murmur. Pediatr Clin N Am 1999;46:167-188.
35. Pelech AN. The cardiac murmur. Pediatr Clin N Am 1998;45: 107-122.
36. Moss AJ. Clues in diagnosing congenital heart disease. West J Med 1992;156: 392-398.
37. Horton LA, Mosee S, Brenner J. Use of the electrocardiogram in a pediatric ED. Arch Pediatr Adolesc Med 1994;148:184-188.
38. Flynn PA, Engle MA, Ehlers KH. Cardiac issues in the pediatric emergency department. Pediatr Clin N Am 1992;39:955-968.
39. Barone, MA, ed. The Harriet Lane Handbook. 14th ed. Baltimore: Mosby; 1996:137-138.
40. Lees MH, King DH. Cardiogenic shock in the neonate. Pediatr Rev 1988;9: 258-266.
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