14
Heart Murmurs: Congenital Heart Disease
Alan J. Spotnitz
Objectives
1. To understand the significance of a heart murmur in an infant.
2. To understand the classification of congenital heart disease.
3. To understand the difference between palliative and corrective surgery for congenital heart disease.
Case
A 6-month-old baby is brought to your office by his mother. He has been having frequent upper respiratory infections. The mother says she thinks he is short of breath at times and does not eat as well as his older brother did at the same age.
Introduction
The identification of a heart murmur early in life may be indicative of a significant congenital malformation of the heart. Such malformations may be present in 0.5% to 0.8% of all live births. It is important to be able to differentiate potentially life-threatening lesions from benign processes. To do this, a basic understanding of these potentially complex lesions is necessary. When the diagnosis of a significant heart murmur seriously is considered, these infants must be referred to a pediatric cardiologist and pediatric cardiac surgeon for appro- priate diagnosis and corrective or palliative procedures.
A relatively simple way to classify these potentially confusing lesions is according to categories based on the major presenting symptom: con- gestive heart failure or cyanosis (Table 14.1).Diagnosis of these lesions frequently can be made on the basis of the history and physical examination as well as with some basic noninterventional testing,
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including chest x-ray, electrocardiogram, and echocardiogram.
Cardiac catheterizationin the diagnosis of these patients is required in fewer than 20% of all cases. (See Algorithm 14.1.)
Congestive Heart Failure
The infant described in the case presented above is likely to be having signs of congestive heart failure. Infants and children with congestive heart failure are symptomatic for either of two reasons: obstructing lesionsor overcirculation of the lungs.
Obstructive lesions leading to signs and symptoms of congestive heart failure involve the heart valves or the aorta. These include aortic stenosis, mitral stenosis, and various degrees of narrowing of the tho- racic aorta between the aortic valve and the level of the ductus arte- riosus. Initial presentation can range from a benign sounding heart murmur to life-threatening congestive heart failure. The symptoms caused by the obstructive lesion are attributed to blood backing up into the pulmonary circulation, causing pulmonary edema or congestion.
Congestive heart failure also can be caused by left to right shunting of arterial blood, leading to overcirculation of the lungs. This can occur Table 14.1. Presentation and classification of congenital heart disease.
Congestive heart failure
Left-to-right shunt Obstructive lesions (increased pulmonary blood flow)
Patent ductus arteriosus Aortic stenosis Atrial septal defect Mitral stenosis Ventricular septal defect Pulmonic stenosis Atrioventricular canal Coarctation of the aorta Truncus arteriosus Interrupted aortic arch Aortopulmonary window
Cyanosis
Right-to-left shunt Complex lesions (decreased pulmonary blood flow)
Tetralogy of Fallot Transposition of the great arteries With intact ventricular septum With ventricular septal defect Tricuspid atresia Total anomalous pulmonary venous
connection Pulmonary atresia Cor triatriatum
With intact ventricular septum With ventricular septal defect
Hypoplastic left heart syndrome Miscellaneous
Anomalous origin of the left coronary artery from the pulmonary artery Corrected transposition of the great arteries
Ebstein’s anomaly Vascular rings
Source: Reprinted from Backer CL, Mavroudis C. Congenital heart disease. In: Norton JA, Bollinger RR, Chang AE, et al, eds. Surgery: Basic Science and Clinical Evidence. New York: Springer-Verlag, 2001, with permission.
at several levels of the heart. Abnormal communication can exist at the level of the atria (atrial septal defect), ventricles (ventricular septal defect), or in an extracardiac location (aortopulmonary window or patent ductus arteriosus signs). The most common symptoms that occur in this setting include recurrent upper respiratory infection, tachypnea, tachycardia, and failure to thrive. Oxygenated blood flows from the left side to the right side of the circulation because of the lower resistance and pressures in the right side of the heart. Excessive flow of blood through the pulmonary vasculature results in congestive heart failure and pulmonary hypertension. Enlargement of the right atrium and ventricle will occur. Pulmonary vascular resistance gradually increases due to this overcirculation from a complex interaction of factors. Ultimately, the pulmonary resistance becomes high and irre- versible. If the resistance becomes high enough, flow reversal may occur, with right to left shunting and cyanosis (Eisenmenger’s syn-
Heart murmur
CHF Cyanotic No symptoms
Echo, probable follow Complex CHD
Echo
Anatomy defined
OR for palliation or correction, depending on diagnosis
Yes
Cardiac catheter
No Yes
No further treatment Closed with indomethacin Yes (PDA in neonate)
Echo
No
Algorithm 14.1. Algorithm for the diagnosis and treatment of a child with a heart murmur. CHD, congestive heart disease; CHF, congestive heart failure; PDA, patent ductus arteriosus.
drome). The goal of surgical therapy is to correct these lesions. Fre- quently, this can be accomplished with a low operative mortality. As pulmonary resistance increases, so does the operative risk. Even before Eisenmenger’s syndrome occurs, a high fixed resistance may preclude surgical correction.
The infant in the case presented above is consistent with an infant who has either an obstructive lesion or a shunting lesion. The presence of congestive heart failure and the absence of cyanosis places the infant in this category.
Cyanosis
The cyanosis related to cyanotic congenital heart disease is due to the significant mixing of oxygenated and nonoxygenated blood within the heart and the output of this blood to the systemic circulation. For this to occur, either an intracardiac defect with pulmonary outflow obstruction (forcing blood to shunt right to left) or a complex congen- ital anomaly must exist. When the absolute level of desaturated blood in the systemic circulation exceeds 5 g/mL, cyanosis appears. As noted, two basic categories exist. In the first, septal defects similar to those that occur in left to right shunting are present, but these are asso- ciated with some form of pulmonary outflow obstruction (subvalvu- lar, supravalvular, or atresia of the pulmonary arteries). The result is right-to-left shunting and cyanosis. The classic lesion is known as tetralogy of Fallot (ventricular septal defect, overriding aorta, pul- monary arterial obstruction, and right ventricular hypertrophy).
The other lesions causing cyanosis, in which markedly abnormal anatomy exists, such as transposition of the great vessels and total anomalous pulmonary venous return, are referred to as “complex lesions.”
History and Physical Examination
The history is obtained from the parent or from observations of the infant at the time of delivery. The parent usually is most observant of abnormalities in the child’s behavior, especially if there is an older sibling with whom to compare the child’s behavior, as in the case pre- sented above. Family history is relevant, as there may be as much as a threefold increase in the incidence of congenital disease when a prior sibling has been born with a congenital defect. Signs and symptoms of congestive heart failure should be sought from the parent, espe- cially recurrent respiratory infections or difficulties feeding (shortness of breath, sweating). Cyanosis may appear early in neonates born with transposition of the great vessels or some other complex lesion. Perfu- sion of the pulmonary circulation may have been dependent on a patent ductus arteriosus communicating between the descending tho- racic aorta and the pulmonary artery. As the ductus begins to close in the first hours and days of life, decreased pulmonary blood flow and cyanosis, either from hypoxia or new right to left flow, occurs.
Prostaglandin may be necessary to maintain this fetal circulation (patent ductus) until diagnostic studies can be completed. Other infants do not develop signs of cyanosis until they are a few months of age.
There may be a history of cyanosis related to crying. Signs of cyanosis related to tetralogy of Fallot may not appear until several months of life as pulmonary outflow obstruction (and right-to-left shunting) increases.
The physical examination is directed to a systematic evaluation of the infant or child. Findings consistent with congestive heart failure or chronic hypoxemia are sought.Low weight and poor nutrition are not uncommon. The pulmonary exam may reveal fine rales and rhonchi. The cardiac exam usually reveals the presence of a heart murmur. With obstructive lesions, this usually is consistent with the murmurs of aortic or mitral stenosis. Ventricular septal defects usually have a continuous “machinery-type” murmur over the ante- rior chest. The murmur of an atrial septal defect is related to increased blood flow across the pulmonic valve and not to the flow across the atrial septum.This murmur is thus loudest over the pul- monary outflow tract to the left side of the sternum. A systolic murmur heard loudest in the back is suggestive of coarctation of the aorta, especially if lower extremity pulses are decreased.It is likely to be continuous. Hepatomegaly may be a consistent finding in the presence of congestive heart failure. Examination of the periphery is crucial in looking for signs of cyanosis, clubbing, or microemboli, which may be present in right-to-left shunting.
Diagnostic Studies
Routine chest x-ray may be diagnostic, especially to a well-trained pediatric radiologist. Over- or undercirculation of the lungs may be present along with cardiomegaly and other deformities of the base of the heart. The classic “figure of eight” appearance of the heart is asso- ciated with transposition of the great vessels. When the cardiac sil- houette has the appearance of a boot and the infant is cyanotic, tetralogy of Fallot will be suspected. The electrocardiogram can reveal left or right ventricular hypertrophy as well as conduction abnor- malities associated with some complex congenital deformities.
Echocardiography is an accurate diagnostic tool and can be used for definitive diagnosis and planning for surgical correction in the majority of infants and children requiring surgical intervention.
Cardiac catheterization and angiography may be required to confirm the diagnosis and aid in planning surgical correction in more complex situations.
Treatment
The ultimate goal of therapy is to reverse symptoms or, alternatively, restore as normal an anatomy as possible. In the emergency setting, palliation may be all that is possible by surgical intervention. Defin-
itive correction is best performed on an elective basis. Pharmacologic methods used to maintain the patency of a patent ductus or to enhance its closure have made many surgical interventions less of an emergency. In many situations, early corrective surgery is possible.
The infant is maintained by medical treatment of congestive heart failure until the proper time for surgery arrives.
In contrast to surgery in the adult, stenotic lesions in infants and children can be quite challenging due to the absence of a suitable valve substitute. Pulmonic stenosis usually is corrected transvenously by balloon dilatation in the catheterization laboratory. Any resulting pulmonic insufficiency, if the stenosis is the only lesion, is not of concern. Mitral stenosis may be amenable to open commissurotomy, but some form of shunting and correction to bypass the stenotic lesion may be necessary. Aortic stenosis, if the annulus is of adequate size, may be susceptible to open commissurotomy. Otherwise, the Ross pro- cedure, in which the patient’s own pulmonic valve is transplanted to the aortic position, seems to be the best option since there is the likeli- hood that the valve will continue to grow as the child grows.
Severely cyanotic infants or those in profound heart failure may require immediate diagnosis and surgical intervention. Especially in complex situations or when the remainder of the heart has not devel- oped, palliative procedures are performed.When this is necessary, the goal is to establish sufficient blood flow to maintain life. Emergent atrial septostomy may be required for a neonate with transposition of the great vessels. Profoundly cyanotic infants may require the creation of adequate blood supply to the pulmonary circulation. This is done by the creation of a left-to-right shunt. A modification of the classic Blalock-Taussig shunt (subclavian artery to pulmonary artery)is per- formed and can be closed when the definitive procedure is performed.
The presence of profound pulmonary overcirculation, which may occur with a large ventricular septal defect or aortopulmonary window, may require pulmonary artery banding to restrict pulmonary blood flow.
The dominant approach to many of these lesions now is one of total correction in infancy rather than palliation with later correction.
Lesions that lead to overcirculation of the pulmonary vasculature must be corrected early in life or palliated before irreversible pulmonary hypertension develops. Repairs of atrial septal defects usually can be delayed until a child reaches 3 or 4 years of age and can be corrected before he/she begins school. The risk of endocarditis is increased sig- nificantly in these patients as well as in older patients with a patent ductus.
Results
With increasing refinements in the techniques of pediatric cardiac surgery, the operative mortality for many of these procedures has dropped dramatically with improved long-term survival. It is no longer uncommon to see adults who have undergone corrective surgery as children parenting their own children.
Summary
A heart murmur present in a child or an infant with signs and symp- toms of congestive heart failure or cyanosis is indicative of a signifi- cant mechanical lesion within the heart. A relatively simple method of classification of these potentially complex lesions is based on the pre- senting symptom of the patient, either congestive heart failure or cyanosis. Prompt referrals to experts in this area result in the best out- comes possible.
Selected Readings
Backer CL, Marroudis C. Congenital heart disease. In: Norton JA, Bollinger RR, Chang AE, et al, eds. Surgery: Basic Science and Clinical Evidence. New York:
Springer-Verlag, 2001.
Castaneda AR, Jonas RA, Mayer JE, Handley FL. Cardiac Surgery of the Neonate and Infant. Philadelphia: WB Saunders, 1994.
Townsend CM, Beauchamp DR, Evers MB, Mattox KL, Sabiston DC. Sabiston Textbook of Surgery, 15th ed. Chapter 54 “The Heart,” Sections 3 through 13 and 15 and 16. Philadelphia: Saunders, 1997: 1961–2082, 2118–2135.
