Symposium on Pediatric Cardiology

Acyanotic Lesions with Increased Pulmonary Blood Flow

James Geoffrey Stevenson, M.D.*

As in the preceding article, the more common defects are discussed in terms of the schema of branching logic in diagnosing congenital heart disease (see p. 726). Though the schema perhaps suggests a need to determine whether or not pulmonary blood flow is increased or ventricular hypertrophy present, it will work equally well if one merely judges pulmonary flow as upper normal, or normal to increased, and for electrocardiogram relies on dominance of rightsided or left-sided forces, regardless of whether strict criteria for hypertrophy are met.

ATRIAL SEPTAL DEFECT Significant defects in the atrial septum are common and account for about 10 per cent of congenital heart disease in children.6-8 Of atrial defects, those in the higher portion of the atrial septum, near the region of the fossa ovalis or foramen ovale, are most common and are termed secundum defects. Less common are those in the lower portion of the atrial septum, near the atrioventricular valve plane. These ostium primum defects are associated with abnormalities of the atrioventricular valves, usually the mitral valve, and are discussed later under endocardial cushion defects. The timing of clinical detection of uncomplicated atrial shunts follows the early childhood changes in pulmonary resistance and compliance. In contrast to ventricular and great vessel level shunts, atrial level shunts occur between chambers of low pressure. Since pulmonary resistance is high in the perinatal period, and the right ventricle relatively stiff or noncompliant, there is usually little shunting at atrial level, since blood returning to the atria sees essentially similar compliance in both the right and left ventricles. As pulmonary resistance falls, and the right ventricle becomes thinner-walled and more com*Assistant Professor, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington

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pliant, differences arise between circulations in the right and left heart, favoring atrial level flow from left to right. Since there is less shunt in infancy and early childhood (and because the murmur resulting from an atrial septal defect is usually not loud and the course is infrequently complicated by pneumonia, and because auscultation may be hampered by cooperation and extraneous respiratory sounds), atrial defects are usually not detected until three to five years of age; of all youngsters with congenital heart disease first noted to have a murmur in the three to five year age group, atrial defects are the most common. The history is usually unremarkable. In contrast to other defects, youngsters with atrial septal defects are not frequently plagued with pneumonias, though some have a history of several episodes of "bronchitis" or mild "chest colds." These children usually have grown and developed quite well. Exercise tolerance and endurance are rarely different from that of peers, though on extreme exertion there may be some complaints of tiredness. A history of congestive heart failure is very uncommon. Of the clinical findings, those on physical examination may be subtle. Coloring is acyanotic and blood pressure is normal. Except with very large shunts, the precordium may seem normal on palpation. The first heart sound is normal, and there usually is a soft systolic murmur maximal at the second left interspace; less commonly a loud murmur is present, and at times no murmur at all may be appreciated. The murmur is secondary in importance to the second heart sound. A prime differential point between "innocent pulmonary flow murmur" and the murmur of atrial septal defect is the second heart sound. With a significant left to right atrial shunt, pulmonary closure is delayed, and the second heart sound will remain split throughout the entire examination; it mayor may not vary in the degree of splitting. Pulmonary closure should be normally soft, since an uncomplicated atrial shunt should have normal pulmonary resistance. After evaluation of the second heart sound, close attention should be directed to the diastolic interval for detection of a low-pitched inflow diastolic murmur at the lower sternal border. The presence of this murmur is frequently associated with a shunt magnitude of surgical significance. These inflow murmurs are among the most difficult to hear, and often seem to be an "absence of silence" in diastole, rather than crisp, discrete murmurs. In that congestive heart failure is rare in atrial defects, organomegaly is not to be expected and peripheral pulses in perfusion should be normal. Findings on chest x-ray films are as shown (Fig. lA). Because the shunt is from left to right, fullness (to enlargement) of the right heart chambers and the pulmonary arterial tree is common. On the lateral view, the right heart can be seen to be full, filling in behind the sternum (Fig. lA). The left atrium is usually inconspicuous. The electrocardiogram frequently shows prolongation of the P-R interval, though first degree atrioventricular block is not required for the diagnosis. Often there is an rsR' pattern in Vi> and the right bundle branch block pattern is commonly seen (Fig. IB).

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Figure 1. A, Chest x-ray film in a four year old with an atrial septal defect, with pulmonary flow greater than twice normal. The overall heart volume is increased, with right and left heart borders rounded, giving a globular appearance to the silhouette. Pulmonary blood flow is increased. Note the full right heart, filling in behind the sternum, on the lateral view. B, Electrocardiogram of the same patient, showing right bundle branch block.

The echocardiogram is helpful in detecting the results of atrial level shunts, and can serve as a rough guide as to shunt size. Since the right ventricle must enlarge to accommodate the volume increase of the left to right shunt, enlargement of right ventricular dimension may be seen if the shunt magnitude is significant. As pulmonary flow approaches twice normal, abnormalities of septal motion are usually seen, with paradoxical septal motion expected if the shunt is large. The echocardiographic findings are not specific for atrial septal defect however, but merely reflect right ventricular volume overload. Pulsed Doppler echocardiography can provide positive evidence of the jet of the atrial septal defect in many cases, and can be useful in excluding other causes of right ventricular volume overload, such as tricuspid or pulmonic valve insufficiency. Management Since children with uncomplicated atrial septal defect have a low pressure shunt, good exercise tolerance, good growth and development, and rarely have signs of congestive heart failure or pulmonary hypertension, their clinical management usually is not difficult. These children need no exercise restrictions and have a low risk for infective endocarditis. t ,2 Those with significant cardiomegaly or with a tricuspid inflow murmur, or those suspected of having additional defects, should be sent for evaluation at an early age. Surgical repair of atrial septal defect is recommended in childhood, usually in pre-school years, for those with significant shunts. The risk of operative repair is quite low and excellent results should be expected. Heart size on the chest x-ray film may not decrease dramatically immediately after surgery, but usually returns to normal with the added somatic growth occurring several months to one to two years postoperatively. While catheter closure of atrial septal de-

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Figure 2. Chest x-ray film in a youngster with physical findings of a large atrial septal defect. The arrow points to an anomalously draining pulmonary vein. Most partial anomalies of pulmonary venous drainage are not this obvious.

feet has been accomplished, it is still investigational, and at present operative closure seems preferable for most youngsters. A word about partial anomalous pulmonary venous return is in order. The findings and considerations previously discussed merely reflect left to right shunts at atrial level, and are the same whether the shunt is from an atrial septal defect or from pulmonary venous drainage entering the heart on the wrong side of the atrial septum. For practical purposes, it is exceptionally difficult to differentiate between atrial septal defect and partial anomalous pulmonary venous return. At catheterization, the findings are similar, and it is usually only in unusual cases that a clue may be present as to the anomalous drainage (Fig. 2). If the anomalous drainage occurs at the cardiac level, such as partial anomalous pulmonary venous return to superior caval, right atrial junction, the final diagnosis rests with surgical visualization, and the distinction is unimportant as long as the surgeon carefully assesses the pulmonary venous orifices at the time of repair of the atrial septal defect.

VENTRICULAR SEPTAL DEFECTS Defects within the ventricular septum are common cardiac malformations, and are usually cited as accounting for about 20 per cent of congenital heart disease in children. The spectrum of ventricular septal defect is quite broad, ranging from tiny defects with well localized murmurs (Maladie de Roger) to large ventricular septal defect with complicating pulmonary hypertension. The position of a given patient in this spectrum depends upon the size of the ventricular septal defect, pulmonary vascular resistance, and combined determination of hemodynamics. These relationships may change with time, either with tendency for spontaneous ventricular septal defect closure or development of pulmonary hypertension or pulmonary stenosis. 6-8 The clinical findings in children with ventricular septal defects are variable and depend upon age, size of the defect, and pulmonary resistance. Since right and left ventricular pressures are essentially equal at birth, there is usually no gradient between ventricles across the ventricular septal defect, hence no shunt, and no murmur. It is not surprising, then, that ventricular septal defect murmurs are more

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commonly detected after nursery discharge, and are frequently detected at the six week office check-up. Children with small volume shunts tend to do quite well, since the hemodynamic load is small. In contrast, children with large defects may manifest their intolerance of the large left to right shunt by increasing their respiratory rate, and by slowness of feeding associated with sweating, failure to thrive, and onset of congestive heart failure at a few weeks or months of age. It is generally believed that failure to thrive should not be a problem in the absence of significant congestive failure, and that congestive heart failure, if it occurs, tends to occur in the first several months of life, with an initial episode of failure after a year of age being unusual. On physical examination, children with small ventricular septal defects appear healthy and acyanotic. Their harsh nearly pansystolic murmurs are frequently loud, grade 3 to 4/6 or louder, and well localized to the left lower sternal border; the louder murmurs will have their thrill localized in that area. Muscular defects may have murmurs that undulate throughout systole. Since the shunt magnitude is small, inflow murmurs across the mitral valve are not heard and pulmonary closure should be normal. Children with large ventricular septal defects are quite frequently in the lower percentiles for growth and are frequently taller than heavy and therefore appear thin. One may get a clue to enlarged cardiac volume by notation of the deformed prominent left anterior chest wall, which reflects chest wall development around the large heart. The murmurs in large defects are usually maximal at the left lower sternal border and may be somewhat lower pitched, if not distinctly rumbling in quality; wide radiation is frequent. Pulmonary closure may be rather prominent, and there is usually an inflow murmur across the mitral valve with larger defects. Just as with the inflow murmur across the tricuspid valve in atrial septal defect, the mitral inflow murmur in a large ventricular septal defect may not be a crisp discrete murmur, but appear more as an "absence of silence" in diastole. With the faster heart rates that are encountered as the child attempts to compensate for his inefficient heart, the systolic and diastolic murmurs and loud split second sound may combine to give the impression of a very busy heart. Peripheral pulses and perfusion are normal in the absence of congestive heart failure. The liver edge is normal in small defects, but may be rounded or enlarged as increases in shunt size and congestive failure are encountered. Coloring should be normal in the absence of pulmonary hypertension or pulmonary stenosis. On the extreme end of the spectrum, children with significant pulmonary hypertension may have unimpressive murmurs, but loud, booming, second heart sounds from accentuated pulmonary closure; if pulmonary resistance is high enough to reverse the direction of ventricular septal defect shunt, these children will manifest their right to left shunts by systemic desaturation and clubbing of the nail beds. Electrocardiogram is normal in children with small ventricular septal defects; a truly normal electrocardiogram weighs against the presence of significant pulmonary hypertension or a large left to right shunt. With uncomplicated left to right shunt of significance, left ven-

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A

Figure 3. A, Chest x-ray film of an infant with a ventricular septal defect. The heart volume, judged from the frontal and lateral view, is increased, with the arrow emphasizing the left ventricular contour. Note the prominent left atrium and increased pulmonary blood flow. B, Electrocardiogram of the same infant. Note the prominent anterior and posterior forces across the precordium and the deep Q-waves. This tracing is consistent with com· bined ventricular hypertrophy, with the left ventricle being dominant.

tricular dominance or left ventricular hypertrophy may be seen (Fig. 3). Prominence of right heart forces or the presence of right ventricular hypertrophy suggests pulmonary hypertension or pulmonary stenosis; since pulmonary hypertension is a frequent complication of large ventricular septal defects, the finding of combined ventricular hypertrophy in younger infants with large ventricular septal defect is not unexpected.

Chest X-Ray Films Those with small defects usually have normal heart size and configuration and pulmonary blood flow. Since there is no stress from hemodynamic load or hypoxia, the thymic shadow may be rather prominent. In children with larger left to right shunts, prominence of left atrium, left ventricle, and pulmonary vascular markings are seen (Fig. 3).

M-mode echocardiography does not visualize the actual hole in the ventricular septum in most cases, but will reflect the shunt volume by enlargement of left atrial and left ventricular dimensions. In the absence of additional defects, the echo determination of left-sided dimensions may be helpful in serial estimation of shunt size. If pulmonary hypertension complicates ventricular septal defect, suggestive evidence may be obtained from the pulmonary valve echo. Pulsed Doppler echocardiography is a useful recent development, allowing detection of the ventricular septal defect jet, determination of the location of the defect within the ventricular septum, and differentiation of the ventricular septal defect flow abnormality from those induced by other defects.

Management The clinical evaluation of an infant and younger child with ventricular septal defect murmur requires frequent assessment, especially in early infancy. Since the level of pulmonary resistance is high near

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birth and falls days or weeks later, classic findings of "small defects" may be seen at three weeks of age, with progression to congestive heart failure from large left to right shunt associated with the falling pulmonary resistance. It is useful to have the parents pay attention to the infant's feeding pattern. This can be done without causing undue alarm because they will be reassured that the child is doing well if the feeds are vigorous, without sweating, heavy breathing, or pausing. If congestive heart failure is to occur, an early manifestation is poor feeding, and clinical evaluation should reveal cardiomegaly, hepatomegaly, resting tachycardia and tachypnea, as well as the presence (or suspicion) of an inflow diastolic murmur at the apex. Children with larger ventricular shunts are at increased risks for penumonias, as the lungs are very wet, and cardiomegaly may interfere with normal bronchopulmonary toilet. Since pneumonia may be life-threatening to an infant with a large ventricular shunt, earlier evaluation for pneumonia is prudent. In the serial evaluation of children with ventricular shunt, one should run down a mental check-list reflecting the possible natural history of ventricular shunts. For example, the presence of a larger heart or occurrence of an inflow murmur in a young infant whose pulmonary resistance has fallen may herald an increase in shunt size and onset of failure. A smaller heart or development of right ventricular hypertrophy on the electrocardiogram and an increase in the intensity of pulmonary closure may indicate the development of pulmonary hypertension. More favorable, perhaps, in a child with a smaller heart, right ventricular hypertrophy and a very soft pulmonary closure may indicate the development of pulmonary stenosis. Spontaneous closure of ventricular septal defects does occur in a fair number of cases; it tends to occur earlier rather than late and is probably more frequent in smaller defects. Other defects may occur in patients with ventricular shunts, but may be masked by the prominent clinical findings of ventricular septal defect. Coarctation of the aorta should be detectable by physical examination and blood pressure determination; a decrescendo diastolic murmur at the base should suggest aortic valve insufficiency or patent ductus arteriosus. In the absence of pulmonary hypertension, no exercise restrictions are required. 2 Maintenance of good dental hygiene and precautions against infective endocarditis are very important.!

Operability Small ventricular defects do not require surgical repair, since the hemodynamic load is small, life expectancy is normal, and the risk of operation exceeds the expected natural history. In larger defects, the timing of surgery usually depends on the presence or absence of various complicating factors. Pulmonary hypertension begs early intervention when appropriate, usually involving open repair in infancy. If pulmonary stenosis develops, it is usually reasonable to proceed with open repair prior to the onset of cyanosis. If frequent or life-threatening pneumonia impedes a child's growth and development, surgical repair may be recommended rather early. In the majority of instances, open

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repair of a ventricular septal defect is preferable to palliation by pulmonary artery banding. Generally good results may be expected from surgical repair of ventricular septal defect in appropriate candidates. Occasionally, incomplete closure may be encountered in the postoperative period. Less frequent complications are those of heart block or development of aortic insufficiency.

ENDOCARDIAL CUSHION DEFECTS (ATRIOVENTRICULAR CANAL) Abnormal development of the endocardial cushions may lead to defects of the atrial septum, ventricular septum, and the atrioventricular valves. When the ventricular septum is intact, the defect is termed partial or incomplete endocardial cushion defect, and consists of a defect low in the atrial septum, an ostium primum atrial septal defect associated with a variable degree of atrioventricular valve (usually mitral) abnormality. If mitral valve function is adequate, the child may function as those with other atrial level left to right shunts. When the ventricular septum is involved in the defect, the defect is termed a complete endocardial cushion defect. These children, especially if atrioventricular valve insufficiency is severe, may develop severe congestive heart failure. The clinical findings in ostium primum atrial septal defect may present as other atrial level shunts, but can often be distinguished by electrocardiograph and/or their murmur of mitral insufficiency. Children with complete endocardial cushion defect may present early with severe congestive heart failure, and may present very difficult management problems. There is an association between endocardial cushion defect, usually complete, and Down's syndrome. Physical examination in a child with simple ostium primum atrial septal defect usually reveals a healthy-appearing child, whereas those with complete endocardial cushion defect may have severe failure and mild de saturation. In the absence of significant mitral insufficiency, the physical findings in an ostium primum atrial septal defect may be very similar to those previously discussed for other atrial level shunts. Similarly, in the absence of mitral insufficiency, the auscultatory findings in a complete endocardial cushion defect may be rather similar to those previously described for ventricular septal defect. However, the presence of a blowing pansystolic apical murmur, with radiation to the axilla, betrays mitral insufficiency, and suggests that the atrial septal defect or ventricular septal defect may not be simple. Findings of pulmonary hypertension, manifest by loud pulmonary valve closure, are common in complete endocardial cushion defects, contributed to both by the mitral insufficiency and the left to right ventricular and atrial level shunt. Electrocardiogram is helpful when one entertains the possibility of endocardial cushion defect, since nearly all cases will have a superior QRS axis, with or without an intraventricular induction defect or first degree atrial ventricular block (Fig. 4). Left ventricular hypertrophy

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Figure 4. A, Electrocardiogram of an infant with an endocardial cushion defect. The negativity of QRS is I and AVF should immediately suggest an abnormal (superior) axis, which is characteristic of endocardial cushion defect. The T waves are prominent, and the P-R interval is prolonged. Precordial leads with tall R in VI and deep S in V. show right ventricular hypertrophy. B, Chest x-ray film of the same patient, showing impressive generalized cardiomegaly and increased pulmonary blood flow. C, Chest x-ray film of an older child with endocardial cushion defect. The heart is large, with prominence of all chambers. Though pulmonary blood flow is increased, it is not nearly so striking as the heart size; the heart size is increased to a greater extent than is expected for the degree of pulmonary blood flow because of atrioventricular valve regurgitation.

and/or p-mitrale can be seen if the mitral insufficiency is severe. Right ventricular hypertrophy is expected if pulmonary hypertension complicates the defect. The findings on chest x-ray film depend greatly on the type of defect. While the left atrium is usually inconspicuous in simple atrial septal defect, there may be some perceptible left atrial enlargement if mitral regurgitation is a significant factor. In complete endocardial cushion defect, biventricular enlargement may also be seen. If tricuspid insufficiency is present, the right atrial contour additionally may be prominent. With the element of atrioventricular valve insufficiency that is expected in endocardial cushion defect, one frequently encounters a heart size that appears somewhat greater than would be expected on the basis of an increase in pulmonary blood flow (Fig. 4C). With significant left to right shunt, an increase in pulmonary blood flow is expected, and a change consistent with pulmonary venous congestion mayor may not be detected. Marked cardiomegaly and increased flow may occur early. An echocardiogram can be helpful when entertaining the diagno-

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sis of endocardial cushion defect. The mitral valve echo usually appears abnormal and appears to be displaced somewhat anteriorly within the left ventricular cavity, with narrowing of the left ventricular outflow tract, corresponding in part to the angiocardiographic finding of "goose-neck deformity" of the left ventricular outflow tract. Additionally, the valve leaflets appear abnormal, and in complete forms of endocardial cushion defect may frequently be followed through the ventricular septum, fused into tricuspid valve tissue. Pulsed Doppler echocardiography is a useful adjunct in detecting mitral and tricuspid valve insufficiency. Contrast echocardiography and sector scan techniques may offer noninvasive differentiation of incomplete from complete endocardial cushion defect. Management The management considerations for uncomplicated ostium primum atrial septal defect are rather similar to those discussed for other atrial level shunts, except that precautions against infective endocarditis are quite necessary because of mitral valve insufficiency. In complete endocardial cushion defect congestive heart failure is a frequent and troublesome problem as are pneumonias. Management guidelines are otherwise similar to those for patients with ventricular septal defects, including little need for exercise restrictions in the absence of pulmonary hypertension. 2 Unfortunately, children with complete endocardial cushion defect are often in need of surgical asistance because of severe failure. With recent surgical advances, endocardial cushion defects are being repaired with reasonable success. Since pulmonary artery banding has been associated with a very high mortality for the banding procedure alone (in the range of 70 per cent), attempts at primary repair are increasingly preferred. Guidelines for repair are similar to those for other defects, except that the severity of atrial ventricular valve abnormality may alter the timing of surgical intervention. Operative and postoperative complications include heart block and continued abnormality of the atrioventricular valves. Precautions against infective endocarditis are appropriate before and after surgery.!

PATENT DUCTUS ARTERIOSUS The ductus arteriosus is a fascinating structure, histologically different from either the aorta or pulmonary artery, the histologic structural difference having to do with expected closure. It is generally believed that the ductus begins to close within 10 to 15 hours of age in a term infant, with complete closure occurring within two or three weeks. Some of the factors involved in closure are the level of p02' which is maturation dependent, and the action of vasoactive substances such as prostaglandins, which are also maturation dependent. The presentation and manifestation of persistent patency of the ductus have to do with the size of the structure, pulmonary and systemic resist.illlCeS, and the maturity and condition of the patient. If the ductal

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structure is large, an increasing shunt magnitude may be seen as pulmonary resistance decreases. As the shunt is from aorta to pulmonary artery, pulmonary vascular bed, left atrium, and left ventricle, a significant ductus is usually a left heart problem unless pulmonary hypertension and lung disease complicate. If a term infant suffers from any condition causing hypoxia (such as meconium aspiration), a delay in closure of the ductus may occur. While persistent patency of the ductus is quite common in the premature infant, it is somewhat less commOn in term infants and children, and is usually felt to account for about 10 per cent of congenital heart disease in children, excluding premature infants. There is an association with congenital rubella syndrome and scarring of the ductal structure from the intrauterine infection, hence lack of closure. The clinical findings of patent ductus may be quite variable. If the ductus is large, the infant may have difficulty with congestive heart failure and present as do infants with other high pressure left to right shunts. If the ductus is smaller, the child may be fully asymptomatic. In those with significant increases in pulmonary blood flow, lower respiratory tract infections may be more frequent. On examination, the findings in a child with a small volume shunt will include a normal precordial examination, normal peripheral pulses, and normal coloring. With larger shunt magnitude, precordial activity in left ventricular impulse may be more prominent, pulses may be prominent to bounding, and widening of the pulse pressures may occur. The murmur of patent ductus arteriosus is helpful if it is typical, conforming to the classic "machinery" or continuous murmur throughout systole and diastole. In smaller infants however, typical murmurs seem less common; there may be only a short but distinctly crescendic systolic murmur usually at the left upper sternal border, and later, as pulmonary resistance decreases, one may hear it spill into diastole. Depending on factors such as the ratio of pulmonary to systemic resistance and the size and configuration of the ductal structure, a continuation of the diastolic murmur right through to the first heart sound may occur, giving a murmur throughout systole and diastole. During the examination, presence of a venous hum should be excluded by positional or neck maneuvers and by close attention to the continuous "murmur." While a ductal murmur peaks at the second heart sound and may obliterate it with spill into diastole, the venous hum has diastolic extenuation and can usually be obliterated by compression of the neck vein, or by assumption of a supine position. Although the great majority of continuous murmurs at the upper left sternal border are the result of persistent patency of the ductus, the possibility exists that other defects, such as truncus arteriosus, aorticpulmonic window, and various arteriovenous fistule, could present similar auscultatory findings. With truly continuous murmurs, evaluation of the second heart sound is sometimes difficult, as it is obscured. If, however, pulmonary hypertension is a complicating factor, the duration of flow in diastole may be limited and pulmonary closure may become accentuated and obvious. It is difficult to use the continuity of the murmur as an ab-

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Figure 5. A, Chest x-ray film of a three month old infant with a large patent ductus arteriosus. The ventricular contour in the frontal view is more left than right. In the lateral view, the large left heart is outlined by the upshifted bronchus. Pulmonary blood flow is increased. Though this patient has a ductus, similar radiographic findings could be found with ventricular septal defect (compare with Figure 3A). B, Electrocardiogram of the same patient, with evidence of left ventricular hypertrophy (tall R waves II , III AVF, V, and V6 ). The Twave abnormalities suggesting "strain" are emphasized by the arrows.

solute indicator, since we have encountered children with very large left to right shunts with no murmur, and children with pulmonary hypertension complicating ductus with a murmur that spills well to diastole. The electrocardiographic findings vary with the degree of left heart overload, the duration of that overload, and the age of the patient. The presence of a small ductus in a newborn infant may have no electrocardiographic manifestations, with the tracing showing only the normal degree of right ventricular dominance for age. Those with longer-standing shunts of significant size will usually have increases in left ventricular forces and may show left ventricular hypertrophy. If a very large shunt is contributing to an elevation of pulmonary artery pressure, or is associated with other diseases that increase pulmonary artery pressure, combined ventricular hypertrophy may be seen. Evaluation of the chest x-ray film in children .suspected of having a patent ductus should be directed toward examination of left atrium, left ventricle, and pulmonary blood flow (Fig. 5). With significant left to right shunt, the pulmonary venous return to left atrium should produce enlargement of that chamber, the left ventricle, and though sometimes difficult to detect, of the aorta. In the absence of an increase in pulmonary blood flow or chamber enlargement, it is unlikely that a significant shunt exists. Extreme difficulty may be encountered in the radiographic evaluation of premature infants with both lung disease and ductal patency, and ultrasound evaluation of chamber size is probably more reliable. The echocardiogram can be very useful in assessing shunt magnitude in patent ductus arteriosus. 5 However, the echocardiogram is not specific for patent ductus arteriosus, since a left to right shunt at the ventricular level will also yield enlargement of the left atrium and left ventricle. Pulsed Doppler echocardiography is specific for patent ductus arteriosus, can be useful in excluding other lesions that may be masked by the ductal murmur, and by timing the duration of diastolic

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flow, may provide a clue as to the presence of pulmonary hypertension complicating ductal patency.lO Management In the absence of congestive failure or evidence of pulmonary hypertension (loud pulmonary closure, right ventricular hypertrophy), children with patent ductus arteriosus usually do quite well and may undergo elective ductus repair at a convenient time. This is usually done in the pre-school age group. In those with atypical ductus, congestive failure or suspected pulmonary hypertension, early referral is advised, since not all that presents as a "simple ductus" is truly just a ductus. Just as left to right shunts at the ventricular level may be disposed to inflammatory pulmonary disease, so may large ductal shunts. Recurrent or severe difficulty with pneumonias may be an indication for earlier surgical intervention. A surgical approach for patent ductus arteriosus is relatively safe, the left thoracotomy scar cosmetically satisfactory, and the surgery may well be curative unless a bicuspid aortic valve or other defect is also present. Excellent results should be anticipated from surgery. In the absence of pulmonary hypertension, children with patent . ductus arteriosus do not require exercise restriction. 2 They do require precautions against infective endocarditis, and if the ductus is associated with a bicuspid valve, precautions against infective endocarditis should continue after ductal surgery.1 Two new developments should be mentioned that pertain to patent ductus arteriosus. The first is catheter closure of the ductus, a technique used with considerable success in a large number of patients both in Japan and in Germany. These techniques make use of the fact that flow is from aorta to pulmonary artery, and that many ductal structures have a smaller pulmonic end than aortic end. Hence they lend themselves well to a "plug" closure deposited by a catheter. While operative intervention is the procedure of choice at the present time in this country, with demonstrated low morbidity and mortality, we will follow the investigation in other countries with interest. We have found the use of pulsed Doppler echocardiography quite useful for youngsters with ductus arteriosus. Through that technique's ability to detennine direction and quality (smooth vs. rough) of blood flow at known sites, a specific ductal jet can be detected as it enters the pulmonary artery. One should be able to exclude the presence of a ventricular septal defect, and therefore have greater reliability in presu!ning that the degree of left atrial and left ventricular enlargement stems only from a ductus; a large ventricular septal defect or a ventricular septal defect combined with ductus !night give the same left atrial and left ventricular enlargement. Additionally, the technique allows for the detection of turbulent flow in the aorta that may stem from the bicuspid aortic valve, and may be useful in deciding which patients with patent ductus need infective endocarditis prophylaxis after ductal surgery. Since pulmonary hypertension as a complication of patent ductus is a factor of some importance, the noninvasive as-

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sessment of pulmonary resistance is of interest. By timing the duration of diastolic flow, we have been able to separate those children with normal pulmonary resistance from those with high pulmonary resistance by pulsed Doppler echocardiography.lO This offers the possibility of noninvasive detection of pulmonary hypertension as a complication of ductus, and avoidance of invasive study in children in whom the presence or absence of pulmonary hypertension is the only indication for catheterization. While the older child with patent ductus arteriosus is usually not much of a problem, the presence of patent ductus arteriosus in premature infants has become a problem of near epidemic proportions in some (but not all) nurseries. The problem is likely one contributed to by multiple factors, the factors affecting the prevalence of the problem, and proper management. The clinical presentation may be quite variable in the premature infant. Some will have classic continuous murmurs, bounding pulses, left ventricular hypertrophy on electrocardiogram, and chest x-ray films showing prominent left atrium and left ventricle, with prominent increase in pulmonary blood flow. The presentation is markedly clouded, though, by the multiple problems common to prematurity. The association of ductal patency complicating respiratory distress syndrome can provide special problems in assessing the degree of pulmonary blood flow; as respiratory distress begins to resolve and the ductal shunt perhaps increases, one is hard-pressed to say which radiographic changes are due to increases in pulmonary blood flow, and which are due to parenchymal pulmonary disease. Similarly, there is difficulty in the proper interpretation of "fullness of pulses" in the premature infant whose arteries are just under the skin. Also, murmurs may be obscured by respirator noise, but with the respirator connected briefly, some murmur can usually be heard. We have found that the magnitude and character of the murmur have little to do with the shunt size, and indeed the murmur may vary greatly from moment to moment. The proper use of echocardiographic dimensions can be exceptionally helpful in providing an objective measurement useful in estimating the size of left to right ductal shunt. s One must, however, perform a complete examination to screen for suggestions of structural intracardiac disease, and be aware of proper methods of measurement. If the left atrial and left ventricular dimensions exceed "normal values" in the presence of normal to usually increased indices of left ventricular contractility, there is echocardiographic support for presence of a left to right shunt distal to the mitral valve (ventricular septal defect and/or patent ductus arteriosus). A variety of means are available to demonstrate the presence of the left to right shunt at greater vessel level, including contrast echocardiography, injection of radiopaque material through the indwelling thoracic aortic catheter with fluoroscopic or single plane or cineangiocardiographic filming, or pulsed Doppler echocardiography. The latter has the advantage of providing

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evidence of the presence or absence of additional defects, and of detecting the presence of pulmonary hypertension. Noninvasive assessment may not always be possible, and if question exists invasive study may be indicated. ' The medical management of significant patent ductus arteriosus in the premature infant consists of fluid restriction or modification of fluid administration to a range appropriate for the size of the infant, in light of his insensible water losses. l l If the simple fluid overload seems to have precipitated a ductal problem, diuresis may be beneficial, and many children will require digitalization to cover the possibility of congestive heart failure. It is likely that a large proportion of premature infants may develop "wet lungs" and/or pulmonary edema, simply from fluid volume increases, and not be pushed into congestive heart failure. If failure is present and is uncontrollable with digitalization, diuresis, and fluid restriction, or if the infant manifests hemodynaInic intolerance to a fluid load required to permit growth, consideration should be given to intervening for ductal closure. There is some urgency in intervening for ductal closure if medical treatment has not achieved success in 48 to 72 hours, especially if the lack of success hinders the weaning from high oxygen concentrations and pressures frequently required in respiratory support. Two methods are currently used for abolition of the ductal shunt. Surgical ligation of the ductus has been shown to be a reasonable approach, with a risk considerably lower than initially might have been suspected. It does require the assistance of a skillful, fast-working, and experienced cardiovascular surgeon, and an anesthesiology staff familiar with the extent of pressure and rate required to maintain acceptable gas exchange intraoperatively. A surgical approach may not be reasonable in some centers, because of lack of resources or other factors felt to affect adversely the surgical candidacy of the child. While ductal ligation is our current preference, pharmacologic attempts at closure may be reasonable if surgical ligation is not feasible. Those who have had considerable experience with pharmacologic closure of patent ductus arteriosus in premature infants through the use of indomethacin,3. 4 a prostaglandin synthatase inhibitor, indicate that the use of these agents still should be considered to be investigational. Prospective studies are as yet incomplete in defining the proper candidate for pharmacologic closure and perhaps the optimal dosage regimen. 9 The long-term effects of interference with naturally occurring vasoactive substances is not known, but neither has it been demqnstrated to be a significant problem. Contraindications to pharmacolo. gic closure include hematologic abnormalities, gastrointestinal or central nervous system bleeding, and hyperbilirubineInia. Even though pharmacologic closure of the ductus is still considered to be investigational, wide disseInination of the technique has led to considerable random usage. 3. 4 If surgical intervention is not feasible, the use of pharmacologic measures probably carries less risk than not treating the ductus at all.

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JAMES GEOFFREY STEVENSON

REFERENCES 1. American Heart Association Committee Report: Prevention of bacterial endocarditis. Circulation, 56: 139A, 1977. 2. American Heart Association Committee Report: Report of the Intersociety Commission for Heart Disease Resources. Circulation, 44:A-208, 1971. 3. Friedman, W. F.: Medical management of ductus arteriosus. Perinatal Care, 77:18. 1977. 4. Friedman, W. F., Heymann, M. A., and Rudolph, A. M.: Commentary: New thoughts on an old problem - Patent ductus arteriosus in the premature infant. J. Pediat., 90:338, 1977. 5. Hirschklau, M. J., DiSessa, T. G., Higgins, C. B., et al.: Echocardiographic diagnosis: Pitfalls in the premature infant with a large patent ductus arteriosus. J. Pediat., 92:474, 1978. 6. Moss, A. J., Adama, F. H., and Emmanouilides, G. C.: Heart Disease in Infants, Children and Adolescents, Edition 2. Baltimore, Williams and Wilkins Co., 1977. 7. Nadas, A. S., and Fyler, D. C.: Pediatric Cardiology. Edition 3. Philadelphia, W. B. Saunders Co., 1972. 8. Rudolph, A. M.: Congenital Diseases of the Heart. Chicago, Year Book Medical Publishers, 1974. 9. Sharpe, G. L., and Altshuler, G.: Ductal manipulation - A note of caution. J. Pediat., 90:335, 1977. 10. Stevenson, J. G., Kawabori, 1., Dooley, T. K. et al.: Pulsed Doppler echocardiographic detection of pulmonary hypertension in patent ductus arteriosus. Circulation, 56(Supp. III):40, 1977. 11. Stevenson, J. G.: Fluid administration in the association of patent ductus arteriosus complicating respiratory distress syndrome. J. Pediat., 90:257, 1977. Department of Pediatrics University of Washington School of Medicine Seattle, Washington 98195

Acyanotic lesions with increased pulmonary blood flow.

Symposium on Pediatric Cardiology Acyanotic Lesions with Increased Pulmonary Blood Flow James Geoffrey Stevenson, M.D.* As in the preceding article...
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