chapter 44 echocardiography in congenital heart disease · stenosis, and the presence of atrial...

Transthoracic multiplane imaging by two-dimensional (2-D) echocardiography defines theanatomy of the heart and the great vessels.Analysis of each cardiac segment allows com-plete definition of the configuration and theposition of the cardiac structures and their spa-tial interrelations. The cardiac chambers and theintracardiac valves are shown with high resolu-tion. Because tortuous vessels may be difficultto define by a “slice” technology such asechocardiography or magnetic resonance imag-ing, color Doppler echocardiography is custom-arily used to provide a map of blood velocityand direction that complements the 2-D image.Small septal defects and fistulous connectionsmay be recognized only by perturbations inblood flow when the anomaly is too small to bevisualized clearly. Pulsed and continuous waveDoppler echocardiography provide excellenttime resolution that allows precise quantifica-tion of blood velocity. Positional and velocityinformation are combined to assess the pres-ence and the severity of a valvular obstructionor insufficiency, the position and the size of jetsassociated with septal defects, and abnormalflow in large vessels in congenital lesions such asanomalous systemic and pulmonary venousreturn, coarctation of the aorta, and patent duc-tus arteriosus.

CONGENITAL HEART DISEASE

Transesophageal echocardiography (TEE)allows imaging planes different from thoseobtained in a standard transthoracic study.Miniaturization of transducer components nowallows TEE to be performed in infants who weighas little as 2.5 kg. Structures not well visualizedby transthoracic echocardiography (TTE), prima-rily those located posteriorly are well visualizedby TEE. In the older child or a child in whomthere are poor transthoracic windows, TEE canalso be very useful in the evaluation of congeni-tal heart disease. Oftentimes during cardiac sur-gery it is important to address specific issues.The presence of abnormalities such as anom-alous pulmonary venous return, pulmonary veinstenosis, and the presence of atrial baffle flowcan be determined with intraoperative TEE. Inaddition, an immediate intraoperative or post-operative assessment of the adequacy of surgi-cal repair is possible. These perioperative exam-inations are usually targeted, however, and arenot a substitute for a complete preoperativetransthoracic evaluation.

Fetal echocardiography is the newest frontierin pediatric echocardiographic imaging. Withthe use of transvaginal transducers, detailedfetal cardiac anatomy can be seen as early as 12weeks of gestation. Transabdominal imagingcan be performed by 16 weeks, although the

429

Multiple-plane cardiac imaging by echocardiography can noninvasively define the anatomy of theheart and the great vessels by delineating the configuration and the position of the cardiac structuresand the spatial interrelations of these structures. The information obtained can be used to accuratelydiagnosis and for prognosis in complex congenital heart disease. In many pediatric cardiac tertiarycare centers, echocardiography is the only diagnostic test performed before neonatal congenitalheart surgery. With advances such as pulsed and color Doppler echocardiography and improve-ments in the size and capabilities of transducers and other imaging equipment, pediatric echocar-diography has gained rapid acceptance. The technology allows real-time three-dimensional imaging,assessment of myocardial function, and precise definition of cardiac anatomy from the fetal stagethrough adulthood. For all of these reasons, echocardiography has become the standard noninvasivediagnostic imaging modality for pediatric cardiology.

John L. Cotton and G. William Henry

Chapter 44

Echocardiography in Congenital Heart Disease

optimal time for fetal echocardiography isapproximately 18 weeks. Abnormalities detect-ed at 18 weeks by echocardiography may beimportant in the decision for further imaging,chromosomal testing, or even termination of thepregnancy. As with TTE of infants, fetal echocar-diography can identify intracardiac anatomy,blood flow across all the valves in the heart, sizeand orientation of the great vessels, cardiac func-tion, and cardiac rhythm. The order and the win-dows used in a fetal echocardiogram depend onthe position of the fetus, the amount of fluid inthe uterus, and the size and motion of the baby.

TRANSTHORACIC IMAGING IN PEDIATRICS

Each pediatric echocardiography laboratoryhas a specific protocol for acquiring a completestudy of the cardiac anatomy in children.Because patient cooperation is needed, inyoung children and infants all images may notbe obtained using standardized positions.Some centers use conscious sedation for allpatients under a certain age to ensure uniformi-ty of studies. Another option is “video seda-tion”: child-friendly videos played during thestudy to distract the patient and allow time toobtain diagnostic images. As long as clear pic-tures are obtainable, scanning can be per-formed with the patient sitting in a parent’s lap,feeding, or even in a stroller. This approach sub-stantially decreases the number of patients whomust be sedated.

The protocol for a complete study includesviews from the four major echocardiographicwindows: parasternal, apical, subxiphoid, andsuprasternal. Each window provides the imageof the heart from a different angle, allowing mul-tiple, corroborating views of the same struc-tures. The image from each window begins froma standard reference view; then a sweep of theheart is made, first with 2-D scanning and thenwith color Doppler. The color Doppler mappingdefines the location for pulsed Doppler scan-ning in each plane. Once the pertinent informa-tion is obtained, the transducer is rotated 90˚ toperform an orthogonal sweep. The sonographerand the interpreting physician can reconstructmultiple 2-D images into a three-dimensionalrepresentation of the cardiac anatomy.


ECHOCARDIOGRAPHY IN CONGENITAL HEART DISEASE

Cardiac function and blood flow are calculat-ed from Doppler mapping and from the 2-Dimages obtained. For example, pulmonary andaortic flow are calculated from the mean veloci-ty and diameter of the vessel at the area of inter-est as follows:

Blood flow = (mean flow velocity) 5(time) 5 (cross-sectional area of vessel)

Peak instantaneous gradients are calculatedfrom a simplified Bernoulli equation, using peakflow velocity within the stenotic jet in the fol-lowing formula, where V is the peak flow veloc-ity measured by spectral Doppler scanning:

Peak pressure gradient = 4V2

This gradient is used to estimate pressures inthe different cardiac chambers. Several differentmethods can be used to quantify left ventricular(LV) function. LV fractional shortening (FS) is ameasurement of the percentage of change in LVdiameter:

FS = (LV end-diastolic dimension – LV end-systolic dimension) / (LV end-diastolicdimension)

Ejection fraction is similarly calculated, usingmeasured LV volumes.

In the discussion that follows, echocardio-graphic examinations are described for somecommon congenital heart lesions, with empha-sis on the information needed to plan surgicalintervention and the best techniques to obtainthis information.

ATRIAL SEPTAL DEFECTTransthoracic echocardiography is often suffi-

cient to define the size and the location of anatrial septal defect (Fig. 44-1). Pulsed and colorDoppler echocardiography identify the direc-tion and the amount of shunting at the atriallevel. Other findings can confirm the presenceof a hemodynamically significant shunt. Forinstance, RV volume overload can produce dias-tolic bowing of the ventricular septum to the leftduring diastole, with the left ventricle assumingan elliptical shape. Partial anomalous pulmonary

430



Left Atrium

Right atrium

Atrial septal defect

Atrial Septal Defect

Transducer

431

Figure 44-1



432

veins can be identified by 2-D echocardiogra-phy and should be sought in patients with anatrial septal defect so that they can be correctedat the time of surgery. The flow of these veinscan be traced by color Doppler. TTE and sub-xiphoid echocardiography are usually sufficientto define the anatomy of the atrial septum andthe pulmonary veins in infants and small chil-dren. For older children and adults, TTE may beneeded for full anatomic definition. Cardiaccatheterization is not usually needed in the eval-uation of atrial septal defects.

VENTRICULAR SEPTAL DEFECTMultiple views are needed to visualize the

entire interventricular septum. TTE with 2-Dimaging will usually demonstrate the size and thelocation of the interventricular communications.Color Doppler can be used to determine thedirection of shunting across the ventricular septaldefect (VSD) (Fig. 44-2). By measuring the direc-tion and the velocity of flow across the defect,pulsed and continuous wave Doppler can beused to estimate the pressure gradient across thedefect. Cardiac catheterization is not requiredbefore surgery unless the physical and noninva-sive findings are atypical or contradictory.

ATRIOVENTRICULAR SEPTAL DEFECTEchocardiography is also an important tool for

the preoperative assessment of atrioventricularseptal defects (AVSDs) (Fig. 44-3). 2-D imagingdefines atrioventricular (AV) valve morphology.If the superior bridging leaflet is divided and hasattachments to the crest of the ventricular sep-tum, it is considered a type A valve. Straddling ofcentral superior bridging leaflet attachments to apapillary muscle in the right ventricle defines atype B valve. If the superior bridging leaflet hasno attachments to the crest of the interventricu-lar septum and the valve leaflet is free-floating, itis considered a type C valve. Superior bridgingleaflet septal attachments can obstruct the ven-tricular portion of the defect restricting shuntingor cross the LV outflow tract—either of whichcan cause obstruction to aortic blood flow.Anterolateral papillary muscle insertions tend tobe rotated counterclockwise in AVSDs and sitmuch closer to the posteromedial papillary mus-cle, which may create a “parachute”-like defor-

mity of the left portion of the AV valve. Any sig-nificant length of suturing of the superior andinferior leaflets during surgical repair risks creat-ing LV inflow obstruction. In the intermediateform of AVSD, it is not uncommon to find short-ened and immobile leaflets with thick, chordalattachments that limit the ability to properlyfashion a functioning AV valve. Echocardio-graphic findings can sometimes anticipate thisinsufficiency of valvular tissue.

Color, continuous wave, and pulsed Dopplerechocardiography assess potential gradientsacross the outflow tracts and show the directionof shunting across the septal defect. ColorDoppler interrogation of the AV valve usuallyreveals some degree of insufficiency. A double-orifice mitral valve, present in about 5% ofAVSDs, can be identified by echocardiography.The usual ostium primum atrial septal defect(with or without a shunt at the ventricular level)is also well visualized with 2-D echocardiogra-phy. The VSD component of AVSDs is usuallysingle and in the inlet position; however, multi-ple defects can be ruled out with close colorDoppler interrogation of the septum.

COARCTATION OF THE AORTAEchocardiography can be valuable in making

the diagnosis of coarctation of the aorta (Fig. 44-4). The characteristic narrowing of theaorta with a “posterior ledge” can be identifiedwith 2-D imaging but may be difficult to appre-ciate if a patent ductus arteriosus is present.When a pressure gradient is present, a high-velocity jet will be present at the coarctationsite. At the distal transverse arch, there is dias-tolic and systolic forward flow. Damped pulsatileflow is seen in the thoracic aorta. Often somedegree of hypoplasia of the distal transverse aor-tic arch exists. 2-D echocardiography can usuallydistinguish coarctation of the aorta from inter-rupted aortic arch, but angiography may be nec-essary if the findings are ambiguous. It is alsoimportant to evaluate the patient for other anom-alies that commonly present with coarctation ofthe aorta. As noted previously, VSDs can be welldefined with echocardiography. Bicuspid aorticvalve and mitral valve abnormalities should becarefully examined by 2-D imaging, color flow,and pulsed Doppler probing. LV outflow tract



433

Ventricular Septal Defect

Left ventricle

Transducer

Right ventricle

Ventricular septal defect

Aorta

Figure 44-2



434

Interventricularseptal defect

Right atrium

Left atrium

Interatrialseptal defect

Left ventricle

Right ventricle

Atrioventricular Septal Defect

Ventricular septum

Figure 44-3

Transducer



435

Coarctation of the Aorta

Transverse aortic arch

Coarctation

Figure 44-4

Transducer



436

obstruction and other forms of subaortic obstruc-tion can be seen, including posterior infundibularmalalignment in the presence of a VSD.

TRANSPOSITION OF THE GREAT ARTERIES

Echocardiography can provide a definitivediagnosis of transposition of the great arteries bydemonstrating the origin of the aorta from theright ventricle and the pulmonary artery fromthe left ventricle. Cross-sectional imaging candetermine the presence and size of the interatri-al communication. Echocardiography can oftendefine the origins of the coronary arteries, butconsiderable experience is needed to confident-ly assess more distal branching patterns. Pulsedand color flow Doppler will identify a patentductus arteriosus and delineate the magnitudeof shunting at the atrial and ventricular levels.Ventricular mass and volumes can be quantifiedwith both 2-D and M-mode echocardiography.The shape of the interventricular septum in sys-tole indicates the differential pressures betweenthe right and the left ventricles because the sep-tum will bow toward the chamber with the leastwall stress. In addition, the LV outflow tract canbe interrogated with pulsed and color flowDoppler for signs of obstruction.

TETRALOGY OF FALLOTDiagnosis of tetralogy of Fallot requires delin-

eation of the structures listed in Table 44-1. Sincemost of these structures are well visualized withechocardiography, many infants do not needcatheterization before repair of tetralogy of Fal-lot with a patent main pulmonary artery andcontinuity between the branches (Fig. 44-5). TheRV outflow tract is usually well visualized byimaging in a combination of different echocar-diographic planes. The diameters of the pul-monary valve annulus and the proximal pul-monary arteries are measured from parasternal,subxiphoid, and suprasternal views. Carefulinterrogation of the ventricular septum usingboth color flow and pulsed Doppler techniquescan reveal any additional septal defects, whichare seen with the greatest frequency in patientsless than 1 year of age. Both the origins and theproximal branches of the right and left coronaryarteries must be visualized because the origin of

the left anterior descending coronary from theright coronary artery and the presence of aprominent conal branch are infrequent associa-tions that may significantly influence the surgicalmanagement of the RV outflow tract in patientswho require an outflow patch. There is anincreased incidence of right aortic arch inpatients with tetralogy of Fallot. The presence ofa right aortic arch is usually clearly demonstrat-ed by a combination of plain chest radiographyand TTE. Knowledge of this anomaly is criticalbefore a staged shunt operation is considered.

PULMONARY ATRESIAWhen an initial echocardiographic examination

determines that pulmonary atresia with an intactventricular septum is present (Fig. 44-6), it is veryimportant to define the level of the RV outflowtract obstruction and the RV morphology, includ-ing the inlet, the outlet, and the trabecular com-ponents. The nature of the interatrial communica-tion must be known in order to rule out existing orpotential restriction to essential right-to-left shunt-ing. Subxiphoid views of the interatrial septum willdemonstrate the size and the position of the fora-men ovale or of the septal defect. The flap valve ofthe foramen ovale is usually deviated toward theleft atrium, but the flap valve moves back and forthduring the cardiac cycle unless there is an obstruc-tive communication. The flow dynamics acrossthe atrial septum can be further defined by colorflow and pulsed wave Doppler. Nonpulsatile flowwith a velocity in the range of 2 m/sec is stronglysuggestive of obstructive atrial communication,especially if the patient has hepatomegaly and evi-dence of a low-output state.

Table 44-1 Diagnosis of Tetralogy of Fallot

• Levels and severity of right ventricular outflow tractobstruction

• Pulmonary valve annulus size • Main and branch pulmonary artery size • Ventricular septal defect (single vs. multiple) • Origin of the left anterior descending coronary

artery • Aortopulmonary collaterals • Aortic arch anatomy



437

Tetralogy of Fallot

Right ventricle

Interventricularseptal defect

Aorta

Left ventricle

Leftatrium

Figure 44-5

Transducer

Rightatrium

Leftatrium

Leftventricle

Rightventricle

Pulmonary Atresia



438

Figure 44-6

Transducer



439

TOTAL ANOMALOUS PULMONARYVENOUS RETURN

Two-dimensional echocardiography will accu-rately delineate pulmonary venous anatomy incircumstances in which total or partial anom-alous pulmonary venous return is present. Colorand pulsed Doppler examinations are necessaryto confirm the presence of obstruction. Turbu-lent, nonpulsatile venous flow with a velocity ofat least 2 ms signifies hemodynamically signifi-cant obstruction. The intracardiac anatomyshould also be assessed by echocardiographybecause other significant congenital lesionsoccur approximately 30% of the time, includingpatent ductus arteriosus, atrial isomerism, VSD,single ventricle, transposition of the great arter-ies, and systemic venous anomalies. Total anom-alous pulmonary venous return is strongly asso-ciated with complex congenital heart diseaseand asplenia.

SINGLE VENTRICLEEchocardiography is a powerful tool in defining

the anatomy of the univentricular heart (Fig. 44-7).Both the interatrial and interventricular communi-cations are measured and obstructions notedwith color-directed pulsed Doppler. If an outflowchamber (hypoplastic ventricle) is found to com-municate with a dominant ventricle via a bul-boventricular foramen (VSD), the dimensions ofthe interventricular communication must beobtained with two orthogonal views. With thesedimensions, a prediction can be made aboutwhether the connection may become obstruc-tive in the future. This prediction is made on thebasis of the cross-sectional area of the connec-tion, normalized to the body surface area and itsboundaries, muscular or membranous. Dopplerexamination of the subarterial outflow candetect even mild obstruction by an increase inblood flow velocity. When the aorta arises fromthe hypoplastic chamber, detection of even mildobstruction is particularly important because ofthe danger that subaortic obstruction will devel-op. Hence, serial studies are necessary, particu-larly following interventions that reduce ventric-ular preload or afterload (including medicationuse or surgical procedures).

The anatomy of the AV valve is most clearlydefined by echocardiographic imaging, and any

stenosis or regurgitation should be quantifiedvia color and pulsed Doppler flow imaging. Inpatients with a pulmonary artery band, echocar-diography evaluates the band position, the mor-phology of the proximal pulmonary arterybranches, and gradients at either level.

Ventricular function can be estimated usingechocardiography, but the accuracy of echocar-diography in this circumstance may be limitedby nonuniform ventricular geometry, particularlyin patients with a single morphologic right ven-tricle. Because of large differences in preloadand afterload in patients with a single ventricle,measures of contractility that are less load-inde-pendent, such as the velocity of circumferentialfiber shortening, are of greater value than a sim-ple ejection fraction. However, even theseindices are not reliable with subaortic obstruc-tion or when the ventricular geometry does notconform to a prolate ellipsoid, and alternatemeans for assessment of ventricular function(MRI or radionuclide ventriculography) aresometimes needed. A reliable means for assess-ing ventricular function serially is needed inorder to optimally time the stages of surgicalcorrection and/or palliation (see chapter 50).

TRUNCUS ARTERIOSUSEchocardiography can visualize the large truncal

root overlying a subarterial VSD (Fig. 44-8). Theorigin of the pulmonary arteries may be seen as asingle trunk, or the arteries may be seen arisingseparately from the proximal truncal root. Thenumber of truncal valve leaflets can be deter-mined by a combination of 2-D imaging andDoppler echocardiography. The presence ofvalvular regurgitation or stenosis, or stenosis at theorigin of the pulmonary artery or branches, can,and should, be evaluated by TTE. The appearanceof a small ascending aortic portion and a largerpulmonary portion of the common truncus shouldprompt a careful examination of the aortic archfrom the suprasternal, high parasternal, and subx-iphoid transducer positions to determine whetheran associated coarctation of the aorta or an inter-rupted aortic arch is present.

FUTURE DIRECTIONSRefinements in pediatric echocardiographic

techniques produce a highly accurate picture of



440

Right atrium Left atrium

Left ventricle

Right ventricle

Hypoplastic Left HeartFigure 44-7

Transducer



441

Right ventricle

Left ventricle

Aorta

Pulmonary artery

Common truncal valve

Truncus ArteriosusFigure 44-8

Transducer



442442

the anatomy and the evolving physiology ofcongenital cardiac lesions. For many straightfor-ward lesions, invasive studies may be eliminatedentirely. In some lesions, such as atrial septaldefect, coarctation of the aorta, and patent duc-tus arteriosus, more often than not surgery isperformed on the basis of a noninvasive periop-erative evaluation. A variety of complex lesions,such as AVSDs, single ventricle, and complexconotruncal anomalies, have also been surgical-ly palliated or repaired without cardiac catheter-ization, although the approaches used varylocally by the experience of the diagnostic andsurgical team with each abnormality. Even forcomplex lesions requiring cardiac catheteriza-tion, advances in echocardiography havereduced the number of cardiac catheterizationsneeded in the lifetime of a single patient. As theuse of echocardiography has become dominantin the preoperative evaluation of cardiac lesions,cardiac catheterization has taken on a moretherapeutic role, being used in the closure ofpatent ductus arteriosus and septal defects, theocclusion of vascular structures, and the relief ofoutflow obstructions (see chapter 45). Theseadvances are closely interrelated with the evolu-tion of cardiac surgery toward the repair of

increasingly complex lesions at increasingly ear-lier ages (chapter 46).

REFERENCES George B, Disessa TG, Williams RG, Friedman WF, Laks H.

Coarctation repair without catheterization in infants. AmHeart J 1987;114:1421–1425.

Leung MP, Mok CK, Hui PW. Echocardiographic assessmentof neonates with pulmonary atresia and intact ventricularseptum. J Am Coll Cardiol 1988;12:719–725.

Murphy DJ, Ludomirsky A, Huhta JC. Continuous waveDoppler in children with ventricular septal defect: Nonin-vasive estimation of intraventricular pressure gradient.Am J Cardiol 1986;57:428–432.

Pasquini L, Sanders SP, Parness IA, Colan SD. Diagnosis ofcoronary artery anatomy by two-dimensional echocar-diography in patients with transposition of the great arter-ies. Circulation 1987;75:557–564.

Sanders SP, Bierman FZ, Williams RG. Conotruncal malforma-tion: Diagnosis in infancy using subxiphoid two dimension-al echocardiography. Am J Cardiol 1982;50:1361–1367.

Shimazaki Y, Maehara T, Blackstone EH, Kirklin JW, BargeronLM. The structure of the pulmonary circulation in tetralo-gy of Fallot with pulmonary atresia. J Thorac CardiovascSurg 1988;95:1048–1058.

Smallhorn JF, Freedom RM. Pulsed Doppler echocardiogra-phy in the pre-operative evaluation of total anomalouspulmonary venous connection. J Am Coll Cardiol1986;8:1413–1420.

Snider AR, Serwer GA, Ritter SB. Echocardiography in Pedi-atric Heart Disease. St. Louis: Mosby; 1997:23–75.

chapter 44 echocardiography in congenital heart disease · stenosis, and the presence of atrial...

Documents