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Ventricular Septal Defect (VSD)
Normal Cardiac Examination

Ventricular Septal Defect (VSD)
Flow across the VSD

Findings:

A moderate sized ventricular septal defect (VSD) is identified (arrow). Flow across the VSD is idenitified with color Doppler flow imaging. No other abnormalities of the heart were identified.

Discussion:

Congenital heart defects are the most common structural abnormalities seen in infants born alive. The prevalance of these malformations is 0.1% with a commonly reported frequency of 8 per 1000 live births. Congenital heart disease is said to be responsible for 20% of the perinatal mortality and 50% of the infant mortality from congenital anomalies. Although most affected neonates are born to pregnancies considered to be low risk, several conditions place the pregnancy at higher risk. The history of a previous sibling or father with congenital heart disease may increase the risk to 2-3%, an affected mother may elevate the risk to as high as 18%. Maternal diseases such as diabetes mellitus (non-gestational) and phenylketonuria may increase the risk to 7% and teratogens such as lithium, retinoic acid or rubella may increase the risk as well.

Teratogens and Cardiac Abnormalities

Potential Teratogen

Freq./ Cardiac Defects (%)

Most Common Malformations

Drugs

Alcohol
30

VSD, PDA, ASD

Amphetamines
5

VSD, PDA, ASD, TGA

Hydantoin
3

PS, AS, CA, PDA

Trimethadione
30

TGA, TF, HLHS

Lithium
10

Ebstein, TA, ASD

Thalidomide
10

TF, VSD, ASD, Truncus Art.

Retinoic Acid
10

VSD

Infections

Rubella
35

PA Stenosis, PDA, VSD, ASD

Maternal Conditions

Diabetes Mellitus
5

TGA,VSD,CA

SLE
40

Heart Block

Phenylketonuria
10

TF, VSD, ASD

VSD=ventricular septal defect, PDA=patent ductus arteriosus, ASD=atrial septal defect, TGA=transposition of great arteries, PS=pulmonary valve stenosis, AS=aortic stenosis, CA=coarctation of the aorta, TF=tetralogy of Fallot, HLHS=hypoplastic left-heart syndrome, TA=tricuspid atresia

Adapted from Hess LW, Hess DB, McCaul JF, Perry KG. Fetal Echocardiography. Obstetrics and Gynecology Clinics of North America.; WB Saunders and Company 17:41-79, 1990

Ventricular septal defect is perhaps the most common cardiac abnormality detected in utero and in live born infants. It may, as in this case, appear as an isolated abnormality or may be part of a more complex cardiac abnormality. When this abnormality appears alone there usually is no hemodynamic consequence to the fetus. At the time of sonography, it is identified by an absence of a portion of the interventricular septum. While this case is readily evident, many series show that this lesion, when small, is commonly missed at the time of an initial routine obstetric sonogram even when a four-chamber view is included.

At the present time, the AIUM/ACR and ACOG guidelines recommend that the four-chamber view of the heart be included as part of a basic obstetric sonogram. It is the authors recommendation that each sonographic examination of the fetus should include an evaluation of the: situs, cardiac position, cardiac axis, four-chamber view and outflow tracts. This additional evaluation should take no more than an additional 3 - 5 minutes.

Cardiac Chambers & Outflow Tracts
Copyright © LifeArt Images-TechPool Studios

4-Chamber View of the Heart
Normal Cardiac Axis
Left Ventricular Outflow Tract

Aortic Root
Pulmonary Artery Bifurcation
Pseudo-VSD

The situs is determined by the relationship of the heart to the stomach. Identification of the suprahepatic portion of the inferior vena cava and right atrium and its relationship to the stomach will determine the situs. Abnormal situs may be seen with polysplenia or asplenia and may be the initial clue that there is a cardiac malformation.

The four-chamber view should be obtained in every patient having an obstetrical sonogram. Most series have shown that this view can be obtained in greater than 95% of patients except when there are significant technical difficulties in imaging due to maternal obesity or fetal lie. The sensitivity for the four-chamber view in the detection of cardiac abnormalities varies from as low as 4.5% in reports evaluating the accuracy of a screening routine sonogram to detect abnormalties to as much as 95% in series prospectively evaluating this sign for the detection of cardiac malformations. In a recent review of the four-chamber and aortic root view Kirk et al outlined the criteria for a normal four-chamber view: "1) the atria are approximately equal in size; 2) the ventricles are approximately equal in size; 3) the primum portion of the atrial septum is intact; 4) the foramen ovale is in the left atrium; 5) the atrioventricular valves are offset with the tricuspid valve inserting slightly more apically than the mitral valve; and 6) the interventricular septum is intact." Identifying the individual chambers is usually quite straightforward. The cardiac chamber closest to the spine is the left atrium. The chamber most anterior is the right ventricle.

Clearly abnormalities of the aortic or pulmonary outflow tracts can occur with an apparently normal four-chamber view. It is for this reason that many examiners are now adding this view to their standard exam. A recent review of the sonographic cardiac exam by Frates reported literature stating that an additional 25% of congenital heart anomalies are detected when including views of the aortic and pulmonary outflow tracts. Angling the transducer cephalad with slight rotation toward the fetal right shoulder will allow one to follow the aortic root its outflow tract. The aortic root should be continuous with the interventricular septum. Occasionally a region of discontinuity in the interventricular septum may be seen at the base of the aortic root. This may be artifactual and attempts should be made to evaluate the septum from other angles of inclination. The pulmonary outflow tract can usually be seen in a standard transverse axial plane of section without angulation. By moving cephalad from the standard 4-chamber view, one should be able to image the pulmonary outflow tract. The main pulmonary artery arises from the right ventricle and bifurcates into the right pulmonary artery and the ductus arteriosus. The right pulmonary artery courses 'around' the ascending aorta. The outflow tracts should 'cross' each other at their origin. On a long axis view of the aortic outflow tract the pulmonary artery should be seen in its short axis and on a long axis view of the pulmonary artery, the aorta should be seen in its short axis.

The addition of the outflow tract views and congenital heart disease screening in general are not without their controversy. Paladini has suggested that a cost-effectiveness analysis should be performed to determine whether it is better to teach the outflow tract evaluation to all level I sonographers, with the prospect of suboptimal sensitivity, or if it would be more cost-effective to identify units that would act as screening centers, not only for congenital heart disease but for all fetal anomalies.

Cardiac Abnormalities and the Four-Chamber View

Cardiac Anomalies with Abnormal Four-Chamber View

Mitral Atresia

Triscuspid Atresia

Aortic Atresia

Pulmonary Atresia

Atrioventricular Septal Defect (AV-canal)

Severe Aortic Stenosis

Severe Pulmonary Stenosis with Intact Interventricular Septum Complete Anomalous Pulmonary Venous Drainage without Pulmonary Venous Obstruction

Severe Coarctation of the Aorta

Interrupted Aortic Arch

Double Inlet Ventricle

Severe Ebstein's Anomaly with Tricuspid Dysplasia

Large Ventricular Septal Defect

Very Large Atrial Septal Defect

Cardiac Anomalies with Usually Normal Four-Chamber View

Transposition of the Great Arteries

Tetralogy of Fallot

Pulmonary Atresia with Ventricular Septal Defect

Double Outlet Right Ventricle

Truncus Arteriosus Communis

Mild Ebstein's Anomaly

Small Ventricular Septal Defect

Small Atrial Septal Defect

Mild/Moderate Aortic Stenosis

Mild/Moderate Pulmonary Stenosis

Mild/Moderate Coarctation of the Aorta

Partial Anomalous Pulmonary Venous Drainage

From: Gembruch U. Prenatal diagnosis of congenital heart disease. Prenatal Diagnosis 17:1283-1298, 1997 J. Wiley & Sons

Adapted from Sharland GK, Allan LD. Screening for congenital heart disease prenatally. Results of a 2 1/2 year study in the South East Thames region, Br. J. Obstet. Gynaecol 99:220-225, 1992

Recently a new method of evaluating the great vessel outflow tracts was described in the sonographic literature by Yoo et al. It is based upon a "three-vessel view" which is a transverse view of the fetal upper mediastinum, where normally the oblique section of the main pulmonary artery and cross-section of the ascending aorta and superior vena cava are arranged in a straight line.

Three-vessel view

 

In a more recent article, Yagel et al proposed a comprehensive cardiac sonographic evaluation using five short-axis views. The first and most caudal is a transverse plane of the upper fetal abdomen. The second view being the traditional four-chamber view. The third view being the five-chamber view which includes the aortic root. The fourth view is the bifurcation of the pulmonary arteries. The fifth view is a modification of the view by Yoo et al which is the furthest cephalad and slightly oblique from the four chamber view. It reveals the main pulmonary trunk in direct communication with the ductus arteriosus. The aortic arch (trasnsverse section) is seen adjacent to the pulmonary trunk and ductus and the superior vena cava and trachea are also visualized. A diagram and examples of these planes of sections are seen in the figure below.

The five short-axis views for optimal fetal heart screening. The color image shows the trachea, heart and great vessels, liver, and stomach with the five planes of insonation superimposed. Polygons show the angle of the transducer and are assigned to the relevant gray-scale images (LT, left; RT, right) (I) The most caudal plane, showing the fetal stomach (ST), cross-section of the abdominal aorta (AO), spine (SP) and liver (LI). (II) The four-chamber view of the fetal heart, showing the right and left ventricles (RV, LV) and atria (RA, LA), foramen ovale (FO), and pulmonary veins (PV) to the right and left of the aorta (AO). (III) The five-chamber view, showing the aortic root (AO), left and right ventricles (LV, RV) and atria (LA, RA), and a cross-section of the descending aorta (AO with arrow). (IV) The slightly more cephalad view showing the main pulmonary artery (MPA) and the bifurcation of left and right pulmonary arteries (LPA, RPA) and cross-sections of the ascending and descending aortae (AO and AO with arrow, respectively). (V) The 3VT plane of insonation, showing the pulmonary trunk (P), proximal aorta ((P)Ao), ductus arteriosus (DA), distal aorta ((D)Ao), superior vena cava (SVC) and the trachea (T).

From:Yagel S, Cohen SM, Achiron R. Examination of the fetal heart by five short-axis views: a proposed screening method for comprehensive cardiac evaluation. Ultrasound Obstet Gynecol 17:367-369, 2001

 

The cardiac axis is the angle between a line dividing the thorax into two equal halves and a line drawn through the interventricular septum to the anterior chest wall. The normal cardiac axis is 45 degrees with a range of 22-75 degrees. Two recent series evaluated the positive predictive accuracy of an abnormal cardiac axis. In one study an axis greater than 75 degrees was predictive of cardiac abnormalities while in the other an axis greater than 57 degrees was predictive of conotruncal abnormalities.

Fetal Arrhythmias

An excellent recent review of fetal arrhythmias was reported by Brown. The ideal sonographic study of cardiac rate and rhythm is an M-mode evaluation demonstrating both atrial andventricular contractions simultaneously. When M-mode cannot be performed pulsed Doppler evaluation at the mitral-aortic area may allow adequate study of both atrial and ventricular systole. Most irregular rhythms are due to premature atrial contractions. These are rarely of functional significance. Supraventricular tachycardia is the most frequent sustained tachycardia with rates between 220 and 260 bpm.Ventricular tachycardias are uncommon. Structural cardiac abnormalities are uncommon with the tachycardias. Complete atrio-ventricular block is the most common cause of sustained fetal bradycardia. Approximately 50% of fetuses will have a structural abnormality usually an atrio-ventricular canal defect. Of those fetuses without a structural abnormality, the mother may have a connective tissue disease such as systemic lupus erythematosus.

Non-Cardiac Associations

As with most malformations, congenital heart disease is often associated with either chromosomal or extra-cardiac anomalies. The prevalence of chromosomal abnormalities in this population is said to be twice as high as the rate normally reported at birth. The chromosomal abnormalities most often seen are the autosomal trisomies, monosomy X and unbalanced translocations. Likewise, extracardiac malformations and/or fetal growth restriction are often seen in fetuses with congenital heart disease. In a study by Paladini et al of over 400 cases of congenital heart disease, the associated rate of chromosomal anomalies was 19% and with extracardiac malformations (excluding those with chromosomal abnormalities) was 29%.

References:

Brown DL, Emerson DS, Carter MS, Felker RE et al. Congenital cardiac anomalies: Prenatal songraphic diagnosis. Amer J Roentgenol 153:109-114, 1989

Copel JA, Pilu G, Green J, Hobbns JC and Kleinman CS Fetal echocardiographic screeing for congenital heart disease: The importance of the four-chamber view. Am J Obstet Gynecol 157:648-655, 1987

McGahan JP Sonography of the fetal heart: Findings on the four-chamber view. Amer J Roentgenol 156:547-553, 1991

Vergani P, Mariani S, Ghidini A, Schiavina R et al. Screening for congenital heart disease with the four-chamber view of the fetal heart. Am J Obstet Gynecol 167:1000-3, 1992

Shipp TD, Bromley B, Hornberger LK, Nadel A and Benacerraf BR. Levorotation of the fetal cardiac axis: A clue for the presence of congenital heart disease. Obstet Gynecol 85:97-102, 1995

Smith RS, Comstock CH, Kirk JS and Lee W. Ultrasongraphic left cardiac axis deviation: A marker for fetal anomalies. Obstet Gynecol 85:187-191, 1995

Cooper MJ, Enderlein MA, Dyson DC, Roge CL and Tarnoff H. Fetal echocardiography: Retrospective review of clinical experience and an evaluation of indications. Obstet Gynecol 86:577-82f, 1995

Kirk JS, Riggs TW, Comstock CH, Lee W, Yang SS and Weinhouse E. Prenatal screening for cardiac anomalies: The value of routine additio of the aortic root to the four-chamber view. Obstet Gynecol 84:427-31, 1994

Bronshtein M, Zimmer EZ, Gerlis LM, Lorber A and Drugan A. Obstet Gynecol 82:225-9, 1993

Ott WJ. the accuracy of antenatal fetal echocardiography screening in high- and low-risk patients. Am J Obstet Gynecol 172:1741-9, 1995

Benacerraf BR, Pober BR and Sanders SP. Accuracy of fetal echocardiography. Radiology 165:847-849, 1987

DeVore GD. The aortic and pulmonary outflow tract screening examination in the human fetus. J Ultrasound Med 11:345-348, 1992

Hess LW, Hess KB, McCaul JF, Perry KG. Fetal Echocardiography. Obstetrics and Gynecology Clinics of North America 17:41-79, 1990

Yoo S.-J., Lee Y.-H., Kim ES, Ryu HM et al. Three-vessel view of the fetal upper mediastinum: an easy means of detecting abnormalities of the ventricular outflow tracts and great arteries during obstetric screening. Ultrasound Obstet Gynecol 9:173-182, 1997

Brown DL. Sonographic Assessment of Fetal Arrhythmias Am J Roentgenol 169:1029-1033, 1997

Gembruch U. Prenatal diagnosis of congenital heart disease. Prenatal Diagnosis 17:1283-1298, 1997 J. Wiley & Sons

Frates MC. Sonography of the Normal Fetal Heart: Practical Approach. Amer J Roentgenol 173:1363-1370, 1999

Paladini D. Prenatal screening of congenital heart disease between ethics and cost-effectiveness. Time for a change in current prenatal ultrasound screening policies? Ultrasound Obstet Gynecol 14:225-228, 1999

Yagel S, Cohen SM, Achiron R. Examination of the fetal heart by five short-axis views: a proposed screening method for comprehensive cardiac evaluation. Ultrasound Obstet Gynecol 17:367-369, 2001

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Peter W. Callen, M.D.
Professor of Radiology, Obstetrics, Gynecology and Reproductive Science
University of California Medical Center, San Francisco, California