Diagnostic ultrasound ( PDFDrive )

CHAPTER 37 The Fetal Heart 1273
TABLE 37.2 Recurrence Risks
in Siblings for Any Congenital
Heart Defect a
Defect
SUGGESTED RISK
(%)
If One
Sibling
If Two
Siblings
Fibroelastosis 4 12
Ventricular septal defect 3 10
Patent ductus arteriosus 3 10
Atrioventricular septal defect 3 10
Atrial septal defect 2.5 8
Tetralogy of Fallot 2.5 8
Pulmonary stenosis 2 6
Coarctation of aorta 2 6
Aortic stenosis 2 6
Hypoplastic left heart 2 6
Transposition 1.5 5
Tricuspid atresia 1 3
Ebstein anomaly 1 3
Truncus 1 3
Pulmonary atresia 1 3
a Combined data published during two decades from European and
North American populations.
With permission from Nora J. 252
TABLE 37.3 Suggested Offspring
Recurrence Risk (%) for Congenital Heart
Defects Given One Affected Parent
Defect
AFFECTED PARENT
Father
Mother
Aortic stenosis 3 13-18
Atrial septal defect 1.5 4-4.5
Atrioventricular septal defect 1 14
Coarctation of aorta 2 4
Pulmonary stenosis 2 4-6.5
Tetralogy of Fallot 1.5 2.5
Ventricular septal defect 2 6-10
With permission from Nora J. 252
with literature suggesting a ninefold increase in the incidence
of CHD in monochorionic-diamniotic twin gestations. 19 Lastly,
there appears to be a slightly increased risk of CHD with in vitro
fertilization (IVF), although at least some of this increased risk
appears to be related to the increased incidence of twin pregnancies
associated with IVF. 20 Most fetuses with CHD have no known
risk factors, which underscores the importance of a meticulous
evaluation of the four-chamber heart views and outlow tracts
on all routine obstetric ultrasound examinations. When severe
structural cardiac anomalies are identiied before viability, termination
may be ofered. Certainly, one of the most important
aspects of fetal echocardiography is the psychological relief it
afords parents whenever normal cardiac anatomy and function
are documented in a fetus at risk.
NORMAL FETAL CARDIAC ANATOMY
AND SCANNING TECHNIQUES
he fetal heart is similar to that of the adult, with several anatomic
and physiologic diferences. he long axis of the fetal heart is
perpendicular to the long axis of the body, such that a transverse
section through the fetal thorax demonstrates the four cardiac
chambers in a single view. he adult heart, in contrast, is obliquely
oriented with its long axis along a line between the let hip and
the right shoulder. he four-chamber view is important because
10% to 96% of structural anomalies are detectable on this
view. 21-26
Common Indications for Fetal
Echocardiography
Abnormal heart on routine ultrasound
Hydrops
Polyhydramnios
Fetal arrhythmia
Fetal chromosomal anomalies
Fetal extracardiac anomalies
Family history (congenital heart disease [CHD], syndromes
associated with CHD)
Maternal disease (diabetes, collagen vascular,
phenylketonuria)
Maternal infection (rubella)
Teratogen exposure
Increased nuchal translucency on irst-trimester screening
In vitro fertilization
Monochorionic twins
Monitoring response to intrauterine therapy
Monitoring fetus at risk for decompensation (persistent
tachyarrhythmia, hydrops)
Cardiac axis and position are normally such that the apex of
the heart points to the let and the bulk of the heart is in the let
side of the chest (Fig. 37.1A). his is levocardia. In mesocardia
the heart is central with the apex pointing anteriorly. In dextrocardia
the apex is directed rightward, and the heart is primarily
in the right side of the chest. his abnormality must be distinguished
from dextroposition (Fig. 37.1B), in which the heart
maintains a normal axis but is displaced to the right by an external
process, such as a let chest mass or pleural efusion. Abnormal
cardiac axis is associated with a 50% mortality and abnormal
cardiac position with an 81% mortality. 27
he fetal cardiovascular system contains several unique shunts:
the ductus venosus, foramen ovale, and ductus arteriosus (Fig.
37.2). Antenatally, the placenta rather than the lungs is the fetus’s
sole source of oxygen. Oxygenated blood leaves the placenta
through the umbilical vein and travels through the hepatic
vasculature and ductus venosus to the inferior vena cava (IVC)
and then into the fetal right atrium. As a result of increased
velocity, blood entering the IVC via the ductus venosus is shunted