Diagnostic ultrasound ( PDFDrive )

CHAPTER 37 The Fetal Heart 1291
LV
RA
RV
LA
LV
RV
LA
P
RA
P
D S D S D S D S
A
B
FIG. 37.36 Normal Pulmonary Venous Anatomy. (A) Four-chamber view using color Doppler ultrasound shows two superior pulmonary
veins (P) entering the left atrium (LA). (B) Subcostal four-chamber view using pulsed Doppler ultrasound shows normal waveform and direction of
pulmonary venous low into the LA. D, Diastolic peak; LV, left ventricle; RA, right ventricle; RV, right ventricle; S, systolic peak.
LV
LA
FIG. 37.37 Total Anomalous Pulmonary Venous Return. Apical
four-chamber view shows anomalous insertion of all four pulmonary
veins (P) into the right atrium (RA). LA, Left atrium; LV, left ventricle;
RV, right ventricle.
Coarctation of Aorta
Aortic coarctation is a narrowing of the aortic lumen, usually
occurring between the insertion of the ductus arteriosus and
the let subclavian artery. Its severity ranges from a slight narrowing
at the distal end of the arch to severe hypoplasia of the
entire arch. Of fetuses with CHD, coarctation has an incidence
of 6.8%. 47 Almost 80% of the cases are associated with other
RV
RA
P
P
P
P
cardiac anomalies, including abnormal aortic valve (bicuspid or
stenotic), VSD, DORV, and AVSD. Chromosomal abnormalities
occur in 5%, and almost 5% of coarctations are associated with
maternal diabetes. 59,161 Coarctations are present in approximately
20% of individuals with Turner syndrome (45X). 5
hree embryologic theories have been proposed to explain
the origin of coarctation of the aorta: (1) a primary developmental
defect with failure of connection of the fourth and sixth aortic
arches with the descending aorta 162 ; (2) aberrant ductal tissue
at the level of the aortic arch 163,164 ; and (3) decreased blood low
through the aortic isthmus. 165
Sonographic detection of coarctation is diicult. 25 Ventricular
size discrepancy with a prominent right ventricle and relatively
small let ventricle, 55,165 with a right-to-let ventricle diameter
ratio greater than 2 standard deviations (SDs) above the norm, 166,167
suggests coarctation of the aorta. Likewise, a discrepancy in
pulmonary artery–to–ascending aorta diameter that falls greater
than 2 SDs above the normal ratio of 1.18 to 0.06 167 is suggestive
of coarctation. 166 Color Doppler ultrasound is useful in identifying
the area of narrowing. Spectral Doppler ultrasound may detect
increased velocity distal to the narrowed segment (Fig. 37.38).
Many coarctations do not become evident until closure of the
ductus arteriosus at birth. In addition, infants with coarctation
of the aorta may not develop clinical or echocardiographic signs
of coarctation until 6 to 12 weeks ater closure of the ductus
arteriosus. If coarctation of the aorta is suspected on fetal
echocardiogram, the infant should be followed to at least 1 year
of age. 168 Although isolated coarctation has a good prognosis,
39% mortality is reported when associated anomalies are
present. 169 Treatment is usually accomplished with angioplasty
or stenting with good results. 170