Endocardial Cushion Defect. This is also called an atrioventricular (A ) septal dect or A V canal dect. It has a prevalence of approximately 1 in 2500 births and is associated with trisomy 21 in more than half of cases (Christensen, 2013; Cragan, 2009; Dolk, 2010). The endocardial cushions are the crux of the heart, and defects jointly involve the atrial septum primum, interventricular septum, and medial leaflets of the mitral and tricuspid valves (Fig. 10-30). Approximately 6 percent of cases occur with heterotaxy syndromes, that is, those in which the heart and/or abdominal organs are on the incorrect side. Endocardial cushion defects associated with heterotaxy can have comorbid conduction system abnormalities resulting in third-degree AV block, which confers a poor prognosis (Chap. 16, p. 316).
Hypoplastic Let Heart Syndrome. This anomaly is found in approximately 1 in 4000 births (Cragan, 2009; Dolk, 2010). Sonographically, the let side of the heart may appear "illed-in" or the let ventricle may be so small and attenuated that a ventricular chamber is diicult to appreciate (Fig. 10-31). There may be no visible let ventricular inlow or outflow, and reversal of low may be documented in the aortic arch.
Although this anomaly was once considered a lethal prognosis, 70 percent of afected infants may now survive to adulthood (Feinstein, 2012). Postnatal treatment consists of a three-stage palliative repair or cardiac transplantation. Still, morbidity remains high, and developmental delays are common (Lloyd, 2017; Paladini, 2017). This is a ductal-dependent lesion for which neonatal administration of prostaglandin therapy is essential. Fetal therapy for hypoplastic left heart is discussed in Chapter 16 (p. 326).
FIGURE 10-28 Fetal echocardiography gray-scale imaging planes. A. Four-chamber view. B. Left ventricular outflow tract view. The white arrow illustrates the mitral valve becoming the wall of the aorta. The arrow with asterisk marks the interventricular septum becoming the opposing aortic wall. C. Right ventricular outflow tract view. D. Three vessel and trachea view. E. High short-axis view (outflow tracts). F. Low short-axis view (ventricles). G. Aortic arch view. H. Ductal arch view. I. Superior and inferior vena cavae views. Ao = aorta; IVC = inferior vena cava; LA = left atrium; LV = left ventricle; PA = pulmonary artery; RA = right atrium; RV = right ventricle; SVC = superior vena cava.
branous) portion of the interventricular septum.
B.The left-ventricular outflow tract view of the same fetus demonstrates a break (arrow) in continuity between the interventricular septum and the anterior wall of the aorta.
FIGURE 10-29 Ventricular septal defect. A.oln this four-chamber view of a 22-week fetus, a defect (arrow) is noted in the superior (mem
Tetralogy of Fallot. This anomaly occurs in approximately 1 in 3000 births (Cragan, 2009; Dolk, 2010; Nelson, 2016). It includes a ventricular septal defect; an overriding aorta; a pulmonary valve abnormality, typically stenosis; and right ventricular hypertrophy (Fig. 10-32). he last does not present before birth. Due to the location of the ventricular septal defect, the four-chamber view may appear normal.