Heart



Heart





11.1 Overview of Congenital Heart Disease

Congenital heart disease affects between 8 and 12 per 1,000 live births and 27 per 1,000 stillbirths. The risk of congenital heart disease increases if one parent has congenital heart disease, or if the couple has had a previous child with congenital heart disease. Risks are also increased with various genetic syndromes, both dominant and recessive, and with aneuploidy. Approximately 5% of infants born with cardiac anomalies have a positive family history of congenital heart disease, and approximately 12% have abnormal chromosomes.

Prenatal diagnosis of congenital heart disease can improve outcome by leading to timely management and treatment after birth. Another avenue to improved outcome is the use of fetal interventions for some cardiac anomalies, where in utero balloon dilation procedures or stent placement can prevent worsening of the cardiac abnormality as pregnancy progresses (e.g., aortic stenosis dilation to prevent or minimize development of hypoplastic left heart).


11.2 Hypoplastic Left Heart Syndrome and Aortic Stenosis


Description and Clinical Features

Hypoplastic left heart syndrome is a group of cardiac malformations characterized by a small or absent left ventricle. Hypoplasia of the left ventricle occurs as a result of abnormalities that limit the flow of blood through the left side of the heart, including stenosis or atresia of the foramen ovale, mitral valve, or aortic valve.

Aortic stenosis or atresia most commonly results from an abnormal aortic valve, but occasionally, the obstruction occurs in the subaortic region of the left ventricular outflow tract or beyond the valve. Not all cases of aortic stenosis or atresia lead to hypoplasia of the left ventricle. In particular, in some cases of aortic stenosis or atresia, a ventricular septal defect is present, allowing enough blood to flow through the left ventricle to prevent the development of a hypoplastic left ventricle. Even in cases of aortic stenosis or atresia without a ventricular septal defect, the left ventricle may not become hypoplastic initially but may instead dilate and develop endocardial fibroelastosis, becoming progressively less contractile. Eventually, however, the dilated, globular, poorly contractile left ventricle will shrink and become hypoplastic.

In general, the prognosis for a fetus with hypoplastic left ventricle is poor. Fetuses may develop hydrops in utero and may die before birth. For infants with hypoplastic left heart born alive, survival has improved in the last few decades as a result of the development of palliative surgical interventions and cardiac transplantation.

The prognosis for aortic stenosis is related to the degree of function of the left cardiac ventricle.







Figure 11.2.1 Hypoplastic left ventricle. Four-chamber view of the heart in fetus with hypoplastic left ventricle demonstrating small left ventricle (LV, arrow) and larger right ventricle (RV, arrow) (S, spine).






Figure 11.2.2 Hypoplastic left ventricle with no left ventricular chamber. Transverse image of thorax demonstrating heart with large right ventricle (RV, arrow) and no appreciable left ventricular chamber (LV, arrow). The left atrium (LA, arrowhead) is also small compared to the right atrium (RA, arrowhead).


Sonography

A hypoplastic left ventricle can be diagnosed on a four-chamber view of the heart by demonstrating a small left ventricle (Figure 11.2.1), often with poor contractility. The size of the left ventricular chamber is variable. In some cases, no left ventricle can be identified (Figure 11.2.2). In others, the left ventricle is only somewhat smaller than the right.

With ventricular dilatation and endocardial fibroelastosis as a result of severe aortic stenosis, the left ventricle becomes enlarged and globular, with increased echogenicity along the inner wall and poor ventricular contractility (Figure 11.2.3). As pregnancy progresses, the dilated, globular left ventricle may become progressively smaller in utero until it becomes hypoplastic. The increased echogenicity of the ventricular wall will persist (Figure 11.2.4).






Figure 11.2.3 Dilated left ventricle with endocardial fibroelastosis developing into hypoplastic left heart. A and B: Four-chamber views of the heart in two fetuses demonstrating echogenic left ventricular walls (LV, arrow). Left ventricular contractility was poor. A small pericardial effusion (*) is present in each (RV arrow, right ventricle; S, spine).







Figure 11.2.4 Hypoplastic left ventricle with echogenic walls. Four-chamber view of heart showing very small left ventricle (LV, arrow) with brightly echogenic walls and compensatorily enlarged right ventricle (RV, arrow). A pericardial effusion (*) is also present.






Figure 11.2.5 Aortic stenosis. A: Longitudinal image of left ventricular (LV) outflow tract to aorta (arrowhead) with narrowing of the valve (arrows), which is brightly echogenic. B: Longitudinal images of left ventricular (LV) outflow tract to aorta (arrowhead) in another fetus with aortic stenosis. The aortic valve (calipers) is narrowed and the left ventricle (LV) is dilated.

Aortic stenosis is characterized by narrowing of the aortic valve and decreased movement of the valve leaflets. The narrowed aortic valve can be visualized on a long-axis view of the left ventricle and left ventricular outflow tract (Figure 11.2.5). The width of the valve can be measured and compared with norms for gestational age. The stenotic valve is often brightly echogenic and visible throughout the cardiac cycle. The ascending aorta
may be enlarged due to poststenotic dilation. Color Doppler will demonstrate a narrow, high-velocity jet of flow across the stenotic valve (Figure 11.2.6), instead of the normal broad area of flow.






Figure 11.2.6 Aortic stenosis and mitral regurgitation with color Doppler. A: Oblique color Doppler image showing left ventricular (LV) outflow tract with narrowing of the color jet (large arrow) and aliasing of the color signal, indicating high-velocity flow across the stenotic valve. The ascending aorta is dilated (arrowhead) due to poststenotic turbulence above the valve. Also seen is a large jet of retrograde flow across the mitral valve (small arrow), representing mitral regurgitation, which often accompanies critical aortic stenosis. B: Another fetus with similar findings of a narrowed aortic jet (arrowhead) across the stenotic valve and large jet of retrograde flow across the mitral valve (arrow).

Mitral regurgitation commonly accompanies aortic stenosis when hypoplastic left heart is developing. With color Doppler imaging, the regurgitation appears as retrograde flow across the mitral valve during cardiac systole (Figure 11.2.6).


11.3 Hypoplastic Right Ventricle and Pulmonic Stenosis


Description and Clinical Features

A hypoplastic right ventricle, which is less common than hypoplastic left heart, is characterized by a small or absent right cardiac ventricle. This most often results from pulmonic stenosis or atresia with an intact ventricular septum but can also result from stenosis or atresia of the tricuspid valve. With any of these, there is obstruction of blood flow either into the right ventricle or out of the right ventricle, leading to shunting of blood across the foramen ovale to the left side of the heart. The left ventricle may be enlarged and hypertrophic. A hypoplastic right ventricle may cause fetal cardiac failure and hydrops.

Pulmonic stenosis is characterized by an abnormal pulmonic valve that obstructs the blood flow through the right ventricular outflow tract. The stenosis may be an isolated abnormality of the heart or a component of a more complex congenital cardiac malformation such as tetralogy of Fallot. With isolated pulmonic stenosis, the right ventricle may be small or large depending on the degree of shunting of blood across the foramen ovale and the extent of tricuspid regurgitation.


Sonography

A hypoplastic right ventricle is best diagnosed on a four-chamber view of the heart when the right ventricle is smaller than the left ventricle (Figure 11.3.1). The small right ventricle often has thickened walls, sometimes markedly (Figure 11.3.2), and ventricular contractility is usually poor. In rare cases, no right ventricle can be found (Figure 11.3.3). In the latter case, the distinction between hypoplastic right ventricle and hypoplastic left ventricle may be difficult.







Figure 11.3.1 Hypoplastic right ventricle. Transverse image of fetal thorax at level of four-chamber view of the heart demonstrating a small right ventricle (RV, arrow) and a larger left ventricle (LV, arrow).






Figure 11.3.2 Hypoplastic right ventricle with marked thickening of the ventricular walls and poor contractility. Transverse image of chest at level of four-chamber view of the heart showing a small right ventricle (RV, arrow) with markedly thickened walls, including the septum (LV arrow, left ventricle).

With pulmonic stenosis, there is narrowing at the level of the pulmonic valve (Figure 11.3.4). Measurement of the pulmonic valve can be compared with norms for gestational age to assess the degree of narrowing. Poststenotic dilation of the pulmonic artery may be seen in some cases of isolated pulmonic stenosis (Figure 11.3.5). With pulmonic atresia or critical pulmonic stenosis, retrograde flow may be seen in the ductus arteriosus, carrying blood from the aorta to the pulmonary arteries. The reversed flow in the ductus arteriosus is best seen on a transverse color Doppler image of both the ductal arch and the aortic arch and is diagnosed when flow in the ductal arch is in the opposite direction to flow in the aortic arch (Figure 11.3.6). Careful assessment for accompanying cardiac anomalies is warranted, especially looking for abnormalities of the tricuspid valve and ventricular septum.






Figure 11.3.3 Hypoplastic right ventricle with no right ventricular chamber. Four-chamber view of the heart demonstrating a large left ventricle (LV), enlarged right atrium (RA) and left atrium (LA), but no appreciable right ventricle (arrow). A moderate pericardial effusion (*) is present.






Figure 11.3.4 Pulmonic stenosis. Transverse view of right ventricular outflow tract demonstrating narrowing at the level of the pulmonic valve (arrowhead) between the right ventricle (RV, arrow) and main pulmonary artery to the ductus arteriosus (DA, arrow).







Figure 11.3.5 Pulmonic stenosis with poststenotic dilatation of the pulmonary artery. Oblique image of right ventricular (RV, arrowhead) outflow tract demonstrating narrow pulmonic valve (calipers) with poststenotic dilatation of the main pulmonary artery (arrows) (Post, posterior).






Figure 11.3.6 Severe pulmonic stenosis with reversed flow in the ductus arteriosus. Transverse view of the fetal chest at the level of the ductal arch (arrow) and aortic arch (arrowhead) showing reversed flow in the ductal arteriosus, from the aorta to the main pulmonary artery, and normal antegrade flow in the aortic arch.


11.4 Ebstein Anomaly


Description and Clinical Features

Ebstein anomaly is an anomaly that involves malformation and malposition of the tricuspid valve. The valve is displaced into the right ventricle and is dysplastic and incompetent, leading to tricuspid regurgitation and enlargement of the right atrium. During atrial systole, blood flows from the right atrium toward the apex of the right ventricle. During ventricular systole, the blood regurgitates from the portion of the right ventricle distal to the tricuspid valve, back across the dysplastic tricuspid valve into the right atrium. The right atrium can become markedly enlarged. Hydrops may develop in utero due to fetal cardiac failure.

The prognosis for this cardiac anomaly, when diagnosed prenatally, is poor, with a mortality of 35% to 40%. Some fetuses die before birth and others die in the neonatal period. The prognosis is particularly poor if hydrops develops in utero or when there is pulmonary hypoplasia as a result of compression of the lungs by the enlarged heart. Long-term survivors of Ebstein anomaly often have persistent cardiac arrhythmias.


Sonography

With Ebstein anomaly, the four-chamber view of the heart is abnormal. The heart is markedly enlarged, especially the right atrium, and the tricuspid valve is displaced toward the apex of the right ventricle (Figure 11.4.1). Tricuspid regurgitation can be demonstrated with color or spectral Doppler (Figure 11.4.2).







Figure 11.4.1 Ebstein anomaly. A–C: Transverse images of thorax, with four-chamber views of heart in three different patients, demonstrating (A) and (B) moderately and (C) markedly enlarged right atrium (RA) and mildly enlarged right and left ventricles (RV and LV). The tricuspid valve (arrow) is displaced into the right ventricle below the level of the normally positioned mitral valve (arrowheads) (S, spine).






Figure 11.4.2 Color Doppler of Ebstein anomaly with tricuspid regurgitation. Color Doppler images of four-chamber view of heart demonstrating a large jet of retrograde flow (red with central aliasing) across the abnormal tricuspid valve from the right ventricle (RV, arrow) back into right atrium (RA, arrow) during ventricular systole (LV, left ventricle; S, spine).



11.5 Ventricular Septal Defect


Description and Clinical Features

An opening in the muscular or membranous portion of the interventricular septum is called a ventricular septal defect. These defects may be small and clinically insignificant or quite large, causing significant shunting of blood across the defect. Some of the small defects close spontaneously after birth. Defects in the membranous portion of the septum are more common than those in the muscular septum and tend to be smaller. Prenatally, blood flow through the septal defect is typically from the right to the left ventricle. After birth, shunting across the defect changes to be from left to right due to changes in pressure in the cardiac ventricles.

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Feb 2, 2020 | Posted by in GYNECOLOGY | Comments Off on Heart
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