Thoracic wall defects arise from failure of part or all of the sternum to develop. These defects may involve only the sternum or may be associated with more severe anomalies. The most striking of these is ectopia cordis. Ectopia cordis is defined as a portion or all of the heart being located in an extrathoracic position. Ravitch (1985) has classified sternal defects into three major groups: cleft sternum without associated anomalies, true ectopia cordis, and pentalogy of Cantrell (see Chapter 61) (Table 59-1).

Sternal defects are commonly associated with ectopia cordis. A spectrum of sternal defects also occurs without displacement of the heart (Skandalakis and Gray, 1994). In rare cases, segments of the sternum are absent. The xiphoid process is the sternal element most commonly absent. Byron (1948) reported a case in which only the manubrium remained. Martin and Helsworth (1962) reported a case of clavicles and upper ribs attached to an abnormally small manubrium separated from lower ribs attached to a sternum element. Complete absence of all sternal elements is rare, but has been reported, and can be successfully reconstructed (Asp and Sulamoa, 1961). In contrast to absent sternal elements, failure of sternal fusion may occur with wide separation of all sternal elements. This is most often seen with associated eventration of the heart. However, several cases have been reported with no herniation of thoracic viscera and intact skin covering the defect (Greenberg et al., 1991).

Superior sternal fusion occurs with a V- or U-shaped cleft in the upper sternum, with variable extension inferiorly even to the level of the xiphoid. Jewett et al. reported nine cases, all with skin-covered defects and structurally normal hearts located within the chest cavity. Four of these cases had hemangiomas of the head and neck and a midline raphe indicating a midline fusion defect (Jewitt et al., 1962).

More than 200 cases of ectopia cordis have been reported in the literature (Skandalakis and Gray, 1994). Ravitch (1985) has classified ectopia cordis into four types based on the position of the heart: cervical (3%), thoracic (64%), thoracoabdominal ectopia (18%), and abdominal ectopia (15%). The heart was exposed in 40% of these cases or covered by a serous membrane (31%) or skin (27%) (Schao-Tsu, 1957).

It is important to distinguish true ectopia cordis from failure of sternal fusion in which the heart, though beating prominently beneath the skin-covered gap, is within the chest and is structurally normal. Many cases reported as thoracic ectopia, with intact skin, are more likely examples of isolated failure of sternal fusion.

“Thoracoabdominal ectopia cordis” is better known as the pentalogy of Cantrell and is in part a misnomer, given that the heart is not truly ectopic. In pentalogy of Cantrell the heart is abnormally sited with the apex oriented down, but is positioned within the chest and therefore not true ectopia cordis (see Chapter 61). Both cervical and abdominal ectopia cordis may occur without a sternal cleft. Abdominal ectopia cordis does not belong in this group of anomalies because the defect is diaphragmatic and does not involve the thorax or the anterior abdominal wall.

In true ectopia cordis, internal cardiac anomalies are generally the rule (Medina-Escobedo et al., 1991). Kanagasuntheram and Verzin (1962) suggested that the embryologic basis of ectopia cordis was excessive pericardial coelom formation and subsequent destruction of the transverse septum with rupture of the anterior body wall at 6 weeks of gestation. The frequency of major intrinsic cardiac defects in true ectopia cordis suggests that there may be a primary defect in the splanchnic mesoderm (Ravitch, 1985).

Ectopia cordis is extremely rare. The most common form is thoracic ectopia cordis. Only a handful of cases of cervical and abdominal ectopia cordis have been reported. Schao-Tsu (1957) cited figures for ectopia cordis as high as 5.5 in 1000 births at Tubingen and 0.4 in 1000 at Munich. Abbott (1936) found 8 cases in her series of 1000 congenital heart defects. However, most fetuses are lethally deformed and are either stillborn or have no prospect of extrauterine survival. Males tend to be affected more often than females with a ratio of 2.5:1.5 (Blatt and Zeldes, 1942).

The first case of ectopic cordis diagnosed in utero by sonographic examination was reported in 1960 by Lumsden (1962) in a fetus near term. Advances in ultrasound examination since that time have allowed recognition of this anomaly as early as the first trimester, using transabdominal and transvaginal ultrasound (Flemming et al., 1991; Achiron et al., 1994; Sepulveda et al., 1994; Tongsong et al., 1999)

True thoracic ectopia cordis (Figure 59-1) is perhaps one of the most startling anomalies to be seen sonographically. The heart is seen entirely outside the thoracic cavity (Bianca et al., 2006). The apex of the heart is usually deviated anteriorly but may also be seen angled up toward the chin (Bennett et al., 1991). Color flow Doppler may be particularly useful in defining the location and anatomy of ectopia cordis (Figure 59-2). Transverse scanning through the fetal chest may allow the sternal defect to be visualized (Figure 59-3). Determining the intracardiac anatomy is of paramount importance in establishing a prognosis. Fetal echocardiography should be performed in any fetus diagnosed with ectopia cordis.