32 Ectopia Cordis
Anatomy and Anatomical Associations
Ectopia cordis is a rare but very dramatic congenital malformation in which the heart is located outside of the confines of the chest cavity.1–3 The condition can be classified into four types, depending upon the position of the heart: cervical, thoracic, thoracoabdominal, or abdominal. The most common type is thoracic ectopia in which the heart lies partially or completely outside the chest wall with the ventricular apex pointing cephalad.
Ectopia cordis is commonly associated with other anomalies including intracardiac defects and other “midline” body wall defects. In 1958, Cantrell and coworkers4 described a “pentalogy” of five associated findings including a midline supraumbilical abdominal wall defect, a defect of the lower part of the sternum, a deficiency of the anterior diaphragm, a pericardial defect at the diaphragmatic surface, and a congenital heart malformation. In this syndrome, the heart disease is often a ventricular septal defect or a conotruncal anomaly such as tetralogy of Fallot or double-outlet right ventricle. Diverticulum of the left ventricle apex is also associated, seen in approximately 20% of cases.
Although Cantrell and coworkers described their particular findings as a constellation, in fact patients may have any one of these alone or a wide spectrum of additional anomalies in association with ectopia cordis. These include abdominal wall defects such as omphalocele, diastasis recti, or gastroschisis as well as craniofacial defects such as cleft lip/palate or neural tube defects. Cases of so-called partial pentalogy of Cantrell have been described, in which there is no sternal defect, but rather a large omphalocele with the heart protruding in a thoracoabdominal manner.5 Hence, two mechanisms for evisceration of the heart outside of the chest wall have been proposed. One is a defect in the sternum with direct protrusion through, referred to as thoracoschisis. The other is a reverse diaphragmatic hernia in which there is a defect in the diaphragm with the heart protruding into the abdomen in association with an omphalocele within which the abdominal contents including the heart is outside of the body.6 The embryological mechanisms for these two may be different.
Frequency, Genetics, and Development
Ectopia cordis makes up less than 0.1% of all congenital heart defects. Failure of fusion of the paired cartilage bars of the embryonic sternum leads to a sternal cleft (thoracoschisis), which allows for the potential for the heart to be positioned outside the boundaries of the chest wall. The incidence ranges from 5.5 to 7.9 per 1 million live births. Two thirds of patients are male; one third are born premature or stillborn. Ectopia cordis is part of a developmental field complex defect, which involves deficiency in formation of the sternum, diaphragm, and anterior body wall. A familial pattern has been reported.7 Ectopia cordis can be associated with a number of genetic and chromosomal anomalies including trisomy 188 and can be experimentally induced in animals through a variety of teratogens.9,10
