Dextrocardia

Birth prevalence of approximately 1:10,000; equal sex distribution

25% have PCD, an autosomal recessive disorder

Increased risk of cardiac decompensation, pulm Htn, resp failure, airway obstruction, sepsis, raised intracranial pressure, and death

Increased likelihood of emergent open-heart or abdominal surgery

Heterotaxy syndrome (approximately 40% have dextrocardia)

PCD (approximately 50% have dextrocardia)

Distinguish from dextroposition—right cardiac displacement by extracardiac causes (lung, diaphragm, pericardium abnormalities)

Dextrocardia results from embryologic anomalies. The heart is positioned in the right hemithorax, with base and apex of heart pointing caudally and to the right.

Mirror-image dextrocardia can be asymptomatic incidental finding.

PCD: Associated with:

• Middle ear infections.

• Paranasal sinusitis.

• Lung disease (bronchiectasis, pneumonia).

• Infertility.

• Hydrocephalus.

• Retinitis pigmentosa.

• Situs inversus totalis.

• Heterotaxy.

Heterotaxy (1:6000 live births) is failure of usual R-L asymmetry: Associated with:

• Congenital heart disease (many variants).

• Brain (e.g., encephalocele).

• Skeletal (e.g., spine deformities).

• Facial (e.g., micrognathia).

• Resp (e.g., tracheoesophageal fistula, PCD).

• Gut (e.g., duodenal atresia, volvulus).

• Pancreatic and liver hypoplasia.

• GU tract (e.g., renal agenesis).

• Other (e.g., diaphragmatic hernia).

The human fetal heart develops from a primitive cardiac tube, with sinus venosus, atrium, ventricle, bulbus cordis, and truncus arteriosus connected in series. With growth, the tube loops right or left. Dextrocardia can occur with abnormal looping.

Heterotaxy and PCD result from abnormal structure and function of motile cilia. The ventral node, a transient midline structure present in early fetal life, has specialized monocilia that generate unidirectional extraembryonic fluid flow, which initiates normal R-L asymmetry. Abnormal flow leads to heterotaxy.