Genetics/metabolism

Question 1

What is heterotaxy?
What is isomerism?

Answer 1

Heterotaxy: abnormal arrangement of thoracic and abdominal organs

Isomerism: symmetry of structures that are normally asymmetrical or only found on one side of the body

Question 2

What is right atrial isomerism? What other cardiac anomalies are typically present? How is the spleen typically affected?

Answer 2

Right atrial appendage isomerism or right atrial isomerism (RAI): two right sides with bilateral right atria and atrial appendages and an absence of left-sided structures (eg, coronary sinus).

-patients usually have pulmonary venous anomalies, such as anomalous pulmonary venous connections or small pulmonary veins. Single ventricle physiology is predominant in RAI.

-typically have asplenia, as the spleen is a left-side abdominal organ. (vs left atrial isomerism where patients typically have polysplenia)

Question 3

What is left atrial isomerism? What other cardiac anomalies are typically present? How is the spleen typically affected?

Answer 3

Left atrial appendage isomerism/left atrial isomerism (LAI): two left sides with bilateral left atria and atrial appendages.

-systemic venous abnormalities, such as interruption of the inferior vena cava, are common.

-Polysplenia also occurs more often, as left-sided organs are more frequently duplicated in patients with LAI (vs right atrial isomerism where asplenia is more likely)

Question 4

How can neonates present with right atrial isomerism?

Answer 4

RAI typically presents during the neonatal period with cyanosis due to right-to-left shunting as a result of pulmonary arterial outflow obstruction
-may also have increasing respiratory distress from pulmonary congestion secondary to obstructed pulmonary veins. Physical findings may include an increased palpable right-sided heave and a pulmonary ejection murmur.

vs LAI which typically presents later in life

*RAI anatomy
-single RV with hypoplastic LV
-typically a/w complete AV canal defect
-pulmonary venous return typically drains to extracardiac structures due to the absence of the left atria, mainly to the SVC and the portal system. *

Question 5

How does left atrial isomerism typically present?

Answer 5

Patients with LAI tend to present later in life than do patients with RAI because the degree of pulmonary artery outflow obstruction is of lesser magnitude than that seen in RAI. Tachypnea, when present, is usually secondary to heart failure and not due to pulmonary venous obstruction.

Question 6

Name 4 extracardiac abnormalities that can be seen with either right or left atrial isomerism.

Answer 6

Sepsis (if asplenia or hypoplastic spleen present)

Jaundice d/t association with biliary atresia

Symptoms of bowel obstruction, such as bilious vomiting, d/t a/w malrotation of the gut, with possible volvulus

Anal atresia

●Other rarer extracardiac anomalies:

*RAI has been associated with tracheoesophageal fistula, meningomyelocele, encephalocele, cerebellar agenesis, cleft lip, cleft palate, and horseshoe kidney

*LAI rarely associated with esophageal atresia and congenital short pancreas

*Renal abnormalities have been described in both RAI and LAI

*There is a risk for respiratory disease because of airway ciliary dysfunction in both RAI and LAI