EMBRIOLOGY

Question 1

A 10-day-old newborn presents with cyanosis and difficulty feeding. Echocardiography reveals a single large artery arising from the ventricles, along with a ventricular septal defect. The infant is diagnosed with truncus arteriosus. Which of the following embryological events is most likely responsible for this condition?

(A) Failure of the endocardial cushions to form
(B) Failure of septation of the truncus arteriosus
(C) Incomplete fusion of the atrioventricular septum
(D) Abnormal migration of neural crest cells
(E) Incomplete development of the conus arteriosus

Answer 1

(B) Failure of septation of the truncus arteriosus

Truncus arteriosus is a congenital heart defect where a single large arterial trunk arises from the ventricles, which supplies both systemic and pulmonary circulation. Normally, the truncus arteriosus should divide into the aorta and pulmonary artery during development. This division occurs through the formation of the aorticopulmonary septum.

In truncus arteriosus, this septation fails to occur, resulting in a single arterial trunk. This defect is typically associated with a ventricular septal defect (VSD), as in this case, allowing mixing of oxygenated and deoxygenated blood, which causes cyanosis.

Neural crest cells contribute to the formation of the aorticopulmonary septum, but the direct embryological defect here is the failure of septation of the truncus arteriosus, leading to the single arterial trunk anomaly.

Question 2

What is Ebstein anomaly?

Answer 2

Back: Ebstein anomaly is a congenital heart defect characterized by the downward displacement of the tricuspid valve into the right ventricle, leading to atrialization of part of the right ventricle and tricuspid regurgitation

Question 3

What are the key features of Ebstein anomaly?

Answer 3

Back:

Downward displacement of the tricuspid valve.
Atrialization of the right ventricle.
Tricuspid regurgitation.
Associated right-to-left shunt through ASD or PFO, leading to cyanosis.
Risk of arrhythmias, including Wolff-Parkinson-White syndrome.

Question 4

What are the common clinical presentations of Ebstein anomaly?

Answer 4

Back:

Cyanosis (due to right-to-left shunt)
Heart failure symptoms (fatigue, dyspnea)
Palpitations or arrhythmias (such as supraventricular tachycardia)

Question 5

What congenital heart defect is commonly associated with Ebstein anomaly?

Answer 5

Atrial septal defect (ASD)
or
Patent foramen ovale (PFO)

which can lead to a right-to-left shunt and cyanosis

Question 6

What is the teratogen that lead to Ebstein anomaly?

Answer 6

Lithium