Conotruncal Cardiac Defects:

Recognition on Fetal Ultrasound

R. Dennis Steed, MDAssociate ProfessorDepartment of PediatricsDivision of Pediatric CardiologyEast Carolina University – Brody School of MedicineGreenville, NC

Conotruncal Cardiac Defect:

A cardiac defect occurring early in development, involving faulty septation or connection of heart’s chambers and/or the major blood vessels leaving the heart.

The 4 Most Common Conotruncal Defects: frequency ( per 100,000 live births)

Tetralogy of Fallot 38

Transposition of the Great Arteries 25

Double Outlet Right Ventricle 11

Truncus Arteriosus 6

The 4 features typical of tetralogy of Fallot include:

1. Right ventricular (RV) outflow tract obstruction (RVOTO) (infundibular and valvar)

2. A large ventricular septal defect (VSD) 3. Aortic dextroposition resulting in aortic

override of the VSD4. Right ventricular hypertrophy

Tetralogy of Fallot:

1. The main pulmonary artery will be smaller than the aorta.

2. Large outlet VSD.

3. The overriding relationship of the aorta to the VSD.

Tetralogy of Fallot:Diagnostic features on fetal ultrasound

1.  The great arteries are relatively parallel as compared to near perpendicular relationship in a normal heart.

2. Continuity of the anterior mitral leaflet with the posterior wall of the pulmonary artery.

3. The more anterior position of the aorta within the chest results in a rather elongated appearance of the aortic arch.

Transposition of the Great Arteries: Diagnostic features on fetal ultrasound:

1. The first branch off the MPA courses directly to the right ( right pulmonary artery)

2. The first branch off the aorta courses superiorly (innominate artery)

3. The MPA is considerably shorter than the ascending aorta, ie. The distance from the pulmonary valve to the right pulmonary artery is considerably shorter than the distance from the aortic valve to the innominate artery.

Distinguishing features between the Aorta and the Main Pulmonary Artery:

1. Both great arteries arise wholly or predominantly from the morphologic right ventricle.

2. Multiple anatomic variants based on:

a. The relationship of the great arteries (normally related or transposed.)

b. The relationship of the VSD to the great arteries ( A large subarterial VSD is almost always present).

Double Outlet Right Ventricle:

Diagnostic features on fetal ultrasound:1. Both great arteries arise predominantly from the

morphologic right ventricle.

2. There is infundibular muscle separating the anterior mitral leaflet from the artery which the artery which is anatomically closest to the left ventricle.

3. A large sub-arterial VSD is present in the vast majority of cases.

Double Outlet Right Ventricle:

A single arterial trunk arises from the ventricles with a single semilunar valve and typically overides a large VSD.

Truncus Arteriosus:

Diagnostic Features on Fetal Ultrasound:

1. A single great artery

2. Large subarterial VSD ( the Truncus overides the VSD)

3. A short main pulmonary artery and the branch pulmonary arteries can be identified arising from the truncus just above the truncal valve.

Truncus Arteriosus: