Embryologic Basis of CHD

Question 1

Failure of establishment of connection between left aortic bud and the epicardial arterial plexus.

Answer 1

ALCAPA: Anomalous Left Coronary Artery from Pulmonary Artery

Question 2

Incomplete development of spiral septum

Answer 2

Aortopulmonary window

Question 3

Defect in AV cushion contribution to formation of anterior mitral valve

Answer 3

Cleft mitral valve

Question 4

Name theory: occurs as a consequence of lack of blood flow across aortic isthmus (either because of VSD or left-sided obstructive lesions).

Answer 4

Flow theory for coarctation of the aorta

Question 5

Name theory: Abnormal extension of contractile ductal tissue into the aorta. Contraction and fibrosis of this tissue at time of ductal closure leads to coarctation.

Answer 5

Ductal sling theory (Skoda) for coarctation of the aorta

Question 6

Failure of contribution of AV cushion towards formation of atrial and ventricular septa

Answer 6

Common AV canal

Question 7

Common pulmonary vein gets obliterated after pulmonary systemic connections have disappeared.

Answer 7

Common pulmonary venous atresia

Question 8

Severe lack of ventricular septation most likely caused by total absence of both primitive ventricular septum and component of AV cushion

Answer 8

Common Ventricle

Question 9

Failure of normal development of cusps, which results in primitive gelatinous masses guarding aortic opening.

Answer 9

Congenital aortic stenosis

Question 10

Abnormal connection between the common pulmonary vein and the LA

Answer 10

Cor triatriatum

Question 11

Persistence of the right venous valve, which results in membranous obstruction of the tricuspid valve, RVOT or IVC.

Answer 11

Cor triatriatum dexter

Question 12

Reverse looping of the heart tube (l loop rather than d loop) with malseptation of truncus resulting in both AV and VA discordance.

Answer 12

Corrected transposition (l-TGA)

Question 13

Failure of septum to spiral in usual fashion, which results in ventriculoarterial discordance. Alternative theory: underdevelopment of subpulmonary conus resulting in pulmonary mitral continuity (Van Praagh)

Answer 13

d-TGA

Question 14

Persistence of primitive arrangement where both AV valves empty into LV.

Answer 14

Double Inlet Left Ventricle

Question 15

Rightward shifting of AV canal exceeds normal shifting resulting in both AV valves emptying into RV.

Answer 15

Double Inlet Right Ventricle

Question 16

Leftward shifting of conus exceeds the normal shifting leading to inclusion of both conal derivatives into LVOT.

Answer 16

Double Outlet Left Ventricle

Question 17

Abnormality of spiral septation such that aorta becomes dextroposed. This is greater dextroposition than seen in TOF but lesser than TGA. Persistence of primitive arrangement where RV empties into both outlets.

Answer 17

Double Outlet Right Ventricle

Question 18

Failure of delamination of the septal and posterior leaflets of the tricuspid valve resulting in downward displacement of these leaflets.

Answer 18

Ebstein’s Anomaly

Question 19

Defect in AV cushion contribution to septal component of tricuspid valve, which results in LV to RA communication

Answer 19

Gerbode defect

Question 20

Leftward displacement of septum primum deflects usual volume of blood away from the left side of the heart, which leads to its underdevelopment
Alternative theories: 1) Premature narrowing of foramen ovale, which leads to faulty transfer of blood from IVC to LA. 2) Severe underdevelopment of LVOT, which leads to altered flow pattern in fetus.

Answer 20

Hypoplastic left heart syndrome

Question 21

Failure of normal contribution of AV cushion towards formation of ventricular septum

Answer 21

Inlet Ventricular Septal Defect

Question 22

Failure of normal fusion between the various aortic segments. Type depends upon level of failure of fusion.

Answer 22

Interrupted aortic arch

Question 23

Failure of septum primum to reach the AV cushions.

Answer 23

Ostium primum defect

Question 24

Failure of normal contribution of AV cushion towards lower part of atrial septum

Answer 24

Ostium primum defect

Question 25

Resorption of the septum primum, which normally provides floor of fossa ovalis.

Answer 25

Ostium secundum defect

Question 26

Persistent communication between the PA and Aorta, which fails to close.

Answer 26

PDA

Question 27

Persistence of oblique valvular passage between septum primum and secundum.

Answer 27

Patent Foramen Ovale

Question 28

Failure of pulmonary valve leaflets to open resulting in decreased flow through the tricuspid valve and RV and consequent hypoplasia. Variable
degree of RV hypoplasia depending on the stage at which fault occurs

Answer 28

Pulmonary atresia, intact ventricular septum

Question 29

Abnormal connection between the individual pulmonary veins and the common pulmonary vein. leading to pulmonary congestion

Answer 29

Pulmonary vein stenosis

Question 30

Premature narrowing of foramen ovale or improper angulation of limbus leads to hypoplasia of left-sided heart structures (flow theory)

Answer 30

Shone’s complex

Question 31

Malseptation of conal septum with primitive interventricular septum. May be associated with posterior malaligned VSD when conal septum projects into
LVOT. Subaortic membrane develops as a result of turbulence in abnormally shaped LVOT.

Answer 31

Subaortic stenosis

Question 32

Failure of the common pulmonary vein to connect to the pulmonary venous plexus of the lung buds.

Answer 32

TAPVR

Question 33

Classic theory: Faulty septation of bulbus cordis that results in unequal sized great vessels (i.e., large aorta and small pulmonary trunk).
Alternative theory: Underdevelopment of subpulmonary conus with consequent rightward and superior shift of the aortic valve.

Answer 33

Tetralogy of Fallot

Question 34

Failure of 6th arch arteries to connect with the systemic arteries carried by the lung bud from the primitive foregut and persistence of connections from aorta (AP collaterals). Variable degree of development of true PA depends on stage at which defect sets in.

Answer 34

TOF, Pulmonary Atresia

Question 35

Failure of normal development of the tricuspid valve resulting in hypoplasia of the RV.

Answer 35

Tricuspid atresia

Question 36

Complete failure of septation of distal bulbus cordis.

Answer 36

Truncus Arteriosus

Question 37

Disturbance of normal development of pharyngeal arch arteries. Double aortic arch: Persistence of right dorsal aorta with incomplete resorption of
left. Right aortic arch: Persistence of right dorsal aorta with resorption of left aortic arch.

Answer 37

Vascular Rings

Question 38

Defect between the conal and primitive interventricular septum usually associated with some degree of malalignment.

Answer 38

VSD- Conoventricular

Question 39

Defect of the endocardial AV cushion, most likely the medial cushions

Answer 39

VSD- Inlet (type 3)

Question 40

Defect in the primitive interventricular septum

Answer 40

VSD- Muscular (type 4)

Question 41

Defect in development of the bulbar septum

Answer 41

VSD- Outlet (Type 1)

Question 42

Failure of membranous septum to form completely and may occur because of inadequacy of any of the three contributors.

Answer 42

VSD – perimembranous (type 2)