Embryological Basis forCongenital Heart Diseases

ByDr. Ahmed

Cardiac Anomalies

Epidemiology Incidence : - 8/1000 live births - 3-4/100 still born - 2/100 premature infants excluding PDA - 10-25/100 abortuses

Most of congenital defects are well tolerated during fetal life

Etiology : - Unknown in most case - Genetic factors single gene defect : Di George(22q11) - Chromosomal abnormality : Down syndrome(50%) trisomy18(90%) - Environmental factors: - Maternal diseases ( DM ), - Infection during pregnancy (Rubella) -Drugs(alcohol ,thalidomide) - Obesity  increases the risk of congenital heart disease -Gender differences in type of CHD

Cardiac Anomalies

Cardiac Anomalies

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)B) Anomalies of atrioventricular canalC) Anomalies of interventricular septum(VSD)D) Anomalies of truncus arteriosus & aortico-pulmonary septumE) Anomalies of position of the heart

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)1- Probe patency of the foramen ovale2- Premature closure of the foramen ovale3- Common atrium (cor triloculare biventriculare4-Ostium primum defect5- Foramen secundum defect (most common clinically significant ASD)

Cardiac AnomaliesA) Anomalies of interatrial septum(ASD)1- Probe patency of the foramen ovale cause• incomplete anatomic fusion of septum primum & septum secundum.• oblique passage between septum primum and septum secundum is closed functionally but

remains patent anatomically so that a probe can be passed through it. extremely rare usually of no clinical importance.

Cardiac AnomaliesA) Anomalies of interatrial septum(ASD)2- Premature closure of the foramen ovale Cause closure of the foramen ovale during prenatal life.• Due to excessive development of septum secondum• It results in hypertrophy of the right side of the heart & underdevelopment of the left side of the heart.

leads to death shortly after birth.

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)3- Common atrium (cor triloculare biventriculare) cause• complete failure of septum primum & septum secundum• to develop.• This results in a condition in which there is formation of only one atrium

It is the most serious congenital anomaly of the atria always associated with other defects of the heart

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)4- ostium primum defect Cause• persistence of foramen primum is due either to a) failure of the septum primum to reach the endocardial cushions b) due to defect in the endocardial cushions

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)5- Foramen secundum defect most common congenital anomaly of the atria Cause

• excessive resorption in the septum primum or• failure of development of septum secundum.• there is an opening between the right and left atria.

resulting in left to right shunt increased load on the right side of the heart progressive enlargement of right atrium, rightventricle & pulmonary trunk.

manifests as effort intolerance (fatigue and breathlessness on exertion) Some defects can be tolerated for a long time, with clinical symptoms manifesting as late as

age 30 years

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)5- Foramen secundum defect

X-rays shows • cardiomegaly due to enlargement of RA & RV• LA& LV are normal sized, • enlargement of the pulmonary artery (arrow), • increased pulmonary vascularity.• enlarged pulmonary arteries prevent the aorta from forming the normal left border of the heart (aortic knob is small)..

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)B) Anomalies of atrioventricular canalC) Anomalies of interventricular septum(VSD)D) Anomalies of truncus arteriosus & aortico-pulmonary septumE) Anomalies of position of the heart

Cardiac AnomaliesB) Anomalies of atrioventricular canal20-25% of cases seen in Down’s Syndrome (Trisomy 21).

1- Persistent common AV canal2- Foramen primum defect3- Tricuspid atresia (hypoplastic right heart

Cardiac AnomaliesB)Anomalies of atrioventricular canal1- Persistent common AV canal cause• failure of fusion of the dorsal & ventral AV cushions. results common AV canal• which is never partitioned into the R&L AV canals with large hole center of the heart.• tricuspid & bicuspid valves are represented by one valve common to both sides of the heart. • Accompanied with ASD &VSD as endocardial cushions share in interaterial &interventricular septa

Two common hemodynamic abnormalities area)Left–right shunting of blood from the LA to RA, causing an enlarged RA &RVb) Mitral valve regurgitation, causing an enlargedLA &LV

Cardiac AnomaliesB) Anomalies of atrioventricular canal2- Foramen primum defect cause• Partial (incomplete) fusion of the dorsal & ventral AV cushions lead to• failure of septum primum to join with the AV septum• results in a condition in which the foramen primum is never closed and generally accompanied by an abnormal mitral valve

Cardiac AnomaliesB) Anomalies of atrioventricular canal3- Tricuspid atresia (hypoplastic right heart cause• insufficient amount of AV cushion tissue available for the formation of tricuspid valve lead to fusion of the cuspsOf tricuspid valve ( complete agenesis) so that there is (no communication between RA& RV)

always accompanied bya)patent foramen ovale,b) interventricular septum defect,c) overdeveloped left ventricle,d) underdeveloped right ventricle

associated clinically with marked cyanosis

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)B) Anomalies of atrioventricular canalC) Anomalies of interventricular septum(VSD)D) Anomalies of truncus arteriosus & aortico-pulmonary septumE) Anomalies of position of the heart

Cardiac Anomalies

C) Anomalies of interventricular septum(VSD)• It is most common congenital anomaly of the heart• Includes :

1- Muscular VSD2- Common ventricle (cor triloculare biatriatum3- Membranous VSD• Most common type of VSD

Cardiac AnomaliesC) Anomalies of interventricular septum(VSD)1- Muscular VSD

cause• single or multiple perforations in the muscular IV septum

Cardiac Anomalies

C) Anomalies of interventricular septum(VSD)2- Common ventricle (cor triloculare biatriatum

cause• failure of the membranous and muscular IV septa result in single ventricle

Cardiac AnomaliesC) Anomalies of interventricular septum(VSD)- Membranous VSD• Most common type of VSD• occurs in about 25% of the children• occur singly or in combination with other cardiac defects cause• failure in the fusion of the right bulbar ridge, left bulbarridge, and AV cushions.• It results in a condition in which an opening betweenR &L V allows free flow of blood

this defect allows left-to-right shunting of blood through the IV foramen due to increased left ventricular pressure child complains of excessive fatigue on exertion

Cardiac AnomaliesDiscuss the blood flow in this defect and explain the

cause of excessive fatigue on exertion• Initially, this defect allows L -R shunting of blood, through the IV foramen due to increased left

ventricular pressure

• The child complains of excessive fatigue on exertion due to shunting of blood from left to right• Later on, due to increased pulmonary blood flow pulmonary hypertension . . • pulmonary hypertension causes marked proliferation of tunica intima and tunica media of pulmonary

arteries and arterioles, thus narrowing their lumen.

• Consequently, the pulmonary resistance becomes higher than the systemic resistance and leads to R–L shunting of blood causing cyanosis

• At this stage, the condition is called Eisenmenger complex

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)B) Anomalies of atrioventricular canalC) Anomalies of interventricular septum(VSD)D) Anomalies of truncus arteriosus & aortico-pulmonary septumE) Anomalies of position of the heart

Cardiac AnomaliesD) Anomalies of truncus arteriosus & aortico-pulmonary septum

• It is most common congenital anomaly of the heart• Includes :

1- Persistent truncus arteriosus (PTA2- D-Transposition of the great arteries (complete3- L-Transposition of the great vessels (corrected4- Tetralogy of Fallot (TOF)

• TOF is the commonest congenital cyanotic heart disease.• TOF& PTA are associated with DiGeorge syndrome (22q11).• Transposition of the great arteries is associated with maternal diabetes

Cardiac AnomaliesD) Anomalies of aortico-pulmonary septum1- Persistent truncus arteriosus (PTACause• abnormal neural crest cell migration in such that there is failure of 2 bulbar cushions to form AP Septum result in• one large vessel leaves the heart & receives blood from both R &LV. • accompanied by membranous VS• associated clinically with marked cyanosis R-L shunting

Cardiac AnomaliesD) Anomalies of truncus arteriosus & aortico-pulmonary septum2- D-Transposition of the great arteries (complete cause• abnormal neural crest cell migration such that there is non spiral development of the AP septum.• Aorta arises abnormally from RV.& pulmonary trunk arises abnormally from LV;• systemic and pulmonary circulations are completely Separated from each other. • complete transposition of the great blood vessels is incompatible with life; if there is no PDA or atrial and ventricular septal defects .• infant was able to survive after birth because this anomaly is often associated witha) patent ductus arteriosus,b) ASD, and/or VSD that allows mixing of blood between two circulations

It is associated clinically with marked cyanosis R-L shunting

Cardiac AnomaliesD) Anomalies of truncus arteriosus & aortico-pulmonary

septum3- L-Transposition of the great arteries (corrected cause• aorta and pulmonary trunk are transposed • ventricles are “inverted” such that the anatomical RV lies on the left side and the anatomical LV lies on the right side. • blood flow pattern is normal

Cardiac AnomaliesD) Anomalies of truncus arteriosus & aortico-pulmonary septum4- Tetralogy of Fallot cause• abnormal neural crest cell migration such that there is anterior displacement of the AP septum lead to unequal division to truncus arteriosus • pulmonary trunk obtains a small diameter &aorta obtains a large diameter. • characterized by four classic malformations:a) pulmonary stenosis,b) right ventricular hypertrophy,c) overriding aorta, d) ventricular septal defect, • associated clinically with marked cyanosis R-L shunting • clinical consequences depend primarily on the severity of the pulmonary stenosis

(mnemonic PROVE)

Cardiac AnomaliesD) Anomalies of truncus arteriosus & aortico-pulmonary septum4- Tetralogy of Fallot• child may have 1) cyanotic spells especially during crying. 2) SOB or dyspnea on exertion, which is relieved by assuming squatting position for a few minutes. The reason for this is that squatting blocks the venous return and increases the peripheral resistance of the

arteries so that more blood reaches the lungs

Cardiac Anomalies

A) Anomalies of interatrial septum(ASD)B) Anomalies of atrioventricular canalC) Anomalies of interventricular septum(VSD)D) Anomalies of truncus arteriosus & aortico-pulmonary septumE) Anomalies of position of the heart

Cardiac AnomaliesC) Anomalies of position of the heart1- Dextrocardia• Cause• occurs if heart tube bends to the left instead of the right, the heart is displaced to the right,

• , all the chambers of the heart and associated blood vessels are reversed as a mirror image

• associated with situs inversus (transposition of abdominal viscera).

Cardiac AnomaliesC) Anomalies of position of the heart1- Ectopia cordis • Cause• rare condition• heart lies exposed on the surface of the thorax.• occurs due to nonunion of two sternal plates of developing sternum.• Death occurs in most of the cases during first few days of• the birth.

L - R shunt

R - L shunt

It is important to distinguish a “blue baby” (cyanotic at birth) and a “blue kid” (late-onset cyanosis).

Cardiac Anomalies

Cardiac Anomalies

Cyanotic CHD (R Cyanotic CHD (R L)L) Tetralogy of Fallot (TOF)

Tricuspid atresia (TA)

Total anomalous pulmonary venous return (TAPVR)

Truncus arteriosus

Transposition of the great vessels

Hypoplastic left heart syndrome (HLH) Pulmonary atresia (PA) / critical PS Double outlet right ventricle (DORV)

Acyanotic CHD(LAcyanotic CHD(L R)R)

• Atrial septal defects(ASD)

• Ventricular septal defects(VSD)

• AV canal defects

• Aortic stenosis• Coarctation of aorta• Patent ductus arteriosus

Golden facts to remember Most common congenital anomaly of the heart---------------- Ventricular septal defect Ventricular septal defect is most common in ------------- membranous part of the IV septum Most significant atrial septal defect -------------------------------ostium secundum defect Most common congenital cyanotic heart disease-------------- Fallot’s tetralogy Most common positional anomaly of the heart ----------------- Dextrocardia