Congenital Heart Defects

Congenital heart deffects are cardiac anomalies that involve the heart chambers, valves, and great vessels.

Their cause is unknown in 90% of the cases.

Congenital heart disease is frequently associated with other congenital defects.For example, cataracts, skeletal anomalies and deafness are seeing more commonly in people with congenital heart disease

Predisposing Factors to congenital heart defects

Fetal or maternal infection during the first trimester. The most common infection being Rubella and other teratogenic viral infections, like herpes simplex
Chromosomal abnormalisties such as trisomy21,18 and trisomy 13.
Maternal insulin dependent diabetes mellitus
Teratogenic drugs such as thalidomide and alcohol.
Heredity and genetic factors
Syndromes such as

Turners syndrome that is associated with aortic valve stenosis (AVS), coarctation of the aorta (CoA).
Noonan's syndrome that is associated with dysplastic pulmonary valve.
Down syndrome (Trisomy 21) is associated with artrioventricular (AV) canal defect, Ventricular septal deffect (VSD). About 50% of the children with Down syndrome have a congenital heart defect.

Classification of congenital heart defects

These heart deffects are lassified into three broad categories depending on the presence or absence of cyanosis.

Acyanotic and
Cyanotic
Obstructive

Acyanotic heart deffects (Group I) Left-to-Right Shunt

(A) These are lesions that lead to increase in the volume of blood (load) in the heart.

They are mostly associated with left-to-right shunting.

They include:

Atrial septal deffect (AVD)
Ventricular septal deffect (VSD)
Patent ductus arteriousus (PDA)
Regurgitatitant lesions like Atrioventricular valve regurgitation
Cardiomyopathies such as myocarditis

They result to a return of oxygenated blood back to the heart

the increase in bloof flow to the lungs leads to signs of respiratory dystress such as tachypnea, nasal flaring and chest retractions, shift if fluid to the interstitial causes pulmonary oedema and cardiac failure

(B) Lesions that increase pressure in the cardiac load mostly due to obstruction in blood flow in the heart.

Pulmonic valve stenosis
Aortic valve stenosis
Coarctation of the aorta
Tricuspid or mitral stenosis.

Characteristics of Acyanotic heart defects

These patients present with:

Frequent upper respiratory tract infections, ie bronchopeneumonia
Tachypnea
Absence of cyanosis
Features of congestive cardiac failure
Precordial bulge due to cardiomegaly
Hyperkinetic precordium on palpation
Tricuspid or mitral delayed diastolic murmur
Cardiomgaly, plethoric lung fields on a x-ray

Cyanotic Heart defects (Right-to-Left-Shunt)

These defects can be divided to

Those that decrease pulmonary blood flow include;

Tetralogy of Fallot,
Tricuspid atresia
Transposition of great arteries with
– DORV and PS
– VSD with PS
– Ebstein anomaly

They result from the obstruction in the pulmonary blood flow.

The child may be acyanotic during rest but will get cyanotic ("tet") spells during stress.

Those that increase pulmonary blood flow include;

Transposition of great vessels,
Persistent truncus arteriosus
Single ventricle and
Truncus arteriosus.

Thet result in mixing of systemic and pulmonary blood within the heart.

Characteristics of Cyanotic heart defects

Cyanosis is usually accompanied by polycythemia and finger clubbing
These patients have a normal Pulmonary Arterial Pressure
They have a diminished Pulmonary Arterial Pressure with a decreased pulmonary blood flow too as a result of pulmonary stenosis
They also have increased Pulmonary Arterial Pressure because of:
- Increased pulmonary blood flow with slight cyanosis
- Decreased pulmnary blood flow in moderate to severe cyanosis and irreversible pulmonary arterial hypertension