Congenital Cardiac Defects: Classification of Heart Defects, Symptoms

Congenital heart defects are diseases of the heart and blood vessels that arise during intrauterine development of the embryo and fetus. It is the improper growth of the structures that results in difficulties manifesting themselves immediately after birth. 

Some minor defects may be detected later in childhood or in adulthood.

Congenital heart disease is one of the most common congenital developmental defects.
An approximate prevalence of 20% of all developmental diseases is reported. 
+ 1% of all live births. 
Nowadays there is a lower mortality rate than in the past. 
Thanks to prenatal and early diagnosis.

The heart

The heart is a hollow muscular organ that serves as our pump.

A pump that continuously pumps blood through the body.

The blood carries oxygen, and important nutrients, which is consumed by the cells. It is then pumped back to the lungs where it is re-oxygenated.

The oxygenated blood is then expelled by the heart into the circulation. 

The main force unit of the heart is the heart muscle. It ensures that when it contracts, blood is expelled into the blood vessels. When it relaxes, blood is drawn into the cavities of the heart.

The heart is divided into 4 cavities, compartments:

1. right atrium
2. right ventricle
3. left atrium
4. left ventricle

The deoxygenated blood is fed through large veins into the right atrium.
From the right atrium it goes to the right ventricle through the valve.
It then travels from the right ventricle through the pulmonary artery to the lungs.
In the lungs, the blood is oxygenated.
This is the pulmonary blood circulation.

Systemic circulation: 
After the blood in the lungs is oxygenated, it enters the left atrium through the pulmonary veins.
From the left atrium it moves through the valve into the left ventricle.
The left ventricle, through the valve, discharges blood into the aorta.
Blood from the aorta is carried further into the body. 
Eventually returns to the right heart through the great veins.

Pulmonary circulation = between the heart and the lungs
Systemic circulation = between heart and body

The blood vessels that lead TOWARDS the heart are referred to as veins. The blood vessels leading away FROM the heart are called arteries. The aorta is the largest artery in the human body.

The left ventricle pushes against maximum pressure.
It is approximately three times larger than the right ventricle.

In addition to the heart muscle, there is an inner membrane inside the heart that also forms the valves. It is called the endocardium and it is in contact with the blood. On the surface of the muscle is the epicardium. The whole heart is contained in a sac called the pericardium.

When pumping blood, two phases alternate.

The heart contracts, and this contraction is referred to as systole. This is the phase in which blood is expelled from the cavity of the heart. Diastole, on the other hand, is the relaxation of the muscle, and during it blood is drawn into the cavity of the heart.

The heart valves are also important during the blood pumping process.

The valves serve as a one-way valve. The valve closes, which prevents backflow of blood in the heart. Opening and closing is based on a pressure gradient.

Fetal blood circulation

During the period when the fetus is in the womb, the supply of oxygen and nutrients is provided by the placenta rather than by the lungs.

For this reason, it also has an adapted blood circulation.

The placenta replaces the lungs in this period, and consequently the exchange of nutrients and waste substances from the fetal body takes place here.

Blood - fetal haemoglobin has 60% oxygen saturation, not like adult hemoglobin, about 98 %.

Therefore, the blood bypasses the lungs, which are not used during this period.

The detour is provided by two shortcuts, namely:

1. foramen ovale - opening between the right and left atria of the heart
   • in other words, an opening in the vestibule, or the septum
2. ductus arteriosus Bottali - connects the pulmonary artery and the proximal descending aorta

Oxygenated blood passes through the hepatic duct. 

Another part of the blood is led to the heart, more precisely, the right atrium. Here the blood flow is adjusted so that the oxygenated blood passes through the foramen ovale into the left heart. From the left heart it then passes into the aorta. 

From the aorta, blood then flows to the brain, heart and upper body.

Blood flow is ensured so that the blood also reaches the lower part of the body and the deoxygenated blood is returned to the placenta.

Ductus arteriosus Bottali is a shortcut through which the lungs are bypassed. These are non-functional at this time and only a minimal amount of blood is flowing.

This ensures that the most oxygenated blood reaches the brain and heart.

After delivery...

After birth, the placental circulation is interrupted. The baby begins to breathe through the lungs. Complicated changes in blood oxygen saturation and a gradual change of the fetal blood circulation to that of the newborn occur.

The changes are related to the vascular shunts, umbilical vessels and the opening between the halves of the heart. The ductus closes immediately and the foramen ovale disappears until the third month.

These changes classify blood circulation into the pulmonary and the systemic circulations.

See the article below to answer the following:
What are congenital heart defects?
What causes them?
How do they manifest? 
What is the diagnosis? 
Is there a treatment? 

Congenital heart defects are...

Heart defects are defects that affect the structure of the heart and the blood vessels that connect to the heart. They are generally divided into congenital and acquired. In this article, we describe the congenital group.

Congenital= inborn.

Congenital heart defects (CHD) arise already during the development of the embryo and fetus inside the uterus. 

Congenital heart defects are the most common birth defect. In 2015, they were present in 48.9 million people globally. They affect between 4 and 75 per 1,000 live births, depending upon how they are diagnosed. In about 6 to 19 per 1,000 they cause a moderate to severe degree of problems. Congenital heart defects are the leading cause of birth defect-related deaths: in 2015, they resulted in 303,300 deaths, down from 366,000 deaths in 1990. (Source: Congenital heart defect - Wikipedia)

The severity of the discomfort depends on the structural extent of the damage, the functional impairment and also the area. In the case of severe forms, they manifest themselves already at rest and without effort.

In contrast, defects of lesser severity may only become apparent under load and strain. In some cases, they do not manifest themselves at all. They are detected later in childhood or only in adulthood.

Damage can affect any part of the heart described earlier.

Accordingly, congenital heart defects are classified as follows:

• heart valve defects
  • stenosis - constriction - an increase in pressure to expel blood
  • insufficiency - backflow of blood to the previous compartment of the heart 
  • atresia - absence or partial valve defect
• septal defects, i.e. the walls between the cavities of the heart, also called the septum
  • defect between the atria 
  • defect between the chambers 
  • allows mixing of unoxygenated and oxygenated blood
  • i.e. between the right and left side of the heart
• cardiomyopathy - leading to heart failure
• defective connection of veins or arteries to the heart
  • defective distribution of unoxygenated and oxygenated blood
  • does not reach the lungs or aorta properly

Learn more: Heart Valve Diseases

In the past, congenital heart disease used to be classified into cyanotic and non-cyanotic, i.e. according to whether the defect was manifested by cyanosis or not. 

Cyanosis = change of body tissue color to a bluish-purple hue caused by inadequate oxygenation.

Modern classification:

1. shunt defect, patent ductus Botalli, i.e. the ductus arteriosus fails to close
   • left-to-right shunt
   • right-to-left shunt
2. stenosis defect - stenosis of the aorta, coarctation of the aorta, i.e. a part of the aorta is narrower than usual
3. dislocation defects - transposition of the great vessels, i.e. an abnormal spatial arrangement of any of the great vessels
4. combined defects - such as the tetralogy of Fallot

Another classification is shunt and non-shunt defects.

Table: some congenital heart diseases and their distribution

The exact cause is still not clear.

It is thought to be influenced by genetics and various genetic mutations. Some may also be hereditary and occur together with other diseases.

The main suspicion also falls on external influences during pregnancy, embryo and fetal development.

It is the first weeks of life that are the most sensitive for the embryo.
During the 5th to 8th week, the heart, septum or valves from the endocardium begin to develop.

A variety of external stimuli, such as alcohol, smoking, radiation or certain medications, can have a negative effect.

Risk factors involved in the development of congenital diseases include:

1. biological causes
   • a woman's viral illness during the 5th to 8th week of pregnancy, an example is rubella
   • bacteria - syphilis infection in pregnant women and others
2. chemical cause - alcohol, smoking and offal, some drugs
3. physical cause - radiation, elevated body temperature, flu during pregnancy, for instance
4. heritability - some risk of familial occurrence in some cases, but not the rule
5. genetic factors, chromosomal disorders
6. the wider environment
7. other diseases of the mother, such as diabetes

The exact cause is only clarified in 10% of cases.

Teratogen

Teratogen = it is a kind of influence that interferes with the proper development of an organ or the whole organism, during embryonic or fetal development.

As a result of its action, various congenital diseases and damage to the fetus occur. It can even cause fetal death and miscarriage.

Some known teratogens:

• chemical - certain medications, herbicides, drugs, alcohol, smoking, heavy metals, and other
• biological - certain viruses and bacteria, such as rubella, herpes virus, syphilis, toxoplasmosis
• physical - ionizing radiation, X-ray, radiotherapy
• metabolic - diabetes, folic acid deficiency, phenylketonuria, rheumatic diseases

Embryo = a newly developing human, the time from fertilisation of the egg by the sperm takes approximately 8 weeks = 56 days. 
Fetus, period from the 56th day of life - after delivery, i.e. the birth of a child (newborn). 
"Foetus" is Latin for "offspring, child, small individual".

Next in the article we describe some of the congenital heart diseases.

Non-cyanotic disorders without short circuit and with short circuit

This group of diseases does not have as a manifestation the bluing of the skin - cyanosis. It contains a number of heterogeneous diseases.

In stunt defects, the direction of blood flow is determined by: 
pressure gradient
and
defect location.

Ventricular septal defect - VSD

It is the most common heart defect, representing approximately 32% of all VSDs. It is a left-right shunt. It can occur alone, but also in combination with others.

Shunt = defect in the septum between the atrii.

It is characterised by typical features:

• oxygenated blood returns in part to the right ventricle and into the lungs through the opening between the ventricles
• on the basis of higher pressure in the left ventricle,
  blood flows to the place with lower pressure,
  i.e. to the right ventricle
• the severity of manifestations depends on the size of the defect
• major defects = higher cardiac congestion
  • enlarged  heart chambers - dilatation of the ventricles and left atrium
  • pulmonary hypertension occurs
  • from the 2nd - 6th month of life, heart failure occurs
  • enlargement of the liver
  • early cardiac surgery needed
• minor defects = less severe difficulties
  • in some cases asymptomatic
  • murmur
  • more frequent respiratory infections
  • risk for endocarditis

Most small ventricular septal defects will close on their own by the age of 10.

Atrial septal defect - ASD

It accounts for approximately 16% of all congenital heart defects.

Depending on the extent, symptoms are associated. It is often asymptomatic and therefore not detected until adulthood.

• more common among women than men
• excessive filling of the right heart and increased flow through the lungs
• trhree types:
  • sinus venosus - when the great veins enter the heart
  • ostium primum - in close proximity to the flap between the atrium and the chamber
  • ostium secundum - in the middle region such as the fossa ovalis - an extinct shunt from the fetal period

Ductus arteriosus persistens

During fetal development, a shunt is normally formed - ductus arteriosus. It is a shunt between the pulmonary artery and the aorta. 

The problem arises if it does not close after childbirth. It represents about 12% of all CHD cases.

• the severity depends:
  • on the pressure differences between the pulmonary and body circulations
  • on shunt length
• with higher pressure, pulmonary hypertension occurs
• as a result of the increase in pressure in the pulmonary circulation, deoxygenated blood enters the aorta
• typically in this case there is a machinery, or locomotive murmur

Atrioventricular septal defect - AVSD

It often occurs together with Down syndrome.

The defect is located between the atria and the chambers. With high pressure, blood from the left heart mixes with blood in the right heart. This increases the pressure and flow in the pulmonary circulation.

There is usually an associated valvular disorder. Together this causes congestion of the heart. Early surgical treatment is necessary. 

There are two forms:

• complete atrioventricular (AV) canal - big hole in the centre of the heart
• incomplete AV canal - partial defect

Aortic stenosis - AS

In the case of this disease, the problem is an obstruction that prevents the outflow of blood from the left ventricle. Depending on the type and severity, symptoms are associated.

There are three forms:

• valvular aortic stenosis
  • often proceeds asymptomatically
  • may therefore not be detected
  • confusion with another form of valvular defect is a possibility
  • degenerative process occurs over time
  • thickening and calcification of the valve
• subaortic aortic stenosis
  • a membranous or fibrous ring located below the aortic valve
• supravalvular aortic stenosis
  • continuous narrowing of the part of the aorta extending from the heart
  • ascending aorta
  • mostly starts above the spacing of the coronary vessels, causing
  • increase in pressure in the heart arteries
  • the heart vessels are therefore dilated 
  • frequently and irregularly splashed

Pulmonary artery stenosis

This condition is also an obstruction in the outflow from the heart, but in the part from the right ventricle to the lungs, that is, the pulmonary artery.

Like aortic stenosis, it can take three forms, depending on its location, i.e. above, below or in the area of the valve.

It is reported to be frequent after overcoming rubella during pregnancy.

The mild form may be asymptomatic.

Conversely, the severe form will result in right heart failure. 

Coarctation of the aorta

With this defect, a portion of the aorta is narrowed, at any location. It occurs to a greater extent in boys. Out of the total CHD, approximately 7 percent have this defect.

The occurrence of a mild form is a possibility. It proceeds asymptomatically.

More severe forms are characterized by discomforts typical of an increase in pressure in the upper half of the body. Even when measuring blood pressure, the measured values are higher.

Conversely, pulsations on the femoral artery tend to be attenuated to absent.

The risk is the association of infective endocarditis. However, the brain and the aorta itself are most affected. This is because of the increased rate of a bulging artery, even its rupture - dissection.

This is better known as an aneurysm. 

In the long term, left ventricular failure also sets in.

Right-left shunt + cyanotic defect

A group of diseases with the presence of cyanosis - blue discoloration of the skin.

Tetralogy of Fallot - TOF

It is the most common cyanotic form, representing approximately 6% of all heart defects. 

The increase in pressure in the right ventricle will cause oxygen-free blood to flow into the left ventricle. According to the extent, the degree of cyanosis and other manifestations subsequently depends.

It requires early surgical intervention to correct the defect between the ventricles and the location of the vessels.

There are four typical signs:

1. large ventricular septal defect
2. overriding aorta
3. right ventricular outflow tract obstruction
4. right ventricular hypertrophy

Transposition of the great vessels

Congenital malposition of the great vessels that comes from the heart. 

The confusion involves the aorta and the pulmonary artery.

Normally, the great vessels leave the heart as follows:

1. the pulmonary artery comes out of the right ventricle = it carries DEoxygenated blood from the heart to the lungs, where it becomes oxygenated
2. the aorta comes out of the left ventricle = it carries Oxygenated blood from the heart to the body

In transposition, their positioning is incorrect - reversed.
The pulmonary artery comes out of the left ventricle.
The aorta comes out of the right ventricle.

In this case, a parallel circulatory system is present, that is, the pulmonary circulation is separated from the body circulation. Blood with and without oxygen mixes only through the associated combined defects.

One third of the affected patients also have an atrial septal defect, which paradoxically contributes to the condition of vascular confusion. The other third has an open ductus arteriosus. A third of those affected have a ventricular septal defect.

Hypoplastic left heart syndrome

Hypoplasia =  is underdevelopment or incomplete development of a tissue or organ.

The left ventricle is not sufficiently developed. This is compounded by valve defect and coarctation of the aorta. There is increased pressure in the right half of the heart, which causes enlargement of the right ventricle. 

Newborn heart failure occurs between the second and the fourth day after delivery.

Critical congenital heart defects

The term critical heart defects refers to those diseases that already manifest themselves in the neonatal period, either:

• by heart failure
• by shock
• or by significant cyanosis.

Of the total number of CHD = approximately 25% of cases.

Inside the uterus, the fetus is supplied with oxygen and nourished through the placenta. This is important for normal growth and development. 

Newborns are born well developed.

After delivery, the course depends on the form of the disease, the extent and nature of the defect, e.g. early onset of difficulties is aortic stenosis, coarctation of the aorta, hypoplastic left ventricular syndrome.

Surgical correction of present heart defects is necessary.

Symptoms depend on the specific type of disease. However, general symptoms that result from insufficient oxygen supply to the cells and organs or congestion of the heart are typical.

In the case of some heart defects and with a mild form of the disease, difficulties may not manifest themselves at all. The disease then proceeds asymptomatically, i.e. without symptoms.

Or...

The mild form can only manifest itself with exertion. At rest, there is an improvement in the condition.

Conversely, the more severe form is characterized by the presence of difficulties even at rest.

The main symptoms include:

• slow development of the newborn, i.e. the baby
• nursing strikes - caused by increased exertion and difficulty breathing during breastfeeding/weaning
• fatigue, weakness
• difficulty breathing
• accelerated breathing
• cyanosis - the skin, lips, mucous membranes, nails, peripheral parts of the body become bluish
• increased sweating
• swelling
• enlargement of the heart - cardiomegaly, cardiomyopathy
• non-palpable pulse in the lower limbs
• rapid pulse - tachycardia
• arrhythmia - heart rhythm disturbances
• enlargement of the liver
• a murmur, which, however, may not be present
• pulmonary hypertension
• headache - in coarctation of the aorta
• cold extremities
• more frequent syncope - passing out, collapses

Associated complications in the form of recurrent respiratory tract infections or infective endocarditis are also possible. 

Development of heart failure and shock state may become severe.

In adulthood, the heart defect may not manifest itself, proceeding unrecognized and asymptomatically. Alternatively, difficulties may arise and worsen with physical or psychological stress.

Examples include increased fatigability and intolerance of physical activity, as well as the presence of a murmur.

A harmless murmur is not pathological murmur

This commonly occurs in children and disappears in adulthood. It is a sound produced by the flowing blood rubbing against the walls of the heart and blood vessels.

Systolic murmur - during contraction of the heart muscle and has a low intensity. A pediatrician can well distinguish it from pathological murmurs.

It occurs in approximately 80% of children.

The prenatal screening examination takes place before delivery.

Next, a clinical examination of the newborn or the baby is performed. The following is monitored:

• blood pressure - on upper and lower limbs
• heart rate in all limbs
• oxygen saturation of the blood, also in all limbs
• oxygen test (oxymetry) - 100% oxygen is given for 10 minutes and if decreased saturation persists = suspect CVD or pulmonary cause
• Capillary Refill Test
• pulsations in the upper and lower limbs
• auscultation of the presence of murmur that may not be present in all forms

The diagnosis also requires ECHO, USG, ECG, X-ray, blood and urine sampling for laboratory tests, or in some cases catheterization.

Diagnosis and treatment of childhood heart diseases is done at children's heart centres.