Heart Defects in Newborns
Heart Defects in Newborns
The human heart develops and begins to beat during the first month of intrauterine development. In its further development, there are periods when the heart is particularly vulnerable to adverse effects. If during this time, the mother is exposed to risk factors such as alcohol consumption, certain viral or bacterial infections, certain medications or drug use, it is very likely that the fetus and subsequent newborn will develop a heart defect. There are of course heart defects in newborns that arise from a hereditary basis. Some disorders can be diagnosed during a regular examination of a pregnant woman, but unfortunately sometimes these illnesses are not noticed until sometime after birth. Heart defects affecting newborns are rather vast and varied, but also very important and interesting.
Description and Function of the Human Heart
The heart is an organ divided into two halves, and consisting of four chambers. The right side consists of the right atrium and right ventricle, and the left side consists of the left atrium and left ventricle. Deoxygenated blood from the whole body collects and is transported to the right side of the heart. From here it is directed to the lungs, where it is oxygenated and can continue to the left side, from where it is expelled into the body. Under normal circumstances, the right and left sides are completely separated. The heart of a fetus, which is still located in the uterus, can be organized slightly differently, and have shunts that should disappear by the time the child is born. If certain communications between partitions do not disappear, congenital heart defects occur.
The Partitions and Symptoms of Congenital Heart Defects
Some minor heart defects do not necessarily cause any problems, others however, can be life-threatening. The basic difference in congenital heart defects are the defects with shunts and those without.
Heart Defects with Shunts
In heart defects with shunts, blood flows through the hole that should not be present in a normal heart, and flows either from the left side of the heart into the right, or the other way around depending on which side has higher pressure. Clinically evident are the right-left openings, the ones where the blood flows from the right side of the heart, into the left. This occurs due to the presence of a defect in the barriers between the sections, such as atrial septal defect, causing deoxygenated blood to flow through the body without it first being oxygenated in the lungs. This causes cyanosis, a condition where mucous membranes and the skin turn blue due to a lack of oxygen. Cyanosis can be most often noticed on the lips, which are usually deep red. Some children can be so affected by this condition, that the name "blue babe" has become common. Even with left-right shunts, the heart and lungs can become so stressed that the pressure ratios may change, causing cyanosis. Left-right shunts develop with defects of the ventricular septum.
Heart Defects without a Shunt
Mixing of blood does not occur in congenital heart defects without a shunt. Usually one is dealing with coarctation of the aorta, described below. Heart defects without a shunt belong to the acyanotic defects, where cyanosis is usually not a symptom. However, even these defects can reach various levels of development and can lead to a pressure imbalance, leading to a reversal of blood flow and causing cyanosis.
Examples of Heart Defects in Newborns
As mentioned above, the heart of a fetus is anatomically different from that of a newborn's. This is due to the fetus' blood being oxygenated in the placenta, as the lungs are not yet used for breathing. With the first inhalation of the newborn, the pressure in the respiratory system is increased and is transferred to the heart where the closing and disappearance of communications occur. If, however, these remain open, they lead to the development of developmental heart defects. There are a number of heart defects affecting newborns, the most common being septal defects, tetralogy of fallot, coarctation of the aorta, or congenital valve defects.
The human heart is divided into four chambers; the right atrium, the right ventricle, the left atrium and the left ventricle. All of these chambers need to be separated. According to the organization of these chambers, the atrial septum is located between the right and left atria. There is also the atrioventricular septum, which is located between the atrium and the ventricle of the same side. And last but not least, there is the ventricular septum, located between the right and left ventricles.
- Atrial septal defect is an opening in or complete absence of this partition, where the right and left atria communicate. In the event of a larger defect, a left-right shunt can occur due to the greater expansion of the right atrium, and cyanosis as well. Individuals with this type of defect typically live longer.
- Atrioventricular septal defect is among the most common developmental heart defect and usually accompanies a genetic syndrome such as Down syndrome.
- Ventricular septal defect is the most common heart defect in newborns. It is a communication between the right and left ventricles. This defect is accompanied by a shunt, whose direction is determined by the size of the defect and the pressure ratio between the right and left ventricle. Because the wall of the left ventricle is about three times stronger and is therefore able to create greater pressure during a contraction, ventricular septal defects are usually left-right shunts.
Tetralogy of Fallot
Tetralogy of fallot is a heart defect appearing in newborns, which consists of four different heart defects. Tetralogy of fallot occurs as a result of faulty development of the heart during the 4th to 6th week of pregnancy. Heredity plays a significant role, but risk factors from the outside environment should not be forgotten. Heredity cannot be influenced much, generally it is said that the incidence of tetralogy of fallot is higher in Down syndrome individuals. This heart defect includes a ventricular septal defect, aorta dextroposition, narrowed pulmonary artery, and ventricular hypertrophy. All this leads to the emergence of typical symptoms such as a heart murmur, shortness of breath, and cyanosis, bluing of the lips and fingertips.
Coarctation of the aorta
Coarctation of the aorta is the narrowing of the aorta, the largest artery in the human body. It is classified as a heart disease without a shunt. Depending on the location of the narrowing, preductual and postductual types can be distinguished. With the former type, the aorta and its branches are normally supplied by oxygenated blood, but the open ductus, which is only present in a fetus and should spontaneously close after birth, is fed deoxygenated blood, which is lead into the lower half of the body. This is manifested by bluing of this area of the body. This is a life-threatening defect and needs to be operated immediately. The second type has a left-right shunt at the open ductus, causing oxygenated blood to enter the lungs, putting increased stress on them. In the case that the duct is closed, which occurs in adult hypertrophic left ventricle, the blood pressure is higher in the upper half of the body than in the lower half.
Congenital Valve Defects
Valves are projection of the endocardium, the membrane lining the inside of the heart. They are sections functioning as valves, meaning they prevent back-flow of the blood. Correct valve function rests in their coordinated opening and closing in relation to the heart's contractions. If this is not the case, it is a sign of a valve defect. Congenital valve defects are among the most common heart defects in newborns and mostly affect the aortic and pulmonary valves. The aortic valve lies between the left ventricle and atriums, and the pulmonary valve lies between the right ventricle and the pulmonary artery. Congenital valve defects include their narrowing or even complete closing, or the flaps may be stiff. There can also be the wrong number of cusps in the specific valve, typically a bicuspid aortic valve. Congenital valve defects are manifested by a heart murmur, shortness of breath, swelling of the lower limbs, fatigue, chest pain, as well as loss of consciousness. For an accurate diagnosis of a heart defect, an electrocardiography is used. The only treatment option is surgery.
Diagnosing Heart Defects
A diagnosis of a heart defect is based on the above mentioned symptoms. Nowadays the focus is more on detecting the congenital heart defect before birth, i.e. prenatal diagnosis. Prenatal diagnosis of a congenital heart disease can be invasive or non-invasive.
- Invasive prenatal diagnosis is where penetration of the necessary instrument or tool into the body is necessary. It is performed when under the suspicion of the presence of a specific defect, including developmental heart defects. Some of the most common invasive methods include amniocentesis, chorionic villus sampling and cordocentesis. Amniocentesis is a diagnostic procedure performed outpatient and is based on the piercing of the amniotic sac, where the fetus resides, and sampling the amniotic fluid. Chorionic villus sampling is a method where a needle is inserted through the stomach of the pregnant woman and a sample of the chorionic tissue is taken. Cordocentesis is based on the piercing of the umbilical cord to obtain fetal blood under ultrasound control.
- Non-invasive prenatal diagnosis is when there is no insertion of instruments or tools into the body. It is mainly a biochemical examination of the mother's blood, followed by an ultrasound examination during the first trimester. The ultrasound can be performed even later, during suspicion of a developmental heart defect.
Treating Heart Defects in Newborns
Some types of defects are life-threatening and therefore require immediate surgery. These are primarily defects of the left-right openings. Such as with coarctation of the aorta, surgery is necessary to remove the narrowed section. Other heart defects endanger the individual later during childhood or adulthood. Therefore in these situations, an operation is performed but not necessary right after birth, it can be postponed. Other defects, typically atrial septal defect, are defects that allow longer survival even without treatment.