Tetralogy of Fallot
Tetralogy of Fallot
Tetralogy of Fallot is a congenital heart condition in which there are four defects in the structure of the heart and its protruding blood vessels. The heart is an essential part of the circulatory system; it works as a muscular pump, contracting regularly in order to push oxygenated blood from the lungs further throughout the whole body. At the same time it also draws oxygen-deprived blood and pumps it into the lungs. In order for the heart to function properly, its structure needs to be free of defects. Deoxygenated blood from the body gets into the heart through the superior and inferior venae cavae and first fills the right atrium and then right ventricle. From the right ventricle, the blood flows further through the pulmonary artery into the lungs, where the blood is oxygenated. This oxygenated blood flows into the left atrium and ventricle, followed by the aorta. The aorta is attached to the left ventricle and blood from the heart flows through it, into the rest of the body.
The Essence of Tetralogy of Fallot
The essence of the development of tetralogy of fallot is flawed development of the organ and structures of the heart, occurring most frequently between the 4th and 6th week of pregnancy. As mentioned above, tetralogy of fallot is composed of 4 simultaneous anomalies.
- The first of the four listed defects in the heart's construction is a repositioned aorta. This is known as aorta dextroposition, where this large artery is connected to the right ventricle instead of the left. This results in the change in position of the aorta, causing the heart to pump not only oxygenated blood into the body, but deoxygenated blood as well, which should be pumped into the lungs under normal circumstances. This causes the body to receive less oxygen than needed in order ensure proper organ and tissue function.
- The second defect is ventricular septal defect (VSD), where the septum between the left and right ventricles of the heart is underdeveloped. This causes an opening on the septum, allowing blood to mix from the two ventricles; oxygenated blood from the left ventricle, with deoxygenated blood from the right.
- The third defect is narrowing of the pulmonary artery. This artery is connected to the right ventricle and is responsible for leading deoxygenated blood into the lungs. In the case of its narrowing, the blood flow to the lungs is impaired and blood oxygenation is decreased. This results in deoxygenated blood to flow through the ventricular septum, into the left ventricle all the way into the aorta.
- The fourth defect is enlargement of the right ventricle (right ventricular hypertrophy). The right ventricle works against the increased resistance of the narrowed pulmonary artery, which causes enlargement and thickening of the muscles of its walls as well. Due to increased muscle mass, it is not possible to ensure this part of the heart receives sufficient oxygenated blood, and the heart itself may fail as a result.
Symptoms of Tetralogy of Fallot
Symptoms of tetralogy of fallot are typically present at birth or appear shortly after. A major sign is cyanosis caused by oxygen reduced blood in the body, resulting in bluing of the lips or nail beds. Exertional dyspnea (shortness of breath) or an audible heart murmur may appear as well.
Causes of Tetralogy of Fallot
Tetralogy of fallot, as mentioned above, is a congenital condition heart defect and can be caused by a number of factors. Heredity plays a major role but risk factors of the external environment should not be ignored either. Inheritance itself does not have much of an influence. It is generally reported that a high incidence of tetralogy of fallot appears in individuals with Down syndrome. Risk factors of the outside environment, those that can be influenced and controlled to a certain degree by lifestyle choices, primarily include smoking or alcohol consumption during pregnancy. Therefore it is necessary to avoid these factors. The incidence of heart defects is also higher in mothers who took certain inappropriate medications during pregnancy, such as anti-epileptic drugs. A number of other external risk factors exist that can affect a fetus during pregnancy.
Diagnosing Tetralogy of Fallot
A diagnosis of tetralogy of fallot is made based on clinical symptoms shortly after birth of the individual. A heart murmur and especially bluing of the skin and oral mucous membranes are present. It is also important to use imaging devices during the examination. The most basic imaging method for diagnosing tetralogy of fallot is an ECHO (echocardiograph). This is an ultrasound examination of the heart where the shape and size of the heart as well as its chambers and valves can be evaluated. An x-ray of the heart and lungs can also be made with the help of an EKG (electrocardiograph) and last but not least a heart catheterization can be performed; where thin needles are introduced into the heart allowing the cardiologist to evaluate blood pressure and vascular structures around the heart.
Treating Tetralogy of Fallot
The only treatment option for tetralogy of fallot is surgery done by a specialist in the field of cardiac surgery. This is a procedure focused on renewing anatomical and physiological ratios in the heart, ensuring proper blood circulation. Changes in the heart by restoring its physiological position can be done during a single surgery, though a number of operations are usually necessary. These operations follow each other in varying time intervals. Doctors have the option to choose between palliative surgery or the operation of tetralogy of fallot itself.
- Palliative surgery is focused on establishing a connection between the aorta and the pulmonary artery. This procedure is performed on a closed heart; when the heart's function is not suspended. This procedure doses not solve the problem, however it improves the health of the newborn, enabling further surgery to be postponed.
- Surgery itself is performed on an open heart, where the heart is temporarily stopped and extracorporeal circulation is provided. Circulation is ensured by a machine functioning as a pump that circulates oxygenated blood throughout the body. This type of operation is performed during the treatment of most congenital heart defects. It fixes the already mentioned ratios of the newborn's heart.
Preventing Tetralogy of Fallot
The best way to reduce the risk of the development of heart defects is the avoidance of risk factors during pregnancy, especially the external risk factors. The most basic prevention is avoiding the consumption of alcohol, especially in the first months of pregnancy and limiting smoking, as well as the time spent in smoky areas.