Tetralogy Of Fallot – Symptoms, Diagnosis and Treatment
Tetralogy of Fallot is a complex congenital heart disease, classified as a cynotic heart condition, which associates four defects: ventricular septal defect, pulmonary artery stenosis (right ventricular outflow tract obstruction), right ventricular hypertrophy and aorta dextroposition. If is present interatrial septal defect, then the disease is called pentand of Fallot.
Tetralogy of Fallot always associate stenosis of infundibular septum and the presence of ventricular septal defect and the aorta dextroposition. Right ventricular hypertrophy occurs as a result of ventricular overload. Pulmonary artery stenosis is constantly present and represents the central element of tetralogy of Fallot. It may be a pulmonary valve stenosis in the right ventricular outflow tract or a hypoplasia of the pulmonary artery trunk. Clinical picture of this defect is wide, from asymptomatic forms to extreme form in which the anatomical and functional communication between right ventricle and pulmonary artery is absent (pulmonary atresia with tetralogy of Fallot), with severe clinical expression. May be associated with tetralogy of Fallot: right aortic arch, coronary anomalies, interatrial septal defect.
Pathophysiology of tetralogy of Fallot:
Due to increased pressure in the right ventricle, which is hindered to eject blood into pulmonary artery, will appear a right-left shunt through the ventricular septal defect that causes cyanosis and clinical hypoxic crisis. Shunt size depends on the degree of infundibular stenosis of the pulmonary artery, ventricular septal defect size and peripheral vascular resistances. Hypoxic crises, which represents a classic complication in tetralogy of Fallot, are due to muscle spasm of the pulmonary artery which accentuates the degree of stenosis. To reduce the hypoxic crises, children are adopting a squating position, which increases peripheral vascular resistances by reducing venous return and thus, will reduce right-left shunt.
Symptoms of tetralogy of Fallot:
Symptoms are different, depending on the severity of tetralogy of Fallot complex. Some forms of tetralogy of Fallot go unnoticed at birth and first months of life. A reduced pulmonary artery obstruction and a small right-left shunt, is giving a form of disease, called “pink tetralogy of Fallot”.
In more severe forms of Fallot tetraolgie occur:
- Hypoxic crises;
- Squating position to improve hypoxia;
- Hippocratic fingers;
- Short stature and weight deficit;
- Effort intolerance;
Clinical examination can detect an increased apexian shock, regarding to right ventricular hypertrophy, deep systolic murmur in the area of pulmonary artery.
Diagnosis of tetralogy of Fallot:
The presence of intense cyanosis immediately after birth should lead to suspicion of a severe form of tetralogy of Fallot. Clinical examination of an infant becoming cyanotic lately, which is not developed a properly stature and weight and in whom cardiac auscultation highlight a loud systolic murmur in the pulmonary artery, should be complemented by laboratory investigations, particularly echocardiography, which will specify the correct diagnosis.
- Laboratory test can reveal a poliglobulia.
- ECG – signs of right ventricular hypertrophy, incomplete right bundle branch block and arrhythmias.
- Chest radiography – pulmonary circulation is poor so that lung areas are hypertransparent and heart image is typical(shoe aspect), for right ventricular hypertrophy.
- Echocardiography – identify the characteristic features of tetralogy of Fallot, the presence of ventricular septal defect, the direction of the shunt in Doppler color method, aorta dextroposition , the degree of stenosis of the pulmonary artery and right ventricular hypertrophy. Also, can be examined the valvular apparatus and integrity of the interatrial septum. Estimation of pulmonary artery trunk size is also possible and useful.
- Magnetic Resonance Imaging – View with accurate ventricular septal defect, right ventricular outflow tract and pulmonary artery with its distal branches.
- Cardiac catheterization – is done only when is trying to see pulmonary artery branches and coronary artery anomalies. This exploration gives a anatomic and hemodynamic assessment of the heart and appreciate very specific the oxygen saturation of the cardiac chambers.
Natural evolution of tetralogy of Fallot:
Without an intensive and specialized treatment newborns with severe forms of tetralogy of Fallot die. Classical form of tetralogy of Fallot become symptomatic by the age of 3-6 months, and progressively worsens. Hypoxic crises can occur but are more common in infants and characteristics by age of 2 years. The main complications are neurological injuries, pulmonary or cerebral abscess, and endocarditis in older ages.
Treatment of tetralogy of Fallot:
Medical – It is in crises of hypoxia, when the child is taking the squatting position, administration of beta blockers (propranolol) and correction of acidosis. Propranolol is useful as preventive treatment of hypoxic crisis.
Surgical – depending on the symptoms, newborn weight, the anatomically situation of the defects can be done a palliative or corrective surgery. Newborns with weight under 4 kg, hypoxic crises, symptoms, pulmonary circulation depending on patent ductus arteriosus, and underdeveloped pulmonary artery can benefit in a first stage of palliative surgery, and 6-12 months after, a total correction.
Palliative surgery – Creating a systemic-pulmonary shunt, which is designed to increase pulmonary blood flow, to relief symptoms, allowing development of lung vascularization and infants development up to the final intervention.
Interventional treatment – is trying to expand right ventricular ejection way to relieve symptoms. Also peripheral pulmonart artery stenosis can be dilated.
Overall, perioperative mortality is less than 5%. Long-term survival is good, 80% of patients are asymptomatic after surgery and have 85% survival rate at 30 years after surgery. In evolution may occur various cardiac arrhythmias and sudden cardiac death may occur in 1% – 3% of cases.