Tetralogy Of Fallot
It was described by Etiene-louis Arthur Fallot in 1888. It is the most common of the cyanotic congenital heart diseases and has the best prognosis relatively.
It consists of four main pathologies
1.VSD: It is usually located perimembranous and subaortic.
2.Pulmonary Stenosis (Pulmonary stenosis): It is usually infundibular (subvalvular) type and sometimes valvular and supravalvular pulmonary stenosis may accompany it. It is the degree of pulmonary stenosis that most affects the clinical and prognosis of the patient.
3.Right ventricular hypertrophy: It develops secondary to pulmonary stenosis. It is not an anatomical pathology.
4.Dextraposition of the aorta (attached aorta): It is the result of the VSD being a malalignment type and a part of the aorta emerges from the right ventricle.
It can be seen in other pathologies together with TOF. If it is associated with ASD, it is called the Pentalogy of Fallot. The degree of pulmonary stenosis is clinically very important. If pulmonary atresia, severe right ventricular outflow tract stenosis is present from birth and the ductus arteriosus is closed after a while, cyanosis is more severe. The shunt is initially right-to-left and causes cyanosis and an increase in hematocrit. The way to increase pulmonary blood flow in older children is by squatting. Thus, by increasing the systemic resistance, the right-left shunt is reduced, thus increasing the pulmonary flow. Paradoxical embolism, cerebral or pulmonary thrombosis, and subacute bacterial endocarditis complications may occur in untreated cases.
- Right ventricular outflow tract is narrow. Therefore, less blood goes to the lungs than normal.
- Right ventricular pressure is equal to or higher than the left ventricle due to PS.
- Some of the blood from the systemic veins passes into the systemic circulation via the VSD instead of the pulmonary artery due to pulmonary stenosis.
- The more severe the pulmonary stenosis, the greater the right-to-left shunt, and the more pronounced the cyanosis and other clinical findings.
- If PS is very severe, pulmonary blood supply only depends on the development of PDA or collaterals for survival.
- In cases where pulmonary stenosis is mild, sufficient blood goes to the lungs, there may be a slight bidirectional shunt from the VSD and no cyanosis, this is called Pink Fallot. In this, the clinical findings of the patient are very mild.
- Almost ¼ of patients with tetralogy of Fallot also have ASD.
- Some authors also call it Pentalogy.
- Three out of every four cyanotic patients over the age of two have FT.
- 1/3 of cases are born cyanotic. 1/3 develop cyanosis in the first six months and 1/3 develop cyanosis in the first two years.
- Club finger
- Exercise dyspnea
- Hypoxic seizure
- Murmur (related to PS) and trill
X-ray: Lung blood supply is decreased. The pulmonary issue is unclear. The heart is of normal size. Such a heart appearance resembles a wooden shoe (Coeur en Sabot).
ECG: Right axis deviation, right ventricular hypertrophy. (Spiked R's are seen in the right chest lead. R/S ratio in V5-6 is in favor of S.)
Echo: All anatomical findings of FT are seen. The degree of PS can be measured with Doppler.
- Hypoxic seizures: This is the most common problem. It is caused by spasm of the infindubular muscle mass at the exit of the right ventricle. Severe seizures may cause loss of consciousness and convulsions. (It is time for surgery in a patient with hypoxic seizures.)
- Cerebral thrombosis
- Brain abscess
- Cyanosis and Precordial systolic murmur
- Hypoperfusion of the lungs, absence or smallness of the main pulmonary artery segments, and elevation of the cardiac apex on PA chest X-ray
- Right ventricular hypertrophy on EKG.
- Angiography and cardiac catheterization
Hypoxic Seizure Treatment:
1. Position: The prone knee-elbow position is given or the infant is taken on the lap and the knees are pressed to the abdomen.
2. Oxygen is given for hypoxia and bicarbonate is given for acidosis.
3. SUBCUTAN MORPHINE SULFATE (0.2 mg/Kg/Dose) It both sedates the patient and relieves infundibular spasm.
4. PROPRANOLOL: 0.1-0.2 mg/Kg IV (Continued orally from a prophylactic dose of 1-4 mg/kg/day after Spell has passed.)
Anemia should be treated as it increases the tendency to seizures. (It should not be decided according to the Hb and htc values) It should be kept between 15-17. If Hb rises above 17 g/dl, care should be taken since blood viscosity increases too much.
If the patient has very severe PS or pulmonary atresia, PGE1 infusion is essential since his life depends on the duct.
Important Parameters To be Evaluated Before Surgical İntervention
- Number, size, and localization of VSD
- Severity of right ventricular outflow tract obstruction and pulmonary artery stenosis
- Development and distribution of pulmonary arteries
- Origin and branching of coronary arteries (especially LAD)
- Presence of APCAs (Aortico-pulmonary collaterals)
Indication Of Surgery and Surgical Treatment
Surgical correction should be performed as soon as possible in cases with tetralogy of Fallot. In cases where the distal pulmonary structures are not sufficient, palliative shunt operations are performed first. The aim of palliative shunt surgery is to increase pulmonary blood flow.
Blalock-Tausing surgery: It is a shunt operation performed between the subclavian artery and the pulmonary artery.Modified Blalock-Tausing surgery: It is a shunt operation performed with a prosthetic graft material such as PTFE between the subclavian artery and the pulmonary artery. Shunts can be made on both sides.
Central Aorta-pulmonary shunt surgery: It is a shunt made between the aorta and the main pulmonary artery.Glenn shunt: It is a shunt operation performed between the superior vena cava and the right pulmonary artery.
Total correction surgery: Before total correction surgery, pulmonary structures should be evaluated angiographically and Mc Goon and Nakata indexes should be calculated. If the development of the pulmonary artery is sufficient, this operation is performed with extracorporeal circulation. The VSD is closed and the infundibular stenosis area is resected, and the right ventricular outflow tract and pulmonary artery are reconstructed.
It is the ratio of the sum of the diameters of the right and left pulmonary arteries to the diameter of the descending aorta at the level of the diaphragm. 2 or more of this ratio indicates adequate pulmonary artery structure. 0.8 and below is considered as an indicator of severe pulmonary artery stenosis.
It is the ratio of the total cross-sectional area of the right and left pulmonary arteries to the BSA of the case. The normal index is 330±30 mm²/m². Below 150 indicates insufficient pulmonary artery structure.