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Tetrology of Fallot Dr. M. A. Sofi MD; FRCP (London); FRCPEdin; FRCSEdin TETROLOGY OF FALLOT Tetralogy of Fallot, is one of the most common congenital heart disorders, comprises right ventricular (RV) outflow tract obstruction (RVOTO) (infundibular stenosis), ventricular septal defect (VSD), aorta dextroposition, and RV hypertrophy. The mortality rate in untreated patients reaches 50% by age 6 years, but in the present era of cardiac surgery, children with simple forms of tetralogy of Fallot enjoy good long-term survival with an excellent quality of life Review blood flow through the heart Discuss ToF anatomic abnormalities Etiology Clinical Presentation Labs and Exams Two surgical interventions TOF 4 anatomic malformations: 1. Right Ventricular Hypertrophy 2. Pulmonary Valve Stenosis 3. Transposition of the aorta 4. Ventricular Septal Defect ToF RVH -secondary to PA Stenosis -Increased P on RV leads to RVH Transposition of Aorta -aorta is displaced VSD -”hole in the heart” -mixing of oxygenated and unoxygenated blood -cyanosis PVS -more severe, less blood transported to the lungs and more deoxygenated blood will pass through VSD to aorta to be circulated throughout the body Etiology Theory: destruction of the neuronal crest cells during embryogenesis In the laboratory setting, destruction of these cells reproduced results displayed with certain cardiac malformations. This anomaly accounts for 10% of all congenital heart disease and has an estimated prevalence of 1 in 2000 births Signs and symptoms The clinical features of tetralogy of Fallot are directly related to the severity of the anatomic defects. Infants often display the following: Severe stenosis results in immediate cyanosis following birth. Mild stenosis will not present until later. Growth is retarded – insufficient oxygen and nutrients SOA on exertion Clubbing of fingers & toes Difficulty with feeding Failure to thrive Irritability Episodes of bluish pale skin during crying or feeding (ie, "Tet" spells) Exertional dyspnea, usually worsening with age Heart murmur “Tet Spell” “Tet spells” at 2-3yo, child becomes cyanotic, may experience syncope Physical signs Physical findings include the following: Most infants are smaller than expected for age Cyanosis of the lips and nail bed is usually pronounced at birth After age 3-6 months, the fingers and toes show clubbing A systolic thrill is usually present anteriorly along the left sternal border A harsh systolic ejection murmur (SEM) is heard over the pulmonic area and left sternal border During cyanotic episodes, murmurs may disappear In individuals with aortopulmonary collaterals, continuous murmurs may be auscultated The following may also be noted: RV predominance on palpation A bulging left hemithorax Aortic ejection click Squatting position (compensatory mechanism) Scoliosis (common) Retinal engorgement Hemoptysis Diagnosis Hemoglobin and hematocrit values are usually elevated in proportion to the degree of cyanosis. Patients with significant cyanosis have the following, in association with a tendency to bleed: Decreased clotting factors Low platelet count Diminished coagulation factors Diminished total fibrinogen Prolonged prothrombin and coagulation times Arterial blood gas (ABG) results are as follows: Oxygen saturation varies pH and partial pressure of carbon dioxide (pCO2) are normal unless the patient is in extreme Imaging studies include the following: 1. Echocardiography 2. Chest radiographs 3. Magnetic resonance imaging (MRI) Echocardiography has the following attributes: Color-flow Doppler echocardiography accurately diagnoses ductus arteriosus, muscular VSD, or atrial septal defect The coronary anatomy can be revealed with some degree of accuracy Valvar alterations can be detected with ease In many institutions, echocardiography is the only diagnostic study used before surgery Chest radiographs have the following: Often normal initially Diminished vascularity in the lungs and diminished prominence of the pulmonary arteries gradually become apparent The classic boot-shaped heart (coeur en sabot) is the hallmark of the disorder MRI has the following attributes: Provides good delineation of the aorta, RVOT, VSDs, RV hypertrophy, and the pulmonary artery and its branches[1] Can also be used to measure intracardiac pressures, gradients, and blood flows Plain films may classically show a "boot shaped" heart with an upturned cardiac apex due to right ventricular hypertrophy and concave pulmonary arterial segment. Most infants with TOF however may not show this finding Boot Shaped Heart Cardiac catheterization Cardiac catheterization is extremely useful in any of the following instances: The anatomy cannot be completely defined by echocardiography Disease in the pulmonary arteries is a concern Pulmonary vascular hypertension is possible Cardiac catheterization findings include the following: Assessment of the pulmonary annulus size and pulmonary arteries Assessment of the severity of RVOTO Location of the position and size of the VSD Ruling out possible coronary artery anomalies Angiography & MR and CT angiography Diagnostic angiography is required to identify the origins and contributions of all major aortopulmonary collateral arteries (MAPCAs). All communications between MAPCAs and the true pulmonary artery system must be identified, as surgical planning depends on whether each lung segment receives blood flow from MAPCAs, true pulmonary arteries (isolated supply), or both (dual supply). In addition, all points of stenosis in each MAPCA need to be identified MR and CT angiography — Both magnetic resonance (MR) and computed tomographic (CT) angiography may provide accurate detailed images of the pulmonary architecture. As radiographic technology evolves, it is likely that CT will become more important in delineating complex pulmonary artery anatomy, and may replace or become adjunctive to neonatal cardiac catheterization. Management The great news about ToF is that many people born with ToF do very well over time. Many are now in their 60s, 70s and even 80s. The first surgery for ToF, called a Blalock-Taussig shunt (B-T shunt), was first done in 1944. This was followed by the development of open heart surgery to repair the defects in 1954. The B-T shunt helps babies born with ToF get enough oxygen to their body. Then the baby can have open heart surgery to repair the defects. Primary correction is the ideal operation and is usually performed under cardiopulmonary bypass. Palliative procedures (eg, placement of the modified Blalock-Taussig shunt) may be necessary in patients with contraindications to primary repair, which include the The presence of an anomalous coronary artery Very low birth weight Small pulmonary arteries Multiple VSDs Multiple coexisting intracardiac malformations Management: The management of patients with tetralogy of Fallot with pulmonary valve atresia (TOF/PA) is challenging given the wide spectrum of pulmonary artery architecture. Initial medical management to maintain sufficient pulmonary blood flow for survival. Subsequent management focused on complete separation of the pulmonary and systemic circulations. This is accomplished by restructuring pulmonary blood flow to create a low pressure system, establishing antegrade pulmonary blood flow from the right ventricle (RV), and closing the ventricular septal defect (VSD). The surgical steps include: Unifocalization, which involves detachment of collateral vessels from their aortic origins and anastomosis to the central pulmonary arteries, resulting in creation of a low pressure pulmonary arterial system. Reconstruction of the right ventricular outflow tract (RVOT) using an allograft valved conduit from the RV to pulmonary artery that results in antegrade pulmonary blood flow from the RV into the pulmonary vascular system. VSD closure