Tetrology Of Fallot.docx

TETROLOGY OF FALLOT Tetralogy of Fallot (TOF) is a type of heart defect present at birth. Symptoms at birth may vary from none to severe. Later there is typically episodes of bluish color to the skin When affected babies cry or have a bowel movement, they may develop a "tet spell" where they turn very blue, have difficulty breathing, become limp, and occasionally lose consciousness. Other symptoms may include a heart murmur, finger clubbing and easy tiring upon breastfeeding. HISTORY Tetralogy of Fallot was initially described in 1671 by Niels Stensen. A further description was published in 1888 by the French physician Étienne-Louis Arthur Fallot, after whom it is named. In 1924, Maude Abbott coined the term "tetralogy of Fallot". The first surgical repair was carried out in 1944 at Johns Hopkins.The procedure was conducted by surgeon Alfred Blalock and cardiologist Helen B. Taussig, with Vivien Thomas also providing substantial contributions and listed as an assistant.[3] This first surgery was depicted in the film Something the Lord Made. It was actually Helen Taussig who convinced Alfred Blalock that the shunt was going to work. 15-month-old Eileen Saxon was the first person to receive a Blalock-Thomas-Taussig shunt. Furthermore, the Blalock-Thomas-Taussig procedure, initially the only surgical treatment available for tetralogy of Fallot, was palliative but not curative. The first total repair of tetralogy of Fallot was done by a team led by C. Walton Lillehei at the University of Minnesota in 1954 on an 11-year-old boy. Total repair on infants has had success from 1981, with research indicating that it has a comparatively low mortality rate. Today the adult TOF population continues to grow and is one of the most common congenital heart defect seen in adult outpatient clinics ANATOMY OF HEART The normal heart has four chambers. The two upper chambers known as atria are separated from each other by a fibrous partition known as the atrial septum. The two lower chambers are known as ventricles and are separated from each other by the ventricular septum. Valves connect the atria (left and right) to their respective ventricles. The valves allow for blood to be pumped through the chambers. Blood travels from the right ventricle through the pulmonary artery to the lungs where it receives oxygen. The blood returns to the heart through pulmonary veins and enters the left ventricle. The left ventricle sends the now oxygen-filled blood into the main artery of the body (aorta). The aorta sends the blood throughout the body.

Epidemiology Tetralogy of Fallot is the most common cyanotic heart condition in children who have survived untreated beyond the neonatal age, with the need for an intervention in the first year of life. It accounts for 7% to 10% of congenital defects, affecting males and females equally and occurring in 3 to 5 of every 10,000 live births.

ETIOLOGY Its cause is thought to be due to environmental or genetic factors or a combination. It is associated with chromosome 22 deletions and DiGeorge syndrome.[22] Specific genetic associations include: JAG1,[23] NKX25,[24] ZFPM2,[25] VEGF,[26] NOTCH1, TBX1, and FLT4.[27] Embryology studies show that it is a result of anterior malalignment of the aorticopulmonary septum, resulting in the clinical combination of a VSD, pulmonary stenosis, and an overriding aorta.[18] Right ventricular hypertrophy develops progressively from resistance to blood flow through the right ventricular outflow tract.

RISK FACTORS Risk factors include a mother who uses alcohol, has diabetes, is over the age of 40, or gets rubella during pregnancy.[5][10] It may also be associated with Down syndrome. Four malformations "Tetralogy" denotes four parts, here implying the syndrome's four anatomic defects.[2] This is not to be confused with the similarly named teratology, a field of medicine concerned with abnormal development and congenital malformations (including tetralogy of Fallot). Below are the four heart malformations that present together in tetralogy of Fallot:

Heart with tetralogy of fallot A: Pulmonary stenosis; B: Overriding aorta; C: Ventricular septal defect (VSD); D: Right ventricular hypertrophy

Ventricular Septal Defect The heart has an inner wall that separates the two chambers, called a septum. The septum stops mixing of the blood between the two sides. A ventricular septal defect is a hole in the septum that causes oxygen-rich blood (left ventricle) and the oxygen-poor blood (right ventricle) to mix. Pulmonary Stenosis This defect is the narrowing of the pulmonary valve, which flows oxygen poor blood into the pulmonary artery and from there the blood travels to the lungs to pick up oxygen. Pulmonary stenosis is when the pulmonary valve cannot open fully, making the heart work harder and results in a lack of blood reaching the lung. Right Ventricular Hypertrophy The muscle of the right ventricle is thicker due to the right side of the heart receiving excessive blood flow from the left side of the heart through the ventricular septal defect and working harder. Overriding Aorta In a normal heart, the aorta is attached to the left ventricle and allows oxygen-rich blood to flow throughout the body. In a tetralogy of Fallot heart, the aorta is located between both the left and the right ventricle. This causes oxygen-poor blood from the right ventricle to flow into the aorta instead of the pulmonary artery. If infants with tetralogy of Fallot are not treated, the symptoms usually become progressively more severe. Blood flow to the lungs may be further decreased and severe cyanosis may cause life-threatening complications. The exact cause of tetralogy of Fallot is not known.

Additional anomalies[edit] In addition, tetralogy of Fallot may present with other anatomical anomalies, including:[34][35]

1. 2. 3. 4. 5.

stenosis of the left pulmonary artery, in 40% a bicuspid pulmonary valve, in 60% right-sided aortic arch, in 25% coronary artery anomalies, in 10% a patent foramen ovale or atrial septal defect, in which case the syndrome is sometimes called a pentalogy of Fallot[36] 6. an atrioventricular septal defect 7. partially or totally anomalous pulmonary venous return Tetralogy of Fallot with pulmonary atresia (pseudotruncus arteriosus) is a severe variant[37] in which there is complete obstruction (atresia) of the right ventricular outflow tract, causing an absence of the pulmonary trunk during embryonic development.[38] In these individuals, blood shunts completely from the right ventricle to the left where it is pumped only through the aorta. The lungs are perfused via extensive collaterals from the systemic arteries, and sometimes also via the ductus arteriosus.

Pathophysiology The development of the human heart starts around the 20th day of gestation, with the fusion of the outer endocardial tubes into a single tubular structure, the cardiac tube. Subsequently, the cardiac tube folds and loops, with the development of an atrium that is cranial and dorsal, and a primitive ventricle is moving downward, ventrally and to the right. The right ventricle is the dominant chamber in the embryo and fetus, receiving 65% of the venous return, and is the main contributor to the lower part of the body, the placenta, and the lungs. The right ventricle can be described by three components: the inlet, which consists of the tricuspid valve chordae tendineae and papillary muscles; the trabeculated apical myocardium; and the infundibulum or conus. The exact embryologic process that contributes to the development of tetralogy of Fallot still is unknown, but an association that had been observed is an anterior and cephalad deviation of the infundibular septum that results in a misaligned ventricular septal defect, with an overriding aortic root causing a subsequent right ventricular outflow obstruction. The ventricular septal defects seen in patients with tetralogy of Fallot are usually perimembranous that can extend into the muscular septum. Different factors can contribute with the right ventricular outflow obstruction, including the pulmonary valve that is usually bicuspid and stenotic, the hypoplastic pulmonary valve annulus, the deviation of the infundibular septum that causes a subvalvular obstruction, and the hypertrophy of the muscular bands in this region. The degree of the overriding aorta usually varies and receives blood flow from both ventricles. The physiological process surrounding the hypercyanotic episodes or “Tet spells” in tetralogy of Fallot consist of either a decrease in systemic vascular resistance or an increase in pulmonary resistance contributing to a right-to-left shunt across the ventricular septal defect, causing marked desaturation DIAGNOSIS Congenital heart defects are now diagnosed with echocardiography, which is quick, involves no radiation, is very specific, and can be done prenatally.

Echocardiography establishes the presence of TOF by demonstrating a VSD, RVH, and aortic override. Many patients are diagnosed prenatally. Color Doppler (type of echocardiography) measures the degree of pulmonary stenosis. Additionally, close monitoring of the ductus arteriosus is done in the neonatal period to ensure that there is adequate blood flow through the pulmonary valve.[40] [41] In certain cases, coronary artery anatomy cannot be clearly viewed using echocardiogram. In this case, cardiac catheterization can be done.[42] Form a genetics perspective, it is important to screen for DiGeorge in all babies with TOF.[42] Before more sophisticated techniques became available, chest x-ray was the definitive method of diagnosis. The abnormal "coeur-en-sabot" (boot-like) appearance of a heart with tetralogy of Fallot is classically visible via chest x-ray, although most infants with tetralogy may not show this finding.[43] The boot like shape is due to the right ventricular hypertrophy present in TOF. Lung fields are often dark (absence of interstitial lung markings) due to decreased pulmonary blood flow.[41] Electrocardiography shows right ventricular hypertrophy (RVH), along with right axis deviation.[40] RVH is noted on EKG as tall R-waves in lead V1 and deep S-waves in lead V5-V6 The diagnosis of tetralogy of Fallot is confirmed by clinical evaluation and physical examination. A variety of specialized tests including electrocardiogram, echocardiogram, and cardiac catheterization may be performed to aid in diagnosis and therapy. When tetralogy of Fallot is present, x-ray studies usually reveal a normal-sized heart that is characteristically boot-shaped (coeur en sabot). Periodic measurements of systemic blood oxygen saturation and hemoglobin are also advisable. Infants with this disorder usually have a relatively loud murmur over the upper left breastbone. CLINICAL MANIFESTATIONS Signs & Symptoms The symptoms of tetralogy of Fallot vary widely from person to person. The severity of the symptoms, which may range from mild to severe, is related to the degree of blood flow obstruction from the right ventricle. Tetralogy of Fallot may be present at birth or emerge within the first year of life. The most common symptom of this disorder is abnormal bluish discoloration of the skin (cyanosis). This may occur while the child is at rest or crying. The mucous membranes of the lips and mouth, fingertips, and toenails may be particularly blue due to the lack of oxygen. Affected infants may have difficulty breathing (dyspnea); as a result, they tend to play for short periods and then rest. Other symptoms may include a heart murmur, easy fatigability, poor appetite, slow weight gain, heart murmurs, an abnormal increase in the numbers of red blood cells (polycythemia), fingers and toes with wide, enlarged tips and overhanging nails (clubbing), and/or delayed physical growth. Some infants with tetralogy of Fallot may experience episodes of severe cyanosis and breathing difficulty (paroxysmal hypercyanotic attack or “blue” or “tet” spells). During these episodes, the infant may become restless, extremely cyanotic while gasping for air and nonresponsive to

parent’s voices. In extreme situations, infants may pass out. A characteristic squatting position may be assumed to help assist breathing. Severe attacks may lead to the loss consciousness, and occasionally to convulsions or temporary paralysis on one side of the body (hemiparesis). These spells may last for a few minutes to a few hours and may be followed by periods of muscle weakness and a prolonged period of sleep.

Tetralogy of Fallot results in low oxygenation of blood. This is due to:[15]  

Mixing of oxygenated and deoxygenated blood in the left ventricle via the ventricular septal defect (VSD) Preferential flow of the mixed blood from both ventricles through the aorta because of the obstruction to flow through the pulmonary valve. This is known as a right-to-left shunt.

Infants with TOF -a cyanotic heart disease- have low blood oxygen saturation.[16] Blood oxygenation varies greatly from one patient to another depending on the severity of the anatomic defects.[9] Typical ranges vary from 60% to around 90%.[16] Depending on the degree of obstruction, symptoms vary from no cyanosis or mild cyanosis to profound cyanosis at birth.[9] If the baby is not cyanotic then it is sometimes referred to as a "pink tet".[17] Other symptoms include a heart murmur which may range from almost imperceptible to very loud, difficulty in feeding, failure to gain weight, retarded growth and physical development, labored breathing (dyspnea) on exertion, clubbing of the fingers and toes, and polycythemia.[2] The baby may turn blue with breast feeding or crying.[2] Tet spells Infants and children with unrepaired tetralogy of Fallot may develop "tet spells".[15] These are acute hypoxia spells, characterized by shortness of breath, cyanosis, agitation, and loss of consciousness.[18] This may be initiated by any event -such as anxiety, pain, dehydration, or fever-[19] leading to decreased oxygen saturation or that causes decreased systemic vascular resistance, which in turn leads to increased shunting through the ventricular septal defect.[15] Clinically, tet spells are characterized by a sudden, marked increase in cyanosis followed by syncope.[18] Older children will often squat instinctively during a tet spell.[15] This increases systemic vascular resistance and allows for a temporary reversal of the shunt. It increases pressure on the left side of the heart, decreasing the right to left shunt thus decreasing the amount of deoxygenated blood entering the systemic circulation

MANAGEMENT Standard Therapies Treatment The definitive treatment for tetralogy of Fallot is surgery (i.e., Blalock-Taussig shunting procedure, aortic/pulmonary shunt, intracardiac repair, balloon pulmonary valvuloplasty and/or

valve replacement). Surgical correction of this heart malformation is best accomplished during infancy. Selection of the exact surgical procedure is based on the severity of symptoms and extent of the malformation. The surgeon will widen the pulmonary valve and the passage from the right ventricle to the pulmonary artery is enlarged. A patch covers the hole in the septum to repair the ventricular septal defect. By resolving the VSD and the pulmonary valve problems, it fixes the other two defects. Temporary surgery may be recommended babies are too weak or small to have the full repair surgery; the full repair surgery will be performed when the baby is stronger. A tube or a “shunt” is placed between a large artery branching off the aorta and the pulmonary artery. It creates a pathway for blood to travel to the lungs to get oxygen. The tube is removed during the full repair surgery. When early repair is not possible, other surgical measures may be taken during infancy or early childhood. Prior to surgery, treatment to control symptoms (palliative) may include the maintenance of adequate fluid intake (hydration), monitoring of hemoglobin levels in the blood, and the avoidance of strenuous exercise. Heart medications (i.e., digitalis) may be prescribed to help control irregular heartbeats (arrhythmias), rapid heartbeats, and/or heart failure. Episodes of severe symptoms or “blue spells” (hypoxia) may require the administration of supplemental oxygen, morphine, and/or other drugs that improve oxygen concentration. The knee-chest position may also bring some symptomatic relief. Sodium bicarbonate may be administered to lower abnormally high levels of acid in the blood (acidosis). The drug propranolol may be given to help prevent future spells and to reduce their severity. Drugs that help to remove excess fluid from the body (diuretics), dietary salt restriction, and bed rest may be effective in treating congestive heart failure. Antibiotics may be prescribed to infants with tetralogy of Fallot to help prevent infections (prophylaxis) because children with this disorder are susceptible to bacterial infection of the heart (endocarditis). Respiratory infections must be treated vigorously and early. Children should be given antibiotics at times of predictable risk (e.g., tooth extractions and surgery). Other treatment is symptomatic and supportive. Although the risk for tetralogy of Fallot in the siblings of infants with this disorder is thought to be very low, genetic counseling may be of benefit for parents and other family members. MEDICL MANAGEMENT Tet spells Tet spells may be treated with beta-blockers such as propranolol, but acute episodes require rapid intervention with morphine or intranasal fentanyl[45] to reduce ventilatory drive, a vasopressor such as phenylephrine, or norepinephrine to increase systemic vascular resistance, and IV fluids for volume expansion.[46] Oxygen (100%) may be effective in treating spells because it is a potent pulmonary vasodilator and systemic vasoconstrictor. This allows more blood flow to the lungs by decreasing shunting

of deoxygenated blood from the right to left ventricle through the VSD. There are also simple procedures such as squatting and the knee chest position which increase systemic vascular resistance and decrease right-to-left shunting of deoxygenated blood into the systemic circulation.[46][47] If the spells are refractory to the above treatments, people are usually intubated and sedated. The treatment of last resort for tet spells is extracorporeal membrane oxygenation (ECMO) along with consideration of Blalock Taussig shunt (BT shunt).[46] SURGICAL MANAGEMENT Total surgical repair[edit] Total surgical repair of TOF is a curative surgery. Different techniques can be used in performing TOF repair. However, a transatrial, transpulmonary artery approach is used for most cases.[48] The repair consists of two main steps: closure of the VSD with a patch and reconstruction of the right ventricular outflow tract.[49] This open-heart surgery is designed to relieve the right ventricular outflow tract stenosis by careful resection of muscle and to repair the VSD.[50] Additional reparative or reconstructive surgery may be done on patients as required by their particular cardiac anatomy.[51][52] Timing of surgery in asymptomatic patients is usually between the ages of 2 months to one year.[53] However, in symptomatic patients showing worsening blood oxygen levels, severe tetspells (cyanotic spells), or dependence on prostaglandins from early neonatal period (to keep the ductus arteriosus open) need to be planned fairly urgently.[53] Potential surgical repair complications include residual ventricular septal defect, residual residual outflow tract obstruction, complete atrioventricular block, arrhythmias, aneurysm of right ventricular outflow patch, and pulmonary valve insufficiency.[54] Long term complications most commonly include pulmonary valve regurgitation, and arrhythmias.[55] Total repair of tetralogy of Fallot initially carried a high mortality risk, but this risk has gone down steadily over the years. Surgery is now often carried out in infants one year of age or younger with less than 5% perioperative mortality[56]. Post surgery, most patients enjoy an active life free of symptoms.[56] Currently, long term survival is close to 90%.[57] Today the adult TOF population continues to grow and is one of the most common congenital heart defect seen in adult outpatient clinics.[58] Palliative surgery[edit] Initially surgery involved forming a side to end anastomosis between the subclavian artery and the pulmonary artery -i.e a systemic to pulmonary arterial shunt.[49] This redirected a large portion of the partially oxygenated blood leaving the heart for the body into the lungs, increasing flow through the pulmonary circuit, and relieving symptoms. The first Blalock-Thomas-Taussig shunt surgery was performed on 15-month-old Eileen Saxon on November 29, 1944 with dramatic results.[59] The Potts shunt[60] and the Waterston-Cooley shunt[61][62] are other shunt procedures which were developed for the same purpose. These are no longer used. Currently, palliative surgery is not normally performed on infants with TOF except for extreme cases.[63] For example, in symptomatic infants, a two-stage repair (initial systemic to arterial

shunt placement followed by total surgical repair) may be done.[64] Potential complications include inadequate pulmonary blood flow, pulmonary artery distortion, inadequate growth of the pulmonary arteries, and acquired pulmonary atresia. NURSING MANAGEMENT Specific considerations and routine care  Preoperative considerations o Neonates with tetralogy of Fallot  Management based on the degree of outflow tract obstruction  Mild to moderate outflow tract obstruction 10 o Anticipate discharge until surgery scheduled between 4-6 months o Discharge teaching for parents/caregivers - specific information for hypercyanotic (“Tet”) spells

Complications Short Term Complications Common complications in the immediate postoperative period are residual ventricular septal defects, as well as persistence of right ventricular outflow obstruction. Arrhythmias can follow tetralogy repair, with risk of ventricular tachycardia, atrial fibrillation/flutter, and intra-atrial reentrant tachycardia. ECG will usually appear with a right bundle branch block or left bundle branch block pattern associated with wide complex tachycardia. Sudden cardiac death can present with post-repaired patients. Risk factors for tachyarrhythmias and sudden cardiac death include older age at repair, male gender, transient complete heart block beyond postoperative day three, and QRS duration greater than 180 miliseconds. Long-Term Complications Adult patients with congenital heart disease are increasing in an approximate estimate of 5% per year, surpassing the pediatric population. Longterm consequences seen with these patients include right ventricular volume overload from pulmonary insufficiency, right ventricular aneurysm from outflow patch or from ventriculotomy, distal pulmonary artery obstruction, ventricular hypertrophy, chamber enlargement, biventricular dysfunction, and aortic root dilation and insufficiency. The three leading causes of mortality in patients with repaired tetralogy of Fallot are arrhythmia, heart failure, and complications from reoperations. Risk of sudden death increases after 30 years of procedure to 6% to 9%; some of the factors associated with this risk are QRS duration greater than 180 miliseconds, older age at repair (greater than 3 years), significant pulmonary valve or tricuspid valve regurgitation, history of syncope, multifocal premature ventricular contractions, and ventricular tachycardia. The most common indication for reoperation is pulmonary insufficiency, and criteria for pulmonary valve replacement have been based on the severity measured by the regurgitant fraction on magnetic resonance or CT scan. Parameters seen with these studies are right and left ventricular end-systolic and end-diastolic volume indices, ejection fractions, and presence of aneurysm causing obstructive outflow. Patient can have exercise intolerance, signs and symptoms of heart failure, syncope, and sustained ventricular tachycardia. Pulmonary valve replacement also can be obtained by transcatheter pulmonary valve approach. Pregnancy Complications Women who had complete repair of tetralogy of Fallot have similar outcomes in comparison with the general obstetric population. Increased pregnancy complication are related to the level of pulmonary hypertension and the severity of the pulmonary regurgitation with right or left

ventricular dysfunction. Females with moderate right ventricle hypertension or those who have had a palliative shunt have an increased risk for fetal demise. Offspring of women with tetralogy carry a risk of congenital heart disease in 3% to 5% in comparison with 0.8% of the general population. If 22q11 deletion is present, the chance of transmitting the affected chromosome is 50%, with high risk of having an associated congenital heart defect. Prognosis[edit] Untreated, tetralogy of Fallot rapidly results in progressive right ventricular hypertrophy due to the increased resistance caused by narrowing of the pulmonary trunk.[33] This progresses to heart failure which begins in the right ventricle and often leads to left heart failure and dilated cardiomyopathy. Mortality rate depends on the severity of the tetralogy of Fallot. If left untreated, TOF carries a 35% mortality rate in the first year of life, and a 50% mortality rate in the first three years of life.[66] Patients with untreated TOF rarely progress to adulthood.[55] Patients who have undergone total surgical repair of tetralogy of Fallot have improved hemodynamics and often have good to excellent cardiac function after the operation with some to no exercise intolerance (New York Heart Association Class I-II).[67] Long-term outcome is usually excellent for most patients, however residual post surgical defects -such as pulmonary regurgitation, pulmonary artery stenosis, residual VSD, right ventricular dysfunction, right ventricular outflow tract obstruction, and sudden death- may affect life expectancy and increase the need for reoperation.[56] Within 30 years after correction, 50% of patients will require reoperation.[55] The most common cause of reoperation is a leaky pulmonary valve (pulmonary valve insufficiency).[55] This is usually corrected with a procedure called pulmonary valve replacement.

Summary Tetralogy of Fallot is the most common form of cyanotic congenital heart disease. Cyanosis is the abnormal bluish discoloration of the skin that occurs because of low levels of circulating oxygen in the blood. Tetralogy of Fallot consists of the combination of four different heart defects: a ventricular septal defect (VSD); obstructed outflow of blood from the right ventricle to the lungs (pulmonary stenosis); a displaced aorta, which causes blood to flow into the aorta from both the right and left ventricles (dextroposition or overriding aorta); and abnormal enlargement of the right ventricle (right ventricular hypertrophy). The severity of the symptoms is related to the degree of blood flow obstruction from the right ventricle.