Tetralogy of Fallot
Tetralogy of Fallot is an uncommon, intricate heart defect that affects five out of 10, 000 infants (Anonymous, 2004). It is a hitch of the structure of the heart, and it presents itself at birth. Tetralogy of Fallot is a blend of four cardiac defects, which alters the normal blood flow in the heart. The cardiac defects include:
- Ventricular septal defect (VSD)
- Right ventricular hypertrophy (RVH)
- Right ventricular outflow tract obstruction (RVOTO)
- Dextroposition of the aorta
Blood shunts from the right to left via the VSD permitting unoxygenated blood to blend with oxygenated blood. The combination of unoxygenated blood and oxygenated blood results in cyanosis. The cyanotic heart defect coexists with other congenital acyanotic heart defects such as atrial septal defect and patent ductus arteriosus. Tetralogy of Fallot is the most common type of cynanotic congential heart disease. The estimates of FOT differ significantly but seem to be about 3 percent to 9 percent of all infants born with cardiac defects (Anonymous, 2004). According to Anonymous (2004), tetralogy of Fallot accounts for almost 10% of all congenital defers. It occurs in both boys and girls where one-third of affected children die in infancy before surgical advances (Anonymous, 2004).
The basic tetralogy of Fallot pathology is due to underdeveloped right ventricular infundibulum. This leads to anterior-leftward infundibular septum malalignment, which determines the extent of RVOTO (Right ventricular outflow tract obstruction).
Causes
The etiology of the defect remains unknown and similar to other congenital cardiac defects; TOF happens sporadically (Motta & Wanda, 2012). While the primary causes of Tetralogy of Fallot remain unknown, it takes place after embryonic hypoplasia of the right ventricle outflow tract. The risk factors include fetal alcohol syndrome and the use of thalidomide during pregnancy (Anonymous, 2004). Approximately two-third of TOF patients experience isolated congenital heart disease in the absence of proof genetic syndrome and chromosomal anomaly. However, 30 percent of children affected with TOF have genetic syndromes and extracardic malformations. The chromosomal aberrations linked with TOF include trisomy, 21, 13, 18, and 22q11 microdeletion (Anonymous, 2004).
Signs and symptoms
Syanosis caused by the right-to-left shunt is the major sign of TOF. Other signs include Tet spells (blue spells) characterized by dyspnea fainting, deep, sighing respirations, unconsciousness, bradycardia, seizures, fever, crying, and straining. Due to poor oxygenation, reduced tolerance during exercise, clubbing, growth retardation, augmented dyspnea on exertion and difficulties in eating occur (Anonymous, 2004). Children with TOF experiences a loud systolic murmur heard along the left sterna border which obscure the pulmonic element of S2. In this view, the major signs of TOF include clubbing, cyanosis, loud systolic murmur, apparent right ventricular impulse and prominent inferior sternum linked to right ventricular hypertrophy.
Figure 1: A shows a normal heart while B illustrates a heart with TOF
Note: From http://www.nhlbi.nih.gov/health/health-topics/topics/tof/
Diagnosis
There are certain tests that assist in diagnosing TOF. They include Chest X-rays, which may illustrate decreased pulmonary vascular marking, a boot-shaped cardiac silhouette, and an enlarged right ventricle (Chessa & Giamberti, 2012). An electrocardiography demonstrates right ventricular hypertrophy, right atrial hypertrophy and right axis deviation (See Image 2). Echocardiography identifies septal overriding of the aorta, the VSD, pulmonic stenosis and the hypertrophied right ventricle walls. Laboratory testing also reveals reduced oxygen saturation and polycythemia when the cyanosis is longstanding and critical (Chessa & Giamberti, 2012). In addition, cardiac catheterization identifies the diagnosis through offering pulmonic stenosis, the overriding aorta and the VSD through visualization. Cardiac catheterization also weighs the extent of oxygen saturation in aortic blood.
Figure 2: Showing Critical Right Ventricular Hypertrophy (RVH)
Note: From Motta, P., & Wanda, C. (2012). Transesophageal Echocardiography in Tetralogy of Fallot. Seminars in Cardiothoracic and Vascular Anesthesia, 16(2), p.80
Treatment
In case of TOF, effective management requires steps to prevent and treat complications. This entails measures to alleviate cyanosis and corrective or palliative surgery (Motta & Wanda, 2012). The affected child should assume a knee-chest position and receive oxygen and morphine to enhance oxygenation during cyanotic spells. Palliative surgey with a Blalock-Taussig process that supports flow of blood to the lungs put to remission hypoxia (Motta & Wanda, 2012) (See Image 3). Children with critical hypoxic spells must undergo palliative surgery. The palliative surgery joins the pulmonary artery and the subclavian artery. Administration of Prophylactic antibiotics prevents cerebral abscesses or infective endocarditis.
Figure 3: Image Demonstrating Completed Blocking using Taussig Shunt
From http://emedicine.medscape.com/article/2035949-overview
Complications
Tetralogy of Fallot complications include; pulmonary thrombosis, cerebral embolism, dangers of spontaneous abortion, low birth weight, venous thrombosis and infective endocarditis (Anonymous, 2004)
Outlook
With TOF, insufficient blood gets to the lungs for oxygenation. As a result, unoxygenated blood flows in the body. Children with tetralogy of Fallot experiences cyanosis episodes. Cyanosis refers to a bluish tint in a patient’s skin, fingernails and lips (Motta & Wanda, 2012). This takes place because the level of oxygen is below the required level. TOF is treated through open-heart surgey soon after a child’s birth or before a child reaches the school going age. The surgey timing depends on the size of the pulmonary artery (Motta & Wanda, 2012). The treatment and diagnosis of TOF has significantly improved with most children with TOF surviving through adulthood. However, TOF patients require long-lasting medical care and attention from specialists to assist them stay healthy (Chessa & Giamberti, 2012).
Incidence and Mortality Rate in the United States
The incidence of congenital heart disease detectable through normal clinical examinations is 7.5 in every 1, 000 births. Congenital heart anomalies in neonates seen with detailed echocardiographic examination are 4 to 10 fold higher. The major disparity is clinically insignificant ventricular septal defects and nonstenotic bicommisural aortic valves. Critical types of cardiac anomalies that need surgery or cardiac catheterization or that results in death happen in 2.5 to 3 infants for every 1, 000 births.
Before insistent intervention, 2.3 of 1,000 live births die of cardiac problem during infancy (MacDonald & Seshia, 2005). However, in the United States and other developed countries, infant cardiac mortality has significantly reduced over the last decades because of better postnatal and prenatal recognition. Refinement and development of definitive interventions as well as per-procedural management reduces the mortality late. The fatality rate of infants in the United States by 2000 was 0-15 per 1,000 births (MacDonald & Seshia, 2005). In high volume surgical centers, the commonly occurring cyanotic cardiac anomalies such as tetralogy of Fallot hold surgical mortality rates of 1 percent to 5 percent or less (MacDonald & Seshia, 2005).
References
Anonymous. (2004). Pathophysiology: A 2-in-1 reference for nurses. New York: Lippincott Williams & Wilkins.
Chessa, M., & Giamberti, A.(2012). The right ventricle in adults with tetralogy of Fallot. Texas: Springer,
MacDonald, M., & Seshia, M.(2005). Avery’s neonatology: Pathophysiology and management of the newborn. New York: Lippincott Williams & Wilkins.
Motta, P., & Wanda, C. (2012). Transesophageal Echocardiography in Tetralogy of Fallot. Seminars in Cardiothoracic and Vascular Anesthesia, 16(2), 70-87.
