CARDIAC EMERGENCIES
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Cyanotic heart disease There are five well-known cyanotic congenital heart lesionsdalso known as the ‘‘Terrible Ts.’’ They are Tetralogy of Fallot (TOF), Transposition of the Great Arteries (TGA), Tricuspid Atresia (TA), Total Anomalous Venous Return (TAPVR), and Truncus Arteriosus. Tetralogy of Fallot Tetralogy of Fallot is the most common form of cyanotic congenital heart disease in the post infancy period and represents up to 10% of all congenital heart disease [12,13]. Tetralogy of Fallot consists of four basic lesions. The lesions are a large ventricular septal defect (VSD), right ventricular outflow obstruction (from pulmonic stenosis), an overriding aorta, and right ventricular hypertrophy. Two of the lesions will determine the extent of the disease pathophysiology. There must be right ventricular outflow obstruction and the VSD must be large enough to equalize pressures in both of the ventricles. The extent of obstruction of the right ventricular outflow track will determine the amount of cyanosis present in the patient. Systolic pressures are equally balanced in the right and left ventricle because of the nonrestrictive VSD. There will be a left-to-right shunt, a bidirectional shunt, or a rightto-left shunt depending on the extent of the right ventricular outflow tract obstruction. If the pulmonic stenosis is severe, there will be a right-to-left shunt with subsequent cyanosis and decreased pulmonary blood flow. If there is mild pulmonic stenosis, a left-to-right shunt will occur resulting in an acyanotic Tetralogy of Fallot. In addition to cyanosis, the physical exam may show a systolic thrill at the lower and middle left sternal border. A loud and single S2, an aortic ejection click, and a loud grade 3 to 5/6 systolic ejection murmur in the middle to lower left sternal border will also be found. A continuous patent ductus arteriosus (PDA) murmur may also be present. The ECG will show right axis deviation (RAD) and right ventricular hypertrophy (RVH). A boot-shaped heart with a main pulmonary artery segment is characteristic of the cyanotic Tetralogy of Fallot. The heart size is normal with decreased pulmonary vascular markings. Acyanotic Tetralogy of Fallot will have chest x-rays similar to that of moderate VSDs. Transposition of the great arteries Transposition of the great arteries represents around 5% to 8% of congenital heart disease and is the most common cyanotic heart lesion in the newborn period [14]. There are many variations of the disease, with the underlying factor being that the aorta originates from the right ventricle and that the main pulmonary artery has origins in the left ventricle. Within these