CONGENITAL HEART DISEASE



Congenital heart disease refers to cardiac le­sions present at birth. Even though these abnor­malities exist before birth, they often become clin­ically evident at the time of delivery, when profound physiological changes occur in the cir­culatory system, or months or years after birth. Congenital heart disease (excluding bicuspid aor­tic valve) occurs in approximately 0.8 per cent of live births and results from both genetic and en­vironmental factors. Congenital heart disease may be familial in some instances, although a distinct pattern of inheritance is usually not recognized. It is more common in children of older mothers. Ventricular septal defect and patent ductus arter­iosus are relatively common in premature infants. Environmental factors such as teratogens and ma­ternal rubella are commonly recognized risk fac­tors.
Congenital cardiac defects that are compatible with the fetal circulation (see Chapter 1) may pro­duce symptoms once the child is born. The per­sistence of normal fetal structures in an infant, such as a patent ductus arteriosus allowing a left-to-right shunt, may be detrimental. However, an abnormal connection may be necessary for an in­fant to survive in the presence of another congenital anomaly, such as transposition of the great arteries, which must have a connection between the two circuits (e.g., atrial septal defect, patent ductus arteriosus) to allow oxygenation of sys­temic blood and survival for any period of time after birth. Those at risk for developing endocar­ditis (see Chapter 10) should receive prophylactic antibiotics at appropriate times.
Congenital defects can be classified generally into acyanotic and cyanotic groups. The acyanotic congenital defects are those either without a shunt or with left-to-right shunts. Cyanosis occurs in the presence of a right-to-left shunt. In addition, it is important to identify whether malformations arise in the left or the right heart, the site of shunts if present, the status of the pulmonary blood flow (increased, normal, or decreased), and the pres­ence of pulmonary hypertension (Tables 4-1, 4-2, and 4-3).





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