Congenital heart disease: Pathology, natural history, and interventions

Congenital heart disease (CHD) consists of a wide variety of anomalies and malformations involving the heart and great vessels that develop in utero, are present at birth, and come to clinical attention in infancy, adolescence, or adulthood. The cardiovascular anomalies generally result from defective morphogenesis during embryological development. The malformations may be limited to the cardiovascular system (nonsyndromic) or occur in association with anomalies of other systems as part of defined syndromes (syndromic). A definitive cause of CHD is determined in only about 10% of cases. Nevertheless, multifactorial genetic and environmental etiologic factors have been implicated including chromosomal defects, gene mutations, single nucleotide polymorphisms, and exposures to viruses, chemicals and radiation. Although isolated, sporadic cases of CHD frequently occur, most cases of CHD have a familial history. Evidence for genetic influences is manifest by the 2- to 10-fold increase in the occurrence of CHD in siblings of an affected child or children of an affected parent. In this chapter, the molecular biology of normal and abnormal development of the cardiovascular system is reviewed and linked to normal and abnormal morphogenesis of the heart and blood vessels. Pathological features and clinical correlates of specific forms of CHD are presented based on a classification into three major categories: right-to-left shunts/cyanotic CHDs, left-to-right shunts/acyanotic CHDs, and obstructions. The right-to-left shunts include tetralogy of Fallot, transposition of great arteries, tricuspid atresia, truncus arteriosus, total anomalous pulmonary venous connection, and hypoplastic left heart syndrome; they are often diagnosed prenatally or soon after birth, requiring urgent care and surgical correction to maintain communication between the right and left components of the circulation. The left-to-right shunts include the atrial and ventricular septal defects atrioventricular defects and patent ductus arteriosus. The obstructions include anomalies with defective routing of the great vessels from the ventricles that produce clinical significance only after birth. The catheter-based and surgical approaches to treatment of CHD are discussed with a focus on areas of success and complications. Finally, CHD in adults, now seen with increasing frequency due to treated and untreated anomalies, is discussed.