Associated conditions
Congenital heart defects are associated with an increased incidence of seven other specific medical conditions, together being called the VACTERL association:
V — Vertebral anomalies
A — Anal atresia
C — Cardiovascular anomalies
T  — Tracheoesophageal fistula
E — Esophageal atresia
R — Renal (Kidney) and/or radial anomalies
L — Limb defectsVentricular septal defect (VSD), atrial septal defects, and tetralogy of Fallot are the most common congenital heart defects seen in the VACTERL association. Less common defects in the association are truncus arteriosus and transposition of the great arteries. Causes
The cause of congenital heart disease may be genetic, environmental, or a combination of both. Genetic
Genetic mutations, often sporadic, represent the largest known cause of congenital heart defects. They are described in the table below. Molecular pathways
The genes regulating the complex developmental sequence have only been partly elucidated. Some genes are associated with specific defects. A number of genes have been associated with cardiac manifestations. Mutations of a heart muscle protein, α-myosin heavy chain (MYH6) are associated with atrial septal defects. Several proteins that interact with MYH6 are also associated with cardiac defects. The transcription factor GATA4 forms a complex with the TBX5 which interacts with MYH6. Another factor, the homeobox (developmental) gene, NKX2-5 also interacts with MYH6. Mutations of all these proteins are associated with both atrial and ventricular septal defects; In addition, NKX2-5 is associated with defects in the electrical conduction of the heart and TBX5 is related to the Holt–Oram syndrome which includes electrical conduction defects and abnormalities of the upper limb.
Hypoplasia of the heart is generally a cyanotic heart defect. Obstructive defects
Obstructive defects occur when heart valves, arteries, or veins are abnormally narrow or blocked. Common defects include pulmonic stenosis, aortic stenosis, and coarctation of the aorta, with other types such as bicuspid aortic valve stenosis and subaortic stenosis being comparatively rare. Any narrowing or blockage can cause heart enlargement or hypertension. Septal defects
The septum is a wall of tissue which separates the left heart from the right heart. Defects in the interatrial septum or the interventricular septum allow blood to flow from the left side of the heart to the right, reducing the hearts efficiency. Ventricular septal defects are collectively the most common type of CHD, although approximately 30% of adults have a type of atrial septal defect called probe patent foramen ovale. Cyanotic defects
Cyanotic heart defects are called such because they result in cyanosis, a bluish-grey discoloration of the skin due to a lack of oxygen in the body. Such defects include persistent truncus arteriosus, total anomalous pulmonary venous connection, tetralogy of Fallot, transposition of the great vessels, and tricuspid atresia.