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Congenital Heart Defects

Congenital heart disease (CHD) is the term used to describe heart and great vessel defects. Most of these originate during embryogenesis, when the major cardiovascular structures are formed. The most serious alterations may be incompatible with life after birth, but many are only noticeable post-partum.

Statistics indicate that CHDs occur between 8-10 cases per 1000 newborns in the world. Current diagnostics can detect most of these birth defects before birth, though still with certain limitations.

Distribution of Heart Defects:

  • Ventricular Septal Defect (VSD) 18-20% of the total CHDs.

  • Atrial Septal Defect (ASD) 5-8% of the total CHDs.

  • Patent Ductus Arteriosus (PDA) 5-10%

  • Tetralogy of Fallot ( TOF) 5 -10%

The first three are called acyanotic heart disease because they do not produce cyanosis, or bluish-colored skin and are associated with heart failure, malnutrition and recurrent respiratory infections, and increased pulmonary flow.

In contrast, Tetralogy of Fallot (TOF) is a cyanotic heart disease responsible for approximately 5 - 10% of all heart defects.

Tetralogy of Fallot - is a complex condition consisting of four ("tetra") different birth defects. One is an obstruction of the pulmonary valve, which increases the pressure in the right ventricle. Another element of this medical condition is called ventricular septal defect (VSD), a hole in the muscle wall that separates the right ventricle from the left. Increased pressure in the right ventricle pushes blood without oxygen into the left ventricle through the VSD, from where it will flow through the rest of the body. The amount of blood flowing through the VSD depends on the extent of blockage of the pulmonary valve.

Other Cyanotic Heart Defects:

  • Pulmonary Atresia – The pulmonary valve has three leaflets that open so that blood can flow through the pulmonary arteries and close later to prevent it from returning to the heart. In pulmonary atresia, these three leaflets do not open or do not exist, so there is no connection between the right ventricle and the pulmonary arteries, and blood cannot be pumped to the lungs to be oxygenated. Instead, non-oxygenated blood can go directly from the right atrium to the left atrium through a hole in the wall (the atrial septum) that separates these two cavities. This hole, called Atrial Septal Defect (ASD), normally closes at birth, but can remain open in this situation. Once in the left atrium, the unoxygenated blood passes into the left ventricle and is pumped to the rest of the body.

  • Pulmonary stenosis -Stenosis is defined as the narrowing of a blood vessel or other anatomical conduit. This anomaly causes insufficient blood flow to the lungs, hence, poor blood oxygenation occurs.

  • Transposition of the Great Arteries - In this defect, which accounts for less than 5% of the CHDs, the connection of the main arteries (aorta and pulmonary artery) is transposed. This condition leaves oxygen-poor blood flowing from the heart to the rest of the body.