Your heart has a right side and a left side. Each side consists of an upper chamber called the atrium and a lower chamber known as the ventricle. Blood normally flows from an atrium to a ventricle and then out of the heart. When there are abnormal openings in the chamber walls that separate right from left, blood may flow from atrium to atrium or ventricle to ventricle. Most of those openings are present at birth and may cause symptoms early in life or after several years.
Small Atrial Holes
Small openings between the atria are fairly common. The normal fetus has a small opening between the atria to allow blood from the placenta to flow into the left heart and be distributed to the fetal organs. The opening usually closes after birth, but it remains open in about 25 percent of people. Most are never aware and suffer no ill effects, but the opening can permit clots from the legs or elsewhere in the body to cross to the left heart and cause a stroke.
Larger Openings Between the Atria
Approximately 1 in 1,000 people have larger openings between the atria, and these come to medical attention. Because pressure is higher in the left heart than the right, blood will be shunted from the left atrium, overloading the right heart. The result is right heart failure and abnormally high pressure in the blood vessels of the lung. Shortness of breath, swelling of the legs, abnormal heartbeats and other signs of heart failure may occur.
Openings Between the Ventricles
Among 1,000 babies, approximately 2 to 3 are born with openings between the ventricles. Many of these holes are small and close without treatment. Some are large enough to cause blood shunting and heart failure in infancy. Others increase in size with time and produce symptoms of right heart overload later in life.
Openings Between Both the Atria and the Ventricles
The walls separating the atria and the ventricles are incompletely formed in approximately 2 in every 10,000 babies. The mixing of right and left heart blood causes a blueness of the skin, lips and fingernail beds accompanied by heart murmurs and loud heartbeats. Until surgically corrected, combined defects like these progress to increasing heart failure and fluid overload in the lungs.