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Figure 1. Atrial Septal Defect with Resultant Left-to-Right Shunting.
Blood from the pulmonary veins enters the left atrium, after which some of it crosses the atrial septal defect into the right atrium and ventricle (longer arrow).
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Figure 2. Ventricular Septal Defect with Resultant Left-to-Right Shunting.
When the left ventricle contracts, it ejects some blood into the aorta and some across the ventricular septal defect into the right ventricle and pulmonary artery (arrow).
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Figure 3. Patent Ductus Arteriosus with Resultant Left-to-Right Shunting.
Some of the blood from the aorta crosses the ductus arteriosus and flows into the pulmonary artery (arrows).
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Figure 4. Coarctation of the Aorta.
Coarctation causes severe obstruction of blood flow in the descending thoracic aorta. The descending aorta and its branches are perfused by collateral channels from the axillary and internal thoracic arteries through the intercostal arteries (arrows).
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Source: The New England Journal of Medicine Volume 342:256-263, January 27, 2000
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