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Atrial septal defect (ASD) is a congenital heart defect in which blood flows between the atria (upper chambers) of the heart.Some flow is a normal condition both pre-birth and immediately post-birth via the foramen ovale; however, when this does not naturally close after birth it is referred to as a patent (open) foramen ovale (PFO).
The foramen ovale (from Latin 'oval hole') forms in the late fourth week of gestation, as a small passageway between the septum secundum and the ostium secundum. Initially the atria are separated from one another by the septum primum except for a small opening below the septum, the ostium primum .
As a result, pressure in the left atrium is higher than that of the right, and the increased pressure holds the interatrial flap (which covers the foramen ovale) shut, therefore closing the foramen ovale as well. [2] In normal development, the closed foramen ovale fuses with the interatrial wall.
But for about 25% of people, the opening doesn't close, the American Heart Association estimates. Often people remain unaware they have one unless they experience a heart attack or stroke.
Some of the blood entering the right atrium does not pass directly to the left atrium through the foramen ovale, but enters the right ventricle. This blood consists of oxygenated placental blood and deoxygenated blood returning from the fetal circulation. [2] This blood is pumped into the pulmonary artery. At the pulmonary artery, it is met ...
[2] [3] Although there are many routes an embolism may take to enter the arterial circulation, the term paradoxical embolism most commonly refers to a clot passing through a patent foramen ovale. The formen ovale is open during development of the heart in a developing fetus, and normally closes soon after birth - studies have found that patent ...
The foramen ovale is no longer needed and it closes to leave a depression (the fossa ovalis) in the atrial wall. In some cases, the foramen ovale fails to close. This abnormality is present in approximately 25% of the general population. [20] This is known as a patent foramen ovale, an atrial septal defect.
Foramen ovale (heart), in the fetal heart, a shunt from the right atrium to left atrium; Foramen ovale (skull), at the base of the skull, one of the holes that transmit nerves through the skull; Patent foramen ovale, a small channel in the heart, a remnant of the fetal foramen ovale