The Foramen Ovale: A Temporary Opening in the Heart
The foramen ovale is a small, flap-like opening located in the wall between the two upper chambers of the heart, known as the atria. This temporary passage plays a specific role during development. Normally, it closes shortly after birth, becoming a subtle indentation in the heart structure.
The Foramen Ovale’s Role in Fetal Life
Before birth, a developing fetus receives oxygen and nutrients through the placenta, not its own lungs. The foramen ovale serves as a natural bypass, allowing blood to circumvent the non-functional fetal lungs. Oxygenated, nutrient-rich blood from the placenta travels to the right atrium of the fetal heart.
From the right atrium, a portion of this blood flows directly through the foramen ovale into the left atrium. This direct route ensures that oxygen-rich blood is delivered to the left side of the heart, which then pumps it to the brain and other developing organs.
Changes After Birth
At birth, significant changes occur in a newborn’s circulatory system. As the baby takes its first breaths, the lungs inflate and begin to function, leading to a decrease in the resistance within the pulmonary blood vessels. This change allows blood to flow freely into the lungs for oxygenation.
Simultaneously, the pressure in the left atrium of the heart increases, while the pressure in the right atrium decreases. This pressure shift pushes the flap of the foramen ovale against the atrial septum, closing the opening. Functional closure happens within minutes or hours of birth, though anatomical closure, where the flap fuses, can take weeks, months, or even up to a year.
When the Foramen Ovale Remains Open
In some individuals, the foramen ovale does not fully close after birth, a condition known as a Patent Foramen Ovale (PFO). This occurs in approximately 15% to 35% of the adult population. Most people with a PFO are unaware of its presence because it causes no symptoms.
While often harmless, a PFO is sometimes investigated in relation to certain medical conditions. It has been linked to cryptogenic stroke, which is a stroke of unknown cause, particularly in younger individuals. PFOs have also been associated with migraines with aura and, in divers, with decompression sickness, due to the potential for small air or blood clots to pass from the right to the left side of the heart.
Managing an Open Foramen Ovale
A PFO is often discovered incidentally when diagnostic tests are performed for other health concerns. The primary method for diagnosing a PFO is an echocardiogram, an ultrasound of the heart. A specialized technique called a “bubble study” or saline contrast echocardiogram is frequently used, where a saline solution containing tiny bubbles is injected into a vein. If a PFO is present, these bubbles can be observed crossing from the right to the left side of the heart.
For most individuals with an asymptomatic PFO, no specific treatment is necessary, and observation is the usual approach. When a PFO is suspected to be the cause of a medical event like a stroke, management may involve medications such as blood thinners to prevent clot formation. In certain cases, particularly after a cryptogenic stroke, a catheter-based procedure may be considered to close the PFO.