The foramen ovale is a small hole located in the atrial septum of the heart that is used during fetal circulation to speed up the travel of blood through the heart. The atrial septum is a thin wall that separates the upper two chambers (atria) of the heart. When in the womb, a baby does not use its own lungs for oxygen-rich blood; it relies on the mother to provide oxygen-rich blood from the placenta through the umbilical cord to the fetus. Therefore, blood can travel from the veins to the right side of the baby's heart and cross to the left side of the heart through the foramen ovale and skip the trip to the baby's lungs.
Normally the foramen ovale closes at birth when increased blood pressure on the left side of the heart forces the opening to close. If the atrial septum does not close properly, it is called a patent foramen ovale (PFO). This type of defect generally works like a flap valve, only opening during certain conditions when there is more pressure inside the chest. This increased pressure occurs when people strain while having a bowel movement, cough, or sneeze.
If the pressure is great enough, blood may travel from the right atrium to the left atrium. If there is a clot or particles in the blood traveling in the right side of the heart, it can cross the PFO, enter the left atrium, and travel out of the heart and to the brain (causing a stroke or go into a coronary artery causing a heart attack).
The prevalence of PFO is about 25 percent in the general population. In patients who have stroke of unknown cause (cryptogenic stroke), the prevalence of PFO increases to about 40 percent. This is especially true in patients who have had a stroke at age less than 55 years. PFO can be associated with atrial septal aneurysm, which is characterized by excessive mobility of the atrial septum. Most patients do not have any symptoms with PFO.
About 40 percent of patients who have an ischemic stroke have no known cause (called cryptogenic stroke). PFO is present and associated with an increase in stroke in about 40 percent of cases. The most common symptoms of stroke are:
- weakness or numbness of the face, arm or leg on one side of the body
- loss of vision or dimming (like a curtain falling) in one or both eyes
- loss of speech, difficulty talking or understanding what others are saying
- sudden, severe headache with no known cause
- loss of balance, unstable walking, usually combined with another symptom
Recent studies have shown that migraine headaches are more common in patients with PFO. While it seems as though closure of PFO results in improvement of migraine symptoms, larger studies are needed to confirm this finding. We at our clinic are in the process of finalizing a research trial where patient of severe migraine headache who have PFO could be enrolled in the trial and have a mechanical non surgical closure of the defect.
Patent foramen ovale can be seen on echocardiogram. In some cases the patient is asked to cough or perform the Valsalva maneuver to increase pressure in the right atrium. This can increase the flow of blood from the right to left atrium. The trans-esophageal ultrasound can provide a closer and more detailed view of the PFO.
People with PFO do not need any treatment if there are no associated problems, such as a stroke. Patients who have had a stroke or transient ischemic attack (TIA) may be placed on some type of blood thinner medication, such as aspirin, Plavix (clopidogrel), or Coumadin (warfarin) to prevent recurrent stroke.
Implantation of device in the heart
In some cases a cardiologist and a neurologist may recommend closure of PFO. Most frequently, percutaneous rather than surgical closure is preferred. As part of the procedure, you will undergo a small puncture in your groin and the closure device can then be placed in the hole. During this test, catheters (hollow, flexible tube) will be inserted into the veins in your groins and advanced to your heart. A balloon may be placed across the opening to determine the size and location of the hole in your heart. Measurements are taken of the pressure inside your heart chambers. A tiny catheter with an echo transducer is placed in the heart and then the cardiologist will position the device to close the hole.
Currently there are no devices approved by the FDA specifically for PFO closure; until they are available we use devices for PFO closure that are designed and approved for closing other types of heart defects (such as atrial septal defect, which is in some ways similar to a PFO). The CardioSEAL® device is a small double umbrella arms attached to Dacron fabric. It is folded into a special catheter and inserted into a vein in the leg where it is advanced into the heart and through the hole. The device is slowly pushed out of the special catheter allowing each umbrella to open up and cover each side of the hole (like a sandwich) and close it. When the device is in proper position, it is released from the special catheter. Over time, heart tissue grows over the implant, becoming part of the heart.
The AMPLATZER ® ASD septal occluder device consists of two wire mesh discs filled with polyester fabric. It is also folded into a special catheter which is inserted into a vein in the leg and advanced into the heart and through the hole. When the device is in proper position, the device is slowly pushed out the catheter until the discs of the device sit on each side of the hole. Over time, heart tissue grows over and covers the implant.
We would be able to evaluate you in our office to determine if you are a candidate for a non-surgical PFO repair.
Living with PFO
Patients with a patent foramen ovale are not at an increased risk of endocarditis. Hence an antibiotic prophylaxis is not indicated. For those who have had their PFO closed with a transcatheter device, endocarditis prevention is recommended for at least 6 months following implantation of the device.