Atrial Septal Defect and Patent Foramen Ovale
There are two types of holes which can be present between the upper chambers of the heart: an Atrial septal defect (ASD) and a patent foramen ovale (PFO).
Atrial Septal Defects
Atrial septal defects are present at birth. Some may close on their own, but larger defects sometime do not close on their own, allowing blood to circulate between the upper chambers, which over time can cause damage to the heart.
When blood circulates between the upper chambers of the heart, the right chambers of the heart become enlarged and can grow weaker. In addition, blood pressure in the lungs can rise, a condition called pulmonary hypertension, because of atrial septal defects.
Sometimes atrial septal defects can be associated with other congenital heart diseases, but usually they occur alone, in the absence of any other disease.
Atrial septal defects are dangerous because blood clots formed in the leg could pass through the hole between the upper chambers of the heart and get pumped to the brain, causing a stroke.
Symptoms of Atrial Septal Defect
Usually, bad cases of atrial septal defects are detected in childhood and are repaired at that time. Sometimes, however, the atrial septal defects are not large enough to cause symptoms in childhood, and only become noticeable in adulthood. Typical symptoms of an atrial septal defect include the following:
- Shortness of breath with activity or at rest
- Heart rhythm difficulties, especially atrial fibrillation
- Swelling in the legs or belly
- Fatigue with activity, or declining stamina
- More rarely, ASDs cause paradoxical emboli-blood clots that form in the leg veins can travel through the ASD and get pumped to the brain (causing a stroke), a heart artery (causing a heart attack) or to the arms or legs.
Testing for Atrial Septal Defects
Several tests may be used to diagnose an atrial septal defect:
- Electrocardiogram (ECG) is an electrical tracing of the heart which may have a characteristic pattern in patients with atrial septal defects.
- Murmurs are often heard, due to increased blood flow through the lungs.
- Chest x-ray may show evidence of enlarged right heart chambers, or enlarged pulmonary arteries
- Echocardiography, or cardiac ultrasound, is the most common tool to diagnose atrial septal defect.
- Sometimes a bubble study is performed with echo, where IV fluid is agitated in a syringe to create microbubbles. The IV fluid is then injected into a vein, and the bubbles can be visualized in the right chambers of the heart. If bubbles cross into the left chambers of the heart, it is suggestive of an abnormal communication between the chambers of the heart.
- Transesophageal echocardiography is an ultrasound procedure done in the hospital. After receiving sedation to make them comfortable, patients swallow an ultrasound probe to allow close-up pictures to be taken of the heart, from the patient's esophagus. This is a similar procedure to endoscopy.
Treatments for Atrial Septal Defects
Therapy for atrial septal defects depends on the size and location of the hole(s). For the most common defects, closure devices can be implanted through a small incision in the groin with a high degree success and very low risk of complication.
For very large defects or defects that are more complicated anatomically, surgery can effectively be used to close them.
Patent Foramen Ovale (PFO)
A patent foramen ovale, or PFO, is a special type of hole between the upper chambers of the heart. While an Atrial Septal Defect is always considered a structural abnormality in the heart, everyone at birth has a PFO. In about 75% of patients, the PFO closes on its own after birth, but about a quarter of people may have persistent, although usually very small, amounts of blood which can go across this hole. PFOs are very common: in most patients they are not clinically significant, and do not require specific therapy. The one exception is that in rare cases, a PFO can be a risk factor for stroke.
There are many causes of strokes, such as high blood pressure, age, smoking, atrial fibrillation, and cholesterol deposits in the arteries. Most of the time, even in patients who have a PFO, the stroke is caused by some other mechanism.
Testing for Patent Foramen Ovale
A bubble study is performed with echo, where IV fluid is agitated in a syringe to create microbubbles. The IV fluid is then injected into a vein, and the bubbles can be visualized in the right chambers of the heart. It bubbles cross into the left chambers of the heart, it is suggestive of an abnormal communication between the chambers of the heart. This is particularly useful when diagnosing a PFO: these holes are small enough that they will not cause abnormal murmurs, ECGs, chest x-rays, or an obvious abnormality on echo.
Treatment for Patent Foramen Ovale
If a PFO does not cause symptoms, it does not require any therapy. Patients, especially younger patients under the age 60, who have suffered a stroke should be evaluated for a PFO; this is particularly true if they do not have another cause of, or risk factors for, stroke. If the PFO is felt to be a possible contributor to the stroke, patients may be treated with aspirin or blood thinners such as warfarin. Alternatively, some patients may be considered for a closure device — similar to an ASD closure device — which is inserted through a catheter in the groin.