Patent foramen ovale
Background
Patent foramen ovale (PFO) is a flap-like opening between the atrial septa primum and secundum at the location of the fossa ovalis that persists after 1 year of age. This inter-atrial communication gives potential for right-to-left shunting in the cardiovascular system. Although most patients with an isolated PFO are asymptomatic, there is increasing evidence being found that PFO is the culprit in paradoxical embolic events and therefore, the relative importance of the anomaly is being re-evaluated.
Clinical Features
- History of stroke or TIA of undefined etiology
- Migraine or migraine-like symptoms
- Neurologic decompression sickness (seen in scuba divers)
- Acute myocardial infarction
- Systemic embolism, such as renal infarction
- Fat embolism
- Paradoxical embolism caused by right atrial tumors that increase right atrial pressure
- Left-sided valve disease in carcinoid syndrome
Diagnosis
- Color flow Doppler imaging: small "flame" of color signal may be seen in middle region of atrial septum
- Contrast echocardiography (Bubble Study): After obtaining optimal visualization of atrial septum on TTE or TEE, a bolus of agitated saline is injected to an antecubital vein. Subsequently, microbubbles appear in the right atrium. The study is positive for PFO if microbubbles appear in left atrium within 3 cardiac cycles of their appearance in the right atrium. Valsalva increases right atrial pressure and facilitates right-to-left shunting if present.
- 2D TEE with contrast provides superior visualization and is therefore preferred for detecting PFO. When clinically indicated, 2D TEE with contrast is strongly recommended if transthoracic echo is negative.