Patent foramen ovale echocardiography


 * Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [mailto:kfeeney@perfuse.org]

Overview
Transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), and transcranial Doppler (TCD) are the commonly used diagnostic tools for patent foramen ovale. Each method has its own advantage and disadvantages in diagnosing patent foramen ovale. Transesophageal echocardiography is more sensitive in visualizing the interatrial septum, than transthoracic echocardiography and is the imaging modality of choice. Patients with clinical suspicion of patent foramen ovale and negative results with transthoracic echocardiography should be referred for a transesophageal echocardiography,. Transthoracic echocardiography (TTE) with contrast at rest, with cough, and after valsalva maneuver is generally considered the most definitive diagnostic test for patent foramen ovale. The performance of a bubble study on echocardiography is especially useful with small patent foramen ovale.

Transesophageal echocardiography
Advantage:
 * Gold standard in diagnosing patent foramen ovale.
 * It detects other associated lesions like aortic atheroma, left atrial appendage thrombus and spontaneous left atrial contrast. Thus, helps in finding other occult causes for stroke.

Disadvantage:
 * The patent foramen ovale patients who have failed to be diagnosed with a doppler or a two-dimensional echocardiography are sent for a bubble test. In transesophageal echocardiography the bubble test might not show a shunt because of the following: requirement for patient sedation, positioning in the left decubitus position and the inability to perform a complete valsalva maneuver.

Transthoracic echocardiography
Advantage
 * Bubble test gives better results with transthoracic echocardiography as the patient is in semi-upright position and is able to perform the valsalva maneuver.

Disadvantage
 * Poor image quality can lead to missing some of the patent foramen ovale

Contrast echocardiography

 * For small patent foramen ovale a contrast echocardiography is preferred. In contrast echocardiography or bubble test, after visualizing the atrial septum with either transthoracic echocardiography or transesophageal echocardiography sonicated microbubbles are injected is either pushed through antecubital vein or femoral vein. These bubbles first appear in the right atrium. If bubbles appear in the left atrium within three heart beats, then the study is considered diagnostic of a patent foramen ovale. On echocardiography, there may not be any shunting of blood (i.e. bubbles may not appear in the left atrium and ventricle) except when the patient coughs or performs the valsalva maneuver.  Release of valsalva maneuver increases flow to the right atrium, and increases the transit of bubbles across the patent foramen ovale.

Transcranial doppler
Advantage
 * Patient is able to perform valsalva maneuver
 * Good image quality

Disadvantage
 * Cannot differentiate between different inter-atrial defects like patent foramen ovale (PFO), atrial septal defect (ASD). If transcranial doppler detects a inter-atrial defect then the other details about the site of the shunt, and the presence of associated features such as atrial septal aneurysm etc has to be done by a follow-up transesophageal echocardiography

Patent Foramen Ovale on Echocardiographic Bubble Study
