A comparison of methods to detect and quantitate PFO: TCD, TTE, ICE and TEE

Abstract

At the present time, the diagnosis of a patent foramen ovale (PFO) is based on either imaging of the interatrial septal anatomy that allows direct visualization of the septal defect transesophageal echo [TEE], transthoracic echo [TTE], intracardiac echo [ICE], or by physiologic quantification of the right-to-left shunt (RLS) through the PFO using transcranial Doppler [TCD]. Contrast TEE is currently the standard technique for identifying a PFO and visualization of the atrial septal anatomy. TEE permits an assessment of PFO size, RLS severity and differentiation between an intracardiac and intrapulmonary RLS. A TTE bubble study is the most commonly used imaging modality for the detection of PFO. Though cost-effective and readily available, TTE has a low sensitivity with poor differentiating ability between cardiac and pulmonary RLS. ICE allows detailed visualization of the inter-atrial septum at a resolution comparable to that of TEE. TCD is a highly sensitive test for indirectly assessing the presence of a RLS; some studies report a sensitivity higher than that of TEE but a lower specificity due to TCDs inability to differentiate between cardiac and pulmonary shunts. This chapter will compare the different techniques and describe the benefits and drawbacks of the various imaging options.