Detection of right-to-left atrial communication using agitated saline contrast imaging: experience with 1162 patients and recommendations for echocardiography.

BACKGROUND: Right-to-left shunting via a patent foramen ovale (PFO) has a recognized association with embolic events in younger patients. The use of agitated saline contrast injection (ASCi) for detecting atrial shunting is well documented, but the optimal technique is not well described. The purpose of this study was to assess the efficacy and safety of transthoracic echocardiographic (TTE) ASCi for the assessment of right-to-left atrial communication in a large cohort of patients.
METHODS: A retrospective review was undertaken of 1,162 consecutive patients who underwent TTE ASCi, of whom 195 had also undergone clinically indicated transesophageal echocardiography. ASCi shunt results were compared with color flow imaging, and the role of provocative maneuvers (PM) was assessed.
RESULTS: Four hundred three TTE studies (35%) had paradoxical shunting seen during ASCi. Of these, 48% were positive with PM only. There was strong agreement between TTE ASCi and reported transesophageal echocardiographic findings (99% sensitivity, 85% specificity), with six false-positive and two false-negative results. In hindsight, the latter were likely due to suboptimal right atrial opacification and the former to transpulmonary shunting. TTE color flow imaging was found to be insensitive (22%) for the detection of a PFO compared with TTE ASCi.
CONCLUSIONS: TTE color flow imaging is too insensitive for PFO screening. TTE ASCi, however, is simple and highly accurate for the detection of right-to-left atrial communication, on the proviso that a dedicated protocol, including correctly implemented PM, is followed. It is recommended that TTE ASCi with PM be considered the primary diagnostic tool for the detection of PFO in clinical practice.