Which Technique Is Better for Detection of Right-to-Left Shunt in Patients with Patent Foramen Ovale: Comparing Contrast Transthoracic Echocardiography with Contrast Transesophageal Echocardiography

Background: At present there is no consensus on which technique is more suitable for the detection of right-to-left shunt (RLS) in patients with patent foramen ovale (PFO). The aim of study was to compare the efficacy of contrast transthoracic echocardiography (cTTE) and contrast transesophageal echocardiography (cTEE) in the detection of RLS. Methods: A prospective study was undertaken in 29 patients with PFO. Both cTTE with harmonic imaging modality and cTEE with fundamental imaging modality were performed for all the patients. The severity of RLS were semiquantitatively assessed with a four-level grade system by scaling the numbers of microbubbles (MBs) in the left atrium after complete opacification of the right atrium within the first 3 cardiac cycles. Level 1 represents no MBs, indicating no RLS. Level 2, <= 10 MBs, indicating mild RLS. Level 3, 11-30 MBs, indicating moderate RLS and Level 4, >30 MBs, indicating severe RLS. Results: Contrast TTE demonstrated significantly higher sensitivity for detection of RLS than cTEE (86% vs. 56%, P < 0.05). For cTTE, there were 4, 1, 5, and 19 cases determined at levels 1, 2, 3, and 4, respectively, whereas for the same group of patients 13, 2, 6, and 7 cases were identified by cTEE at levels 1, 2, 3, and 4, respectively. The severity of RLS detected by cTTE was significantly greater than that by cTEE (P < 0.01). Conclusions: Contrast TTE is more efficacious in the detection of RLS than cTEE. The former can be used as an alternative to the latter in clinical practice.