Abstract: AIM Applicating contrast transthoracic echocardiography(cTTE) joint Trans-esophageal Echocardiography (TEE), evaluating the clinical value of right to left shunt (RLS) in patent foramen ovale (PFO). METHODS 246 cases who are paradoxical embolism, and suspected PFO in clinical were examined by cTTE, We observe RLS at the resting state and after Valsalva action, and assess the degree of shunt; Patients with RLS were examined again for TEE, presence of PFO, measurement of PFO open diameter, observation of PFO morphology and other concomitant lesions, To made clear RLS of PFO eventually. Made between the line correlation analysis Between the size of PFO and the severity of RLS in the PFO-RLS group. RESULTS cTTE found 174 examples who with different degrees of RLS, 72 cases without RLS. The detection rate of RLS is significantly higher After Valsalva action than at the resting condition, the difference was statistically significant (P<0.01). 163 patients were found with PFO in 174 cases by TEE. Including 129 cases with color Doppler there is room left to right shunt, 34 cases with not obvious room level shunt. In 163 PFO- RLS cases, there is correlation between the diameter and the degree of RLS, but the correlation is low (P<0.05, CP=0.34). CONCLUSION cTTE can quickly find room level right-to-left shunt and semi-quantitative assess the extent of shunt, cTTE joint TEE can display the morphology and diameter of PFO clearly, and then confirmed PFO-RLS. PFO diameter is low associated with RLS severity.