Pitfalls in Diagnosing PFO: Characteristics of False-Negative Contrast Injections during Transesophageal Echocardiography in Patients with Patent Foramen Ovales

The simultaneous presence of both leftward bulging of the interatrial septum and dense contrast filling of the region in the right atrium, adjacent to the interatrial septum, is a prerequisite for PFO detection, and if either characteristic is missing, the injection is inconclusive.