PFO closure in a patient with hypoxia due to tricuspid valve regurgitation and flow-driven shunt.

A female patient in mid-60s presented with progressive dyspnoea over several months and persistent hypoxia, requiring high-flow supplemental oxygen due to type 1 respiratory failure. Imaging investigations revealed metastatic carcinoid syndrome affecting the tricuspid valve, which led to severe tricuspid regurgitation (TR) directed towards a patent foramen ovale (PFO). A bubble study demonstrated a significant spontaneous right-to-left shunt through the PFO. Right heart catheterisation ruled out significant elevation of right-sided cardiac pressures as a cause of the right-to-left shunt. Thus, the patient's hypoxia was attributed to the severe TR, with the regurgitant jet directed towards the PFO, resulting in a shunt despite normal right-sided cardiac pressures. The patient underwent successful closure of the PFO, leading to an immediate improvement in oxygen saturation and facilitating the weaning of supplemental oxygen.