From the Research
Patent foramen ovale (PFO) causes platypnea-orthodeoxia syndrome by allowing deoxygenated blood to shunt from the right atrium to the left atrium when a patient assumes an upright position, as demonstrated in a recent study published in 2022 1. This condition is characterized by breathlessness (platypnea) and decreased oxygen saturation (orthodeoxia) that worsens when sitting or standing and improves when lying down. In a normal heart, the foramen ovale closes after birth, but in approximately 25% of adults, it remains partially open as a PFO. The mechanism involves both an anatomical component (the PFO) and a functional component that redirects blood flow through the PFO when upright. This redirection occurs due to anatomical distortions that develop with age or disease, such as an elongated, tortuous aorta, right hemidiaphragm elevation, or pneumonectomy, which alter the relationship between the atrial septum and the inferior vena cava. These changes create preferential flow from the inferior vena cava directly toward the PFO when upright, increasing right-to-left shunting. Some key points to consider in the diagnosis and treatment of platypnea-orthodeoxia syndrome include:
- The importance of recognizing this rare syndrome in patients who present with unexplained hypoxia, as highlighted in a case report published in 2015 2
- The role of anatomical distortion of the atrial septum related to a dilated aortic root or shortening of the distance between the aortic root and posterior atrial wall, as discussed in a study published in 2022 3
- The challenges of percutaneous PFO closure in patients with platypnea-orthodeoxia syndrome, including high rates of acute residual shunt, as noted in a study published in 2013 4
- The effectiveness of PFO closure via transcatheter techniques in resolving symptoms in most patients, as demonstrated in a study published in 2022 1. Treatment typically involves PFO closure via transcatheter techniques, which resolves symptoms in most patients by eliminating the abnormal shunt pathway. For example, a study published in 2022 found that percutaneous PFO closure was a successful, durable, and safe method for patients presenting with platypnea-orthodeoxia syndrome, achieving major improvements in both gasometrical parameters and quality of life 1. Similarly, another study published in 2013 found that PFO closure improved arterial oxygen saturation and relieved symptoms in patients with platypnea-orthodeoxia syndrome 5. Overall, the evidence suggests that PFO closure is a effective treatment for platypnea-orthodeoxia syndrome, and that it should be considered in patients who present with this condition.