Patent foramen ovale (PFO): The Daily PANCE Blueprint

The answer is C. 25%

A patent foramen ovale (PFO) is a persistent opening between the right and left atria, present in about 25% of adults, and is usually asymptomatic. PFO results from incomplete postnatal closure of the foramen ovale, a normal fetal structure that allows right-to-left shunting to bypass the lungs. Failure of fusion between the septum primum and septum secundum leads to this persistent interatrial communication. A PFO can lead to a stroke by enabling paradoxical embolism, where a venous thrombus bypasses the pulmonary circulation and enters the arterial system, potentially occluding cerebral arteries. Transthoracic echocardiography with agitated saline (“bubble study”) is initial, but less sensitive. Transesophageal echocardiography is the gold standard. Antiplatelet therapy (e.g., aspirin) is first-line for secondary stroke prevention in most cases. Percutaneous device closure is recommended for select patients <60 years with cryptogenic stroke and high-risk PFO features (large shunt, atrial septal aneurysm).