Central Retinal Artery Occlusion Secondary to Paradoxical Embolism Across a Patent Foramen Ovale

Dear Editor,

A 21-year-old male was referred to our hospital for the closure of the patent foramen ovale (PFO). The patient had a history of sudden painless loss of vision in the right eye two months back. The ocular examination was suggestive of central retinal artery occlusion (CRAO). Electrocardiogram, computed tomography (CT) scan of the head and neck, magnetic resonance imaging brain, and Holter monitoring were unremarkable. Venous Doppler of the lower limb showed no evidence of deep vein thrombosis. Transesophageal echocardiography (TEE) showed a small (PFO) with a left to right shunt seen on Color Doppler interrogation. The PFO was closed percutaneously using Amplatzer septal occluder #12.

CRAO is uncommon in young adults. It is usually associated with systemic diseases such as collagen vascular disorders, malignancies, intracardiac anomalies, and coagulopathy.^[1,2] CRAO due to embolization has been reported following left ventricular assist device implantation, coronary artery bypass grafting, carotid endarterectomy, and carotid stenting.^[3,4] An atrial septal defect is essentially a left-to-right shunt. Embolic cerebrovascular accidents can occur due to paradoxical embolism across a PFO following a Valsalva maneuver, such as coughing or excessive straining. The PFO was closed to prevent recurrent strokes and loss of vision in the other eye.^[5] In case of sudden onset vision loss in one eye, there should be suspicion of paradoxical embolism across a PFO.

PFO is a normal variation seen in 25% of the population and should not be considered pathological. Sometimes, the septum primum and secundum do not close completely, and a small oblique cleft remains. This opening is named probe patent PFO and is around 0.2–0.5 mm in dimension and does not allow intracardiac shunting. A PFO is either simple or of complex type. Complex PFOs are those that have a long tunnel length, multiple openings on the left atrial side or the atrial septal is aneurysmal. Excessively thickened septum secundum (≥10 mm), presence of Eustachian ridge/valve, or Chiari network and opening of the angle between PFO and inferior vena cava <10° are also considered complex PFO. Complex PFO is more prone to develop cryptogenic strokes.^[6] PFO is essentially a left-to-right or bidirectional shunt, never purely a right-to-left shunt. TEE is very helpful in diagnosing the PFO, and injection of agitated saline and Valsalva maneuver increases the sensitivity of diagnosis. All physicians working in the emergency ward or intensive care unit must be aware that PFO is a potential cause of cryptogenic stroke and needs evaluation in that direction.