Caught in Transit: Paradoxical Embolus Traversing a Patent Foramen Ovale During a Bubble Study in a Patient With Cryptogenic Stroke

Abstract

INTRODUCTION: Paradoxical embolus in transit is rarely identified during the work up of a stroke. We present a patient with multiple risk factors for stroke who was identified to have a thrombus crossing the interatrial septum at the time of an IV saline contrast study. CASE PRESENTATION:A 72-year-old woman with a history of diabetes, hypertension, paroxysmal atrial fibrillation, left frontal lobe stroke, and bilateral sub-segmental pulmonary emboli, presented with two months of visual hallucinations and was found to have multiple subacute infarctions affecting the right visual cortex (Fig1). Transthoracic echocardiogram (TTE) identified the etiology of her embolic strokes when a mobile 0.83 cm by 1.07 cm thrombus was seen traversing the interatrial septum from right to left with interatrial shunt following Valsalva maneuver during an IV saline contrast study (Fig2). Patient was also found to have unprovoked right mid-calf vein thrombus of indeterminate age. Diagnosis of paradoxical embolus in transit through a patent foramen ovale (PFO) associated with septal aneurysm was made. Patient did not have any new clinical event associated with the embolus and was treated with aspirin and rivaroxaban for secondary stroke prophylaxis. The decision was made not to pursue PFO closure given concern for medication non-compliance after the procedure.DISCUSSION: Paradoxical embolism is a clinically important entity1. Diagnosis often requires at least two of the following: (1) venous thrombosis, (2) arterial embolus, (3) connection between the right and left side of the heart, (4) and a traversing thrombus1. Demonstration of all of these four elements is rarely identified. Transesophageal echocardiography (TEE) is often required to explore interatrial septal anatomy after a TTE with an IV saline contrast study is performed when PFO is suspected. Identification of a paradoxical embolus during IV saline contrast study (bubble study) is even rarer, yet it establishes the stroke mechanism. Although considered a safe study with no significant residual morbidity, transient neurological symptoms have been reported with high degrees of right to left shunts2. The prevalence and clinical outcomes of paradoxical embolism during bubble study are uncertain owing to the scarcity of studies in this area3. Despite the growing evidence supporting PFO closure when it is associated with an atrial septal aneurysm or an interatrial shunt, the risk of intracranial bleeding from dual antiplatelet therapy following PFO-closure along with the risk of post-PFO atrial fibrillation makes management decision challenging and highly selective based on patient's risk factors.CONCLUSIONS: Paradoxical embolism is an uncommon, yet a clinically important entity. Identification of embolism during bubble study is exceedingly rare. Clinical outcome is uncertain warranting future studies to investigate the possibility of permanent neurological deficits.