The purpose of this review is to raise the index of suspicion for paradoxical embolism among generalists. The review is based solely on anecdotal reports compiled from EMBASE, MEDLINE, Googlescholar and Pubmed. Search terms were 'paradoxical embolism', 'pulmonary embolism' and 'pulmonary arteriovenous malformations'. What emerged was that right-to-left paradoxical embolism could occur with or without concurrent pulmonary embolism, and also with and without proof of the presence of an 'embolus-in-transit'. Potential sites of single or multiple systemic involvement included the central nervous system, the coronary circulation, renal arterial circulation, splenic circulation, the mesenteric circulation and the limbs. In many cases, the deep veins of the lower limbs were the source of thromboembolism. In other cases, thrombi originated from an atrial septal aneurysm, from a central venous line, from a haemodialysis-related arterio-venous shunt, from a popliteal vein aneurysm, internal jugular vein, superior vena cava, from a pulmonary arteriovenous malformation, from tricuspid valve endocarditis (with and without pulmonary embolism) and from the right atrium, respectively. Stroke was by far the commonest systemic manifestation of paradoxical embolism. Some strokes were attributable to pulmonary arteriovenous malformations with or without coexistence of intracardiac shunts. Clinicians should have a high index of suspicion for paradoxical embolism because of its time-sensitive dimension when it occurs in the context of involvement of the intracranial circulation, coronary circulation, mesenteric circulation, and peripheral limb circulation.

Thrombolysis for acute ischemic stroke has been rarely administrated during pregnancy. Paradoxical embolism through a patent foramen ovale (PFO) or pulmonary arteriovenous malformation (AVM) is an identified risk factor for ischemic stroke.

We report a 24-year-old woman at 11 weeks gestation who developed a sudden onset of dysarthria, hemiparesis, and hemisensory loss. She was diagnosed as having an ischemic stroke in the left middle cerebral artery (MCA) territory. She was treated with intra-arterial recombinant tissue plasminogen activator with subsequent resolution of her neurological deficits. Further workup revealed the presence of a PFO with a large right-to-left shunt. After being put on antithrombotic therapy, she presented again at 13 gestational weeks with a new ischemic infarction in the vertebrobasilar territory. Her PFO was closed percutaneously under ultrasonic guidance but the right-to-left shunt persisted. After a normal delivery, she was found to have a large pulmonary AVM which was successfully resected without complication.

This report describes the successful usage of intra-arterial tissue plasminogen activator for acute ischemic stroke during early pregnancy. In patients with presumed paradoxical embolism, careful attention should be paid to rule out a coexistence of PFO and pulmonary AVM.

: An increasing number of patients are being evaluated for percutaneous patent foramen ovale (PFO) closure to prevent recurrent cerebrovascular events, but debate still exists on therapeutic indications and off-label closure device implantation. Pulmonary arteriovenous fistulas (PAVFs) are a rare and heterogeneous malformation prevalently associated with Rendu-Osler-Weber syndrome, and may mimic PFO right-to-left shunt (RLS), leading to unnecessary interventions and in some cases to relapses. Residual shunt is increasingly being observed both after PFO closure and PAVF embolization, even at long-term follow-up, with unclear clinical relevance. This instrumental and possibly therapeutic failure could lie in the presence of pulmonary microfistulas, either pre-existing or following the intervention. Hence, if RLS persists after optimal device placement and reasonable endothelialization time, the presence of a PAVF should be assumed and investigated; if RLS recurs after previous, negative echocontrast studies, presence of device-related complications or pulmonary microfistulas should be taken into consideration.