Paradoxical embolization

Persistence of patent foramen ovale (PFO) into adulthood carries a risk of paradoxical embolization. This risk is accentuated... 

It has become recognized that PFO device closure not only significantly decreases the incidence of paradoxical embolism (47), but can also reduce the incidence of migraine in susceptible patients. Fifty-five percent of patients with aura and 62% of those without aura experienced a reduction of... 

Paradoxical embolism can occur in a patent foramen ovale with a right to left shunt. Embolic material arising from the pelvic or leg veins or elsewhere in the venous system may bypass the pulmonary system and reach the cerebral arteries (Braun et al. 2004). 

Brandt T, Steinke W, Thie A et al (2000) Posterior cerebral artery territory infarcts clinical features, infarct topography, causes and outcome 1. Cerebrovasc Dis 10 170-182 Braun M, Chech V, Boscheri A et al (2004) Transcatheter closure of patent foramen ovale (PFO) in patients with paradoxical embolism. Periprocedural safety and mid-term follow-up results of three different device occluder systems. Eur Heart J 25 424-430... 

Autopsy examples have established that paradoxical embolism can occur from venous thrombi through the right to the left side of the heart. Emboli may pass through a patent foramen ovale, which is found in approximately one-quarter of healthy people, an atrial septal defect or a ventriculoseptal defect (Gautier et al. 1991 Jeanrenaud and Kappenberger 1991 Cabanes et al. 1993). There is an increased incidence of patent foramen ovale in... 

Thrombophilias and other causes of hypercoagulability are rare causes of stroke (Matijevic and Wu 2006). Antithrombin III deficiency, protein C deficiency, activated protein C resistance owing to factor V Leiden mutation, protein S deficiency and plasminogen abnormality or deficiency can all cause peripheral and intracranial venous thrombosis. Thrombosis is usually recurrent and there is often a family history. Thrombophilia may cause arterial thrombosis, although the alternative diagnosis of paradoxical embolism should always be considered in patients with these disorders. It should be noted that deficiencies in any one of the factors associated with thrombophilia may be an incidental finding and cannot necessarily be assumed to be the cause of stroke. 

Mechanisms include thrombocytosis, hypercoagulability, immobility and paradoxical embolism, vasculitis and dehydration. The bowel disease is not necessarily severe at the time of the stroke. Coeliac disease can also be complicated by a cerebral vasculitis but this often presents with an encephalopathy rather than a stroke (Mumford et al. 1996). 

Wahl A, Meier B, Haxel B et al. (2001). Prognosis after percutaneous closure of patent foramen ovale for paradoxical embolism. Neurology 57 1330-1332 Wallis WE, Donaldson I, Scott RS et al. 

Valsalva maneuver (paradoxical embolism, or low flow) Carotid/vertebral dissection (Ch. 6)... 

Chest pain may be indicative of a recent myocardial infarction with complicating stroke, aortic dissection (particularly if the pain is also interscapular) or pulmonary embolism and raises the possibility of paradoxical embolism. 

PAVMs provide a direct capillary-free communication between the pulmonary and systemic circulations with three main clinical consequences (1) pulmonary arterialbloodpassing through these right-to-left shunts cannot be oxygenated which may lead to hypoxemia, (2) the absence of normal filtering capillary bed allows particulate material (air bubbles or clots) to reach directly the systemic circulation (paradoxical embolism) with potential clinical sequelae in the cerebral circulation (transient ischemic attack, stroke, brain abscess), and (3) these abnormal vessels may rupture into the bronchus (hemoptysis) or the pleural cavity (hemothorax) particularly during pregnancy. 

Indications for treatment of PAVMs include three broad categories prevention of hemorrhage, improvement of hypoxemia in patients with exercise intolerance, and, most importantly, prevention of the complications associated with paradoxical embolism. Exercise intolerance consisting of dyspnea and fatigue is difficult to quantify because most patients tolerate quite well significant hypoxemia. In most centers, the primary indication for embolization of PAVMs is prevention of neurologic complications. 

The role of venous sac embolization remains unclear [79]. Venous sac closure is usually necessary in less than 1% of PAVMs when the artery to the PAVM is short (2 cm or less) and has high flow or uneven diameter and there is a risk of paradoxical embolization [6,9,78]. 

Complications tend to occur when pacing catheters are left in place for longer then 72h (35). Infections can track down the catheter and care should be taken whenever the catheter or vascular sheath is manipulated. The catheter should be left within a sterile sleeve that allows for subsequent advancement and withdrawal. Acute thrombosis of the vein can occur, leading to extremity engorgment and to thromboembolic events. Routine anticoagulation, however, is not considered to be necessary unless there is a septal defect that could allow a venous thrombus to cause a stroke (paradoxical embolism). 

Agarwal, S., Bajaj, N.S., Kumbhani, D.J., Tuzcu, E.M., Kapadia, S.R., 2012. Meta-analysis of transcatheter closure versus medical therapy for patent foramen ovale in prevention of recurrent neurological events after presumed paradoxical embolism. Journal of the American College of Cardiology 5, 777-789. 

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