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Introduction
Paradoxical embolism (through a right-to-left shunt) as a mechanism of stroke has been described as early as 1877.^1-4 Patent foramen ovale (PFO) is present in up to 50% of patients with cryptogenic stroke.^5-6 Currently, secondary prevention of recurrent paradoxical embolism in patients with PFO consists of medical treatment with antiplatelet and anticoagulation agents (aspirin, clopidogrel, coumadin), or PFO closure (surgical or percutaneous closure).⁷ The majority of the PFO closures are now performed percutaneously due to relative ease of technique, considerable safety and high rates of success. In a minority of patients, a persistent residual right-to-left shunt is seen several months after the initial transcatheter PFO closure. Such patients are at a higher risk of recurrent embolic events.⁸ Although the best therapeutic approach to treat the residual shunt is unclear, anecdotal reports of second closure with transcatheter closure technique are described in the literature.⁹ In this paper, we report a case of a persistent residual shunt after the initial PFO closure with a 23mm CardioSEAL® (NMT Medical, Boston, MA) device that was successfully treated with a second 28mm CardioSEAL device.

Case Report
A 58-year-old female with a history of stroke and PFO detected by agitated saline contrast on a transesophageal echocardiography underwent percutaneous closure of PFO with a 23mm CardioSEAL device. She was noted to have a small residual shunt after the PFO-closure device deployment. She was discharged on aspirin and clopidogrel. A follow-up transesophageal echocardiography performed 6 months after the initial device deployment showed a moderate-sized persistent residual shunt at the inferior border of the CardioSEAL device (Figure 1). The patient experienced an episode of transient ischemia attack (TIA), manifested as slurred speech and facial numbness, that resolved completely within several hours of onset. She was then taken to the catheterization laboratory for closure of the residual shunt with a second CardioSEAL device.

The procedure was similar to the initial device deployment. Briefly, after obtaining an informed consent, the patient was placed under conscious sedation, and 11F and 9F sheaths were introduced into the right femoral vein. An intracardiac echocardiography (ICE) catheter (AcuNav, Siemens Medical Solutions, Malvern, PA) was introduced through the 11F sheath into the right atrium. Using the previously deployed device as a landmark and under ICE guidance, the interatrial communication was crossed with a 0.035-inch J-tipped guidewire. Once this was achieved, 10,000 U of heparin bolus was given and activated clotting time was maintained at >200 seconds. The delivery sheath was then gently placed across the interatrial communication, taking care to avoid damage to the initial device. Next, a 28mm CardioSEAL device was deployed, “sandwiching” the initial device and eliminating the residual shunt completely (Figures 2-3). The patient was discharged the next day on aspirin and clopidogrel, to be continued for another 6 months.

Discussion
Cryptogenic strokes constitute about 40% of the ischemic strokes.5 PFO is identified in 44-66% patients with cryptogenic stroke, compared with only 9-27% in the control groups.^5-6 PFO-mediated paradoxical thromboembolism is considered the most likely mechanism of stroke in this patient population.¹⁰ Treatment of patients with cryptogenic stroke and PFO remains controversial. Current treatment strategies include medical management with antiplatelet and anticoagulation drugs, surgery or transcatheter closure of the defect. Medical treatment for patients with cryptogenic stroke and PFO carries a high risk of recurrent embolic events of 2.3 to 14.4% per year.^11-17 In addition, anticoagulation confers a risk of hemorrhagic complications of 9 to 15% per year and a 2 to 5% per year risk of severe bleeding (cerebral and/or need for transfusion). Surgical closure of PFO is associated with long hospital stay (mean length of stay of 7-10 days), postcardiotomy syndrome (18%), postoperative bleeding (3.3%) and occasionally sternal wound infection.^18-20 As a result, surgical PFO closure is rarely performed. Transcatheter closure of PFO has been performed for more than 12 years with low complication rates. With the current-generation transcatheter PFO-closure devices, successful PFO occlusion can be achieved in >90% of the patients.

Persistent right-to-left shunt is seen, on occasion, several months after the initial percutaneous PFO closure. Meier et al. reported a persistent minimal residual shunt in 11% of patients, and moderate-to-large persistent residual shunts in up to 10% of patients following the initial transcatheter closure of PFO.⁹ Patients with minimal residual shunt might have complete shunt elimination over time,^21-22 but patients with moderate to large residual shunts after a percutaneous PFO closure rarely show spontaneous regression of the shunt during follow-up. Unfortunately, such residual shunts are not benign. Patients with residual shunt appear to have a four-fold increased risk for recurrent embolic events compared to patients with complete PFO occlusion.⁸ Although the best therapeutic approach to treat the residual shunt is unclear, anecdotal reports of second closure with transcatheter closure technique are described in the literature.⁹ The implantation of a second closure device is similar to and no more technically challenging than the initial procedure.

Conclusion
Persistent moderate to large residual shunts after initial implantation of PFO closure device carry a significant risk of recurrent embolic events. Despite the lack of long-term data, a second transcatheter closure of the residual PFO appears to be technically feasible and safe, circumventing the need for surgical approach.


The authors can be contacted at *link-1**richardheuser@phoenixheartcenter.com

Figure legends
Figure 1. Transesophageal echocardiogram showing the residual defect at the inferior border of the CardioSEAL™ device (arrow).

Figure 2. Intracardiac echocardiogram (ICE) showing the second CardioSEAL™ device (thick arrow) “sandwiching” the initial CardioSEAL™ device (thin arrow) and eliminating the residual shunt.

Figure 3. Fluoroscopic image of the two CardioSEAL™ devices after deployment