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The Amplatzer patent foramen ovale (PFO) occluder faces an FDA advisory committee tomorrow, but the agency's review highlighted problems with a key trial that could indicate a tough day ahead.

St. Jude Medical's Amplatzer is intended to put a stopper on blood shunting across the PFO, which can presumably lead to recurrent ischemic strokes. However, the RESPECT trial failed to show a reduced rate of strokes for patients implanted with the Amplatzer in comparison with their peers on standard medical management.

FDA reviewers honed in on the problems of RESPECT as a clinical trial in the for the advisory panel to consider:

"There is no single standard-of-care anti-thrombotic medical therapy to reduce the risk of recurrent stroke in patients with cryptogenic stroke. The use of multiple acceptable combinations of anti-thrombotic agents in the medical management group presents challenges in defining the probable benefits of the Device vs. medical therapy."

Furthermore, the low number of strokes to be analyzed in the study of 980 patients followed for at least 4 years suggested that "many patients could be potential candidates for an invasive cardiac procedure to implant a permanent device to prevent a relatively uncommon event," the FDA staff wrote. "Unfortunately, there was no particular patient subgroup for whom there is compelling evidence for an enhanced benefit associated with implantation of the Device."

The FDA identified several other problems with the Amplatzer investigation, including:

• High (and unbalanced) rates of participants dropping out from the trial
• Incomplete confirmation of PFO closure
• Potential ties between the device and risk of atrial fibrillation, deep venous thrombosis, and pulmonary embolism

The other PFO occluder trials completed to date -- PC and CLOSURE -- also have not shown effective stroke prevention after device implantation. The REDUCE study with Gore's is ongoing.

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