Medical Device Daily Washington Editor

Magnetic fields are powerful things and magnetic resonance imaging scanners are growing more powerful every year. Recent reports of unanticipated events involving MRI equipment have surfaced over the years since the introduction of the technology, and FDA has responded with a guidance suggesting that makers of passive implants tests those devices against MR energy before going to market.

Perhaps the most conspicuous of these is an incident in 2001 in which six-year-old Michael Colombini of Croton, New York, lost his life when a metal oxygen tank was accelerated from its resting place in an imaging lab, inducing a fatal head injury. However, other incidents have made the news, including burns.

The Aug. 21 guidance refers to testing only for devices that are the subjects of a PMA, 510(k) or investigational device exemption filing, and FDA states that the point of interest is "the safety and compatibility of passive implants in the MR environment" due to the possibility of "magnetically induced displacement force and torque, radio-frequency heating, and image artifacts."

The agency says sponsors of passive implant devices should conduct tests that "encompass the range of sizes you intend to market" or test for "a combination of sizes that represents the worst-case scenario for each test."

Some devices apparently will not need testing. "A scientifically based rationale rather than test data may be sufficient to support identifying an implant as 'MR Safe,'" the guidance states. For implants that fall into the categories of "MR Conditional" or "MR Unsafe," sponsors should test for the four effects mentioned previously. FDA also points out that MRI units generating fields of three Teslas or more "are becoming more common," so a field of 1.5 Teslas will not satisfy worst-case requirements.

As for labeling, FDA states that product labels "should indicate the device was tested under non-clinical conditions and list the conditions under which the device can be safely scanned." Among the parameters of interest are the static magnetic field in terms of Teslas and "the maximum whole body averaged specific absorption" for a given duration of scanning.

FDA publishes label change final rule

The provision of the FDA Amendments Act of 2007 (FDAAA) that dealt with voluntary changes to the safety information in the label for a drug or device has generated more controversy than perhaps the agency anticipated, but FDA has inked the final guidance on label changes despite comments that indicated consternation over the initial proposed rule.

The announcement in the Aug. 22 Federal Register states that FDA will allow further addition of contraindications, warnings and adverse reactions "only if there is sufficient evidence of a causal association" with a drug, device or biologic. However, the notice also remarks that "causation is not a binary issue" in that such a relationship "is often difficult to establish and may require large trials," including ones that examine the specific correlation.

According to FDA, some commenters have indicated a parallel concern that policy should not prevent manufacturers from increasing the number of warnings, "even when the regulations do not require it." However, the agency stated that it does not agree "this rule will make it more difficult to provide appropriate warnings" because the rule "is sufficiently clear and objective enough to allow sponsors to determine whether a medical product's labeling should be amended."

The definition of "new information" in the context of additional warnings "has been revised to clarify that data, whether derived from new clinical studies, reports of adverse events or new analyses of previously submitted data" are all permitted as sources of data to bolster a product's warnings and contraindications. The previous edition of the rule indicated that only adverse events reporting data were permitted as a source to justify changes to a label.

The question of pre-emption also arose in that some comments indicated a belief that the unilateral changes to a label "would create a conflict with congressional intent" with regard to drugs, which may be a question for 510(k) devices under current law and for PMA devices if Congress overturns the current pre-emption paradigm. FDA states that FDAAA "provided additional authority ... to require sponsors to make safety-related changes to their labeling," and that in any case, the law "expressly acknowledged that FDA's regulations are not static and may be subsequently amended by the agency, as FDA is doing here."

FDA to host workshop for leads

Making a narrower lead for a pacemaker or implantable defibrillator has kicked up the law of unintended consequences in some instances, and FDA has said it will hold an Oct. 2-3 workshop to discuss just that problem.

According to the announcement, the workshop will include sessions on returned product analysis, adverse event reporting and post-market surveillance as well as breakout sessions to discuss best practices for these topics. The second day is scheduled for only half a day, during which the breakout groups will report on their discussions.

The agency will accept registration until 120 attendees have signed up for the sessions, which will take place at the Hilton Hotel in Gaithersburg, Maryland.

No Comments