Push vs. Pull: Federal Circuit Reverses $106M Verdict, Finding Estoppel from a Canceled Claim
The CAFC looks at the "public notice" function of prosecution history estoppel
Reminding IP owners and practitioners of the lasting impact of prosecution history, the U.S. Court of Appeals for the Federal Circuit has reversed a nine-figure jury verdict, concluding that the patentee was barred from asserting infringement under the doctrine of equivalents (p. 3).
The panel found that by cancelling a claim reciting a "retracting" mechanism during prosecution, the patent owner had surrendered the very subject matter it later tried to recapture through an equivalence argument against a competitor’s product (pp. 3, 19). The ruling underscores the perils of surrendering claim scope and highlights how a patentee's own arguments can be used to defeat its infringement case.
The precedential case, Colibri Heart Valve LLC v. Medtronic CoreValve, LLC, 2023-2153 (Fed. Cir. July 18, 2025), revolved around a dispute over patented methods for implanting artificial heart valves (p. 2). The Federal Circuit's analysis provides a valuable lesson for patent prosecutors and litigators on the powerful and often unforgiving nature of prosecution history estoppel—as well as an explicit reminder to use continuation applications.
Background of the Dispute
The technology at the heart of this case is Colibri Heart Valve LLC’s U.S. Patent No. 8,900,294, which describes a method for implanting a replacement heart valve (p. 2). A key innovation claimed in the '294 patent is a "do-over" feature that allows a surgeon to partially deploy the valve, assess its positioning, and, if necessary, recapture the valve within the delivery catheter for repositioning before full deployment (pp. 2, 4). This controlled-release method reduces the risk of misplacing the life-sustaining device.
The specific language of the patent’s claims became the central issue. The asserted independent claim, Claim 1, describes the partial deployment step as being achieved by "pushing out the pusher member from the moveable sheath to expose the distal portion of the replacement heart valve device" (p. 7).
During the patent’s prosecution, however, Colibri had originally filed another, separate independent claim (then-claim 39) that described a similar method (pp. 2, 10). Instead of "pushing," claim 39 recited achieving partial deployment by "retracting the moveable sheath to expose a portion of the replacement heart valve device" (p. 11). After the patent examiner rejected claim 39 for lacking written description support, Colibri cancelled it and proceeded only with the "pushing" claim, which eventually issued as part of the '294 patent (p. 2).
Medtronic CoreValve, LLC, a major medical device manufacturer, produces the "Evolut" line of replacement heart valves (p. 7). The implantation procedure for Evolut devices also features a recapture capability (p. 8). However, to deploy the valve, the surgeon retracts an outer sheath while an inner member holds the valve assembly in place (p. 8).
Colibri sued Medtronic, alleging that surgeons using the Evolut system induced infringement of the '294 patent (p. 2). At trial, Colibri abandoned its literal infringement theory and argued solely under the doctrine of equivalents, contending that Medtronic's "retracting" method was equivalent to the "pushing" method claimed in the patent (pp. 2, 12).
A jury in the Central District of California agreed, awarding Colibri more than $106 million in damages (pp. 3, 13). The district court subsequently denied Medtronic's motions for judgment as a matter of law (JMOL) that its product did not infringe, rejecting Medtronic's argument that prosecution history estoppel barred Colibri's equivalence theory (pp. 3, 13).
The Court's Analysis: Prosecution History Estoppel
On appeal, the Federal Circuit reversed, focusing squarely on Medtronic’s argument that Colibri’s equivalence claim was dead on arrival due to prosecution history estoppel (p. 3).
The central legal issue was whether Colibri, by cancelling the "retracting" claim to secure its patent, had surrendered the right to later claim that a "retracting" method was equivalent to its patented "pushing" method (p. 3). The court held that it had (p. 3).
The Federal Circuit found that the district court had erred by taking an overly "formal" view of the prosecution history (p. 20). The lower court reasoned that estoppel did not apply because the "pushing" and "retracting" claims were separate independent claims, and the issued "pushing" claim had never been amended itself (pp. 12, 20). The Federal Circuit disagreed, explaining that the estoppel analysis requires a substantive, not formalistic, inquiry into what a competitor would reasonably conclude was surrendered by the patentee (pp. 19, 20).
In a key passage, the panel articulated its reasoning:
The close substantive relationship between the cancelled and retained claims, by Colibri's own basic-physics logic for its affirmative assertion of equivalence, is enough to cross the estoppel threshold. A skilled artisan reading the prosecution history would understand that some narrowing had occurred through cancelling claim 39. (p. 24)
The court’s reasoning was simple and turned Colibri’s own litigation arguments against it. To prove equivalence at trial, Colibri had argued that "basic physics" dictates that to deploy the valve, one must apply opposing forces (p. 17). That is, to retract the outer sheath without the inner valve coming along for the ride, one must necessarily exert a forward "pushing" force on the inner member to hold it steady against the friction of the retracting sheath (p. 17).
The Federal Circuit seized on this "basic physics" argument (p. 19). If retracting the sheath necessarily requires a pushing force, the court reasoned, then the subject matter of the cancelled "retracting" claim was not meaningfully different from the asserted equivalent (Medtronic's method) (pp. 18, 19).
By cancelling a claim that covered a "retracting" (but implicitly pushing) method, Colibri clearly signaled to the public that it was narrowing the scope of its invention to only the explicitly "pushing" method recited in the allowed claim (pp. 19, 20). Recapturing that surrendered territory through the doctrine of equivalents was therefore impermissible.
Key Takeaways and Concerns for Patent Practitioners
The precendential Colibri decision offers several critical lessons for patent practitioners. It serves as a stark warning about the long-term consequences of prosecution decisions and litigation arguments.
Beware of Parallel Independent Claims Covering Similar Embodiments. Filing two independent claims with slight variations in terminology—such as "pushing" versus "retracting"—can create an estoppel trap. If one claim is cancelled to overcome a rejection, the cancellation can be interpreted as a surrender of that subject matter, precluding an equivalents argument on the surviving claim. The court's focus is not on whether the asserted claim was amended, but on whether the patent's overall scope was narrowed to secure allowance (pp. 21, 23).
Substance Triumphs Over Form. The Federal Circuit, citing its en banc precedent in Honeywell, confirmed that the estoppel inquiry is substantive (p. 22, citing Honeywell International Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131, 1141–44 (Fed. Cir. 2004) (en banc)). Simply keeping an asserted claim pristine during prosecution is not a "get out of jail free" card if other claims are cancelled to narrow the invention's scope. Colibri reiterates that the public is entitled to rely on the applicant's surrender of subject matter, regardless of the formal mechanism of that surrender.
Litigation Arguments Have Estoppel Implications. Colibri was, in a sense, undone by its own "basic physics" argument (p. 17). While necessary to support its theory of equivalence, that same logic convinced the Federal Circuit that the cancelled claim and the accused product were substantively linked (p. 19). This shows how arguments made to prove infringement can inadvertently prove estoppel. Every argument must be vetted for its potential to undermine the patentee's position in other contexts.
Use Continuations to Preserve Scope. The court provided a direct instruction on how this situation could have been avoided. It noted that if Colibri "wished to capture territory involving retraction that was outside the literal scope of claim 1, it could have filed a continuation application" (p. 24). This would have allowed Colibri to continue arguing for the "retracting" embodiment in a separate application without creating an estoppel that would taint the parent patent. This remains a foundational strategy for preserving options and building a robust patent portfolio.
Continuation Policies at Odds with USPTO Guidance? The CAFC’s explicit suggestion to use continuation applications to avoid estoppel is complicated by the USPTO's new continuing application fee surcharge, which imposes significant financial penalties on applications filed more than six years after their earliest priority date. Practitioners must now carefully balance the potent legal risk of prosecution history estoppel against the tangible economic disincentive designed by the USPTO to streamline patent family filings.
Conclusion
The Federal Circuit’s decision in Colibri v. Medtronic is a powerful reaffirmation of the public notice function of prosecution history (pp. 24-25). By cancelling its "retracting" claim, Colibri drew a line in the sand, and the court refused to let it cross that line years later in litigation.
The judgment provides a clear lesson: the choices made during patent prosecution have permanent consequences. Every amendment, every argument, and especially every cancelled claim becomes part of a permanent public record that courts will use to define the ultimate scope of the patentee's rights.
For patent owners and the attorneys who guide them, this case is a compelling reminder that the path to a strong and enforceable patent requires not just technical ingenuity, but also strategic foresight.
Disclaimer: This is provided for informational purposes only and does not constitute legal or financial advice. To the extent there are any opinions in this article, they are the author’s alone and do not represent the beliefs of his firm or clients. The strategies expressed are purely speculation based on publicly available information. The information expressed is subject to change at any time and should be checked for completeness, accuracy and current applicability. For advice, consult a suitably licensed attorney and/or patent professional.