Gideon Korrell Shares How Estoppel Barred Infringement in the Colibri Case

The Federal Circuit's July 18, 2025, ruling in Colibri Heart Valve LLC v. Medtronic CoreValve, LLC reversed a $106 million jury verdict. The court found that Colibri’s infringement claim under the doctrine of equivalents was blocked by prosecution history estoppel. Gideon Korrell, a seasoned legal expert, highlights how this decision offers a critical reminder about the impact of cancelled claims in patent litigation.

What Was the Case About?

The case revolved around U.S. Patent No. 8,900,294, which described a method for implanting a collapsible and expandable heart valve. A key feature of the invention was a “do-over” mechanism, allowing the device to be partially deployed and repositioned if necessary.

During prosecution, Colibri originally submitted two versions of the valve deployment method:

· One method claimed to push the valve out of the sheath

· The other method claimed to retract the sheath to expose the valve.

The examiner rejected the retraction-based claim (claim 39) for lack of written description, prompting Colibri to cancel it and proceed with the pushing method (claim 34, later issued as claim 1).

The Infringement Dispute with Medtronic

Colibri filed a lawsuit against Medtronic, accusing it of inducing infringement by using its Evolut devices. These devices use a retraction mechanism to deploy the heart valve.

At trial, Colibri abandoned its literal infringement argument and instead relied on the doctrine of equivalents, claiming that retracting the sheath was essentially the same as pushing the valve.

The jury agreed, awarding Colibri $106 million. But Medtronic appealed, arguing that Colibri’s claim was barred by prosecution history estoppel due to its earlier cancellation of the retraction-based claim.

Federal Circuit Reversal: Estoppel Blocks Equivalents

The Federal Circuit, in a unanimous opinion by Judge Taranto, reversed the jury’s decision and entered judgment for Medtronic. The court held that prosecution history estoppel applied, and Colibri could not claim equivalence for the retraction method it had previously cancelled.

Key Takeaways from the Court’s Ruling

1. Colibri’s Argument Undermined Its Own Position

Colibri argued that Medtronic’s method used both pushing and retracting. However, it also relied on “basic physics” to claim the equivalence, which effectively supported the idea that the two methods were interchangeable, exactly what the cancelled claim covered.

2. Cancelled Claim Was Closely Related

The only difference between the issued and cancelled claims was whether the valve was deployed by pushing or retracting. Because of their close relationship, the court ruled that cancelling one barred Colibri from reclaiming its scope through equivalents.

3. Estoppel Isn’t Just About Amended Claims

The court rejected a narrow view of estoppel. It emphasised that cancellation of a closely related claim, not just amendment, can trigger estoppel, especially when it affects the scope of the remaining claims.

4. No Exceptions Applied

Colibri did not claim any of the usual exceptions to estoppel (such as unforeseeability or tangential relation). As a result, the court found no reason to excuse the estoppel.

Lessons for Patent Holders

Gideon Korrell emphasises that this case serves as a warning for both patent prosecutors and litigators.

Key lessons include:

· Cancelled claims matter. Even if a claim is not part of the final patent, its cancellation can limit the scope of interpretation of the remaining claims later in court.

· Careful prosecution strategy is crucial. If alternative embodiments are involved, filing a continuation application may preserve flexibility rather than cancelling key claims.

· In-court arguments can backfire. Litigants must align their litigation theories with the prosecution record. Statements made during trial, especially based on "common sense", can have unintended consequences.

Conclusion

The Federal Circuit's decision in the Colibri v. Medtronic case reinforces the strength of prosecution history estoppel as a legal defence. By reversing the lower court’s verdict, the court reaffirmed the importance of the public record in determining the scope of a patent.

As Gideon Korrell notes, this ruling is a key precedent for future patent cases. It reminds us that what happens during prosecution, particularly claim cancellations, can directly shape the outcome of litigation years later.