Case Summary
On July 18, 2025, the U.S. Court of Appeals for the Federal Circuit reversed a $106 million jury verdict in Colibri Heart Valve LLC v. Medtronic CoreValve, LLC, No. 2023-2153, finding that Colibri’s infringement claim under the doctrine of equivalents was barred by prosecution history estoppel. The case involved U.S. Patent No. 8,900,294 (“the ’294 patent”), which claims a method for implanting a percutaneous replacement heart valve that allows for partial deployment followed by recapture if it is positioned incorrectly. Slip Op. at 2.
The ’294 patent issued with an independent claim (claim 1) that recited partial deployment “by pushing out the pusher member from the moveable sheath” to expose the valve. Id. During prosecution, the applicant had also submitted a broader independent claim (claim 39) that described deployment by “retracting the moveable sheath” to partially deploy the replacement heart valve, but that claim was rejected under 35 U.S.C. § 112 for lack of written description and subsequently cancelled. Id.
Colibri sued Medtronic CoreValve under 35 U.S.C. § 271(b), alleging inducement of infringement. Id. At trial, Colibri conceded that Medtronic’s Evolut valve systems—utilizing sheath retraction rather than the claimed pushing method—did not literally infringe, as it involved retraction rather than pushing. Id. Instead, Colibri relied on the doctrine of equivalents arguing that Medtronic’s method was insubstantially different from pushing out the pusher member. Id. The district court denied Medtronic’s motion for judgment as a matter of law (JMOL) of noninfringement and the jury found in favor of Colibri, awarding damages exceeding $106 million. Id. at 3.
On appeal, however, the Federal Circuit held that Colibri was estopped from asserting its equivalence theory due to its prosecution conduct, namely the cancellation of claim 39 relating to retraction expressly, which covered the method Colibri now sought to recapture through equivalency. Id.
Legal Analysis
The Federal Circuit disagreed with the district court’s finding that Colibri’s asserted equivalent—Medtronic’s implantation method using both pushing and retracting—was distinct from cancelled claim 39, which recited only retraction. Id. at 17. Colibri had argued that the accused method was materially different from claim 39 because it involved both actions. Id. The Federal Circuit, however, found this distinction unpersuasive. Id.
Colibri itself had repeatedly acknowledged that “basic physics” require a pushing force to accompany retraction in valve deployment. Id. at 18. Thus, the Court reasoned that Colibri’s asserted equivalent and the cancelled claim 39 involved the same essential mechanism. Moreover, both the cancelled and issued claims used language indicating that the valve was restrained by the sheath, further reinforcing the technical equivalency. Id. Because Colibri failed to rebut the presumption of estoppel or invoke any recognized exception, the Court held that estoppel applied and precluded Colibri from asserting equivalence based on retraction. Id.
The Federal Circuit also agreed that Colibri’s cancellation of claim 39 during prosecution, in favor of pursuing limitations already included in retained claim 34 (which issued as claim 1), constituted a narrowing amendment. Id. at 19. This narrowing gave rise to prosecution history estoppel. Id.
The Court emphasized that a narrowing action need not involve a formal amendment to the specific claim asserted; rather, cancelling a broader claim while retaining a narrower one—especially when both cover closely related subject matter—can give rise to estoppel. Id. In the instant case, both claims recited partial deployment of a heart valve, differing only in how deployment occurs: claim 34 (issued claim 1) used “pushing,” while cancelled claim 39 used “retracting.” Id.
Relying on Colibri’s own arguments, that both pushing and retracting are involved in real-world valve deployment (based on “basic physics”), the Court concluded that the two claims were substantively intertwined. A person skilled in the art would view the cancelled and retained claims as closely related, such that cancelling one effectively narrowed the scope of the other. Id. at 20.
The district court had rejected this estoppel argument on formal grounds—reasoning that because the cancelled and retained claims were independent and not in a dependent relationship, and because Colibri did not amend claim 1, estoppel should not apply. Id. The Federal Circuit rejected that reasoning, stating that substance, not formal claim structure, governs whether estoppel applies. Id.
The Court then surveyed precedent to support this view:
Citing Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002), the Court noted that estoppel arises when the scope of the patent is narrowed during prosecution, regardless of whether a specific claim is amended or cancelled. Id. at 20.-21.
Citing Honeywell Int’l Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131 (Fed. Cir. 2004), the Court noted that estoppel was applied where independent claims were cancelled and dependent claims were rewritten into independent form, even though the rewritten claims were not substantively changed. “‘[T]he fact that the scope of the rewritten claim has remained unchanged will not preclude the application of prosecution history estoppel if, by canceling the original independent claim and rewriting the dependent claims into independent form, the scope of subject matter claimed in the independent claim has been narrowed to secure the patent.’” Id. at 22-23 (citing Honeywell Int’l Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131, 1142 (Fed. Cir. 2004).
The court also referenced Keith v. Charles E. Hires Co., 116 F.2d 46 (2d Cir. 1940), where cancellation of one claim in favor of another gave rise to estoppel despite the surviving claim not being amended.
In applying these principles to the case, the Federal Circuit held that by cancelling claim 39—directed to retraction—Colibri signaled that it was abandoning that scope. Because both claims described essentially the same deployment step but with different language, cancelling the broader claim (claim 39) while pursuing the narrower (claim 34) constituted a narrowing of the invention’s scope. Id. at 24. Thus, estoppel applied.
The Court concluded that Colibri could not now reclaim the territory of the cancelled claim through the doctrine of equivalents. If Colibri wished to protect retraction-based deployment, it should have filed a continuation application. Id. Given the prosecution record and the technological overlap between pushing and retracting, the public-notice function of estoppel demanded that Colibri be precluded from asserting equivalence on that basis. Id.
Ruling
The Federal Circuit reversed the district court’s denial of Medtronic’s JMOL motion, holding that Colibri’s doctrine of equivalents claim was barred by prosecution history estoppel. Id. at 25.
Conclusion and Commentary
Colibri reinforces prosecution history estoppel as a potent limitation on the doctrine of equivalents, particularly where applicants cancel claims encompassing similar subject matter they later attempt to recapture. The ruling affirms that even formal claim distinctions—such as independently filed claims rather than amendments—may give rise to estoppel if the underlying disclosures and patent owner statements signal a narrowing of scope.
Patent owners should be cautious in advancing equivalence theories in litigation that run contrary to any claim amendments that could be construed as narrowing or that ignore the substantive overlap between cancelled and issued claims. Patent owners should also try to avoid relying on the doctrine of equivalents, through claim construction or otherwise. Further, to preserve flexibility in enforcement, patent owners should consider filing continuation applications or adding dependent claims rather than outright cancelling claims that potentially overlap with other claims.
Accused infringers seeking to raise a prosecution history estoppel defense to infringement under the doctrine of equivalents should now consider not just amendments to the asserted claims, but rather scrutinize all potentially relevant claim amendments and cancellations. Accused infringers should focus on the technical overlap between cancelled and issued claims, even if they differ in wording or claim format. A careful reading of the patent prosecution history, combined with a sound understanding of the claimed technology and the patentee’s own positions, may yield a powerful estoppel defense.
