Defining Claim Terms by Implication: Lexicography Lessons from Aortic Innovations LLC v. Edwards Lifesciences Corporation

Claim construction is a key stage of most patent litigations, where the court must decide the meaning of any disputed terms in the patent claims.  Generally, claim terms are given their plain and ordinary meaning except under two circumstances: (1) when the patentee acts as its own lexicographer and sets out a definition for the term; and (2) when the patentee disavows the full scope of the term either in the specification or during prosecution.  Thorner v. Sony Comput. Ent. Am. LLC, 669 F.3d 1362, 1365 (Fed. Cir. 2012).  The Federal Circuit’s recent decision in Aortic Innovations LLC v. Edwards Lifesciences Corp. highlights that patentees can act as their own lexicographers through consistent, interchangeable usage of terms across the specification, effectively defining terms by implication.

Aortic Innovations sued Edwards Lifesciences in the District Court of Delaware for infringement of four patents related to transcatheter aortic valve replacement devices.  The dispute centered on the meaning of the term “outer frame.”  The patentee argued the term should retain its ordinary meaning, whereas Edwards Lifesciences sought a narrower construction.  Upon review of the specification and the rest of the intrinsic record, the district court found that the patentee acted as its own lexicographer and defined the term “outer frame” to be a “self-expanding frame.”  The district court based its finding on the repeated use of these terms to “interchangeably refer to the same structure” in the disclosed embodiments.

The Federal Circuit affirmed, emphasizing that “explicit redefinition is not required for a patentee to act as a lexicographer.”  Rather, a “patent’s consistent and clear interchangeable use of two terms can result in a definition equating the two terms.”

Although the Federal Circuit noted that “[s]imply referring to two terms as alternatives or disclosing embodiments that all use the terms in the same way is not sufficient to redefine a claim term,” it found that the patentee consistently used the terms “outer frame,” “self-expanding frame,” and “self-expanding outer frame,” to refer to the same structure within the same disclosed embodiments.  Moreover, the specification never used optional language for the presence of a self-expanding outer frame, and instead “clearly and consistently conveys” that the self-expanding feature “is present in all embodiments.”

This ruling offers valuable guidance for patent litigators by clarifying the circumstances under which a claim term’s scope can be narrowed from its plain meaning through lexicography.  Consistent interchangeable use of two terms can result in an equating of the two terms, limiting a claim term to the disclosed, narrower embodiment.

For patent drafters, this case serves as a reminder to avoid unintentionally redefining terms through implication.  Maintaining consistent and accurate use of terminology throughout a patent specification is essential. If different terms are used for the same structure or feature, they should be clearly differentiated as alternatives or distinct embodiments to prevent inadvertent narrowing of a claim term’s enforceable scope.