While a patent practitioner's work may not qualify for hazard pay, significant responsibilities include imagining how a patent may be interpreted in the future and avoiding potential negative consequences arising from the words the practitioner used to describe an invention. A powerful tool in a patent professional's drafting toolbox is the ability to assign a particular definition to any term used in a patent – to act as a "lexicographer." As a lexicographer, a patent drafter has the ability to simply restate the common meaning of a term for clarity or to assign an alternate – such as an expanded or narrowed – meaning to the term. The ability to act as a lexicographer is especially useful when the drafter wishes to use a term differently than the term's "ordinary and plain meaning," but can have unintended consequences when careful attention is not given to the specific use of terminology throughout a patent specification. A recent suit, Aortic Innovations LLC v. Edwards Lifesciences Corp.,1/sup> highlights the importance of careful drafting and diligence in consistent use of terminology to avoid unintentionally invoking the power to act as a lexicographer and redefining a claim term in an unintended manner.
In Aortic, the U.S. Court of Appeals for the Federal Circuit (Federal Circuit) issued a precedential ruling affirming a district court judgment of non-infringement of Aortic Innovations LLC's patent claims directed to a transcatheter valve assembly having a self-expanding frame. Aortic had alleged infringement by Edwards Lifesciences for making and selling their SAPIEN 3 Ultra valve, a transcatheter heart valve replacement device having a balloon-expandable frame. At issue was the definition of the term "outer frame" and the related use of the terms "self-expanding frame" and "self-expanding outer frame." Aortic asserted infringement of four patents generally directed to devices for transcatheter heart valve replacement, claiming – among other limitations – an outer frame. Aortic argued that the claimed outer frame covered Edwards' balloon-expandable frame. The district court cited multiple instances of Aortic's interchangeable use of the terms "outer frame," "self-expanding frame," and "self-expanding outer frame" to construe the claimed "outer frame" to mean "self-expanding frame." For this reason, Edwards' balloon-expandable frame device was determined not to infringe Aortic's self-expanding frame device. The district court opinion concluded that – by intermingling the terminology – Aortic had acted as a lexicographer, redefining the ordinary and plain meaning of "outer frame" to mean "self-expanding frame" in all four of the asserted patents.
In the absence of an explicit definition, a claim term will be construed to have its "plain and ordinary meaning," i.e., the meaning as understood by one having ordinary skill in the art. A patent specification is intended to "serve as a glossary to the claim terms," in accordance with Manual of Patent Examining Procedure Sec. 2173.01, and a patent drafter may assign any alternative meaning to a particular term by including an explicit definition for the term in the patent specification. An explicit definition is not required, however, to redefine a term. Courts have repeatedly held that a term may be redefined by implicit use, but the Federal Circuit cautions in Aortic that "[s]imply referring to two terms as alternatives ... is not sufficient to redefine a claim term." The Federal Circuit offered that "consistent and clear interchangeable use of two terms" would, however, be sufficient to redefine a term to have a meaning other than its "plain and ordinary meaning" in the case of the Aortic patents.
To avoid the pitfall of having a claim term interpreted differently than a patent drafter intended, it is important to rigorously maintain a clear and consistent singular use and meaning for each term appearing in the claims. A claim term that is defined in a patent to have a single meaning or use – and is used throughout the patent specification for only its defined purpose – will likely be construed to have the meaning intended by the patent drafter. Any interchangeable use of one term with a second term will open the door for an interpretation of the patent language that is different from what the drafter intended. In Aortic, the patent drafter may have benefitted from structuring the terminology into generic (outer frame) and specific (self-expanding frame) embodiments, rather than intermingling the use of the terms. A description of general embodiments of the transcatheter valve assembly having an outer frame could have been followed with separate descriptions of exemplary embodiments where the self-expanding frame is referred to and described.
In addition to the use of a generic and specific terminology scheme – or as an alternative to doing so, when interchangeable use of terms is desired or is unavoidable – broadening statements may be used to defend against an unintended redefinition of patent terms. Broadening statements are used to convey an intent to maintain an enlarged scope, i.e., to encompass a wide range of alternatives or variations, for a particular term. The broadening statement may simply state that a particular term "is not particularly limited;" but saying so without more carries a risk that the broadening statement will be considered to be only vague "boilerplate" language with no broadening effect. A more helpful and less risky broadening statement may explicitly detail a range of alternatives that are encompassed by the term but not intended to be limiting. For example, a statement that Aortic's "outer frame is not particularly limited and may be a rigid fame, semi-rigid frame, ballon-expanding frame, self-expanding frame, or any other suitable frame as understood by a skilled artisan" may have led to a different outcome in Aortic. Such a broadening statement may have led the Federal Circuit to a different claim construction – where Edwards' balloon-expandable frame was encompassed by Aortic's outer frame – and a resulting finding that Edwards infringed Aortic's patents.
Footnote
1 Aortic Innovations LLC v. Edwards Lifesciences Corp., --- F.4th ---, 2025 WL 2999367 (Fed. Cir. Oct. 27, 2025).
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