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T 1173/22 – Common general knowledge in patent documents?

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The application relates to a replacement heart valve for use within a human body.

Brief outline of the procedure

The application was refused by the ED for lack of clarity.

The replacement valve is supported by a stent and comprises as well an inner fabric (122) and an outer fabric (126), whereby,

1.4 an outer fabric skirt (126) covering an outer surface of the stent component,

1.4.1 wherein the outer fabric skirt serves as a sealing member between the stent component and the native valve, wherein

1.5.1 the topology of the inner surface of the inner fabric skirt is configured to improve blood flow and

1.5.2 the topology of the outer surface of the outer fabric skirt is configured to improve endothelialization,

1.6 wherein the inner and outer fabric skirt (122, 126) form a double fabric skirt which covers the inflow edge of the stent component (100).

The ED refused the patent application on the basis of Art 84, as feature 1.5.2 “topology […] configured to improve endothelialization” was considered as not being clear.

In particular it was not clear for the ED which topology the surface of the skirt should have to improve endothelialization and how much the endothelialization should be improved.

The Board agreed with the applicant that feature 1.5.2 was clear in the context of a surface of a fabric used for the skirt of a replacement heart valve.

The decision is interesting in that it considers prior art patent documents as illustrating common general knowledge.

Conflicting requirements

On the one hand, where blood flows, the blood flow has to be as less disturbed as possible. To this effect, the inner skirt has to present a topology which is configured to improve blood flow and avoid endothelialization.

On the other hand, the replacement valve has to be anchored so as it can effectively replace the defective natural valve. To this effect, the outer skirt can be sutured to the annulus or be anchored in that endothelialization occurs. Scar tissue is created which allows a stable position of the replacement valve when the replacement valve is introduced by minimal invasive surgery.

Due to endothelialization, ordinary stents can be difficult to remove. Some stents are therefore even eluding material avoiding endothelialization.

The board’s position

The board agreed that, as argued by the appellant, the surface topology can be roughened for improving endothelialization of implants. As an example only, a coarse textile or a textile with a structured surface can be chosen for the fabric to provide a rough surface which promotes formation of scar tissue.

The board found that this is part of the general knowledge of a skilled person in the field of replacement heart valves which is reflected by several prior art patent documents cited in the procedure. :

Document D2=US 2004/106976 cited in the search report of the application in suit describes in paragraph [0021] that “The graft is preferably a biocompatible, fatigue-resistant membrane which is capable of endothelialization, and is attached to the stent body member on at least portions of either or both the lumenal and ablumenal surfaces of the stent body member by suturing to or encapsulating stent struts.”

Additionally D1=US 2007/213813 mentions in paragraph [0028] that for an occluder a “second material may be coarser than the first material. This may facilitate the formation of scar tissue on the outer portion and speed the heeling process.” No further details are given as it is clear for the skilled person what is meant with “coarser” having in mind the materials commonly used.

Furthermore, as disclosed in documents D7=WO 2004/008941, D8=WO 94/02101, D9=US 2002/169359 and D10=US 3,843,974 filed by the applicant during examination proceedings, a woven structure of a fabric skirt or a porous material in general has a surface with a topology that is configured to improve endothelialization.

Therefore, even if feature 1.5.2 is defined in a broad sense, the skilled person has the technical knowledge to identify those surface topologies of a fabric skirt which are configured for improving endothelialization and which are not.

Feature 1.5.1 “wherein the topology of the inner surface of the inner fabric skirt is configured to improve blood flow”, is likewise clear for a skilled person. The capability of improved blood flow is opposite to that of endothelialization, i.. e. the surface of the fabric is designed to be as smooth as possible. This prevents tissue from growing on the surface.


It can be agreed that refusal for lack of clarity was not correct. Features 1.5.1 and 1.5.2 are absolutely clear to a skilled person in the field of stents.

The contradictory requirements requiring a good blood flow on the one hand and requiring an absence of endothelialization, and on the other hand the creation of scar tissue by endothelialization are well known requirements and could be found in any standard book on stents.

The insistence upon the lack of clarity shows a lack of fundamental knowledge of the members of the ED.

What is however surprising is that the board and the applicant needed to resort to patent documents in order to define common general knowledge.

Common general knowledge is in principle to be found in standard books and reference works, see T 1641/11, T 263/12 and not in patent documents.

Patent literature is not representative of common general knowledge, cf. T 1819/14, T 263/12 or T 1540/14.

This also applies to specialized journals, cf. T 1997/11 or scientific papers, cf. T 1651/13.

A doctoral thesis is also not representative of common general knowledge, cf. T 1832/14.

Let’s hope that this decision will remain a one off as it clearly goes against existing case law.

The board should at least have respected Art 20 RPBA.

The present board (3.2.01), and its chairman in the present case, are alas accustomed to this kind of behaviour.

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