Surgery – Instruments – Internal pressure applicator
Patent
1993-09-14
1995-05-09
Pellegrino, Stephen C.
Surgery
Instruments
Internal pressure applicator
128899, A61M 2900
Patent
active
054135869
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the field of anti-pulmonary embolism filters.
More precisely, the present invention relates to improvements to the anti-pulmonary embolism filter described in French Patent Applications No. 89 13160 of 9, Oct. 1989 and No. 89 16538 of 14, Dec. 1989 and PCT Patent Application No. PCT/FR90/00721 filed on 9, Oct. 1990.
Various anti-pulmonary embolism filters have already been proposed. Regarding this point, reference may be made for example to documents FR-A-2,616,666, EP-A-121,447, EP-A-323,333 and DE-A-3,203,410.
The anti-pulmonary embolism filters described in the aforementioned documents are not however completely satisfactory.
Document EP-A-323,333 in particular describes a filter made of resilient metal wire with spring effect.
Its particular geometrical shape defines two loops in the shape of ellipses with perpendicular, equal and coplanar axes, giving four points of permanent contact with the wall of the vena cava in which it is implanted.
This latter type of filter has actually been the subject of production and experimentation on animals, and then on man. However, such difficulties of medical nature appeared, both in the procedure for fitting the filter and in its mode of operation once in place, that general use of this filter cannot be recommended medically.
More precisely, a first difficulty resides in that the filter, which initially has the aforementioned shape of double ellipses with perpendicular axes, after its temporary straightening inside the fitting catheter, sometimes risks, when released from the catheter, inside the inferior vena cava, not resuming its initial shape. This drawback results from fairly long quasi-straight parts which connect the quasi-circular parts of the elongate quasi-ellipses. Thus, there are unacceptable risks of the filter returning to the shape of an elongate S or 8, and no longer of crossed ellipses. Bearing against the walls of the vena cava at four balanced points is not obtained and, because of this, the vein is not sufficiently flattened, so that the filter can migrate by moving along the vein after it is fitted.
Furthermore, the planes of these ellipses are quasi-coplanar, and the filter effect is guaranteed only if the four points of bearing of the filter against the wall of the vena cava are in the correct position, which is not yet guaranteed as explained above, on the one hand, and very greatly flatten the vena cava in order greatly to reduce the cross-section of the vein and thus to obtain the filter effect, on the other hand.
Finally, one end of the filter is fitted with a sharp tip which is inclined with respect to the plane of the ellipses and is used as an anchoring point in the vena cava. This sharp tip has two drawbacks: it makes it difficult to introduce it into the catheter, on the one hand, and risks traumatizing or even perforating the wall of the vein, on the other hand.
The filter described in French Patent Applications No. 89 13160 of 9, Oct. 1989 and No. 89 16538 of 14, Dec. 1989, as well as in the corresponding PCT Patent Application No. PCT/FR90/00721 of 9, Oct. 1990, made it possible to improve this situation. This filter comprises a resilient wire with remanent spring effect shaped into a spiral with three non-touching turns, the middle turn of which has a diameter greater than those of the other two turns, the diameter of the middle turn being preferably chosen close to the value of half the circumference of the vena cava in the zone where the filter is to be implanted, in order optimally to ensure the function of holding the filter in place by flattening the vena cava.
The object of the present invention is further to improve the filter of the aforementioned type by improving the filtering effect obtained, whilst allowing both easy fitting and withdrawal of the filter.
This object is achieved according to the present invention by virtue of the structure defined in the attached claim 1.
Other features, objects and advantages of the present invention will emerge on reading the detailed description whic
REFERENCES:
patent: 4994069 (1991-02-01), Ritchart et al.
Cragg, Martin, et al. "Nitinol Spiral Vena Caval Filter". Seminars In Interventional Radiology. vol. 3, No. 3, Sep. 1986.
Catteau Gilles
Dibie Alain
Musset Dominique
Prou Philippe
Ethnor
Lewis William W.
Pellegrino Stephen C.
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