Patent Description:
Pulmonary embolism (PE) is a common disease, causing a high mortality rate. According to a statistical data, a mortality rate caused by untreated pulmonary embolism is <NUM> to <NUM> percent. Every year, new cases are about <NUM> percent of the population. There are <NUM>,<NUM>,<NUM> new cases according to the population of <NUM> billion of China.

Various exfoliated emboli in systemic circulation may cause the pulmonary embolism. Thrombi are the most common pulmonary emboli. There are various factors in the formation of thrombosis, including slow venous blood flow and blood stasis, blood stasis, or increase of thrombocyte and blood coagulation factors and enhancement of blood adherence which may all caused by traumatism or bone fracture, trauma, relatively big surgery, extensive burn, gestation, childbirth, being confined to bed by long illness, sedentariness in a long-distance bus or a flight, long-time sitting still and squatting and the like. These thrombi are generally slightly adhered to a lumen wall and are prone to fall off, and dropped emboli may cause severe lesions such as the pulmonary embolism. A venous thrombus may be formed in any part, most commonly in the lower limb.

It has been clinically proven that a vena cava filter (hereinafter referred to as "filter") is a safe and effective measure for preventing pulmonary embolism and may reduce a incidence rate of pulmonary embolism. However, after the filter has been implanted into an inferior vena cava for a certain time, a filter supporting rod would be climbed and covered by endothelial cells to varying degrees because of stimulation to a blood vessel, so the filter is difficult to take out, and then may only be implanted as a permanent filter for a long time in the human body. And the permanent filter implanted into the human body may cause certain risks. For example: the filter is in contact with blood and blood vessel endothelium for a long time, which probably leads to protein adsorption and platelet adhesion and eventually causes thrombosis, and the thrombosis will result in venous blockage or recurrence of pulmonary embolism; and there is a risk that the filter implanted for a long time in the human body may deform, tilt, shift, break or even penetrate the blood vessel, and the like.

At present, there are mainly two solutions in the industry to solve the problem that the filter is not easy to be removed from the human body. One solution is to form a coating layer for preventing cell growth on the surface of the filter through a surface modification method, so as to prevent an endangium from climbing over the surface of the filter. The other solution is a method of structural design, by which the filter has two closed ends and open supporting rods abutting with the blood vessel wall to separate the filter from the blood vessel wall.

The Chinese patent No. <CIT> is a typical example of the first solution, which uses the surface modification method to deposit a polyethylene glycol-like thin film on the surface of the filter and makes use of anti-protein and cell adhesion characteristics of polyethylene glycol to inhibit the cell growth on the surface of the filter and prevent endothelial cells from covering the supporting rods, so as to achieve a withdrawability of the filter. However, a film layer prepared by the solution may only prevent the cell growth within a period of time because of its water solubility, so that there is a stringent requirement for selection of the removal time.

For the second solution, as the filter is compressed in a sheath before being put into the blood vessel, and after the sheath delivers the filter to a required position and releases it, the filter would spread in the blood vessel to expand the blood vessel wall. When the filter contracts or spreads, the open supporting rods may be probably twisted with one another, which leads to a failure of successful spreading of the filter in the blood vessel and reduces the usability of the filter and results in impossibility to successfully perform a surgery. Furthermore, there is a risk that the tail end of each open supporting rod punctures through the blood vessel wall, so that the incidence rate of postoperative complications is increased.

Therefore, how to guarantee reliable fixing of the vena cava filter, high thrombus filter efficiency, low blood vessel puncture risk, minimized endothelium climbing over and the withdrawability is an urgent problem to be solved.

The present disclosure provides a vena cava filter which would not puncture through a blood vessel wall or cause twisting and has a higher usability, so as to overcome the defects in the prior art.

The technical solution adopted by the present disclosure is as follows: a filter, including a proximal end, a distal end and a filter main body connected between the proximal end and the distal end. The filter main body includes a first filter unit and a second filter unit which are both of conical mesh structures, and a plurality of middle connecting rods for connecting the first filter unit with the second filter unit. A supporting rod is arranged on the middle supporting rod. The supporting rod includes a transition section extending from the middle connecting rod towards a direction far away from the axis of the filter, and a supporting section bending from the transition section towards a direction close to the axis of the filter and extending towards the distal end.

The supporting section includes a body bending and extending from a tail end of the transition section, and a flexible section connected with the body. The rigidity of the flexible section is less than that of the body.

In one embodiment of the present disclosure, the radial size of at least one part of the flexible section in a lengthwise direction of the flexible section is less than that of the body.

In one embodiment of the present disclosure, a cross section of the flexible section along the lengthwise direction of the flexible section has an upper contour line and a lower contour line opposite to the upper contour line in a spacing manner, and the upper contour line and the lower contour line get close to each other along an extending direction of the flexible section.

In one embodiment of the present disclosure, a cross section of the flexible section along the lengthwise direction of the flexible section has an upper contour line and a lower contour line opposite to the upper contour line in a spacing manner, and both the upper contour line and the lower contour line are wavy lines.

In one embodiment of the present disclosure, a wave crest of the upper contour line is opposite to a wave crest of the lower contour line, and a wave trough of the upper contour line is opposite to a wave trough of the lower contour line.

In one embodiment of the present disclosure, a wave crest of the upper contour line is opposite to a wave trough of the lower contour line.

In one embodiment of the present disclosure, the radial size of the flexible section along a lengthwise direction of the flexible section is equal, and is less than the radial size of the body.

In one embodiment of the present disclosure, the flexible section is made of a flexible material.

In one embodiment of the present disclosure, an included angle between the body and the middle connecting rod is less than <NUM> degrees.

In one embodiment of the present disclosure, an included angle between the flexible section and the body is obtuse angle, and the flexible section and the body are in smooth transition.

In one embodiment of the present disclosure, each supporting section further includes a protruding portion that has a smooth outer contour and arranges at the tail end of the flexible section, and the protruding portion and the flexible section are in smooth transition.

In one embodiment of the present disclosure, supporting rods on two adjacent middle connecting rods are in staggered distribution.

The tails of the supporting rods of the filter of the present disclosure are provided with the flexible sections and the protruding portions having the smooth outer contours, and the parts, transitioned to the flexible sections, of the outer contours of the protruding portions are in smooth transition, so this structural design reduces the risk that the supporting sections puncture through a blood vessel wall, and avoids postoperative complications caused by the fact that the supporting sections puncture through the blood vessel wall, and solves the problem of mutual twisting of the open supporting rods during contracting or spreading of the filter, and improves the availability of the filter and guarantees a surgical success.

The present disclosure will be further described below in combination with accompanying drawings and embodiments. In the drawings:.

To understand technical features, objectives and effects of the present disclosure more clearly, specific implementation modes of the present disclosure are described in detail now in combination with the accompanying drawings.

As shown in <FIG>, a filter <NUM> includes a distal end <NUM>, a proximal end <NUM> and a filter main body connected between the distal end <NUM> and the proximal end <NUM>. The filter main body includes a first filter unit <NUM>, a second filter unit <NUM> and multiple middle connecting rods <NUM> for connecting the first filter unit <NUM> with the second filter unit <NUM>. The multiple middle connecting rods <NUM> are uniformly distributed around a connecting line between the distal end <NUM> and the proximal end <NUM> in a spacing manner. The first filter unit <NUM> is of a conical mesh structure and formed by gathering multiple Y-shaped filter mesh rods <NUM> at the distal end <NUM>, and the second filter unit <NUM> is of a conical mesh structure and also formed by gathering multiple Y-shaped filter mesh rods <NUM> at the proximal end <NUM>. Furthermore, the number of the Y-shaped filter mesh rods <NUM> of the first filter unit <NUM> is half than that of the Y-shaped filter mesh rods <NUM> of the second filter unit <NUM>, so that the filter <NUM> is of an overall asymmetric structure. This asymmetric structure is selective for thrombi to be filtered, that is, the filter only filters the thrombi causing pulmonary embolism, so as to guarantee long-term patency of a vena cava. Meanwhile, the distal end <NUM> of the filter is also provided with a withdrawing hook (not marked) connected with a catcher when recycling a temporary filter.

Supporting rods <NUM> abutting with the blood vessel wall are also arranged on the middle connecting rods <NUM> to enable the middle connecting rods <NUM> to get far away from the blood vessel wall, so as to prevent a problem of short recovery window caused by the adhesion of the endangium to the surface of the filter. The supporting rods <NUM> include transition sections <NUM> extending from the middle connecting rods <NUM> towards a direction far away from the axis of the filter <NUM>, and supporting sections extending from the transition sections <NUM> towards the proximal end. At least part of the supporting sections are used for replacing the connecting rods <NUM> to abut with the blood vessel wall. Fixing anchors <NUM> for puncturing into the blood vessel wall are also arranged on some of the supporting rods <NUM>. The fixing anchors <NUM> may enable the filter to be fixed more stably in the blood vessel.

Furthermore, in the present embodiment, only one supporting rod <NUM> is arranged on one middle connecting rod <NUM>, and the positions of the supporting rods <NUM> on adjacent middle connecting rods <NUM> are different, and the supporting rods are arranged in a staggered manner, so that the supporting rods may provide a more uniform and stabler supporting force for the filter, and it is able to prevent thrombus filtration effect of the filter from weakening due to inclination and displacement of the filter in the blood vessel, and the risk of postoperative pulmonary embolism may increase after surgery. In other possible embodiments, two or more supporting rods also may be arranged on each middle connecting rod. These supporting rods may be fixed at any position on the middle connecting rod as long as a direction of an opening defined by the transition sections and the supporting sections of the supporting rods are opposite to a direction in which the filter is removed. As shown in <FIG>, each supporting section includes a body <NUM> bending and extending from the tail end of each transition section <NUM> and abutting with the blood vessel wall, a flexible section <NUM> extending from the body <NUM> towards the proximal end, and a protruding portion <NUM> arranged at the tail end of the flexible section <NUM> and having a smooth outer contour. The protruding portion <NUM> and the flexible section <NUM> as well as the body <NUM> and the flexible section <NUM> are in smooth transition. The smooth transition mentioned in the present disclosure means that a joint of two elements is in arc transition or chamfering transition. The rigidity of the flexible section <NUM> is less than that of the body <NUM>. There are various implementing methods to make the rigidity of the flexible section <NUM> less than that of the body <NUM>. In the present embodiment, the implementing method is to make the radial size of at least part of the flexible section <NUM> in a lengthwise direction less than that of the body <NUM>. Through reducing the radial size, the flexibility of this part of the supporting section may be improved, so that it is able to prevent the supporting section from puncturing through the blood vessel wall when the supporting section abuts with the blood vessel wall. In other implementation modes, the flexible section <NUM> also may be made of a flexible material, such as silica gel.

Further, an included angle between the body <NUM> and the middle connecting rod <NUM> is less than <NUM> degrees. It can be predicted that in case that the included angle between the body <NUM> and the middle connecting rod <NUM> is equal to <NUM> degrees, when the filter spreads in the blood vessel, the body <NUM> would point to the blood vessel wall, which undoubtedly increases the risk that the supporting section punctures through the blood vessel wall. In case that the included angle between the body <NUM> and the middle connecting rod <NUM> is more than <NUM> degrees, for example, when the body <NUM> and the transition section <NUM> are located on the same straight line, the body <NUM> still points to the blood vessel wall and is unable to support the blood vessel wall. In the present embodiment, the flexible section <NUM> and the body <NUM> define an obtuse angle or are located on the same straight line, but the flexible section <NUM> and the body <NUM> shall not define an acute angle, and reasons are as mentioned above.

The part, having the radial size less than that of the body <NUM>, of the flexible section <NUM> may be defined by means of stripping, and the flexible section <NUM> may have different shapes. Specific descriptions are made below through several specific embodiments.

As shown in <FIG>, the cross section of each flexible section <NUM> along the lengthwise direction of the flexible section <NUM> has an upper contour line 63a and a lower contour line 63b opposite to the upper contour line 63a in a spacing manner, and the upper contour line 63a and the lower contour line 63b gradually get close to each other along an extending direction of the flexible section <NUM>. That is to say, the radial size of the flexible section <NUM> is gradually reduced in its extending direction. The flexible section <NUM> and the body <NUM> are in arc transition. The tail end of the flexible section <NUM> is provided with a protruding portion <NUM> of a quadrangular cross-section shape. The four side edges of the cross section of the protruding portion <NUM> are all in smooth transition, and the protruding portion <NUM> and the flexible section <NUM> are also in arc transition. The protruding portion <NUM> may have a smooth outer contour by a mechanical method such as mechanical sand blasting and polishing, or by chemical method or by argon arc welding. The protruding portion <NUM> added at the tail end of the flexible section <NUM> can further reduce the risk that the supporting section punctures through the blood vessel wall.

As shown in <FIG>, the cross section of each flexible section <NUM> along the lengthwise direction of the flexible section <NUM> has an upper contour line 63c and a lower contour line 63d opposite to the upper contour line 63c in a spacing manner. In the present embodiment, the lower contour line 63d and the contour line of the body <NUM> are located on the same straight line. The upper contour line 63c gets close to the lower contour line 63d along the extending direction of the flexible section <NUM>, and the radial size of the whole flexible section <NUM> is equal. In addition, the upper contour line 63c of the flexible section <NUM> and the outer contour of the body <NUM> are in chamfering transition. From the appearance, the flexible section <NUM> is a section of sunken groove formed in the tail section of the supporting section by means of stripping. It can be understood that the flexible section <NUM> also may be two sections of grooves formed in the upper and lower sides of the tail section of the supporting section by means of stripping, and has an equal radial size along its extending direction. In the present embodiment, the cross section of the protruding portion <NUM> arranged at the tail end of the flexible section <NUM> is of an approximately track shape, and the protruding portion <NUM> and the upper contour line 63c of the flexible section <NUM> are in chamfering transition.

As shown in <FIG>, the cross section of the flexible section <NUM> along the lengthwise direction of the flexible section <NUM> has an upper contour line 63e and a lower contour line 63f opposite to the upper contour line 63e in a spacing manner, and the upper contour line 63e and the lower contour line 63f are both wavy lines. The wave crests of the upper contour line 63e are opposite to the wave crests of the lower contour lines 63f, and the wave troughs of the upper contour line 63e are opposite to the wave troughs of the lower contour lines 63f. In the present embodiment, the cross section of the protruding portion <NUM> arranged at the tail end of the flexible section <NUM> is of a water drop shape, and the protruding portion <NUM> and the flexible section <NUM> are in arc transition. The flexible section <NUM> and the body <NUM> are in arc transition.

As shown in <FIG>, as in the previous embodiments, the cross section of the flexible section <NUM> along the lengthwise direction of the flexible section <NUM> has an upper contour line 63e' and a lower contour line 63f opposite to the upper contour line <NUM> e' in a spacing manner, and the upper contour line 63e' and the lower contour line 63f are both wavy lines. But in the present embodiment, the wave crests of the upper contour line 63e' are opposite to the wave troughs of the lower contour lines 63f, and the wave troughs of the upper contour line 63e' are opposite to the wave crests of the lower contour lines 63f. In the present embodiment, the cross section of the protruding portion <NUM> arranged at the tail end of the flexible section <NUM> is circular, and the protruding portion <NUM> and the flexible section <NUM> are in arc transition. The flexible section <NUM> and the body <NUM> are in arc transition.

In all the above-mentioned embodiments, the protruding portion <NUM> may be of any shape. For example, the protruding portion may be elliptical as long as its outer contour is treated to be smooth to avoid the risk of puncturing through the blood vessel wall. Furthermore, when multiple supporting rods <NUM> are arranged on each middle connecting rod <NUM>, the protruding portions <NUM> may be selectively arranged at the tail ends of the flexible sections <NUM>.

Claim 1:
A filter, comprising a proximal end, a distal end and a filter main body connected between the proximal end and the distal end, the filter main body comprises a first filter unit and a second filter unit which are both of conical mesh structures, and a plurality of middle connecting rods for connecting the first filter unit with the second filter unit; a supporting rod is arranged on the middle supporting rod; wherein the supporting rod comprises a transition section extending from the middle connecting rod towards a direction far away from the axis of the filter, and a supporting section bending from the transition section towards a direction close to the axis of the filter and extending towards the proximal end; the supporting section comprises a body bending and extending from a tail end of the transition section, and a flexible section connected with the body; and the rigidity of the flexible section is less than that of the body.