Catheter for Recanalizing Constricted Vessels

The invention relates to a dilatation catheter for treating a constricted blood vessel. Dilatation catheters have been employed for some time in the treatment of vascular obstructions generally known as angioplasty. Such catheters have an elongated tubular body with a balloon at the distal end that is inflatable and deflatable under fluid pressure. A guide wire is typically first inserted within the vessel to the location of the constriction. The catheter is then inserted (with the balloon deflated) over the guide wire with the balloon positioned at the location of the constriction. By way of an externally accessible internal lumen leading through the support tube, the balloon is filled with fluid, so that it expands causing the occluding tissue to be pressed outwardly into the vessel wall.

A disadvantage of the angioplasty procedure is that the treatment of severe constrictions takes a comparatively long time and can require periodic interruption in order to avoid distal ischemia. It has also been found that the treatment is sometimes unsuccessful because the occluding tissue is not removed but merely pressed to the wall of the vessel and restenosis can eventually occur. The success of such a treatment can be improved if a substance that will dissolve the impairing tissue, as for example a plasminogen activator, is introduced into the vessel to be treated.

It is an object of the present invention to provide a dilatation catheter in which vascular constrictions can be treated with a suitable therapeutic (tissue dissolving) fluid resulting in greater long-term success.

This object is achieved by the present invention in which a catheter for treating an occluded blood vessel comprises an elongated tubular body having an internal lumen, a proximal portion and a distal portion, and includes an inflatable dilatation element on the distal portion thereof. The dilatation element is in communication with the lumen and is adapted to be inflatable and deflatable by the application of a suitable tissue dissolving fluid pressurized within the lumen. The dilatation element includes a wall having microporus openings adapted to be permeable by the fluid applied to inflate the dilatation element. The fluid, which is pumped into the interior space of the dilatation element, under sufficient pressure, presses through the microporus wall directly on and into the adjacent tissue. The fluid tends to dissolve the tissue, thereby treatment time is considerably shortened and the long-term success of the treatment is improved, since the impairing tissue is not only dislodged but also dissolved from the vessel. The fluid has a rapid and focused effect because it is brought directly to the action site and thereby requires only a minimal quantity of the therapeutic fluid.

The invention will be better understood from the following detailed description taken in conjunction with the drawing.

FIG. 1 shows a longitudinal section of the catheter of the present invention in the distended state;

FIG. 1a is a sectional view taken along the line I--I of FIG. 1;

FIG. 2 shows a longitudinal section of a blood vessel having the catheter of FIG. 1 inserted therein; and

FIG. 3 is a sectional view taken along the line III--III of FIG. 2.

Referring to the figures, the catheter of the present invention is illustrated, by an example, in which an elongated tubular body 3 has a dilatation balloon 1 attached to the distal end thereof. The interior of the dilatation balloon is in communication with an internal lumen 4 through an opening 9 of a connecting piece 6. The lumen 4 is accessible at the proximal portion of the body to inflate and deflate the balloon with a suitable fluid respectively by a typical suction and pressure pump (not shown).

The dilatation balloon 1 is deflated into a compressed or folded state for the purpose of introduction into a blood vessel. For such introduction of the dilatation balloon 1, a stenosed section of vessel (see FIG. 3) is first probed utilizing a well-known technique by a guide wire 2 and the catheter and the dilatation balloon 1 is then inserted onto the guide wire 2 and extended to the section of vessel to be dilated. Radiopaque marking elements 8 are mounted on a tubing piece 7 and are clearly visible on x-ray to facilitate the proper location of the balloon.

When the dilatation balloon 1 is in the desired location of the vessel, it is filled with a suitable therapeutic fluid 13 under controlled pressure by means of a pressure pump, until it assumes the cylindrical shape. The dilatation balloon 1 is designed so that after reaching a determined shape, it will not assume a larger diameter even when considerably greater pressure is exerted. This prevents the vessel from being inadvertently excessively distended and damaged.

The dilatation balloon 1 is formed for example, of polyvinyl chloride and has, a cylindrical wall 5 provided with microporus openings 12. The openings 12 are preferably arranged evenly in the radial and longitudinal surface so that in the dilated state, the fluid 13 presses uniformly radially outwardly through the wall 5. The openings 12 have a comparatively small diameter, for example 0.05 mm, so that the wall 5 is microporus yet permeable to the fluid 13.

In FIGS. 2 and 3, the obstructions is schematically illustrated as a tissue 11 forming a stenosis in vessel 10. In the dilated state, the outer surface of the wall 5 lies adjacent to the tissue 11 and the fluid 13 is forced into the tissue 11 through the openings 12. The fluid 13 is thus delivered directly to the tissue 11.

The openings 12 are uniformly distributed on the wall 5 at approximately the same intervals, in order to ensure a suitably uniform and distributed delivery of the fluid 13 to the tissue 11.

The fluid 13 contains a suitable therapeutic agent and contrast medium. In the case of treatment of a occlusion the therapeutic agent is specifically a drug which dissolves the tissue 11. Such drugs are known for example as lytic agents such as plasminogen activator; although substances other than lytic agents can also be effective. During treatment the vasoconstrictive tissue 11 is pressed onto the vascular wall 10 and simultaneously a specified amount of the therapeutic fluid is introduced under pressure directly into the tissue 11. The constricting tissue 11 can thus be eliminated in a fast and gentle manner.