AU687410B2 - Device for detaching sclerotic plaques by means of ultrasound and treatment set with such a device - Google Patents

Abstract

An apparatus, provided with an ultrasound transmitter connectable to an ultrasound generator (17), for detaching atherosclerotic plaque by means of ultrasonic vibrations, comprises a probe (7; 8) fastened on a handle (1). The probe (7; 8) comprises an essentially transversally oscillating working part and an essentially longitudinally oscillating transmission part. The transmission part is completely enclosed by a tube carrying liquid which serves to wet the working part of the probe (7; 8), a channel being provided in the handle (1) for supply of liquid into the tube. The tube is made of a material whose coefficient of friction is negligible relative to the liquid, and there are means for wetting the working part with liquid on all sides. <IMAGE>

Description

Device for Detaching Sclerotic Plaques by Means of Ultrasound and Treatment Set with Such a Device The invention relates to a system for detaching sclerotic plaque and to a treatment set comprising such a system.

The removal of arterial obturations or occlusions resulting from the development of atherosclerotic plaques with the aid of ultrasound is one of a plurality of conventional procedures.

Classical endarterectomy, in which the thrombus situated at the site of arterial occlusion and the inner arterial wall adhering thereto, the intima, and, if necesssary, also the media are removed, is carried out either as so-called "open endarterectomy" with lengthwise opening of the artery or as so-called "semi-open endarterectomy" starting from two cross sections of the artery, making use of so-called ring strippers.

Though open endarterectomy has the advantage that removal of the thrombus can be 1: 15 inspected visually, the sutures of the restored artery are a possible cause of stenoses. In semi-open endarterectomy, by contrast, the problem is that especially in the case of S long obstructions mechanical removal by means of a stripper often results in irregular arterial inner-wall surfaces. But if the media are removed only partially, or if it is injured, postoperative hyperplasias are often the consequence.

In angioplasty, occluded arteries are expanded with the aid of a balloon-tipped catheter. But this procedure, which is often carried out as a preparatory or additional measure to angioplasty, is always traumatising to some extent. Secondary stenoses due to miointimal hyperplasias are the consequence.

Plaques of relatively small extension are removed also with the aid of lasers; S: 25 there is the risk of thermal irritation or injury of the inner wall of vessels, even vessel perforations are possible.

The use of ultrasound for removing atherosclerotic plaques has been proposed too, for example in US Patent 3,565,062 which describes a hollow vibrating probe, with an associated slotted catheter taking in plaque strips cut from the vessel's inner wall. US Patent 3,526,219 describes the removal of tissue portions, with the ultrasound energy being used to comminute the tissue into extremely small particles ("micro chopping") which can be sucked IN ll i [fl n DMB -2off. In both cases as noted already in US Patent 4,870,953 in regard to the procedure described in US Patent 3,526,219 traumatising effects on the media may occur, on the one hand, and, on the other hand, the real size of the occlusions removed is uncertain.

US Patent 4,962,755 describes a procedure in which a short, bent ultrasound probe is inserted into an incision in the artery. Fluid is admitted to the vibrating active part of the probe via a small rigid tube extending parallel to the probe. Since the vibrating active part is situated between the detached plaque or the media and the adventitia, on the one hand, and since the tube with the fluid is not pushed in upon further insertion into the artery, on the other hand, wetting of the vibrating active part takes place on one side only and is conditional. Thus, after loosening the plaque from an incision made at the centre of the occlusion or from a distal and a proximal incision, removal of the plaque by means of a forceps is necessary. Obviously, such a procedure can be carried out only on occlusions of very small area since otherwise upon removal of the possibly only partly detached plaque by means of the forceps, tearing the plaque from the media or rupture and, hence, only incomplete removal of the plaque, may be the consequence. Traumatising the media cannot be ruled out.

Furthermore, there the problem of perfect dissection of the "end point" is not solved. This problem, which as early as in classical endarterectomy could not be resolved in satisfactory fashion, originates from the fact that the transition region between the treated inner wall of the artery and the artery's inner wall section in which untreated intima and media remain, must be homogeneous and uniform since otherwise this might be one of the possible causes for postoperative thromboses.

Austrian Patent 340,572 describes ultrasound probes which are designated for the removal of both small-area and extended plaques. In the short, bent probe, which is similar to that described in US Patent 4,962,755, the fluid as one of two alternatives described is admitted via a channel inside the probe to the vibrating active part through exit openings provided at the transition point to the bent portion. Since the active part performs transverse vibrations, the fluid will not pass to the tip of the active part but will spatter before the same. Even in the case of the long probe, which is configured as a ring stripper, the fluid again as one of two alternatives 6 81z/jrb is admitted to the ring performing transverse vibrations via a channel provided inside the probe. Apart from the fact that wetting of the ring is again inadequate, the effectiveness of the long probe will be continually reduced during its insertion into the interior of the artery because the long rod, which supports the ring performing transverse vibrations and has an internal channel, moves forward within the narrow gap space between adventitia and detached plaque or detached media. In this way a pressure, which results in a significant decrease in the probe's effectiveness, is exterted by the vessel's inner wall and the detached layers upon the rod performing longitudinal vibrations. Finally, since nodes are formed, no transverse vibrations of the ring can develop.

In view of this, the problem underlying the invention is to provide a system which facilitates the detachment of sclerotic plaques and media regardless of the degree of atherosclerotic affection of the same while the artery remains closed except for a small incision, with traumatising effects on the remainder of the vessel wall being at 15 least substantially avoided.

There is disclosed herein a system for detaching atherosclerotic plaques by means of ultrasound vibrations by detaching the media from the adventitia, comprising an ultrasound transducer adapted to be connected to an ultrasound generator, a handle, a probe adapted to be attached to said handle, with the probe having an active part and a transmission portion and with a small tube completely enclosing the transmission portion for supplying fluid which serves to wet the active part of the probe, wherein, for the purpose of supplying the fluid to the small tube on, or in, the handle there is provided a channel characterised in that the small tube is made from a material with low friction properties, that the small tube completely encloses the transmission portion, and that there are provided means for wetting the active part on all sides with fluid.

Since there are provided means facilitating wetting with fluid the entire surface of the active part which, in general, is put into transverse vibrations, with the fluid admitted via the small tube fully enclosing the transmission portion which is put into substantially longitudinal vibrations, the probe's effectiveness defined basically by the presence of cavitation is improved in the complete detachment of the media (and the plaque) from the adventitia. Furthermore, since the small tube enclosing the transmission portion is made from a material with low friction properties, it is possible to protect the transmission portion from energy losses which would originate particularly in the case of direct contact with the artery's inner wall since negative feedback to the transmission portion and, hence, the active part of the probe by transmission of vibrations or the development of vibration nodes does not occur.

'Cu IN 'IlIt tIt10658 DM1 -4- Access to the interior of the artery becomes easier if the active part of the probe is bent relative to the longitudinal axis of the transmission portion, with the specific form of the active part depending upon the required treatment, like type and lumen of the artery and extension of the plaque.

A spatula.-shaped active part appears suitable for detaching small-area plaques, and this may be effected from two incisions made into the artery i'i distal and proximal positions. An active part configured in this way is used also for dissecting the distal point, the so-called "end point," at which the media is detached from the adventitia, whereafter a differently shaped probe can be introduced into the artery through the little incision. Such a probe, the active part of which is configured as a ring whereas its transmission portion is configured as a long, thin rod in the form of the ring stripper known from classical- semi-open endarterectomy proved to be advantageous for removing extended obliterated regions, in the femoral artery.

As described above, similar forms of such probes are known for use in classical endarterectomy and also in the case of probes working with ultrasound. But traumatic influences, as well as incomplete removal of the atherosclerotically affected media cannot be ruled out in both the classical enarterectomy and the detachment of plaque with the aid of ultrasound by means of a probe of the type described in Austrian Patent 340,572.

In comparison, the probe according to the invention is distinguished by the fact (it is operated on relatively low frequencies around 30 kHz) that it facilitates unclogging the obstructed region over the entire length of the artery with gentle, non traumatising yet complete detachment of the media from the adventitia because even when the probe was pushed far into the artery, the annular active part vibrates with substantially unchanged energy and frequency and, at the same time, is wetted uniformly with fluid over its entire annular surface.

The transmission portion of a such a probe, termed annular probe in what follows, is formed preferably by a thin steel rod having a diameter of about 1 mm and a length of up to 60 cm and more so that guiding without drag is possible even in the case of slightly curved arteries. The small tube, which is the duct of the fluid and encloses the transmission portion, is moulded preferably from a dimensionally stable plastic which is flexible over its length, with polytetrafluoroethylene (PTFE) being particularly appealing 981z/jrb 5 because of its excellent non-adhesive properties. In this way both improved sliding of the probe in the gap space between the detached media and adventitia and inert response to vibrations which might be transmitted via the fluid are achieved.

For the annular active part of the annular probe to be wetted with fluid over its entire annular surface, the fluid is discharged through an annular opening which, optionally, is given by the diameter of the small tube proper.

Since the fluid exits under pressure from this opening, it is distributed over the vibrating ring on both sides of the point of application between the ring and the transmission portion.

The probe with the spatula-shaped active part, termed spatula probe in what follows, in principle can be designed like the annular probe as far as the transmission portion and the small tube for admitting the fluid are concerned. But since this probe in general will be used to treat a region adjacent to the incision into the artery, where only the working part is slid into the artery, less attention need be paid to the problem of the tube ,aterial's ability to slide and to its rigidity and flexibility. For example, even a material such as PVC appears suitable, the material being workable in a simpler and less expensive way while similar advantageous features in regard to avoiding energy losses are preserved.

Although configuring the active part as a spatula is preferred since with it the guiding between the detached media and adventitia is simplified, other configurations can be contemplated, too, for example rod-like or fillister head-shaped. The small tube admitting the fluid may completely enclose the spatula-shaped active part at the transition to the transmission portion, and this will appear convenient especially if it is made from a relatively soft material. Then for discharging the fluid there should be provided at least two openings arranged on both sides of the spatula so that the fluid, which exits under a certain pressure, is distributed over the entire surface of the active part. Similarly, there may be provided a plurality of openings, in any case distributed symmetrically around the circumference of the active part which may be configured in some way.

A treatment set, which facilitates rapid, treatment-specific interchange of the probes during a procedure, will advantageously simplify and optimise the execution of the procedure.

981z/jrb -6- In what follows, the invention is described by examples with reference to a drawing. There show: Figure 1, an ultrasound generator to which two systems for detaching atherosclerotic plaque are connected; Figure 2, a probe suitable for introduction into the interior of an artery; Figure 3, a probe suitable for detaching small-area plaques; Figure 3a, the probe of Figure 3, viewed under a different angle; Figures 4a successive steps in the detachment of an elongated occlusion to 41 in the femoral artery; and Figure 5, an embodiment with a bypass of the fluid channel.

Figure 1 shows an ultrasound generator 17 having two sockets 18, 19 to which two systems according to the invention for detaching atherosclerotic plaques are connected via cables 23. At their respective handles 1 the two systems have probes 7 and 8, respectively, of different form, as can be more readily recognised in Figures 2 and 3 and 3a, respectively, with the specific application described with reference to Figures 4a to 41. In the handles 1 there are provided piezoelectric ultrasound transducers which are excited by the output signals of the generator with the appropriate frequency and power.

Sterile fluid is passed from a vessel 20 by means of a peristaltic pump 21 via a line 22 to the fluid channels 2 provided in the respective handles I of the two systems (Figures 2 and A spindle valve 24 is provided for admitting the fluid to the probe which is being utilised. Fluid lines and lines 23 have common sections.

The particular system to be operated can be selectJ by a pedal switch and admission of the fluid can be initiated by energising the pump 21.

A display 26 shows all the required data such as the system selected, the ultrasound frequency or the duration of the procedure.

Figure 2 illustrates the probe 8 which is suitable for insertion into an incision made in an artery. Such a probe 8 is termed an annular probe in what follows because a ring-shaped so-called active part 4 is attached to a long, rod-shaped transmission portion 6 under a small angle relative to the longitudinal axis 13 of the transmission portion 6. The transmission portion 6 is attached to handle 1 which includes the ultrasound transducer and has in its interior the channel 2 for the sterile fluid forced out of it through an 981z/ jrb -7 opening 27 into the interior of a volume delimited by a small tube 10 enclosing the transmission portion 6.

As can be inferred from Figure 5, the fluid-supplying channel 2a alternatively can be arranged so that it forms a bypass line to the ultrasound transducer 60 P+ the handle. The fluid admitted via the fluid line 23 is passed througi bypass channel 2a to the small tube 10 enclosing the transmission portion 6. As an additional feature, this configuration can prevent possible attenuation of the ultrasonic energy made available via the ultrasound transducer The small tube 10 is made from an intrinsically strong plastic, preferably PTFE, which is flexible in the longitudinal direction of the probe and, in addition to those properties, has particularly good low-friction features. This will become obvious by the mode of operation described with reference to Figures 4a to 41.

The small tube 10 is open at the end facing the active part 4 so that the fluid which is forced by the pump 21 (Figure 1) into the channel 2 exits from this circular opening 15 under a given pressure and, hence, wets all sides of the annular active part. The active part 4 performs basically transverse vibrations; cavities develop by cavitation in the fluid, and pressures of 2 to 3 atm develop upon collapse of these cavities and act upon the surrounding material. Depending upon the internal arterial diameter, the ring diameters of such annular probes 8 will vary.

Figures 3 and 3a show a short probe 7 which is suitable for the removal of small-area plaques and specifically for the dissection of the so-called "end point" or "proximal point." The active part 3 of this probe 7 is spatulashaped; a section of the transmission portion 6 is bent relative to the axis 14 defined by the common axis of the handle 1 and the adjacent transmission portion. The transmission portion 5 is fully enclosed by a small tube 9 which is the conduit of the fluid. As in the case of the annular probe 8 (Figure the fluid is forced by the pump 21 (Figure 1) via the channel 2 in the handle 1 through the opening 27 into the gap between the small tube 9 and the transmission portion 5. The spatula-shaped active part 3 is exposed and protrudes from the tube 9 which bears firmly against the probe 7 in this transition region from the active part 3 to the transmission portion 5. On 98.1zljrb -8both sides of the spatula-shaped active part 3 there are provided two openings 16 (detail A of Figure 3a) through which fluid unde, pressure is forced onto the active part 3 so that even when the active part is vibrating the fluid cannot be sprayed off directly near the opening(s) (as, for example, in Austrian Patent A 340,572); the active part is rather uniformly wetted on all sides.

If necessary, the design of such a short probe may be different, depending upon the required application. The transmission portion may be rectilinear as in the case of the annular probe, and the active part can be, for example, rod-shaped or fillister head-shaped. Type and number of fluid exit openings in the small tube will have to be chosei accordingly. It is important that trhe openings are arranged substantially symmetrically around the circumference if the active part.

The small tube of the so-called spatula probe 7, which, in general, is not introduced into the interior of an artery or of which only the active part 3 is introduced (see Figures 4a to 41), is made from plastics, with, for example, PVC being attractive because of its advantageous features, as indicated above.

The system according to the invention can be used for disobliterations [complete removal of occlusions] in greatly dissimilar vessels, either in coronar scleroses or the artherosclerosis of the entry portion of the subclavicular artery. The use of the system according to the invention is described via the disobliteration of a peripheral vessel, namely the femoral artery 31 which may have extended atherosclerotic obliterations with reference to Figures 4a to 41. The technique of detaching sclerotic plaque by means of the system according to the invention proves to be particulary successful since the procedure can be carried out on a closed artery and traumatising effects on the remaining vessel wall can be precluded.

After having established the extension of the plaque obliterations 38 in the femoral artery 31, for example by x-ray radiography (Figure 4a), the artery 31 is exposed in the region of the so-called "end point" 32 and an incision is made. This incision 12 has a length of about 1 to 1.5 cm. In order to minimise the risk of postoperative thromboses, the "end point" 32 must be prepared in such a way that the transition from treated to untreated inner arterial wall is smooth, without salient tissue scraps or tissue edges.

;981z/jrb -9- The incision 12 is near the "end point" 32 and, hence, at a point where there are no more obliterations. The vibrating spatula probe 7 is held against the vessel wall (Figure 4b), and because of the cavitation-induced pressure of about 2 to 3 atm on the tissue, the media 29 becomes detached from the adventitia 30 as the connection between these two arterial wall layers is relatively weak (Figure 4c). Specifically this relatively weak connection betwwen the media not affected by plaque and the adventitia was in the known techniques one of the reasons for some of the coarsely irregular surfaces of the remaining arterial inner walls in the dissection of the "end point." It is noted that merely by applying the rounded tip of the vibrating spatula probe 7 to the wall layer, detachment (though only slight detachment) of the media 29 from the adventitia 30 is caused (Figure 4c) so that thereafter, a small forceps 33 can be used to make a small transverse incision 34 of about 0.5 to 1 mm length in the media 29.

The rounded tip of the spatula probe 7 is introduced into this small transverse incision 34 (Figure 4e) and run transversely around the inner wall of the artery (Figures 4f, 4g). Owing to the pressure by cavitation, there a regular and smooth detachment of the muscle fibres bearing in the form of a circle onto the inner vessel wall and of the intima takes place without making a cut. In this way dissection of the "end point" is achieved without other procedures as might be the application of sutures to the interior of the artery. Figure 4g shows the full separation of the media layer 29 detached from the adventitia 30 from the media layer 29a adhering to the adventitia The second phase of the procedure involves total unclogging of the cylinder occluding the artery. To this end the annular probe 8 is inserted into the incision 12 so that the vibrating annular active part 4 is between the detached media 29 and the adventitia 30 (Figure 4h). The diameter of the ring 4 of the annular probe 8 is chosen in dependence upon the lumen of the artery. The media 29 and, hence, the obstructing plaque 28 are detached from the adventitia 30 in the above-described manner, under a pressure of 2 to 3 atm acting on the tissue layers, without any concurrent traumatising effect on the vessel wall. Since the small tube 10 which encloses the vibrating transmission portion 6 is made from a material having a low coefficient of sliding friction, further sliding within the artery 11 is unimpeded, and the transmission portion's 6 ability to vibrate is not reduced by the wall pressing onto the same nor eliminated (Figure 41).

981z/jrb 10 This second step of the procedure, in which the annular probe 8 is gently moved forward and, if necessary, also backwards in accordance with the arrows of Figure 4i, ends at the "proximal point" 36, at a point where the artery is without occluding plaques 28 (Figure 4j).

This "proximal point" 36 is then prepared in a last step like the "end point" 32. After withdrawing and removing the annular probe 8 through the incision 12 at the "end point" 32 (Figures 4a, 4b), an incision is made in the longitudinal direction of the artery 11, at first a small-area detachment of the media 29 is effected by means of the spatula probe 7, a small transverse incision into the detached media 29 is made in the manner described with reference to Figure 4d, and after that the vibrating spatula probe 7 is introduced, and, by rotating the same, detachment of the media 29 from the adventitia 30 is effected (Figure 4k). As in the dissection of the "end point," the line of separation of the detached media from the remaining media is distinct and smooth; the risk of the development of postoperative thromboses is minimised.

The entire occluding cylinder 37 can be pulled out through one of the two incisions 12 or 12a at the "end point" or at the "proximal point;" the incisions 12 and 12a are sutured and blood flow in the unclogged arterial region is re-established (Figure 41).

The remaining inner wall of the jnclogged artery is free of irregularities since the entire media of this region was removed, regardless of the particular degree of atherosclerosis.

981z/jrb

Claims (10)

1. A system for detaching atherosclerotic plaques by means of ultrasound vibrations by detaching the media from the adventitia, comprising an ultrasound transducer adapted to be connected to an ultrasound generator, a handle, a probe adapted to be attached to said handle, with the probe having an Cive part and a transmission portion and with a small tube completely enclosing the transmission portion for supplying fluid which serves to wet the active part of the probe, wherein, for the purpose of supplying the fluid to the small tube on, or in, the handle there is provided a channel characterised in that the small tube is made from a material with low friction properties, that the small tube completely encloses the transmission portion, and that there are provided means for wetting the active part on all sides with fluid.

2. The system according to Claim particularly for insertion into an incision made in an artery, characterised in that the active part is configured as a ring connected on one side to the transmission portion and that the surface of the ring includes with the longitudinal axis of the transmission portion preferably an angle greater than zero.

3. A system for detaching atherosclerotic plaques, particularly in the proximal region of an incision into an artery, as per Claim 1, characterised in that the active part is rod-shaped configured particularly in the form of a spatula and preferably includes an angle greater than zero with the longitudinal axis of the transmission portion-referred to its region directly adjacent the handle.

4. The systen according to any one of the preceding claims, 25 characterised in that one extremity of the small tube is affixed to the handle and at the other extremity there is provided an opening such that the fluid can be discharged for wetting all sides of the active part.

The system according to Claim 4, characterised in that at the active part's extremity far from the handle, the small tube encloses the active part at a region of transition from the active part to the transmission portion, with at least two openings provided in symmetric position on both sides ol the active part.

6. The system according to any one of the preceding claims, characterised in that the transmission portion and the small tube are flexible.

7. The system according to any one of the preceding claims, characterised in that the small tute is made from plastics, preferably from PVC or PTFE. IN:\l.Il(t.l.1 152:(IJG 12

8. A treatment set comprising a system for detaching atherosclerotic plaques according to any one of the preceding claims and an ultrasound generator, characterised in that the following components are associated with the ultrasound generator: at least two sockets each for at least one of the systems according to Claims 2 or 3, particularly in the form according to any one of Claims 4 to 7; at least one amplitude transformer associated with the sockets; at least one vessel for the fluid, with an input line to the channel of the respective system and a feeder pump provided in the input line.

9. A system for detaching atherosclerotic plaques by means of ultrasound vibrations by detaching the media from the adventitia, substantially as hereinbefore described with reference to the accompanying drawings. A treatment set, substantially as hereinbefore described with reference 15 to the accompanying drawings. Dated

10 November, 1997 Antonio La Rosa Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON C a a a. a a a. a a. N 11.13111 q 2 11MB