TECHNICAL FIELD

The present invention relates to the field of methods and systems for treating blood vessel lesions, and more particularly to methods and systems for treating lesions using mechanical waves.

BACKGROUND

Cardiovascular disease remains a leading cause of death worldwide. Atherosclerosis consists of plaque accumulation along the inner wall of arteries. This can reduce the size of the flow passage and this is known as stenosis. When the blood vessel is completely blocked this is known as an occlusion. The reduction in blood flow due to lesions such as stenosis or occlusion can impair or harm the tissues and organs relying on this blood flow. The blood flow through these lesions can be restored through procedures known as percutaneous transluminal angioplasty (PTA) techniques. In many cases the lesion contains hard calcified structures and dense fibrotic tissues that may be difficult to treat using traditional PTA techniques and apparatuses, and together with the vessel size and tortuosity, may be the cause of the potential complications. Some experts therefore believe that new devices and technologies in the field of PTA may improve the success rate and reduce the procedure time for restoring blood flow through calcified and/or fibrotic lesions.

Over the years, various apparatus and methods have been developed and proposed to help in blood vessel recanalization of calcified and/or fibrotic lesions through minimally invasive procedures. For example, devices have used a mechanical impactor with or without the use of a transmission member, a narrowband ultrasonic source with a transmission wire, and various other methods of energy deposition near the lesion.

For procedures performed using a mechanical impactor, a projectile is accelerated and impacts a proximal end of a transmission member or a distal cap that is in direct contact with the lesion. The projectile can be accelerated using a pneumatic source, a solenoid, a mechanical spring or other means. The mass of the projectile and its speed at impact produce high stresses at the impact surface and therefore require commensurate maintenance. Also, this method may offer very limited control over the parameters of the mechanical pulse that is generated. Moreover, such devices may be noisy and may lack durability.

Another prior art example consists in a system comprising an ultrasonic wire excited at resonance with a horn and an electromechanical transducer. This constitutes a first example associated with the use of a narrowband source. This arrangement is used to amplify the displacement at the distal end of the device in contact with the lesion. The ultrasonic wire is usually used inside a dedicated catheter with cooling fluid circulation to prevent overheating of the device. By doing so, the device becomes bulkier and thus is limited in its ability to reach lesions in small and tortuous anatomy. Considerable loss (due to signal distortion and nonlinearity) and/or mode conversion (from axial to transverse) may also occur at a bend when the device is activated. The frequency of operation (typically around 20 kHz) may create large stress, strain and heat at the ultrasonic wire junction with the horn and within the ultrasonic wire itself. This may contribute to weaken the ultrasonic wire resulting in higher risk of failure.

Other prior art forms of energy deposition can be used near the lesion. For example, electromechanical transducer(s) can be used at or near the distal end of a catheter to produce mechanical waves near the lesion. Such a method may be limited in terms of the power that can be generated considering its miniature size. Moreover, the fabrication of this transducer may be complex and expensive especially considering that the device must be discarded after utilization to prevent contamination. Also, electrical wires are needed to drive the transducer(s) which can leak current inside the body and impact normal heart rhythm.

Laser energy may be used with optical fibers to effectively deliver pulses of high intensity light at the lesion. However, the inherent fragility of optical fibers makes them prone to break, especially when used in tortuous anatomy. Moreover, this form of energy, i.e., heat deposition, may be difficult to control and thus be unsafe to nearby healthy tissues; this also necessitates costly laser sources.

Radiofrequency (RF) energy is another prior art source of energy that can be delivered at the lesion site using electrodes and high voltage (i.e. 1 kV or higher). Like laser energy, RF energy may be limited in terms of control capability and may tend to create large heat deposition resulting in damage to nearby healthy tissues. Electrical spark discharge can also be used to generate shockwaves near the lesion, which requires even higher voltages (i.e., greater than 2 kV). For certain designs, erosion and mechanical wear of the electrodes may represent safety and reliability issues. Furthermore, for safety issues, devices using electrical discharges in the heart need to be synchronized with the subject's heart rhythm, which must thus be predictable and constant.

Chemical detonations can also be used to accelerate a distal hard mass causing it to impact a nearby lesion. Chemical reactions may be difficult to control and contain, especially in in-vivo environments. Toxic and potentially hazardous products can also be associated with detonations and explosions.

Therefore, it appears that impactors, narrowband energy sources and other prior art methods of energy deposition near vascular lesions all present drawbacks.

Therefore, there is a need for an improved method and system for treating lesions, especially calcified and/or fibrotic lesions.

SUMMARY

According to a first broad aspect, there is provided a method of treating a vascular lesion comprising: inserting a waveguide into a vessel of a subject, a lesion being present in the vessel and the waveguide extending longitudinally between a proximal end and a distal end; positioning the distal end of the waveguide adjacent to the lesion; generating a high amplitude mechanical pulse and propagating the high amplitude pulse from the proximal end to the distal end of the waveguide; and propagating at least a portion of the high amplitude pulse from the distal end of the waveguide to the lesion.

In some embodiments, the method further comprises imaging a portion of the body of the body comprising the vessel having the lesion therein.

In some embodiments, the step of inserting a waveguide comprises inserting a waveguide having a marker positioned at the distal end thereof.

In some embodiments, the method further comprising deflecting the at least a portion of the high amplitude mechanical pulse before reaching the lesion.

In some embodiments, the step of deflecting occurs at the distal end of the waveguide.

In some embodiments, the step of deflecting occurs away from the distal end of the waveguide.

In some embodiments, the step of generating comprises generating a plurality of mechanical waves having a first amplitude and combining the mechanical waves, thereby obtaining at least one high amplitude mechanical pulse each having a second amplitude greater than the first amplitude.

In some embodiments, the step of said combining comprises focusing the mechanical waves on a focus zone.

In some embodiments, the step of combining comprising propagating the mechanical waves into a temporal concentrator.

In some embodiments, the step of combining comprises propagating the mechanical waves in a taper.

In some embodiments, the step of combining comprises propagating the mechanical waves in a reverberating cavity

In some embodiments, the step of combining comprises propagating the mechanical waves in a dispersive medium.

In some embodiments, the at least one high amplitude mechanical pulse each have a center frequency fc comprised between about 20 kHz and about 10 MHz and a duration of about 1/fc.

In some embodiments, an amplitude of the at least one high amplitude mechanical pulse when reaching the distal end of the transmission member is comprised between about 1 MPa and about 1000 MPa.

According to another broad aspect, there is provided a system for treating a vascular lesion, comprising: a pulse generator for generating at least one high amplitude and short duration mechanical pulse; and a waveguide extending between a proximal end and a distal end, the proximal end being coupled to the pulse generator for receiving the at least one mechanical pulse therefrom, the transmission member for propagating the at least one mechanical pulse from the proximal end to the distal end and transmitting the at least one mechanical pulse at the distal end, the distal end being adapted to be introduced into a vessel of a subject comprising the lesion

In some embodiments, the pulse generator comprises: a plurality of broadband sources each for emitting a respective mechanical wave having a first amplitude; and a wave concentrator for combining the mechanical waves in order to obtain the mechanical pulse having a second amplitude greater than the first amplitude.

In some embodiments, the wave concentrator is a spatial concentrator.

In some embodiments, the wave concentrator is a temporal concentrator.

In some embodiments, the wave concentrator is adapted to focus the mechanical waves on a focus zone adjacent to the proximal end of the transmission member.

In some embodiments, the wave concentrator comprises a parabolic reflecting surface for reflecting at least some of the mechanical waves generated by the broadband sources towards the focus zone.

In some embodiments, the wave concentrator is a taper.

In some embodiments, the wave concentrator comprises a spatial concentration stage and a temporal concentration stage.

In some embodiments, the at least one high amplitude mechanical pulse each have a center frequency fc comprised between about 20 kHz and about 10 MHz and a duration of about 1/fc.

In some embodiments, an amplitude of the at least one high amplitude mechanical pulse when reaching the distal end of the transmission member is comprised between about 1 MPa and about 1000 MPa.

In some embodiments, the waveguide is flexible.

In some embodiments, the system further comprises a deflector for deflecting and orienting the mechanical pulse.

In some embodiments, the deflector is integral with the waveguide.

In some embodiments, the deflector comprises a beveled face.

In some embodiments, the deflector projects from the distal end of the waveguide.

In some embodiments, the deflector has a truncated conical shape.

In some embodiments, the deflector is independent from the waveguide.

A mechanical wave may have an arbitrary amplitude, duration, waveform, frequency, and/or the like. For example, a mechanical wave may have a high/low amplitude, a short/long duration, different waveforms, and any frequency content.

For the purpose of the present description, a mechanical pulse should be understood as a short duration mechanical wave. The duration of a mechanical pulse is of the order of about 1/fc.

Furthermore, a mechanical waveguide should be understood as a waveguide adapted to propagate mechanical waves or pulses along its length. In the present description, the expressions “waveguide”, “mechanical waveguide” and “transmission member” may be used interchangeably. The shape and dimension of a waveguide may vary. For example, a waveguide may have a cylindrical shape. The diameter of the waveguide may be constant along its length. Alternatively, the diameter of the waveguide may vary along its length. For example, the diameter of a waveguide may decrease along its length so that the waveguide corresponds to a taper.

In one embodiment, a mechanical waveguide may comprise a single elongated element adapted to propagate mechanical waves and/or pulses therealong. In another embodiment, a mechanical waveguide may comprise a plurality of elongated elements each adapted to propagate mechanical waves and/or pulses therealong.

