The present invention relates to an apparatus for intravascular or intraluminal deployment of a probe, and is particularly applicable to the deployment of an intracardiac ultrasound probe.

Intracardiac ultrasound probes are a key tool in many cardiac interventions. They are used for example to assist with structural heart interventions, for example with treatment (e.g. closure) of atrial septal defects, patent foramen ovale, left atrial appendage closure, percutaneous valve deployment and

pulmonary/aortic stenting. They may also be used to assist with electrophysiology, such as ablation for arrhythmia.

Great care must be taken to ensure that the intracardiac probe is brought into position in a controlled and safe manner. This also applies for intravascular deployment of other types of probe. It may be necessary for the probe to navigate tortuous and/or delicate vasculature and/or be position or aligned with accuracy at the deployment site. In the case of deployment of an intracardiac probe it is critical to avoid any damage to delicate cardiac structures like valves and their supporting apparatus and to allow complex positioning, for example in an "S-bend" shape through the heart.

"Intracardiac Echocardiography Off Piste? Closure of the Left Atrial Appendage Using ICE and Local Anesthesia ", by Simon T. MacDonald, James D. Newton, and Oliver J. Ormerod, Catheterization and Cardiovascular Interventions 77: 124-127 (2011) discloses an example prior art use of an intracardiac ultrasound probe under local anesthesia to guide left atrial appendage (LAA) occlusion, as an alternative to transoesophageal echo-cardiography under general anesthesia, in a high-anesthetic risk patient. The disclosed method places an intracardiac echo probe via a Mullins sheath in the right ventricular outflow tract and pulmonary artery. This allowed accurate visualization of device deployment in the LAA.

The placement using a Mullins sheath is implemented after deploying a guidewire to the desired location and then feeding the Mullins sheath, with a tubular dilator inserted within the Mullins sheath to provide the required rigidity to the sheath, along the guidewire. The Mullins sheath and dilator thus have open ends to allow the guidewire to pass through their longitudinal lumens. It is difficult safely to deploy a sheath without first deploying a guidewire because the lack of adequate guiding can increase the risk of wrong turns and/or tissue damage during the insertion procedure. Once the sheath is in place the dilator and guidewire can be removed and the probe safely inserted along the sheath to the site of interest. The sheath thus acts to guide the probe and prevent the probe causing damage to the vasculature or intracardiac anatomy.

A problem with such use of intracardiac probes is that they are relatively expensive devices and cannot be reused after they have been brought into contact with the patient's blood or luminal secretions.

EP 1605987 A discloses a multi-lumen catheter in which an optical imaging probe is positioned within a closed-end lumen. The optical imaging probe is thereby isolated from body fluids in use and can be reused. However, the device requires an additional lumen for a guidewire and a further lumen for a penetrator, both of which increase the width of the device. There is also no provision for inserting a sheath with a removable dilator in a separate step, after insertion of the guidewire and before insertion of the probe. Thus the catheter has to have considerably greater rigidity and therefore thickness than the Mullins sheath discussed above. This device is therefore less suitable for use with an ultrasonic probe in locations which can only be reached by narrow and/or tortuous vasculature, for example regions within the heart.

US 5,421,338 A discloses the provision of an ultrasonic probe in a closed-ended lumen of a catheter. In a disclosed embodiment the dimensions of the catheter are chosen to be suitable for insertion into coronary arteries. However, in order to make the dimensions sufficiently small, the catheter is provided with a single internal lumen for the probe, with a saddle being provided near a distal tip of the device for engagement with a guidewire. There is no provision for inserting a sheath with a removable dilator in a separate step, after insertion of the guidewire and before insertion of the probe. Indeed, neither the closed- end lumen nor the saddle is capable of guiding such a dilator. Thus, the catheter may not have the flexible rigidity of the Mullins sheath discussed above and can only be made suitably narrow by providing a single lumen for the probe. The restriction to a single lumen limits the way the device of US 5,421,338 A can be used. It is difficult for example to perform distal sampling or pressure recording.

It is an object of the invention to provide an apparatus for intravascular or intraluminal deployment of a probe that allows the probe to be brought safely via narrow and/or tortuous vasculature or other body lumens to a site of interest and which allows the probe to be reused by preventing contact between the probe and body fluids of the patient during use.

According to an aspect of the invention, there is provided an apparatus for intravascular or intraluminal deployment of a probe, comprising: an elongate sheath configured for insertion to a target site via the vascular system or one or more other internal lumens of the body; first and second elongate lumens formed in the sheath and extending from a proximal portion to the distal portion of the sheath, the proximal portion being configured to remain outside of the body in use, wherein: the first lumen is open at the distal portion; the second lumen is closed at the distal portion; the first and second lumens are separated from each other by a flexible wall such that the sheath can selectively adopt a sheath deployment mode, in which the cross-sectional area of the first lumen is larger than the cross-sectional area of the second lumen due to the presence of an elongate strengthening member in the first lumen and the absence of the probe in the second lumen, and a measurement mode, in which the cross-sectional area of the second lumen is larger than the cross-sectional area of the first lumen due to the presence of the probe in the second lumen and the absence of the elongate strengthening member in the first lumen.

Thus, an arrangement is provided which allows a sheath to be deployed prior to the insertion of a probe in order to ensure safe deployment of the probe and which allows the probe to be reused, while at the same time allowing the overall dimensions of the sheath to be sufficiently small and flexible to be deployable through narrow and/or tortuous regions of vasculature or other body lumens. The provision of two separate lumens, one of which is open-ended and the other of which is closed- ended, allows the sheath effectively to function both as an open-ended sheath and as a closed ended sheath. Safe deployment of the sheath is achieved by inserting the elongate strengthening member into the open- ended lumen, which acts to provide a degree of stiffness to the sheath that is suitable for the insertion process, thus effectively using the sheath as an open-ended sheath. The tapered end of this dilator/ strengthening member prevents the blunt end of the sheath causing vascular or luminal trauma. In a subsequent step, the elongate strengthening member is removed and the probe inserted into the other, closed- ended lumen, thus effectively using the sheath as a closed-ended sheath. The closed-ended lumen can be isolated from any contact with bodily fluids of the patient and thus allows the probe to be reused.

The flexible wall between the two lumens ensures that the overall cross-sectional area of the sheath can be considerable less than the sum of the cross-section areas of the elongate strengthening member and the probe because these elements do not need to be present in the sheath at the same time. Thus, the sheath can be used to introduce the probe safely through regions of narrow, delicate and/or tortuous vasculature.

The provision of an open-ended lumen that is separate from the lumen into which the probe is to be inserted makes it possible to use a guidewire to guide deployment of the sheath and to leave the guidewire in place during use of the probe. The stability of the sheath during imaging can thus be improved.

The open-ended lumen makes it possible to perform processes via the open end. For example, fluid can be supplied to or extracted from the open end, allowing for example distal sampling to be performed. The open end may provide access for pressure measurements. In an embodiment, the probe is an ultrasound probe. However, the invention is also applicable more generally, for example to probes used for interventional radiology and other fields of medicine where internal imaging is required.

In an embodiment, the second lumen is configured to be connectable to a vessel comprising a coupling medium. In an embodiment, the probe is an ultrasonic probe and the coupling medium is a saline solution, which is readily available, cheap, and provides good ultrasonic coupling between the probe and the portion of the walls of the second lumen adjacent to the region of the probe that emits and receives the ultrasonic signal. Saline solution also has low viscosity which assists with effective deployment of the medium into the second lumen and reduces the risk of bubbles impeding the passage of ultrasound to and from the probe.

In an embodiment, an isolation sock can be attached around the entrance to the second lumen. A region that is isolated from the patient can thus be created that includes the interior of the closed ended second lumen and a region outside of the apparatus. The probe can thus be inserted and removed with a lower risk of contamination to or from the patient.

In an embodiment, a radio-opaque marker is provided in a distal portion of the second lumen. The provision of a radio-opaque marker allows the position of the probe to be determined accurately using fluoroscopy (X-rays). Providing the radio-opaque marker in the closed-ended second lumen reduces the risk of the marker embolyzing into the patient, which would be a considerable stroke and thromboembolism risk and has been known to occur in prior art arrangements in which the marker is not isolated from the patient's blood. A marker may also be provided in the open-ended first lumen.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which corresponding reference symbols represent corresponding parts, and in which:

Figure 1 is a side view of an apparatus for intravascular or intraluminal deployment of a probe in a sheath deployment mode;

Figure 2 is a view of a cross-section taken along line A-A of the apparatus of Figure 1 ;

Figure 3 is a schematic side view of an apparatus for deployment of a probe in a measurement mode;

Figure 4 is a view of a cross-section taken along line A-A of the apparatus of Figure 3;

Figure 5 is a perspective view of a proximal portion of the apparatus of Figures 1-4.

Figures 1-5 depict an apparatus 2 for intravascular or intraluminal deployment of a probe 4. In an embodiment, the apparatus is switchable between a sheath deployment mode and a measurement mode. Figures 1 and 2 depict the apparatus in the sheath deployment mode and Figures 3 and 4 depict the apparatus in the measurement mode.

Figures 1 and 3 are schematic side views of the apparatus 2. The upper portion in each of these figures depicts a side view of a proximal portion of the apparatus 2, which in use will remain outside of the patient. The lower portion in each of the figures, below the break 50 (which represents a length of the sheath 6 that is omitted from the figures in the interests of clarity) depicts a side sectional view, or cut-away view, showing the interior structure of the sheath 6. A region of the sheath 6 delimited by the broken line circle 52 is shown in a magnified form in the right-hand part of each figure.

The apparatus 2 comprises an elongate sheath 6 having a distal portion 14 that can be inserted to a target site via the vascular system or other body lumens while a proximal portion 12 remains outside the body. In an embodiment the target side is a region inside the heart. In an embodiment the probe is an ultrasound probe. In an embodiment, the probe may have a phased array of crystals allowing sector shaped imaging with the capability of 2D echo imaging, M-mode, pulsed wave, tissue Doppler, continuous wave and colour Doppler in addition to 3D/4D imaging. Several of these probes exist (e.g. Siemens Intracardiac AcuNav Ultrasound catheter or St Jude Viewflex catheter) which are between 9Fr and lOFr in diameter, 90- 110cm in length, and allow imaging using frequencies between 4-10MHz, allowing tissue imaging at up to depths of 15cm (there being a trade off between resolution of the image and depth of ultrasound imaging). Such imaging may allow continuous monitoring during valve/stent/ device deployment or ablation, continuous monitoring of the pericardial space or exact implantation and inspection of a pacing lead or device. Alternative imaging probes that could be used include those with a single crystal rotated around in a circle or a circular phased array to generate a 360 degree picture around the probe. Such probes tend to use high frequency ultrasound of 20-45mHz (such as those by Volcano or Boston Scientific) and limited imaging depth diameters to 20mm, being of 4-6Fr size in diameter. Other types of probe could be used, such as a temperature or other sensing probe, optionally with the ability to be moved back and forth in the closed end lumen as desired and having the potential to be re-used as they are kept separate from a patient's luminal secretions.

In an embodiment, the sheath 6 may be adapted to accommodate a probe in the range of 4Fr to 22Fr. This may be achieved in a single example sheath 6 (i.e. the example sheath can accommodate a probe having any diameter in the range of 4Fr to 22Fr without adaptation of the sheath). Alternatively, different example sheaths 6 may be provided that are each capable of accommodating probes having thicknesses is different sub-ranges within the range 4Fr to 22Fr. In other embodiments, the sheath may be configured to accommodate probes that are smaller than 4Fr or larger than 22Fr.

A first lumen 101 and a second lumen 102 are formed in the sheath 6, the lumens 101,102 extending longitudinally and continuously from the proximal portion 12 to the distal portion 14. The first lumen 101 is provided with an opening 18 in the distal portion 14 (e.g. at the tip of the sheath 6 or on a side of the sheath 6 near the tip). The first lumen 101 may be referred to as an open lumen or an open-ended lumen.

The second lumen 102 does not have any opening in the distal portion 14. The distal portion 14 can thus be brought into position at the target site without any fluid connection being made between the interior of the second lumen 102 and the patient. The interior of the second lumen 102 is thus isolated from the patient at all times. The second lumen 102 may be referred to as a closed-ended lumen or a blind lumen.

The first and second lumens 101, 102 are separated from each other by a flexible wall 20 (shown in Figures 2 and 4). The flexible wall 20 allows the sheath 6 to be switched between the sheath deployment mode and the measurement mode by deforming in response to the respective insertion of an elongate strengthening member 22 into the first lumen 101 or the probe 4 into the second lumen 102. In the sheath deployment mode, as illustrated in Figures 1 and 2, the elongate strengthening member 22 is inserted along the first lumen 101 and the second lumen 102 is empty (no probe or other device is present in the second lumen 102). In the measurement mode, as illustrated in Figures 3 and 4, the probe 4 is inserted along the second lumen 102 and the first lumen 102 does not contain the elongate strengthening member 22 (although it may contain a guiding element such as a guidewire 30). Thus, an apparatus 2 in the sheath deployment mode can be switched to the measurement mode by removing the elongate strengthening member 22 from the first lumen 101 and inserting the probe 4 into the second lumen 102.

The flexible wall 20 allows the apparatus selectively to adopt the sheath deployment mode and the measurement mode without the overall cross-sectional area of the sheath 6 becoming too large to be suitable for insertion along narrow, delicate or tortuous lengths of vasculature and minimizes the size of the puncture site required on entering a vessel, known to correlate with later vessel closure complications. The flexible wall 20 allows the first lumen 101 to be larger (i.e. to have a larger cross-sectional area) than the second lumen 102 in the sheath deployment mode (due to the presence of the elongate strengthening member 22) and to be smaller (i.e. to have a smaller cross-sectional area) than the second lumen 102 in the measurement mode (due to the absence of the elongate strengthening member 22 and the presence of the probe 4).

The provision for accommodating an elongate strengthening member 22 in the sheath 6 makes it possible for the sheath walls 24 to be very thin (a millimetre or fractions of a millimetre for example, with the material comprising a type of plastic, optionally with a hydrophilic coating, polytetrafluoroethylene/ fluorinated ethylene propylene, or a material having similar impermeability to water, flexibility and strength as polytetrafluoroethylene/ fluorinated ethylene propylene), thus facilitating reduction of the overall cross- sectional area of the sheath in the measurement mode. Substantially all of the rigidity that is required for pushing the sheath into position during deployment can be provided by the elongate strengthening member 22. In an embodiment, the elongate strengthening member 22 comprises a tapered region 26 at the tip to assist with the insertion process. In the embodiment shown in the figures the elongate strengthening member 22 is straight, but this is not essential. In other embodiments, the tip of the elongate strengthening member may be curved so that rotation of the sheath about its longitudinal axis can be used to change the direction that the tip of the sheath points, which can be used help guide the sheath through curved regions of vasculature during deployment.

In an embodiment, the elongate strengthening member 22 comprises an internal lumen 28 which allows, for example, for the guiding of a guidewire 30 through the elongate strengthening member 22 (as shown in Figures 1-4). Thus, the apparatus can be inserted via the following steps, for example: 1) insertion of a guidewire 30 through vasculature (or other body lumens) to the target site for the probe 4 (guidewires suitable for safe insertion to most regions of the vascular system are commonly available); 2) insertion of the apparatus 2 in the sheath deployment mode along the guidewire 30 (with the guidewire 30 passing through the internal lumen of the elongate strengthening member 22 which in turn is within the first lumen 101); 3) removal of the elongate strengthening member 22 from the first lumen 101, leaving the guidewire in the first lumen 101; and 4) insertion of the probe 4 into the second lumen 102. Thus steps 3) and 4) effectively switch the apparatus 2 from the sheath deployment mode to the measurement mode. Leaving the guidewire 30 in place within the first lumen 101 while the probe 4 is making measurements may provide additional stability, thus improving safety and/or imaging quality.

In an embodiment, the outer diameter of the elongate strengthening member 22 (in a non-tapered region) is in the range of 4Fr to 22Fr in size, accepting guidewires 0.032 or 0.038 inch for example. The elongate strengthening member 22 may comprise a type of plastic, optionally with a hydrophilic coating, polytetrafluoroethylene/ fluorinated ethylene propylene, or a material having similar impermeability to water, flexibility and strength as polytetrafluoroethylene/ fluorinated ethylene propylene.

When the apparatus 2 is in the measurement mode, as illustrated in Figures 3 and 4 for example, and deployed such that an active region 46 of the probe 4 is positioned at the target site, the probe 4 may start to collect data. In order to reduce reflections from interfaces between the probe 4 and the tissue to be measured, a coupling medium 32 may be provided between at least the active region 46 of the probe 4 and the inner surface of the second lumen 102. In an embodiment, the coupling medium 32 is a liquid and the portion of the second lumen 102 that is not occupied by the probe 4 is substantially filled with the liquid during use. This prevents air being in the system and interfering with imaging. In an embodiment, a vessel 48 containing the liquid is connected to the second lumen 102 via a valve 36, which may comprise a haemostatic valve for example. Alternatively or additionally, the valve 36 may comprise a 3 way tap to allow fluid to be delivered or sampled from the lumen. In an embodiment, the valve 36 is configured to allow flushing of the second lumen 102 to avoid or remove bubbles of air, which might otherwise interfere with the measurements.

The valve 36 may comprise an entry port or valve 44, which may be a haemostatic valve for example, for allowing the probe to be inserted into and/or maintained safely within, the second lumen 102. The valve 36 may further comprise a port 43 for allowing coupling medium to be introduced into the second lumen 102 and for allowing the second lumen 102 to be easily de-aired. The coupling medium can also be displaced through the port 43 as the probe 4 is advanced into the second lumen 102.

In an embodiment, the probe 4 is an ultrasonic probe and the coupling medium 32 is a saline solution. Saline solution acts as an effective coupling medium for ultrasonic waves (reducing unwanted reflections from interfaces between the probe and the tissue to be measured), has low viscosity, which facilitates effective deployment of the medium into the second lumen 102 (better, for example, than a gel medium), and is widely available and cheap.

In an embodiment a further valve 42, which may be a haemostatic valve for example, is provided for allowing the elongate strengthening member 22 and/or guidewire 30 to be inserted into and/or maintained safely within, the first lumen 101.

In an embodiment a further valve 41, which may be a haemostatic valve for example, is provided for allowing independent access to the first lumen 101, for example to supply fluids and/or to flush the first lumen 101. Alternatively or additionally, the further valve 41 may be a 3 way tap to allow fluid to be delivered or sampled from the lumen.

In an embodiment, a radio-opaque marker 70 is provided in the second lumen 102, for example adjacent to the active region 46 of the probe 4. The radio-opaque marker 70 facilitates accurate

determination of the position of the probe 4 using fluoroscopy and the end of the blind ending lumen.

Providing the radio-opaque marker in a closed-end lumen reduces the risk of the marker embolyzing into the patient. However, in other embodiments a marker may also (or alternatively) be provided in the first lumen.

In an embodiment, an isolation sock may be attached around the entrance to the second lumen to isolate in use the interior of the second lumen and a region directly adjacent to the entrance of the second lumen from the patient. The isolation sock may be attached to a funnel 60 (see Figure 5) or other attachment skirt/ receptacle device.

In an embodiment, a kit is provided for intravascular or intraluminal deployment of a probe 4. The kit may comprise an apparatus 2 according to any of the arrangements discussed above. The kit may further include an elongate strengthening member 22 for insertion into the first lumen 101 of the apparatus to allow deployment of the apparatus. The kit may further include the probe 4 for insertion into the second lumen 102 to switch the apparatus into the measurement mode and for taking measurements.