Patent Application
20240366309
Systems and methods for navigation of catheters through vessels including intracranial venous vessel access are described. In addition, systems and methods for the treatment of vasculature conditions including aspiration from the cerebral venous sinus are described. Generally, the system includes a co-axial combination of a microwire, a support catheter having an oval section and an aspiration catheter. Methods of advancing the system through the vasculature including the venous vasculature with narrow sections are also described.
Cerebral venous thrombosis (CVT) refers to occlusion of venous channels in the cranial cavity. These can generally be sub-characterized as dural venous sinus thrombosis (DVST), cortical vein thrombosis and deep cerebral vein thrombosis. These conditions often co-exist and the clinical presentation can be very similar and nonspecific. Furthermore, the diagnostic imaging features can be subtle.
DVST is the most common condition. DVST is most likely to affect women on the contraceptive pill. However, other risk factors include lifestyle factors, other hormonal factors, drugs, anatomical/trauma and disease conditions. As such, more specific risk factors can include smoking, pregnancy, puerperium, steroids, and hyperthyroidism, prothrombotic haematological conditions including protein S deficiency and polycythaemia, COVID-19 and COVID-19 vaccination, local factors including skull abnormalities, infections (especially mastoid sinus—dural sinus occlusive disease) and head injury (especially skull fractures that extends to a dural venous sinus) and systemic illness including dehydration, sepsis, malignancy and connective tissue disorders. DVST may also be from idiopathic causes.
Presentation is variable and can range from asymptomatic to coma and death. Typically, patients complain of headache, nausea, and vomiting. Neurological deficits are variable. Since DVST obstructs the brain's venous outflow, venous pressure increases, backpressure builds up and cerebral swelling may occur. The subsequent venous hypertension can lead to edema and haemorrhage.
Once diagnosed, treatment can be challenging. Presently, systemic anticoagulation (e.g. heparin and warfarin) is still the first-line treatment for dural venous sinus thrombosis. Anticoagulation is usually required even in the setting of venous hemorrhage.
Interventional management includes microcatheter thrombolysis or thrombectomy (mechanical removal of thrombus material from the cerebral veins and sinuses using microcatheters and other endovascular tools). As discussed in greater detail below, microcatheter intervention can be challenging with currently available catheter systems. That is, due to the relative rarity of venous thrombosis (as compared to arterial ischemic stroke), no catheters dedicated to venous thrombectomy are available, and physicians must use catheter systems designed and/or engineered for cerebral artery access and thrombectomy.
However, the specifics of CVT and cranial venous anatomy both have particular features that can limit the effectiveness of arterial access/thrombectomy catheters in the venous system.
Structurally, arterial access catheters are characterized by a maximum outside diameter (OD) of about 8 French (2.67 mm) (and usually much smaller). That is, due to the characteristics of arterial ischemic stroke including the progressive narrowing of the distal arterial vessels and the blood pressure of the arterial system, the maximum diameter of larger distal access catheters (DACs) is about 8 French. As a result, arterial recanalization procedures typically use various combinations of bi-, tri- and quadra-axial catheter systems to progressively gain access to more distal regions of the cerebral arteries where the thrombosis may be located.
For reference, Table 1 shows the comparison of French, metric and imperial units used in catheters.
The design of arterial access catheters is specific to the arterial anatomy and various features and properties are incorporated into arterial catheters to enable their successful progress into the cranial vasculature to conduct various recanalization procedures.
In contrast, the cranial venous system has its own specific anatomical features that create unique problems to the navigation of catheters into the venous vasculature. Similarly, DVST is morphologically dissimilar to arterial thrombosis.
For example, as shown in schematically in
The residual lumen may be as little as 1 mm. Hence, placement of arterial access catheters within the dural sinus and aspiration of a clot using an 8 French (2.67 mm) distal access catheter may simply create a relatively small channel through the clot which does not significantly reduce the clot burden or alleviate the condition as shown in
Arachnoid granulations also present an access and navigation challenge to catheter access. As shown in
Accordingly, there has been a need for catheter systems specifically designed for and having the functionality to be effectively positioned within the cerebral venous vasculature to enable DVST treatment and that are able to navigate unique features of the cerebral venous system.
A catheter system to aid in navigating a catheter through a vessel having a narrow section or tortuous section of a patient's vasculature is described, the catheter system having an outer catheter (OC) having an OC distal end having an OC distal end inner diameter (ID) and inner perimeter (IP); a support catheter (SC) having an SC distal tip end, an SC proximal end and an SC expanded section adjacent the SC distal tip end, the SC expanded section having a distal taper, a proximal taper and an outer perimeter (OP), the OP substantially corresponding to the IP of the OC the expanded section for flattening the OC distal end during catheter placement.
In various embodiments:
In another embodiment, a catheter system to aid in navigating a catheter through a vessel having a narrow section or tortuous section of a patient's vasculature is described having, an outer catheter (OC) having an OC distal end having an OC distal end inner diameter (ID) and inner perimeter (IP); a support catheter (SC) having an SC distal tip end, an SC proximal end and an SC expanded oval section adjacent the SC distal tip end, the SC expanded section having a distal taper, a proximal taper and an outer perimeter (OP), the OP substantially corresponding to the IP of the OC the expanded section for flattening the OC distal end during catheter placement; and, one or more radio-opaque dot markers adjacent the distal tip of the OC.
In various embodiments, the distal taper is 4-12 cm, the proximal taper is 4-12 cm and/or the expanded section is 4-12 cm.
In another aspect, a method of advancing a catheter system as described herein through vessels of a patient having a narrowed section is described, comprising the steps of: a) introducing the catheter system into the patient at an access point; b) advancing an SC and OC from the access point towards the narrowed section; and c) engaging the OC over the expanded section to distort the OC distal tip to an oval shape and pushing the supported OC distal tip past the narrowing.
The method may also include the step of collecting and cleaning recovered blood and reintroducing recovered and cleaned blood back to the patient.
Various objects, features and advantages of the disclosure will be apparent from the following description of particular embodiments as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention. Similar reference numerals indicate similar components.
With reference to the figures, systems and methods for accessing cerebral venous thrombi are described.
Key structures within the human vasculature including the venous anatomy make it difficult to navigate larger diameter catheters into areas of the body including the brain. For the purpose of this description, catheter systems are described with reference to venous cerebral vasculature although it is understood that the systems and methods described herein can be used in other areas of the body for treatment of conditions specific to those areas.
In a typical procedure, using available arterial cerebral access catheters, access to the cerebral venous system is obtained through femoral veins. Catheters are advanced to the inferior vena cava, through the right atria to gain access to the superior vena cava (SVA). From the SVA, access to the internal jugular vein (IVA) is achieved, followed by access to the sigmoid sinus, transverse sinus, torcula and superior sagittal sinus. Alternatively, direct access to the internal jugular vein through percutaneous puncture in the neck is also feasible.
For a larger diameter catheter, navigation from the generally more pliant neck vessels (i.e. internal jugular vein) to the contained cerebral vessels (i.e. sigmoid sinus) is the most challenging. Both pliancy of the vessels and tortuosity can create issues in the navigation of larger diameter catheters.
Cerebral Venous Thrombosis (CVT) is a rarer form of stroke occurring in the venous system. As shown schematically in
Moreover, the relative size of cerebral catheter systems compared to venous vessels can be problematic insomuch as the relatively smaller diameter and design of cerebral catheter systems can present problems as shown schematically in
Further, the occurrence/presence of arachnoid granulations (AGs) can result in localized narrowing of vessels that create significant navigational obstructions to the advancement of catheters as shown in
Arachnoid granulations are rigid, hard outpouchings of the dura that bulge into the cerebral veins and sinuses. Often, the inner diameter of the vein/sinus gets narrowed substantially by these AGs, with a diameter reduction of 50% or more. AGs are not compressible and thus, a catheter that would otherwise fit into the cerebral vein/sinus often gets stuck at AGs, which acts as a ledge and prevents the catheter from moving forward. Since the AG cannot be compressed by the catheter, the catheter cannot reach the site of occlusion if there is an AG proximal to the occlusion.
Large AGs are particularly common in the transverse and superior sagittal sinuses, which are the most common locations in which cerebral venous thrombosis occurs.
In a first embodiment, as shown in
As shown in
As shown in
Each of the distal taper, oval section and proximal taper are designed to support a larger bore aspiration catheter (AC) or outer catheter (OC) that may be advanced over the support catheter and wire and specifically to enable the AC to be advanced past localized narrowing of a vessel such as an AG and/or to prevent a gap 17 from forming between the AC and SC.
As shown in
With reference to
The following description relates to the sequence of steps to progress an AC past a narrowing and the structure of the SC in particular that enables this. For the purposes of description, the vessel is assumed to have a diameter of approximately 8 mm, the AC has an outer diameter of 6 mm (18 F), the narrowing may extend up to about 4 mm into vessel and the wire has an outer diameter of 1 mm.
As shown in
As shown in
As the distal taper begins to engage with the AG, the distal taper may also deflect/orient itself relative to the AG such that oval section can fill the non-obstructed space as shown in
As shown in
As the AC is pushed forward, the distal tip 34a engages with the proximal taper 32e of the support catheter which, like the distal taper, transitions from the circular cross section to the oval cross section. The proximal taper stretches/distorts the distal tip 34a as the distal tip engages with the proximal taper such that the distal tip region of the AC assumes the underlying oval shape of the SC as shown in
The combined system, now past the AG, can be pushed/navigated to a desired position to initiate the procedure, such as aspiration.
Once in position, the SC and wire can be withdrawn as shown in
Of note, aspiration catheters normally have a radio opaque marker in the form of a metal band or ring at their distal tip as shown in
The SC is generally designed such that the outer perimeter length of the oval section corresponds to the inner perimeter length of the AC with sufficient tolerances that the AC can slide over the oval section. The relative ratio of lengths between the major and minor axes of the oval section are about 1.5 to 1, for example 6 mm on the major axis and 4 mm on the minor axis.
The lengths of the distal and proximal tapers will typically be about 3 cm and the total length of the oval section about 6 cm, although these dimensions can be greater or smaller as shown in Table 2.
As shown in
Each of the wire, SC and AC typically have a total length of about 1.1-1.2 m and otherwise have sufficient length to be advanced from the femoral vein to the cerebral venous vessels. Shorter length catheters may be utilized if designed for jugular vein access or to access other parts of the vasculature.
Generally, the differences in the lengths of each of the inner and outer catheter components will be in the range of 10-20 cm. That is, the inner components will be around 10-20 cm longer than the outer components.
As described above, the distal taper and oval section of the support catheter provides support to the wider inner diameter of the AC. In addition to the ability to advance the AC past a narrowing, the system may also be used to facilitate movement through areas of high vascular curvature and/or pliancy where there is otherwise a risk that a gap 17 opens between the distal tip of the AC and the narrower sections of the support catheter.
That is, if there is an area of higher tortuosity, the AC may be advanced over the oval section to prevent a gap from opening.
In addition, it should be noted that the oval section will typically have greater flexibility in the direction of the minor axis as compared to the flexibility in the direction of the major axis. As such, in areas of tight tortuosity, the oval section will generally have a tendency to align itself such that the minor axis of the oval section is aligned towards the center of curve and provide greater bend around a tight corner.
As described above, the system may be used to access an intracranial occlusion through a patient's venous vasculature. Generally, after the surgeon has gained access to the patient's vasculature at the femoral vein, the following general steps are followed:
Noted advantages of this solution are:
In variations of the methodology, blood that is removed through the AC may be returned to the body after cleaning to remove any blood clot debris. This step is desirable given the relatively larger volumes of blood being aspirated as a result of the larger diameter vessels and larger diameter catheters.
Units of measure used in this specification are consistent with the units used in the field of endovascular surgery. That is, both imperial and metric units are used where lengths are typically expressed in metric units while diameters can be expressed in imperial units.
Key features of the cerebral venous catheter system (CVCS) are shown in Table 2.
Each of the catheters will preferably include proximal and extracorporal markings on their bodies that correspond to the relative end points of the catheters to assist the physician in understanding the relative position of each catheter to one another during a procedure.
Corresponding changes in length for systems designed for intra-jugular access can be implemented.
