Patent Description:
Mechanical circulatory support system such as ventricular assist device (VAD), in particular the left ventricular assist device (LVAD), has evolved into a standard care modality for treating advanced heart failure. Currently, the heart failure patients indicated for VAD application are those who are irresponsive to medical therapy, being classified as terminal stage with imminent death threat if without heart transplant or mechanical circulatory support. To date, the worldwide VAD registry has exceeded <NUM>,<NUM> implants since the approval of the continuous-flow durable LVADs (rotary pumps) including Heartmate <NUM>, Heartmate <NUM> and HVAD. It is anticipated that the use of LVADs as advanced heart failure therapy will receive more acceptance along with further advancement of the VAD technologies.

Implantation of VAD generally requires an inflow and an outflow cannula be established for connecting VAD, in-series or in-parallel, to the device recipient's native circulation system. In-parallel connection has been widely accepted by VAD implantation because of its anatomic and hemodynamic advantages. For such prosthetic flow circuit establishment, inflow cannula is placed with its first end connected to the ventricle or atrium and the second end to the VAD inlet. Blood flow, hence, is withdrawn from the heart (ventricle or atrium), entering into and being energized by the pump actuator, and finally returns via the outflow cannula to the large artery of the assisted circulation. Surgically, the establishment of LVAD inflow cannula is most invasive and skill dependent, commonly requiring coring a large hole (<NUM>-<NUM> in diameter) through the ventricular apical wall, followed by a carefully planned and time-consuming suturing process for fixation and seal of the inflow cannula around the cored myocardial wall. Intraoperative bleeding and air embolization at suturing site have been generally associated with the anastomotic skills and experiences of the surgeon. Pump malposition or migration, occurring peri- or post-operatively, have been related to the inflow cannula design and the insertion planning and execution as well. The cannula implantation related adverse events include, but are not limited to, perioperative surgical bleeding and the postoperative inflow obstruction and thrombotic complications. Often, such cannula-induced complications may result in devastating postoperative pump thrombosis, thromboembolism and infarction in organs, as well as serious stroke or neurological injury and cerebral dysfunctions.

A representative example showing a centrifugal rotary pump <NUM> implanted to a left ventricle (LV) is illustrated in <FIG>. In general, the rotary pump <NUM> comprises an inflow cannula <NUM>, an outflow cannula <NUM>, a rotor or impeller <NUM> in which embedded with a permanent magnet, a stator <NUM> wound with electric coils, and a controller <NUM> that regulates the rotor speed for designated blood flow delivery. With the spinning of the rotor <NUM>, hemodynamic suction is generated to drain the blood stored in the left ventricle (LV) chamber via the inflow cannula <NUM> into the rotary pump <NUM>. This pump inflow will be energized by the impeller-actuated mechanical energy conversion process, flowing through the impellor and collected in the volute <NUM> and finally delivered from the outflow cannula <NUM> into the aorta Ao to assist circulation. Likewise, other types rotary pumps, adopting axial or diagonal flow design, will have similar inflow and outflow cannula design for bypassing the blood flow through the artificially established bypass flow route. For the LVAD implantation shown in <FIG>, a coring of LV apex is first performed to create a through-hole <NUM> in the myocardial wall, then a sleeve anchor <NUM> is inserted and sutured around the through-hole <NUM>, working as an adapter to receive the inflow cannula <NUM> of the LVAD. Such inflow cannula establishment involves with several intraoperative surgical risks and postoperative cannula-induced complications, as explained in the following.

Comparing to pump actuator design, inflow and outflow flow characteristics and cannula design have been less studied. As a rule of thumb, the guidelines for inflow cannula design suggest that, first, it ought to protrude above the endocardium of the ventricular wall and second, be oriented to point at the mitral valve and in parallel to the interventricular septum <NUM>, as shown in <FIG>. The first guideline was suggested based on the past experiences that a short inflow cannula <NUM> with tip lower than the endocardium (see <FIG>) often caused myocardial tissue <NUM> in-grown into the cannula <NUM>, resulting in a progressive pannus overgrowth and obstruction of the inflow tract. In addition, in-situ clot will be formed on top of these in-grown tissues <NUM> and dislodged into the pump-propelled blood stream, becoming the sources of thromboembolism related complications including cerebral dysfunction, stroke, and visceral organ infarction. The second guideline arose as to prevent inflow cannula from inclining toward the ventricular septum <NUM>, which, if not properly implemented, would impede inflow entrainment, jeopardize support efficacy, and induce detrimental low-speed flow in the pump leading to pump thrombosis. As a matter of fact, these two cannula insertion guidelines are mutually exclusive. A longer inflow cannula <NUM> tends to satisfy the first protrusion requirement but may incur flow blockage penalty if the cannula is misaligned slightly by a few angular degrees.

Clinically, often a diseased heart is ill-shaped with irregular wall thickness distribution, or pathologically dilated and presented with fibrotic or weakened tissues. The inflow cannula <NUM> establishment, hence, often encountered practical difficulty in implantation. Frequently, the suggested location of insertion and the actual orientation of the pump implant may deviate from what is originally planned. Moreover, even if the inflow cannula <NUM> is positioned as planned, the altered intraventricular morphology (protruded cannula in the ventricular chamber) may dismantle the native vortex structure and hence hamper the washout effect inside the ventricular chamber, or generates low-speed or recirculated flow zones around the protruded cannular root (see <FIG>), predisposing the ventricular chamber to become a thrombogenic origin. In other words, the inflow cannula configuration and the corresponding surgical method or cannula-induced perturbed blood flows in the ventricle are the causal factors leading to pump thrombosis and the resultant thrombotic complications.

The present invention aims to design a novel inflow cannula that enables an easier and safer insertion procedure without reliance on skill-dependent suturing, and in the meantime, improves intraventricular hemodynamics to mitigate all the aforementioned device-induced thrombotic complications associated with the existing LVAD inflow cannula design. Relevant prior art is disclosed in e.g. <CIT>.

To address the deficiencies of conventional ventricular assist device (VAD) inflow hemodynamics, the present invention provides an inflow cannula assembly, for transporting blood between a heart chamber and a VAD, having the features of independent claim <NUM>.

In some embodiments, the bellmouth has a gradually thinning wall thickness toward its tip, and the tip is literally sharp-edged.

In some embodiments, an overlay portion of the conduit in contact with a cored myocardium is roughened so as to promote cell and tissue ingrowth for hemostasis and immobilization purposes.

In some embodiments, porous materials are attached to the female fastener cap in contact with an epicardium for promoting cell and tissue ingrowth for hemostasis and immobilization purposes.

In some embodiments, the beak of the VAD inlet adapter and the second end of the flow cannula are interfaced over the flange ramp, with the inner diameter of the beak slightly larger than the inner diameter of the flow conduit, wherein an interface surface of the flange ramp is inclined generally <NUM> to <NUM> degrees to a centerline of the cannula.

In some embodiments, the VAD coupler includes an anti-decoupling latch and a collar contour that catches simultaneously onto the entire peripheral rim of the flange base during the closing of the collars for locking purpose.

In some embodiments, the inflow cannula assembly further includes a stent embedment disposed in the cannula.

In some embodiments, the stent is made of Nitinol material.

In some embodiments, the stent has a zig-zag ring structure, and the stent is distributed over regions covering the bellmouth and the conduit.

In some embodiments, the stent includes a plurality of arrays of zig-zag rings, wherein the arrays of zig-zag rings having a tubular shape being disposed in the conduit and a cone-shaped array of zig-zag rings disposed in the bellmouth.

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:.

The making and using of the inflow cannula embodiments of the assist devices are discussed in detail below. It should be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. It should be appreciated that each term, which is defined in a commonly used dictionary, should be interpreted as having a meaning conforming to the relative skills and the background or the context of the present disclosure, and should not be interpreted in an idealized or overly formal manner unless defined otherwise.

As shown in <FIG> and <FIG>, an embodiment of the present inflow cannula assembly CA for connecting a ventricular assist device (VAD) <NUM> to a heart <NUM>. This inflow cannula assembly includes a deformable polymeric cannula <NUM>, a pair of male and female fasteners <NUM>, <NUM>, a VAD coupler <NUM>, and a VAD inlet adapter <NUM>. <FIG> schematically shows how an inflow cannula <NUM> of a rotary pump is connected to left ventricle, whereas a sectional view illustrating the flow passage and the interconnected cannula assembly components with respect to a centrifugal type VAD is provided in <FIG>.

The distal orifice, defined as the farther cannula end viewed from the connected VAD <NUM>, is configured in a bellmouth <NUM> (the first end of the cannula <NUM>) extension of the cannula <NUM> with gradually increasing cone diameter. The cone angle of this bellmouth <NUM> is typically <NUM>-<NUM> deg relative to the axis of revolution of the conduit <NUM>. The central portion of the cannula <NUM> is the conduit <NUM> with an axi-symmetric cross sectional distribution. This said funnel-shaped cannula <NUM> constitutes a geometric locking mechanism when inserted across a cored through-hole <NUM> in the ventricular wall of the heart <NUM>. Prior to the cannula <NUM> insertion, the original diameter of the through-hole <NUM> is generally in the range of <NUM>-<NUM>, which is substantially smaller than the outer diameter of the inserted conduit <NUM>. Deformability of the present cannula invention, hence, is essential, which allows the cannula <NUM> be crimped into a smaller prepacked delivery form to facilitate insertion. Following bellmouth <NUM> insertion into the LV chamber and the release of the crimping constraints, the squeezed cannula <NUM> will restore to its original form having its conduit be snuggly embraced with oversize to the cored myocardial through-hole <NUM>. Similarly, the bellmouth <NUM>, as freed from crimping constraints, will self-expand and hence constitute an anti-dislodging anchorage against the contacted endocardium, as shown in <FIG>.

In some embodiments, the cored hole size (<NUM>-<NUM> in diameter) required for the present cannula <NUM> implantation can be substantially smaller when compared to that of a rigid-walled inflow conduit (<NUM>-<NUM> in diameter) pertaining to the contemporary rotary pumps. Excising lesser amount of tissue mass from the cardiac wall is surgically and anatomically advantageous. It not only reduces a permanent loss of contractile muscle, but also mitigates the risk of injury to papillary muscle and chordae tendineae that is responsible for atrioventricular valvular opening and closing as well as the associated valve flow regurgitation if the valve is not fully closed during systole.

There are two cardiac valves, namely aortic and mitral valves, situated in the left ventricle for regulating one-way flow into and out of the ventricular chamber. Notice that aortic valve regurgitation may impair VAD support efficacy and promote intraventricular thrombus formation. On the other hand, mitral valve regurgitation would lead to pulmonary congestion and hypertension, potentially causing pulmonary edema and death-threatening right heart failure. In recent years, rotary pump thrombosis complication was effectively annihilated using pump speed modulation strategy. As pump speed is lowered to allow intermittent valve opening and closing, a functional valve opening/closing is important. Coring-induced chordae tendineae and papillary muscle injury will adversely affect the valvular function, and the accompanying valve flow regurgitation may jeopardize the support efficacy as well as induce valve associated complications stated above. Hence, reducing the cored tissue volume around the LV apex, as the present invention does, may significantly improve the VAD implantation safety and efficacy and reduce the postoperative thrombotic event rate.

Two embodiments of such funnel-shaped cannula <NUM> are shown in <FIG>, <FIG>, and <FIG>, respectively. For these embodiments, polymeric elastomer such as silicone or polyurethane can be adopted as the material, which can be mold casted or injected into a seamless cannula with smooth blood-contacting surface. At the distal end of the bellmouth <NUM> is a sharp-edged tip <NUM> that can be attached to the endocardium with minimal geometric discontinuity. In addition, because the wall of the bellmouth <NUM> around its tip <NUM> end is gradually thinned, the rigidity of the bellmouth <NUM> reduces in proportion to the wall thickness toward the tip <NUM>, rendering the bellmouth <NUM> flexible and shape-conformal when compressed against the endocardium. There are multiple protruded stubs <NUM> disposed in the middle region of the conduit <NUM> to allow locking engagement to the male fastener <NUM>.

As shown in <FIG>, an overlay portion <NUM> of the conduit <NUM> in contact with the cored myocardium can be roughened to promote tissue ingrowth during the wound healing period. The surface of the overlay portion <NUM> can be made by attaching a felt with appropriate porosity or by depositing a thin layer of polymeric filaments generated, for example, by electrospinning. This rough overlay portion <NUM> can help immobilize or seal the implanted cannula <NUM> via tissue ingrowth and hence maintain a long-term hemostasis effectiveness postoperatively.

Another embodiment is to have the previous embodiment (<FIG> and <FIG>) embedded with a stent <NUM> or a stent reinforcement, as shown in <FIG>. In some embodiments, the stent <NUM> is flexible, and has a metallic material, such as super-elastic Nitinol material. By embedding the stent <NUM> inside the cannula <NUM> wall, the wall thickness can be further thinned to decrease the outer diameters of the cannula <NUM> (including the bellmouth <NUM> and the conduit <NUM>). Hence, the implantability of the stent-embedded cannula would be upgraded without compromising the hemodynamic performance which is dominated by the inner diameter <NUM> of the conduit <NUM>. Moreover, the stent <NUM> may share a substantial amount of the pulsatile pressure loading exerted on the conduit <NUM>, hence enhancing the conduit durability and safety. Mechanically, the stent <NUM> is able to endure large deformation without structural yielding that meets the foldability requirement of the present cannula <NUM>.

A lateral and perspective view of a representative Nitinol stent insert is illustrated in <FIG> and <FIG>, respectively. The stent <NUM> has a zig-zag ring structure, and includes a plurality of arrays of zig-zag rings <NUM>, <NUM> and connection members <NUM>.

The arrays of zig-zag rings <NUM>, <NUM> are responsible for resisting the radial load, whereas the connection member <NUM> clusters the arrays of rings <NUM>, <NUM> to resist the axial stretching force. In particular, the arrays of zig-zag rings <NUM> have tubular shape and are embedded in the wall of the conduit <NUM>, whereas the arrays of rings <NUM> having cone-shaped structure are embedded in the wall of the bellmouth <NUM>. For a thin-walled bellmouth <NUM> the radial strength is gradually weakened along with the increase of the cone diameter toward the distal tip <NUM>. Notice that when bellmouth <NUM> is locked with female fastener <NUM>, insufficient radial strength in bellmouth <NUM> may lead to structural buckling and loss of shape-conformality, resulting in massive bleeding in use. The stent <NUM> can improve this polymeric material strength by providing sufficient anti-buckling capability without a need to increase the wall thickness of the bellmouth <NUM>.

In the manufacturing of the stent <NUM>, an array of interconnected zig-zag ring structure <NUM>, <NUM> is first cut out from a thin-walled, straight Nitinol tube using a laser cutter. This tubular zig-zag array structure is shown in <FIG> in an expanded planar view. Following the standard expansion and heat treatment process the tubular array assembly <NUM>, <NUM> can be step-by-step shaped into the stent <NUM> having a bellmouth intake. Surface grinding and electronic polishing are subsequently applied to remove the oxidized outer layer formed on the heat-treated surface of the stent <NUM>. The final product is accomplished by mold co-injection of stent <NUM> with silicone or polyurethane elastomers, as illustrated in <FIG>.

Unlike the existing inflow cannula attachment designs that commonly require <NUM>-<NUM> suture stitch pairs, circumferentially placed around the cored myocardial hole <NUM>, to attach a VAD <NUM> onto a heart <NUM>, the present invention innovates a sutureless fixation approach. Conventional suture fixation relies on the tension force generated in the string by pulling tight the anchored suture pair. In a sharp contrast, the present sutureless pump attachment adopts a completely different fixation and force generation mechanism provided by a fastener pair <NUM>, <NUM>. This new attachment design simultaneously locks and seals the inflow cannula <NUM> with respect to the connection site myocardium. Sutureless fixation of cannula <NUM> to the contacted myocardium is accomplished by a pair of male and female fasteners <NUM>, <NUM>, which are shown in <FIG>, <FIG> and <FIG>, respectively.

Depicted in <FIG> and <FIG> are the sectional and perspective views of the male fastener <NUM>. A screw thread <NUM> is carved on the external surface of the male fastener <NUM>, from end to end, with multiple slots <NUM> made approximately in the middle region of the male fastener <NUM>. The inner diameter of the male fastener <NUM> is substantially equal, with a small clearance, to the outer diameter <NUM> of the cannula conduit <NUM>. When mounted onto cannula <NUM>, the protruded seats <NUM> on the conduit <NUM> will interlock with the slots <NUM> (<FIG>) and thereby work as a support base to provide counteracting axial and lateral forces required for screw locking with the female fastener <NUM>.

Referring to <FIG> and <FIG>, the female fastener <NUM> is a lock nut having a funnel-shaped distal cap <NUM> to be compressed against epicardium for locking and seal purposes. The angle of the cap <NUM> is approximately equal to the angle of the bellmouth <NUM>. As the screws of male and female fasteners <NUM>, <NUM> are tightened together, compression force will be generated and evenly distributed in the sandwiched myocardium between the cap <NUM> and the bellmouth <NUM>. Moreover, the cone of bellmouth <NUM> will deform slightly, in compliance with the fitted endocardium terrain, to simultaneously achieve the functions of seal (bleeding prevention) and cannula fixation. Around the outer rim of the cap <NUM>, a cone cuff <NUM>, made of surgical felt, is attached. The soft-contact porous feature provided by the felt is another guarantee of hemostasis. Tissues or cells may be ingrown into the void space in the cone cuff <NUM> along with the postoperative wound healing process. A few stay sutures can be placed around the cuff rim to further help fix the screwed female fastener <NUM> with the epicardium during the acute healing period.

The present sutureless flow cannula implantation may encounter postoperative tissue atrophy at the clamped connection site. Such tissue atrophy will jeopardize the seal effectiveness and potentially causes bleeding at the connection site. In <FIG> and <FIG> are shown another embodiment of the female fastener <NUM> intended to mitigate this atrophy-induced postoperative bleeding. The cuff <NUM> is additionally supported by a cone-shaped Nitinol stent 35N similar to that of the bellmouth stent <NUM> illustrated in <FIG> and <FIG>. As the female fastener <NUM> is compressed onto the epicardium, the deformed super-elastic Nitinol stent 35N will provide a contact spring load to assure that the cuff <NUM> always adheres to the epicardium during the wound healing process, hence obviating the risk of postoperative atrophy-induced blood leak.

<FIG> shows the integrated fasteners <NUM>, <NUM> as mounted on the cannula <NUM>. Forces and strain involved in cannula deformation confers a special design feature of the present invention. Material elasticity consideration, in fact, need to be carefully incorporated in the present design. In mounting these fasteners onto the cannula body, the deformability ability of the cannula <NUM> is required as a prerequisite. The proximal or second end <NUM> (the flange ramp) of the cannula <NUM> ought to be crimped into a smaller profile so as to pass the end <NUM> through the ring-shaped fasteners <NUM>, <NUM> sequentially. The male fastener <NUM> is first mounted and, along with the release of the crimped profile, locked onto the cannula conduit <NUM> via an engagement of those slots <NUM> in the fastener wall with the multiple protruded seats <NUM> on the conduit <NUM>. The female fastener <NUM> is inserted following the same crimping and release of the cannula proximal end <NUM> and then screwed onto the male fastener <NUM>.

Fixation of cannula <NUM> with heart <NUM> is accomplished by advancing the female fastener <NUM> forward until in contact with the epicardium with predetermined compression force. Suitable compression force required for a successful locking fixation and leakage seal can be determined by the surgeon or controlled using a torque wrench.

Mechanically, by screw tightening the male and female fasteners <NUM>, <NUM>, the bellmouth <NUM> and the cap <NUM> of the female fastener <NUM> will clamp the sandwiched myocardium from both sides across the insertion hole <NUM> to satisfy the fixation and leak-free requirements. It is worth noticing that the bellmouth <NUM> is shape-conformal to endocardium when compressed. The semi-rigid bellmouth <NUM> can be adaptively fit with the endocardial terrain, forming a seal barrier to obviate blood leakage concern. The male fastener <NUM> of the fastener pair, which is anchored on the protruded seats <NUM> of the conduit <NUM>, however, works as a support base to counteract the locking force generated.

It is worth mentioning that the present sutureless attachment possesses an intrinsic positive feedback mechanism built for bleeding control. As ventricle contracts and ventricular pressure increases, the compression force acting on the bellmouth <NUM> will increase accordingly and better seal off the attached flow cannula <NUM>. The concern of bleeding at hypertension is hence literally ruled out. This positive feedback effect is lacking in the conventional fixation by means of suturing as illustrated in <FIG>. For conventional suture fixation, often, surgeon must check bleeding, based on a drug-induced temporary hypertension, after the completion of anastomotic suture attachment of the flow cannula <NUM>. In <FIG> is illustrated a sectional view of how the present invention is in lock position with a connected ventricular wall. Compression type locking mechanism enables a distributed force be exerted around the clamped myocardial area in contact. The soft contact nature over bellmouth <NUM> and female fastener cap <NUM> avoids the traditional problem of suture string cutting generated within the stitched myocardium, which, often leads to bleeding through enlarged suture fissure at hypertension. Cardiac muscle is particularly vulnerable to string cutting associated with conventional suturing anastomosis, a problem that is much dependent on the mastery of suturing skills possessed by the surgeon.

Around the proximal end <NUM> of the cannula conduit <NUM>, the blood-contacting inner surface is configured to have a smooth geometric transition to the inlet of the connected VAD <NUM>. As shown in <FIG> and <FIG>, the VAD inlet adapter <NUM> is a body of revolution comprising a wedge-shaped beak <NUM>, a beak flange <NUM> and a base <NUM>, forming an extension of a VAD inlet housing. There are multiple eyelets <NUM> drilled on the base <NUM>, which are used to integrate the inlet adapter <NUM> with the VAD <NUM>. The beak <NUM>, or the foremost part of the inlet adapter <NUM> of a connected blood pump or VAD, has an inner diameter <NUM> slightly larger than the inner diameter <NUM> of the flow cannula <NUM>. Referring to <FIG>, in order to enhance the fault tolerance associated with step discontinuity generated at interface, the interface surface of the flange ramp <NUM> is sloped with an inclination angle <NUM> to the stream direction. Such ramp interface design keeps step or gap from being generated at interface surface of the flange ramp <NUM> due to limited manufacturing precision or matching concentricity associated with conventional butt connection. Nevertheless, this cone-shaped flange ramp <NUM> has an intrinsic shortcoming in fulfilling a concentric centerline alignment of the joined counterparts. This problem is solved by a special coupler design, as described below.

The coupler <NUM>, shown in <FIG>, is specially designed in attempt to satisfy the hemodynamic and thromboresistance requirements when connecting the proximal cannula end <NUM> to the VAD inlet adapter <NUM>. Illustrated in <FIG> are the components of the coupler <NUM> that constitutes the integration function. The coupler <NUM> includes a flange base <NUM>, a pair of collars <NUM>, and hinges <NUM> that join together the collars <NUM> with the flange base <NUM>. Spring coils <NUM> are loaded in the hinge joint <NUM>, maintaining the collars <NUM> in an opening position when unlocked (<FIG>). The collars <NUM> are grooved internally as shown in <FIG>, <FIG>. The collars <NUM> have an internal grooved slot <NUM> to receive and compress sandwiched the flange base <NUM>, the flange ramp <NUM> of the cannula <NUM>, and the beak flange of the inlet adapter.

Quick-connection type locking can easily be carried out by closing the collars <NUM> that will be latched without a concern of unintentional unlocking, as depicted in <FIG>. A leaf spring type latch <NUM> is installed at the tip of one collar <NUM> by welding a slab <NUM> on top of the latch <NUM> to attain the required spring force. The latch <NUM> will be bent as it slides on a ramp <NUM> on the opposing collar in the course of locking. As latch <NUM> clears the top of the ramp <NUM>, it will drop down to the base of said ramp <NUM> by an elastic restoring force, thereby working as a safe for preventing incidental latch unlock or collar opening ascribed to pump vibration or rocking in long-term use. For pump explant or exchange that requires component decoupling, the latch <NUM> can be bent and lifted upward by a tool, permitting an unlocking force to be exerted to rotationally open the collars <NUM> and hence disengage the VAD <NUM> from the cannula <NUM>.

For the design of coupler <NUM> that is able to connect a rigid beak <NUM> with the semi-rigid cannula flange ramp <NUM> concentrically, a simultaneous catching around the entire peripheral rim of flange base <NUM> is critical. Whenever simultaneous catching/locking engagement fails to be accomplished, the initially caught cannula flange ramp <NUM> will be strained more than the other free portion, creating a tendency to tilt or disposition the unevenly contacted ramp surface <NUM> leading to an eccentric pump connection. Such an eccentric connection often is the causal factor that generates step or gap at the interface that leads to thrombus formation. This drawback is remedied by having the collar contour <NUM> of the distal flange of the coupler <NUM> configured in such a way that the locking engagement simultaneously includes all circumferential contact areas. When locked, the edge of the metallic beak <NUM> will sink slightly into the compressed silicone ramp <NUM> with controlled depth and further reduces the interface discontinuity when exposed to blood stream. Hence, the conventional interface thrombus can be substantially minimized or annihilated by administrating a moderate anticoagulant regimen.

Integration of the inflow cannula <NUM> to the VAD <NUM> is accomplished by a clamping mechanism using the deformable cannula proximal end <NUM> serving as a "gasket" between the connected rigid flanges <NUM>, <NUM> of the coupler <NUM> and the VAD inlet adapter <NUM>, respectively. <FIG> illustrates an integrated relationship between the joined inflow cannula <NUM> and the inlet adapter <NUM> of the VAD <NUM>, locked together by the coupler <NUM>. The present interface connection between pump and cannula has two hemodynamic merits for reducing thrombus formation in-situ. First, there will be literally no obvious step or gap type joint discontinuities generated as observed in the conventional butt connection. Second, stasis flow located in the interface of the beak leading-edge <NUM> can be minimized. Hence, blood stream flowing over the connection interface will be maintained with high-speed, substantially improving the butt connection drawback, namely the forward- or backward-facing step existing at the interface, that generates flow stasis and promotes thrombotic adverse events in-situ and in the blood stream.

Implantation of the present inflow cannula invention <NUM> and connection of said cannula <NUM> to rotary blood pump <NUM> are summarized below. The step-by-step procedural instructions that enable such implantation are described as follows:.

In summary, an embodiment of the present disclosure provides an inflow cannula assembly, for transporting blood between a heart chamber and a ventricular assist device (VAD), which includes a deformable polymeric cannula, a pair of male and female fasteners, a VAD coupler, a VAD inlet adapter, and a VAD inlet adapter. The cannula includes: a first end, with a bellmouth intake to be inserted into heart chamber; a second end, with a flange ramp; and a conduit, wherein the first and second ends are integrally joined by the conduit, and the entire inner surface of the cannula is smooth and seamless. The male and female fasteners are screw interconnected with the male fastener anchored on the cannula. The second end is configured to interface with the VAD inlet adapter. The VAD coupler connects the second end with the VAD inlet adapter, and the VAD coupler includes a flange base and a pair of collars pinned on the flange base, wherein the collars have an internal grooved slots to receive and compress the sandwiched flange base, the flange ramp of the cannula, and a beak flange of the VAD inlet adapter; and the VAD inlet adapter includes a wedge-shaped beak to be interfaced with the cannula's second end, the beak flange to be accepted by the coupler, and a base integrated with the VAD.

Use of ordinal terms such as "first", "second", "third", etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having the same name (but for use of the ordinal term) to distinguish the claim elements.

Claim 1:
An inflow cannula assembly (CA), for transporting blood between a heart chamber and a ventricular assist device (VAD) (<NUM>), comprising:
a deformable polymeric cannula (<NUM>), comprising:
a first end, being used as an intake to be inserted into heart chamber, and being formed to have a bellmouth (<NUM>);
a second end, being formed to have a flange ramp (<NUM>); and
a conduit (<NUM>), wherein the first end and the second end are integrally joined by the conduit (<NUM>), and an entire inner surface of the cannula (<NUM>) is smooth and seamless;
a male fastener (<NUM>) and a female fastener (<NUM>), wherein the male fastener (<NUM>) and the female fastener (<NUM>) are screw interconnected with the male fastener (<NUM>) anchored on the cannula (<NUM>);
characterized in that the inflow cannula assembly (CA) further comprises:
a ventricular assist device (VAD) coupler (<NUM>); and
a ventricular assist device (VAD) inlet adapter (<NUM>) configured to interface with the VAD (<NUM>), wherein:
the second end is configured to interface with the VAD (<NUM>) via the VAD inlet adapter (<NUM>);
the VAD coupler connects the second end with the VAD inlet adapter, and the VAD coupler (<NUM>) includes a sandwiched flange base (<NUM>) and a pair of collars (<NUM>) pinned on the sandwiched flange base (<NUM>), wherein the collars (<NUM>) have at least one internal grooved slot (<NUM>) to receive and compress the sandwiched flange base (<NUM>), the flange ramp (<NUM>) of the cannula (<NUM>), and a beak flange (<NUM>) of the VAD inlet adapter (<NUM>); and
the VAD inlet adapter (<NUM>) includes a wedge-shaped beak (<NUM>) to be interfaced with the second end, the beak flange (<NUM>) to be accepted by the VAD coupler (<NUM>), and a base (<NUM>) integrated with the VAD (<NUM>).