Conduit for a mechanical circulatory device

Surgery – Cardiac augmentation

Reexamination Certificate

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Reexamination Certificate

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06290639

ABSTRACT:

FIELD OF INVENTION
The present invention relates to mechanical circulatory devices, and in particular to a conduit for a mechanical circulatory device.
BACKGROUND OF THE INVENTION
Mechanical Circulatory Devices (MCDs) such as artificial hearts, Ventricular Assist Devices (VADs) and other blood circulating systems have become increasingly recognized as life saving devices for patients whose heart is diseased or has been injured by trauma or heart attack or other causes. VADs in particular, are recognized as a major life saving modality for assisting patients who suffer from congestive heart failure.
MCDs must be cormected to the natural blood circulation system of the body such as the heart and aorta. When designing an artificial heart or VAD, the inflow and outflow conduits are one of the most critical components. The conduits generally need to deal with a pulsatile or with a non-pulsatile flow, as well as with the flow negative pressures created by the MCD. The artificial conduit must finction within or outside the host patient's body. It must not introduce or allow the entry of bacterial or other contamination into the host's body or circulatory system. If the conduit does not fulfil these requirements, it may cause thrombosis pannus formation, blockage, twisting, knocking, and pulling or compressing the heart and adjacent organs.
Almost all blood conducting devices exhibit some degree of thrombus (blood clot formation). Thrombosis is a multifactorial phenomenon. Two major factors are the blood flow pattern and the properties of the material in contact with the blood. Research shows that the major causes of clotting in the current blood flow conduits are the use of thrombogenic materials and of designs which create undesired flow patterns such as turbulence, separation, recirculation, stasis (pooling), and high and very low shear stresses. Among specific factors related to the above, undesired flow patterns are often generated by the existence of crevices or the lack of smoothness on interior surfaces or at joints in the conduits. The risk of twisting and folding of the conduits can be extremely dangerous.
Another persistent problem with current conduits relates to their durability. Compression, tensile and torque forces act on the conduits, and current conduits have an insufficient fatigue resistance to these forces and are prone, to varying degrees, to be distorted. Moreover, suction generated by the MCD exposes the conduit to a negative pressure, which causes it to collapse.
Accordingly, there is a need of use of a conduit which provides sufficient strength and durability to prevent crevices or deformation where stress is exerted. In order to use such a strong conduit, there is a need to provide a suitable coupling to connect such a conduit to the MCD or a natural blood circulatory system. Flexibility, angulation, size and orientation of a conduit are all important factors that have to be considered in designing a conduit that is optimal in terms of performance, compression exerted on adjacent organs such as the lungs, heart, great vessels and displacement of the heart. The human chest anatomy, with various sizes and types for different bodies, is also one of the factors, dictating how these factors have to be considered in achieving anatomical fitness. The coupling needs to provide smooth internal transition between coupled components to reduce turbulence in the blood flow.
Therefore, there is a need of a conduit assembly which allows use of a conduit which provides sufficient strength and durability, and also provides flexibility in positioning such a conduit and smooth internal transition between coupled components.
SUMMARY OF THE INVENTION
According to one aspect of the invention, there is provided a conduit assembly for attachment to an MCD having an orifice surrounded by an orifice rim and a blood bag for forming a blood chamber in the MCD. The blood bag has an open end extends through the orifice. The conduit assembly comprises a tube, a coupling and a washer. The tube is provided for conducting blood between a patient and the orifice of the MCD. The tube has an orifice end. The coupling attaches the orifice end of the tube to the orifice of the MCD with the open end of the blood bag folded over the orifice rim of the MCD. The coupling is movable between a rotatable position wherein the tube is rotatable relative to the MCD, and a locked position wherein the tube is immobile relative to the MCD. The washer is placed between the orifice end of the tube and the blood bag folded over the orifice rim of the MCD. The washer has an inner section which has a shape corresponding to a space between the orifice end of the tube and the blood bag folded over the orifice rim of the MCD so as to smooth the transition between the tube and the blood bag at the orifice of the MCD to reduce turbulence in blood flowing between the tube and the blood bag.
According to another aspect of the invention, there is provided a method for implanting a circulatory apparatus in a patient. The apparatus comprises an MCD having an orifice surrounded by an orifice rim and a blood bag forming a blood chamber in the MCD and having an open end extending through the orifice, and a conduit assembly for attachment to the MCD.
The conduit assembly comprises a curved rigid tube for conducting blood between a patient, the tube having orifice end; a coupling for attaching the orifice end of the tube to the MCD, the coupling being movable between a rotatable position wherein the tube is rotatable relative to the MCD, and a locked position wherein the tube is immobile relative to the MCD. The method comprises folding the open end of the blood bag over the orifice rim of the MCD; providing a washer on the blood bag folded over the orifice rim of the MCD, the washer having an inner section which has a shape corresponding to a space between the orifice end of the tube and the blood bag folded over the orifice rim of the MCD so as to smooth the transition between the tube and the blood bag at the orifice of the MCD to reduce turbulence in blood flowing between the tube and the blood bag; attaching the orifice end of the tube to the orifice rim through the washer and the blood bag as being folded over the orifice rim of the MCD with the coupling in the rotatable position; positioning the MCD relative to the patient; rotating the tube until a desired position of the tube relative to the patient is achieved; and moving the coupling to the locked position.


REFERENCES:
patent: 4104005 (1978-08-01), Poirier
patent: 4508535 (1985-04-01), Joh et al.
patent: 5810708 (1998-09-01), Woodward et al.
Sugita et al., “In Vivo Evaluation of a Permanently Implantable Thermal Ventricular Assist System” vol. XXXII Trans Am Soc Artif Intern Organs, 1986, pp. 242-247.
Blubaugh, A.L., Development of An Implantable Integrated Thermally Powered Ventricular Assist System, vol. I, Technical Proposal N85-2, Dec. 12, 1985, pp. 1-322.
Olan, R.W., “National Heart, Lung, and Blood Institute Division of Heart and Vascular Diseases Contract No. N01-HV-28002” Quarterly Report, 1986, pp. 1-76.

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