Patent Application
20060135912
A Myocardial Infarction (MI) or heart attack, occurs when the blood supply to some part of the heart muscle (myocardium) is abruptly stopped. This is often due to clotting in a coronary blood vessel. Blood supplying the heart muscle comes entirely from two coronary arteries, both lying along the outside surface of the heart. If one of these arteries or any part of one suddenly becomes blocked, the area of the heart being supplied by the artery dies. The death of a portion of the heart muscle is a myocardial infarct, and the amount of the heart affected by the sudden occlusion will determine the severity of the attack. If the heart continues to function, the dead portion is eventually walled off as new vascular tissue supplies the needed blood to adjacent areas.
According to the American Heart Association, in the year 2000 approximately 1,100,000 new myocardial infarctions occurred in the United States. For 650,000 patients this was their first myocardial infarction, while for the other 450,000 patients this was a recurrent event. Two hundred-twenty thousand people suffering MI die before reaching the hospital. Within one year of the myocardial infarction, 25% of men and 38% of women die. Within 6 years, 22% of Men and 46% of women develop chronic heart failure, of which 67% are disabled.
An MI starts when a coronary artery suddenly becomes occluded and can no longer supply blood to the myocardial tissue. When a myocardial infarction occurs, the myocardial tissue that is no longer receiving adequate blood flow dies and is replaced with scar tissue. Within seconds of a myocardial infarction, the under-perfused myocardial cells no longer contract, leading to abnormal ventricular wall motion, high wall stresses within and surrounding the infarct, and depressed ventricular function. The infarct expansion and ventricular remodeling are caused by these high stresses at the junction between the infracted (not contracting) tissue and the normal myocardium. These high stresses eventually kill or severely depress function in the still viable myocardial cells. This results in a wave of dysfunctional tissue spreading out from the original myocardial infarct region.
Left ventricular remodeling is defined as changes in shape and size of the Left Ventricle (LV) that can follow a MI. The process of LV enlargement can be influenced by three independent factors that is, infarct size, infarct healing and LV wall stress. The process is a continuum, beginning in the acute period and continuing through and beyond the late convalescent period. During the early period after MI the infarcted region is particularly vulnerable to distorting forces. This period of remodeling is called infarct expansion. The infarct expansion phase of remodeling starts on the first day of MI (likely several hours after the beginning of the MI) and lasts up to 14 days. Once healed, the infarcted tissue or “scar” itself is relatively non distensible and much more resistant to further deformation. Therefore late enlargement is due to complex alterations in LV architecture involving both infarcted and non-infarcted zones. This late chamber enlargement is associated with lengthening of the contractile regions rather than progressive infarct expansion. Post infarction LV aneurysm (a bulging out of the thin weak ventricular wall) represents an extreme example of adverse remodeling that leads to progressive deterioration of function with symptoms and signs of congestive heart failure.
Effective treatments for MI are acute and can be only implemented immediately after the occlusion of the coronary vessel. The newest approaches include aggressive efforts to restore patency to occluded vessels broadly called reperfusion therapies. This is accomplished through thrombolytic therapy (with drugs that dissolve the thrombus) or increasingly with primary angioplasty and stents. Reopening the occluded artery within hours of the initial occlusion can decrease tissue death, and thereby decrease the total magnitude of infarct expansion, extension, and ventricular remodeling. These treatments are effective but clearly not satisfactory alone. In many cases, patients arrive at the appropriately equipped hospital too late for these acute therapies. In other cases, their best efforts fail to reopen blood vessels sufficiently to arrest expansion of the infarct. These therapies are also associated with considerable risk to the patient and high cost.
Scientific studies show that constraining the heart in the hours and days following the acute MI can reduce the extent of damage to the heart. Benefits exhibited by constraining the heart during and after the infarct expansion can be traced down to the relationship between the changing geometry of the heart and the stress in the heart muscle that forms the ventricular wall. An example of a treatment for constraining the heart is disclosed in U.S. Patent Application Publication 2004/0193138 A1.
A treatment device and method has been invented for clinical use that constrains the heart by placing biodegradable viscoelastic substance acting as a hydraulic heart constrainer in the pericardial sac for a controlled period of time.
An embodiment of a novel treatment device for a biodegradable pericardial constraint comprises: (i) a cannula placed in the pericardial sac, (ii) an external system for delivery of a hydraulic heart constrainer in controlled manner, and (iii) a biodegradable viscoelastic substance (BES) acting as a hydraulic heart constrainer. The treatment method may include the following steps: (i) placement and securing of the cannula for the injection of the biodegradable viscoelastic substance into the pericardial space, (ii) connection of the delivery system containing biodegradable viscoelastic substance to the cannula, (iii) controlled biodegradable viscoelastic substance injection into the pericardial space, (iv) extraction of the cannula, and (v) sealing of the transpericardial incision.
A system has been developed for injecting a biodegradable pericardial constraint comprising: a biodegradable viscoelastic substance (BES); an external injection container for the BES; a cannula having a distal section adapted to be inserted into a pericardial sac of a mammalian heart and a proximal section connectable to the external injection container; wherein BES from the injection container is injected into the pericardial sac through the cannula. The BES may comprises a natural biopolymer, such as lipids, collagen, polysaccharides and polyglyconates, cellulose, gelatin, starch, cross linked collagen gel, a Hyaluronic Acid or a synthetic polymer such as polylactide (PLA), polyglycolide (PGA), poly(lactide-co-glycolide) (PLGA), polyanhydride, PEG and polyorthoesters.
A method has been developed comprising: placement and securing of a cannula to inject a biodegradable viscoelastic substance into a pericardial space of a heart of a mammalian patient; connecting a delivery system containing the biodegradable viscoelastic substance to the cannula, and controlling the injection of the biodegradable viscoelastic substance injection into the pericardial space. The cannula may be inserted through a transpericardial incision in the pericardial sac and the method may include sealing the pericardial sac after extracting the cannula.
A treatment system has been developed for a biodegradable pericardial constraint comprising: a cannula placed in a pericardial sac of a mammalian patient; an external system connectable to the cannula for delivery of a hydraulic heart constrainer in a controlled manner, and a biodegradable viscoelastic substance (BES) to be delivered by the external system to the pericardial sac, wherein the BES acts as a hydraulic heart constrainer when injected into the pericardial sac.
A method has been developed to constrain a mammalian heart comprising: positioning a cannula in a pericardial sac of the heart; introducing a biodegradable viscoelastic substance (BES) though the cannula into the pericardial sac, and extracting the cannula from the pericardial sac after introducing the BES.
A preferred embodiment and best mode of the invention is illustrated in the attached drawings that are described as follows:
First the pericardium is tapped with a needle. After the position of the needle is confirmed, the needle is withdrawn and replaced with a soft, pigtail catheter using the Seldinger technique. After dilating the needle track, the cannula is advanced over the guidewire into the pericardial space. In order to prevent undesirable oozing of the implantable substance around the cannula during the injection different methods of securing the cannula can be utilized.
A straightforward surgical approach is to place sutures 307 around the cannula in the purse string manner and tighten it up. Another method of securing the cannula in place utilizes inflatable balloon positioned at the distal end of the cannula as shown in
The balloon can also be inflated by infusion of the tissue sealant such as BioGlue produced by CryoLife Inc. It will enable inflatable balloon to provide a dual function of anchoring the cannula in place and sealing of the transpericardial incision at the end of the procedure.
Yet another way of closing the transcardial incision shown in
The balloon can also be inflated by infusion of the tissue sealant such as BioGlue produced by CryoLife Inc. Using the tissue sealant enables the inflatable balloon to provide a dual function of anchoring the cannula in place and sealing of the transpericardial incision at the end of the procedure.
Besides securing the cannula in place and prevention of the BES leakage during the injection, the dual function balloon can deliver a tissue sealant directly to the insertion site. The combined anchoring and sealing mechanism demonstrated by
Alternative embodiment of the combined anchoring and sealing mechanism depicted in
The injectable biodegradable viscoelastic substance 304 used to create a hydraulic heart constrainer may be one or more biodegradable biomaterials. It may be chosen from the natural biopolymers and substances such as: lipids, collagen, polysaccharides in the form of proteoglycans and glycosaminoglycans and polyglyconates specifically hyaluronic acid (HA) and its derivatives, cellulose, gelatin, starch, as well as synthetic polymers such as polylactide (PLA), a polyglycolide (PGA), poly(lactide-co-glycolide) (PLGA), polyanhydride, PEG, and/or polyorthoesters. The desirable injectable biodegradable viscoelastic substance may have an array of properties allowing it to produce a therapeutic effect during a desirable therapeutic window and to dissipate afterwards without any toxic product of degradation. The therapeutic window is determine to be between 14 and 60 days. In order to produce desirable therapeutic effect, BES should have a viscosity range of 10000 CST to 15000 CST. The desirable induced interpericardial pressure should be in the range of 12 mmHg to 32 mmHg. That combination of requirements suggests a number of potential candidates from the above described groups of biomaterials. In this preferred embodiment a chosen material is a cross linked collagen gel. Collagen has been used extensively in medicine and in surgery. Collagen is a fibrous protein and constitutes the major protein component of skin, bone, tendon, ligament, cartilage, basement membrane and other forms of connective tissue. Collagen based devices have been used as nerve regeneration tubes, as sutures, haemostatic fiber and sponges, wound dressings, neurosurgical sponges, injectable implants for soft tissue augmentation, pharmaceutical carriers, ophthalmic aqueous-venous shunts, contact lenses and the like. The Injectable collagen products that gained widespread use for subcutaneous, subdermal, and intradermal and periuretheral injections are commercially available and sold under different names such as Zyderm, Zyplast produced by Collagen Corporation and Contigen produced by CR Bard. Typically Injectable collagen material is suspended in media tailored for the specific application, and is packaged in syringes ready for injection through small gauge needles.
The properties of collagen which favor its use as a biomaterial are many. Collagen is biodegradable, and when implanted in the body, is absorbed at a rate that can be controlled by the degree of intra or intermolecular cross-linking imparted to the collagen molecule by chemical or physical treatment. Collagen products can thus be designed such that, on implantation, they will completely be absorbed in a few days or in months. The collagen can also be chemically treated so that it becomes non-absorbable while still retaining its hydrophilic character and its good tissue response.
The main sources of collagen for commercial applications are bovine tendons, calf, steer or pig hide. All are readily available at relatively low cost. Generally, reconstituted collagen products are prepared by purification of native collagen by enzyme treatment and chemical extraction. The purified collagen is then dispersed or dissolved in solution, filtered and retained as such, or is reconstituted into fiber, film or sponge by extrusion or casting techniques which are well known to those skilled in the art. Suitable collagen material for the hydraulic heart constrainer implant may be available from, for example, DEVRO, Integra Life Sciences, Collagen Matrix and Kensey Nash, among others. The present invention preferably employs collagen in acid swollen solution as a starting material. An acidic solution of an atelopeptide form of bovine skin collagen is commercially available from DEVRO Pty. Limited. Typically this material is in a solution or gel form with concentration in the range of about 4-60 mg/mL. The concentration of collagen can be adjusted downwards, if necessary, by simple dilution to achieve desirable viscosity.
The embodiments of the present hydraulic heart constrainer implant may be selectively biodegradable and/or bio-absorbable such that it degrades and/or is absorbed after its predetermined useful lifetime is over. An effective way of controlling the rate of biodegradation of embodiments of the present hydraulic heart constrainer implant is to control and selectively vary the number and nature (e.g., intermolecular and/or intramolecular) of crosslinks in the implant material. Control of the number and nature of such collagen crosslinks may be achieved by chemical and/or physical means. Chemical means include the use of such bifunctional reagents such as aldehyde or cyanamide, for example. Physical means include the application of energy through dehydrothermal processing, exposure to UV light and/or limited radiation, for example. Also, a combination of both the chemical and the physical means of controlling and manipulating crosslinks may be carried out. Aldehydes such as glutaraldehydes, for example, are effective reagents of collagenous biomaterials. The control and manipulation of crosslinks within the collagenous solution or gel of the present hydraulic heart constrainer implant may also be achieved, for example, through a combination of dehydrothermal crosslinking and exposure to cyanamide.
Yet another embodiment of the present hydraulic heart constrainer implant may be Hyaluronic Acid or hyluronan which is a naturally occurring, high viscosity, linear mucopolysaccharide comprised of alternating glucuronic acid and N-acetyl-glucosamine residues that interacts with other proteoglycans to provide stability and elasticity to the extracellular matrix of all tissues. Hyaluronic acid is a clear, viscous fluid, manufactured and commercially available from numerous domestic and foreign vendors and sold under different names such as AmVisc and OrthoVisc produced Anika Therapeutics, just to name a few. It is used for ophthalmic vitreous body implants, viscosurgery, and synovial joint replacements. Purified hyaluronic acid is believed to cause very little tissue reaction once spilled into the soft tissue. Suitable Hyaluronic Acid for the hydraulic heart constrainer implant may be available from, for example from Biomatrix Inc, Anika Therapeutics, Genzyme Corp. Lifecore Biomedical, among others.
There are many ways in which hyluronan can be crosslinked to resist enzymatic biodegradation. An effective way of controlling rate of biodegradation of embodiments of the present hydraulic heart constrainer implant is to utilize a small amount of an aldehydes such as glutaraldehydes or formaldehyde to produce a BES with very desirable properties. Crosslinking can also be achieved with divinyl sulfone and polyvalent cations (ferric, aluminum, etc.) and aziridines (e.g. cross-linker CX-100).
The hydraulic heart constrainer implant may also contain a therapeutic or biologically active agent and combinations thereof such as angiogenesis-promoting factors, vascular endothelial growth factor (VEGF), peptides, oligopeptides, just to mention a few.
The amount of injected injection of biodegradable substance should be sufficient to: (a) distribute substance around in-between the heart and the sack, and b) constraint the heart so that its size is substantially reduced as a result of tension generated by the substance. For an adult human heart, the amount of biodegradable substance to be injected is preferably in a range of 40 ml to 100 ml, but greater or less amounts of the biodegradable substance may achieve the desired therapeutic effect of constraining the heart. The biodegradable substance may constrain the heart by at least partially enveloping the heart mussel circumferentially and squeezing or reducing diameter of the enveloped portion of the heart. The aperture in the pericardium made to inject the biodegradable substance is to be sealed after the injection. The aperture may be sealed by injection of a sealing substance, e.g., a biocompatible glue, a suture or other means which ensures that the aperture will not allow for the leakage of a substantial amount of the biodegradable substance.
In an exemplary, method a therapeutic amount of biodegradable substance is injected into the pericardium in an amount sufficient to envelope a substantial portion (or all) of the heart mussel, the injection aperture in the pericardium is sealed after injection, the heart is constrained (e.g., reduced by 10% of the heart volume) as a treatment for acute MI, and the biodegradable substance dissipates in the body after two weeks to twelve weeks (more or less) and preferably within a period of four to eight weeks.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
This application is a continuation-in-part (CIP) application of U.S. patent application Ser. No. 10/808,397, entitled “Method and System To Treat and Prevent Myocardial Infarct Expansion” filed Mar. 25, 2004, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional application 60/457,246, filed Mar. 26, 2003, and this application also claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 60/628,923, entitled “Biodegradable Pericardial Constraint”, filed Nov. 19, 2004, the entirety of all of these related applications are incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 60628923 | Nov 2004 | US | |
| 60457246 | Mar 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10808397 | Mar 2004 | US |
| Child | 11282694 | Nov 2005 | US |
