Patent Application
20060063970
The invention relates to devices and methods for treating dilatation of the valves at the base of the heart by external stabilization of the base of the heart, which subtend the atrio-ventricular valves of the heart. Such devices also include an extension thereto for the treatment of localized myocardial defects, scars and damage.
Dilatation of the base of the heart occurs with various diseases of the heart and often is a causative mechanism of heart failure. In some instances, depending on the cause, the dilatation may be localized to one portion of the base of the heart (e.g., mitral insufficiency as a consequence of a heart attack affecting the inferior and basal wall of the left ventricle of the heart), thereby affecting the valve in that region. In other cases, such as cardiomyopathy, the condition may be global affecting more of the heart and its base, causing leakage of particularly the mitral and tricuspid valves. Other conditions exist where the mitral valve structure is abnormal, predisposing to leakage and progressive dilatation of the valve annulus (area of valve attachment to the heart). This reduces the amount of blood being pumped out by the ventricles of the heart, thereby impairing cardiac function further.
In patients with heart failure and severe mitral insufficiency, good results have been achieved by aggressively repairing mitral and/or tricuspid valves directly, which requires open-heart surgery (Bolling, et al). The mitral valve annulus is reinforced internally by a variety of prosthetic rings (Duran Ring, Medtronic Inc) or bands (Cosgrove-Edwards Annuloplasty Band, Edwards Lifesciences Inc). The present paradigm of mitral valve reconstruction is therefore repair from inside the heart, with the annulus being buttressed or reinforced by the implantation of a prosthetic band or ring. Since this is major open-heart surgery with intra-cavitary reconstruction, there is the attendant risk of complications and death associated with mitral valve surgery. Another approach has been to replace the mitral valve, which while addressing the problem, also requires open-heart surgery and involves implantation of a bulky artificial, prosthetic valve with all its consequences. Because every decision to perform major surgery requires some risk vs. benefit consideration, patients get referred for risky surgery only when they are significantly symptomatic or their mitral valve is leaking severely.
In contrast to the more invasive approaches discussed above, in specific instances of inferior left ventricular wall scarring causing mitral regurgitation, Liel-Cohen and co-workers have suggested localized pressure or support of the bulging scar of the inferior wall of the heart from the outside (Liel-Cohen. N. et al. (2000) “Design of a new surgical approach for ventricular remodeling to relieve ischemic mitral regurgitation: insights from 3-dimensional echocardiography”. Circulation 101 (23):2756-2763).
Another less invasive approach to preventing global heart dilation is ventricular containment with a custom made polyester mesh, or cardiac support device (U.S. Pat. Nos. 6,077,218 and 6,123,662). These devices are designed to provide a passive constraint around both ventricles of the heart, and constrain diastolic expansion of the heart. Other devices include ventricular assist devices that provide cardiac assistance during systole and dynamic ventricular reduction devices that actively reduce the size of the heart. However, this technique does not specifically address valve leakage using a device that reinforces the base of the heart in all phases of the cardiac cycle.
Accordingly, there is a need to provide a less invasive, simple technique of repairing, reinforcing, reducing or stabilizing the base of the heart and its underlying valves (mitral and tricuspid valves) from the outside. In one embodiment, such devices circumvent the atrio-ventricular junction to provide for basal ventricular stabilization. When the device also includes at least one extension thereto, it is capable of simultaneously providing myocardial reinforcement/restraint.
The invention addresses the problems discussed above by providing a device for the treatment of certain heart disorders, in particular mitral and/or tricuspid valve insufficiency. The device aims to reduce the size of the base of the heart that contains these valvular structures. In addition, the invention can be used to address progressive dilatation of any localized area of the heart, such as the atrial or ventricular myocardium, or the cardiac base. It does so by providing external re-enforcement or remodeling of the cardiac base. As used herein, the surgical procedure for implanting the device is referred to as ibasal annuloplasty of the cardia externally (“BACE”) and the device is referred to as the external cardiac basal annuloplasty system (“ECBAS”) or BASE System.
The invention also provides a BACE device with an extension thereto (“BACE-PLUS”) for treating valvular regurgitation and simultaneously reinforcing the myocardium.
In one embodiment, a customized or specially constructed biocompatible strip is implanted along the base of the heart at the level of the atrio-ventricular groove. In one aspect, the strip encircles the heart. The strip or mesh is between 2 and 5 cms wide and can be secured by 2 rows of clips or sutures, one on the atrial side and the other on the ventricular side of the atrio-ventricular groove. Specific care is taken to avoid injury to the circumflex and right coronary arteries and the coronary sinus. This procedure may be performed either as a stand-alone procedure or as an adjunct to other cardiac surgery. Additionally, it may be performed with or without the aid of cardiopulmonary bypass.
Another embodiment of this approach is a device or strip, which once implanted at a certain size, can be tightened over time either by inflation of an attached chamber or programmed to return to a pre-formed size (based on elasticity or pre-existing memory) of the material used.
Another embodiment of this device, while externally stabilizing the base of the heart, also provides a localized increase in contraction along any segment of the base to improve contractile function. This may be accomplished by the aid of contractile metal, biomaterial or modified muscle or other cells.
Variations of the device include a complete stabilization of the base of the heart, or a partial stabilization around the expansile portions of the mitral and tricuspid valves by a biocompatible strip.
Another variation uses ports along the device that will facilitate delivery of specialized drugs, gene therapeutic agents, growth factors, etc.
A specific variation incorporates the use of epicardial bi-ventricular pacing electrodes implanted along with the BACE-System, where multi-site pacing might be indicated.
The invention also provides a method of implantation, which may be through a conventional full median sternotomy with the strip being secured by sutures, or a minimally invasive approach whereby the device/strip may be implanted by a specialized implantation system using adhesives, self-firing clips, sutures, etc.
Another modification of this technique is the local application of prosthetic material to stabilize scars of the heart to prevent their expansion (local ventricular stabilization).
In an alternate embodiment, the device incorporates additional strips to be used in concert or as an extension to provide localized support to areas of ventricular reconstruction or areas of fresh infarction or old scar.
The invention is directed to and external support device for the base of the heart. The support functions to decrease, and/or prevent increases in, the dimensions of the base, and in particular the atrio-ventricular junction, beyond a pre-determined size. The device is designed to reduce the size of the cardiac base in a manner similar to an internal annuloplasty band or ring.
This invention is particularly suited for use in regurgitation of the mitral and tricuspid valves. The device may also be used prophylactically in heart failure surgery to prevent further cardiac basal dilation or expansion even if the underlying mitral and tricuspid valves are competent. The device may be used in moderate or advanced heart failure to prevent progression of basal dilation or reduce the size of the dilated base.
As used herein, “cardiac base” refers to the junction between the atrial and ventricular chambers of the heart, also known as the atrio-ventricular junction marked externally by the atrio-ventricular groove. This is easily identified in the change of appearance of the cardiac muscle and also the presence of arteries and veins.
The heart is enclosed within a double walled sac known as the pericardium. The inner layer of the pericardial sac is the visceral pericardium or epicardium. The outer layer of the pericardial sac is the parietal pericardium. The term “endocardial surface” refers to the inner walls of the heart. The term “epicardial surface” refers to the outer walls of the heart.
The mitral and tricuspid valves sit at the base of the heart and prevent blood from leaking back into the atria or collecting chambers. See
Dilatation of the mitral annulus occurs maximally in the posterior portion of the annulus, which is not supported by the cardiac fibro-skeleton.
Mitral valve repair or replacement at present is always performed from inside the heart with the aid of cardiopulmonary bypass. Rings are implanted along the inner surfaces of the entire or expansile portions of the mitral and tricuspid annuli (
Overview
The basal ventricular stabilization of the invention works by using a prosthetic material such as polyester mesh anchored or sutured to the base of the heart at the level of the atrio-ventricular groove. This serves to stabilize the mitral and tricuspid annuli from the outside (
Many patients with moderate degrees of mitral regurgitation are not treated surgically, because the risks of surgery outweigh the potential benefits in this group of patients. However, patients with conditions such as chronic heart failure tend to get very symptomatic even with moderate degrees of mitral regurgitation. These groups of patients would benefit from the less invasive procedures, which are the subject of the invention. Thus, the potential of this technique in treating mitral regurgitation as a minimally invasive procedure has great appeal as the population ages and more patients manifest with symptoms of heart failure. It also can be applied en passant in patients undergoing coronary artery surgery without the aid of a heart-lung machine.
Device Parameters
The device of the invention can be constructed of any suitable implantable material. Examples of such materials are well known in the art and include, e.g., synthetic polymers such as polyester, polytetrafluoroethylene, polypropylene, Teflon felt, etc., as well as metallic materials such as stainless steel, mitinol and the like. Such metals may provide “memory”, such that they return to a specific shape after deformation, and in this manner provide an element of dynamic contraction. In yet another embodiment, the device may be constructed either partially or completely by natural materials, such as polyglycolic acid or compressed and/or crosslinked collagen, which may or may not be reinforced with synthetic polymers or other means. Any material is suitable that is biocompatible, implantable, and has a compliance that is lower than the heart wall. Other variations include incorporation of elastic material or elastin ingrowth into the biomaterial.
As shown in
The center portion of the device may be in the form of a solid single or multi-layer sheet, but is preferably of an open mesh, porous or woven design, such that the exterior of the heart is not completely covered and therefore remains exposed to the surrounding tissue. The size of the openings in the mesh can vary, for example from 2 mm to 2 cm, and can take any shape, such as circular, square, octagonal, triangular, or irregular. In a preferred embodiment, the center portion of the device is a mesh as depicted in
The center portion may also be adapted for the delivery of various therapeutic agents, such as growth factors or plasma proteins. In addition, it may be adapted to facilitate cellular growth, which in turn may facilitate anchorage of the device.
The device may be designed to completely circle the base of the heart, or it may be a “C” shape, in which case it is specifically designed and implanted so as to not impede blood flow through the aorta and pulmonary artery.
The biomaterial from which the device is constructed may also be radiolucent, radio-opaque or have radio-opaque markers at present intervals to monitor the movement of the cardiac base in real-time using fluoroscopy and to facilitate implantation.
The device may be completely rigid prior to implantation, or may have regions of varying rigidity. However, it is important that the device is sufficiently flexible to move with the expansion and contraction of the heart without impairing its function. It should, however, be designed to prevent expansion of the cardiac base during diastolic filling of the heart to a predetermined size. Since the size expansion parameters of a beating heart are well known, this can be accomplished by testing the device in vitro by applying forces that mimic heart expansion.
The edges of the device, which are depicted in
Device Extensions
In one embodiment, a limited extension of the BACE device may be applied to reinforce an area of myocardium that is in need thereof. This treatment may serve as an alternative to surgical reconstruction of the myocardium.
These areas may be akinethic or dyskinetic and may contribute to worsening cardiac function and mitral regurgitation. Such a dual-purpose device is referred to herein as a BACE-PLUS device.
The extension consists of biocompatible patch material that is made of the same material or a material similar to, but not necessarily identical to, the BACE device, such as biopolymers, mitinol and other materials described above for the BACE. The shape of the extension or patch is, for example, oval or circular to cover/encompass the whole region of the affected ventricle. In one embodiment, the extension has some degree of stiffness and additional reinforcement to prevent the “give” of a progressively enlarging heart. Such an embodiment would synergistically diminish heart enlargement while at the same time providing myocardial support.
The structure of the extension may be porous, cross-linked, woven, etc., as with any other relatively flat implantable material. The configuration of the materials provide a platform for impregnation of biomolecules such as growth factors, and also promote the propagation and growth of new myocardial repair cells along specific patterns that would optimize cardiac contraction.
The extension may be secured to the heart with sutures, specially designed staples or clips. Alternatively, the extension is secured with transmural neo-chords or non-reacting tensioning chords, akin to guide ropes of a sail or parachute. Finally, the extension may incorporate special Velcro type fastening material on one side that facilitates anti-slip and firm adhesion to the epicardial surface of the ventricles.
The BACE-PLUS device is adapted for administration to a patient population that has not undergone surgical myocardial reconstruction (i.e. surgical removal of the aneurism or scar). Indeed, the BACE-PLUS device may function by cellular or mechanical reconstruction of the myocardium as an alternative.
Device Attachment
The device may be attached to the outside of the base of the heart by any known method. For example, attachment may be biological, chemical or mechanical. Biological attachment may be brought about by the interaction of the device with the surrounding tissues and cells, and can be promoted by providing appropriate enhancers of tissue growth. Alternatively, chemical attachment may be provided by supplying a mechanism for chemical attachment of the device, or portions thereof, to the external surface of the heart. In yet another embodiment, the rigidity and tightness of the device around the heart may provide for sufficient mechanical attachment due to the forces of the heart against the device without the need for other means of attachment. In a preferred embodiment, however, as depicted in
Device Size
Although the size of the device depends on the purpose for which it is being implanted, it is contemplated that the device will be wide enough (measured from the outside of the first or top edge, i.e. the base edge, to the outside of the second or bottom edge, i.e. the apex edge) to provide efficient support to the atrio-ventricular grove. Accordingly, in one embodiment, the device is between 2 and 5 centimeters wide. In other embodiments, the device may be adapted to provide support over a larger area of the heart. This would provide specifically for reinforcement of areas of scar or muscular weakness as in dyskinetic infracted areas of the myocardium.
As shown in
Implantation
The ECBAS or BASE system may be implanted through a conventional midline total sternotomy, sub maximal sternotomy or partial upper or lower sternotomy. Alternatively, the device may be implanted through a thoracotomy incision, or a Video Assisted Thoracoscopic (VAT) approach using small incisions. The BASE system can also be implanted by a sub-costal incision as in the Sub-Costal Hand-Assisted Cardiac Surgery (SHACS). Additionally, the BASE system may be implanted with sutures onto epicardium or clips, staples, or adhesive material that can secure the device on the heart accurately. The device may also be implanted using robotic placement of the device along the posterior aspects of the base of the heart.
The method of implantation and the adequacy of the external annuloplasty can be dynamically assessed by intra-operative trans-esophageal echocardiography, epicardial echocardiography or trans-thoracic echocardiography. The size of the device is assessed based on external circumference measurements of the cardiac base in the fully loaded beating heart state.
Versions of the BACE Systems
a. Complete Versus Partial BACE
The ECBAS may completely encircle the cardiac base or just partially support the mitral and tricuspid valve portion of the cardiac base.
b. BACE with Extensions
In one embodiment, a limited extension of the ECBAS or an extension member may be applied to reinforce an area of myocardium. For example, the extension can served to support an area of the myocardium that has been reconstructed to exclude an aneurysm or scar. The extension typically extends from the bottom edge of the ECBAS. The extension can extend from the base of the heart towards the apex but does not need to reach the apex of the heart. The extension may be contiguous with the ECBAS material or may be a separate and/or different biocompatible material.
c. BACE with Pace
In another embodiment, the ECBAS has attached close to, or within it, epicardial steroid eluting pacing wires that can facilitate multi-site ventricular pacing for heart failure.
d. Dynamic BACE
In this embodiment, the device has fluid filled chambers that may be inflated gradually over time, to gradually reduce the size of the cardiac base. These chambers may also effect passive transfer of energy to facilitate diastolic and systolic support with a closed pericardium
e. Smart & Dynamic BACE
In this embodiment, the bio-material would have the capability to shrink to a pre-formed size over a period of time, based on the memory of the material or some other programmable characteristic. This would achieve controlled reduction over a period of time of the base of the heart.
f. Cellular BACE
In this embodiment, the bio-material uses available matrix technology, and seeding of appropriate cells to provide dynamic reduction and assistance to the cardiac base.
BACE Procedure:
Over a 12 month period, ten patients underwent Basal Annuloplasty of the Cardia Externally (BACE), to correct moderate mitral regurgitation. This technique involves securing a specially constructed polyester mesh like device to the epicardial surface of the cardiac base, at the level of the atrio-ventricular groove. These procedures were performed in conjunction with coronary artery surgery in all patients. All patients demonstrated a dramatic improvement in functional status, quality of life, mitral regurgitation and function of the heart. BACE can be performed safely with expectation of a good clinical outcome as an adjunct to conventional heart surgery.
Clinical Approach and Experience:
Careful pre-operative screening included radionuclide ventriculography to document left ventricular ejection fraction, a detailed trans-thoracic echocardiogram, a coronary angiogram, and in most cases a stress thallium and/or a Positron Emission Tomographic Scan looking for myocardial viability. The functional status of the patients were carefully documented by a heart failure cardiologist and nurse.
Ten patients who were undergoing conventional cardiac surgery, usually in the setting of poor cardiac function with moderate mitral regurgitation, were enrolled. All of these patients had coronary artery bypass surgery. All of them had at least moderate mitral regurgitation pre-operatively and intra-operatively (confirmed by trans-esophageal echocardiography). All of these patients had the Basal Annuloplasty of the Cardia Externally (BACE) performed with a polyester mesh constructed intra-operatively, based on the measured circumference of the cardiac base.
Surgical Technique:
The circumference of the base of the heart at the level of the atrio-ventricular groove was measured before the patient was connected to cardio-pulmonary bypass (CPB). Based on these measurements, a strip of polyester mesh measuring 2.5 to 3 cm in width was cut to size and fashioned, such that its length would be less than the basal circumference by about 2.5 to 4.5 cms. Once the patient was connected to cardiopulmonary bypass, the coronary artery bypass grafts were performed. Left ventricular reconstruction was performed when indicated.
The constructed BACE mesh was anchored posteriorly at the level of the atrio-ventricular groove, on atrial and ventricular sides with combination of 4/0 Ticron™ sutures and hernia staples, which were placed about 1.5 to 2 cm apart. The mesh was secured laterally as well. Final assessment of the tension and the securing of the BACE system was performed with the patient weaned off cardio-pulmonary bypass with the heart filled to pre CPB levels. The mesh was then tightened and secured just as the mitral regurgitation was abolished on trans-esophageal echocardiographic monitoring.
Post-Operative Course:
All these patients had trivial to mild mitral regurgitation at the completion of the procedure. At follow-up, 3, 6 and 12 months post-operatively, all of these patients demonstrated improved cardiac function (as measured by left ventricular ejection fraction), improved functional status and quality of life, and were able to maintain their improvement in the degree of mitral regurgitation. Radionuclide ventriculography was used to determine the left ventricular ejection fraction pre- and post-operatively. Compared to a preoperative value of 25.+−0.3.1% (n=8), the ejection fractions improved to 40.+−0.14.2% and 39.3.+−0.5.7% after 3 and 6 months post-operatively, respectively (p<5). Likewise, the New York Heart Association (NYHA) classification was used as an index of functional heart status. Compared to a pre-operative value of 3.11.+−0.0.33 (n−8), the NYHA improved to 1.17.+−0.0.41 after 3 months post-operatively (p<5). Mitral regurgitation (graded 1 to 4) was also observed to improve dramatically from 3.01 pre-operatively to 0.1 post-operatively after 6 months (p<5). In addition, there was improvement in tricuspid regurgitation as well.
Discussion:
Dilatation of the cardiac base often accompanies heart failure. This may be a secondary development due to volume overload and increased left ventricular wall stress. In cases of mitral or tricuspid valvular heart disease, annular dilatation occurs along with decompensation of the regurgitant lesions. Severe annular dilatation accompanies severe regurgitation. However, significant basal dilatation may co-exist with moderate or moderately severe atrioventricular valve regurgitation. Since repair of these conditions requires intra-cavitary repair of the affected annulus, the majority of surgeons tend to leave moderate and moderately severe mitral and/or tricuspid regurgitation alone. Using the methods and apparatuses of the invention, these conditions can be corrected from the outside of the heart. Furthermore, the correction can be tailored under trans-esophageal echocardiographic guidance. This avoids intra-cavitary manipulation. In selected cases, this procedure could be performed with heart beating also and without using the heart-lung machine, making it an “off-pump” procedure.
Twelve patients were treated with the BACE procedure as described in Example 1. All of the patients had pre- and post-operative studies at 3, 6, 12 and 18 months, including echocardiography and radionuclide ventriculography to look at cardiac function, amount of mitral regurgitation and the size of the hearts. All twelve patients were very symptomatic, with the majority in New York Heart Association (NYHA) class III status. The mean left ventricular ejection fraction (LVEF) was 25% preoperatively and all patients had moderate mitral regurgitation.
The BACE procedure was performed on cardio-pulmonary bypass with the heart decompressed. The procedure took approximately 15 minutes of extra bypass time and about 5 minutes of extra cross-clamp time.
The results are shown below in Table 1. As shown, the BACE procedure dramatically improved cardiac function and was at least equivalent to mitral valve repair eighteen months post-operatively.
All publications and patents mentioned in the above specification are herein incorporated by reference. Various modifications and variations of the described method and system of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in hematology, surgical science, transfusion medicine, transplantation, or any related fields are intended to be within the scope of the following claims.
This application is a continuation-in-part of U.S. Ser. No. 10/796,580 filed on Mar. 8, 2004, pending, which is a continuation application of U.S. Ser. No. 10/236,640 filed on Sep. 6, 2002, which issued as U.S. Pat. No. 6,716,158 on Apr. 6, 2004, and which claims priority of U.S. Provisional application 60/318,172, filed on Sep. 7, 2001.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10236640 | Sep 2002 | US |
| Child | 10796580 | Mar 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10796580 | Mar 2004 | US |
| Child | 11156004 | Jun 2005 | US |
