Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Flexible leaflet
Reexamination Certificate
2000-06-21
2002-03-19
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Flexible leaflet
C623S002130, C623S023720, C623S002110
Reexamination Certificate
active
06358277
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is in the field of heart valve prostheses. More specifically, the present invention is directed to the replacement of the atrioventricular valves with an anatomically designed mitral valve. The present invention is also directed to obturators and sizers to measure the host's valve annulus diameter and select the appropriate size of the prosthesis, to a holder to maintain the prosthesis during implantation, and to a measuring instrument to determine the locations for suturing parts of the prosthesis to the papillary muscles of the patient.
2. Brief Description of Background Art
Replacement of the diseased heart valves is a frequent operation in cardiac surgery. As is known, heart valves (aortic, pulmonary, mitral and tricuspid) function essentially as check valves operating hemodynamically in synchronization with the pumping action of the heart, allowing blood to flow in a downstream direction and blocking flow in the opposite or upstream direction. In disease, this function is impaired either through narrowing of the valve or regurgitation. The natural heart valves are of two distinct basic configurations. The sigmoid valves (aortic and pulmonary valves) are situated on the outflow of the left and right ventricles and are made of three small and similar cusps inserted into the base of the aorta or pulmonary trunk. The atrioventricular valves (mitral and tricuspid valves) consist of several large leaflets of different size attached at their base to the valve annulus and held at their free edge with a complex variety of tendons called chordae tendinae that are inserted into the papillary muscles of the ventricles.
The chordae tendinae are of two main types: those extending from the papillary muscles to the free edge or margin of the leaflets are called “marginal chords” and those extending from the papillary muscles to the undersurface or ventricular surface of the leaflets are called “basal chords.” Among these basal chords, two thicker chords are attached to each papillary muscle and to the undersurface of the anterior mitral leaflet close to its base in the mitral annulus. These chords have been labeled “principal,” “strut,” or “stay” chords. The marginal and basal cords serve different functions. The marginal chords are essential for the competence of the atrioventricular valves. During diastole the valve is open to allow for the passage of blood, the leaflets are separated and the marginal chords are slack. During systole, the pressure in the ventricle closes the valve by bringing the leaflets together. The marginal chords become taut to maintain the leaflets in contact. In a diseased heart rupture or elongation of the marginal chords results in prolapse of the leaflets towards the atrium and consequently, valve insufficiency. The basal chords hold the body of the leaflets during systole, and the strut chords remain taut during the whole cardiac cycle and fulfill the function of maintaining the overall geometry of the ventricles.
The above-described functions of the chordae tendinae were ignored until recently as far as atrioventricular valve replacement was concerned. In surgery, when a diseased atrioventricular valve needed replacement, the whole mitral apparatus was excised including the leaflets and marginal and basal chords. However, recent experimental and clinical observations have shown that maintaining the continuity or attachment between the papillary muscles and the mitral annulus is essential to preserving the pumping action of the ventricles (Miki et al. Mitral Valve Replacement with Preservation of Chordae Tendinae and Papillary Muscles. Annals Thoracic Surgery 1998;45:28-34). Therefore, relatively recently the art has recognized the need to maintain annulo-papillary continuity when replacing an atrioventricular valve, but attempts to do so have met less than full success.
Proximally, the valve leaflets are attached to the annulus. This structure is not rigid and changes in shape continuously during the cardiac cycle. During diastole the atrio-ventricular annulus becomes circular and therefore of the largest possible diameter to allow maximum blood flow. During systole, the annulus area is significantly reduced, becoming smaller and “D” shaped, and facilitating the apposition of the valve leaflets. In this description of the prior art and ensuing description of the invention the terms “proximal”, “distal” “anterior” and “posterior” are used in the anatomical sense. “Proximal” means “upstream” as far as blood flow is concerned, “distal” means downstream; “anterior” means closer to the sternum, and “posterior” means closer to the spine.
Restoration to normal function while maintaining whole the atrioventricular valves is sometimes possible with specific repair techniques (Duran Perspectives in Reparative Surgery for Acquired Valvular Disease. Advances in Cardiac Surgery, 1993;4:1-23). Although the results of this surgery have been shown to be superior to valve replacement, the distortion of the valve often makes its replacement imperative. The standard replacement of the mitral and tricuspid valves is with either mechanical or bioprosthesis. All these prior art prostheses are not anatomical, i.e. they do not reproduce the normal atrioventricular valves. Usually, a single design is used for all positions, be it sigmoid or atrioventricular. The mechanical valves used for replacement resemble neither the sigmoid nor the atrio-ventricular valves.
The commercially available bio-prostheses are porcine or pericardial aortic valves. The prostheses used for mitral or tricuspid replacement are in fact aortic prostheses differing only in their sewing ring, not in the actual valve mechanism. Furthermore, both the mechanical and the bio-prosthesis are mounted on a rigid casing that does not allow for the normal changes in shape and size of the atrioventricular annulus. This rigidity of the annulus of the replacement valves of the prior art has been shown to reduce the efficiency of ventricular function. Because the mitral valve is subjected to much higher pressure and stress and has a lower flow velocity than the other heart valves, its prosthetic replacement carries the worst clinical results and prognosis in terms of durability and thromboembolism.
The only anatomically designed mitral valve used clinically is the mitral homograft. In this case, the whole mitral valve apparatus from a cadaver is transplanted into the recipient (Doty, et al. Mitral Valve Replacement with Homograft. Annals Thoracic Surgery 1998;66:2127-31 and Duran, Mitral Valve Allografts. An opportunity. J Heart Valve Disease;1995:4:29-30). This procedure is technically difficult, and its results are still controversial. Probably, there are not more than 200 cases worldwide.
More closely anatomically designed mitral valves made of pericardium have also been designed and tested, mostly experimentally, in the prior art. In 1964 Van der Spuy (Completely Anatomical Autogenous Whole Mitral Valve. Thorax 1964; 19:526-29) described a mitral valve prosthesis made of two pairs of pieces of pericardium shaped as two large anterior and two smaller posterior leaflets. Several strips of ilio-tibial ligament were sutured to the leaflets (sandwiched between each pair of leaflets) and the other extremities tied together into two bundles which were anchored to the papillary muscles. A semicircular length of thick nylon thread was sutured around the upper margin of the anterior and posterior leaflets to provide stability to the valve. The author implanted this valve in two patients; one died 10 hours after surgery and the other was reported alive 6 weeks after implantation. No further information on this technique is available.
In 1968 Holdefer, et al. described two designs of a mitral valve made of autologous pericardium. (An Experimental Approach to Mitral Valve Replacement with Autologous Pericardium. Journal of Thoracic & Cardiovascular Surgery 1968;55:873-81) In the first design, two separate pieces of pericardium were trimmed to reproduc
Jackson Suzette J.
Klein & Szekeres LLP
The International Heart Institute of Montana Foundation
Willse David H.
LandOfFree
Atrio-ventricular valvular device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Atrio-ventricular valvular device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Atrio-ventricular valvular device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2883257