Heart valve disease is a significant cause of morbidity and mortality, resulting from a number of ailments including rheumatic fever and birth defects. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves, and each has leaflets to control the directional flow of blood through the heart. Worldwide, approximately 300,000 heart valve replacement surgeries are performed annually, and about one-half of these patients receive bioprosthetic heart valve replacements, which utilize biologically derived tissues for flexible fluid-occluding leaflets.
Heart valve prostheses are either of the mechanical type that originally used a ball and cage and more recently a pivoting mechanical closure, or a tissue type or “bioprosthetic” valve typically constructed with natural-tissue valve leaflets. The most successful bioprosthetic materials for flexible leaflets are whole porcine valves and separate leaflets made from bovine pericardium stitched together to form a tri-leaflet valve. However, flexible leaflets formed of polymeric, fiber-reinforced, and other synthetic materials have also been proposed. The most common flexible leaflet valve construction includes three leaflets mounted to a peripheral support structure and commissure posts that project in a downstream or outflow direction. The leaflets have free edges between the commissure posts that meet or coapt in the middle of the flowstream to permit one-way flow. A suture-permeable sewing ring around the inflow end typically provides a platform for anchoring sutures.
Prosthetic valves typically have a delivery holder centrally located and sutured thereto, and an elongated delivery handle coupled to the holder for manipulating the valve assembly during implant. For the standard delivery approaches, the holder is attached to the inflow side such as the sewing ring for mitral valves and to the outflow side such as the stent cusps or outflow commissure tips for aortic valves.
When placing a flexible leaflet prosthetic valve in the mitral or tricuspid position, the commissure posts are on the leading or blind side of the valve during delivery and implant, and the surgeon uses the holder and an attached handle to slide (parachute) the valve down an array of sutures that have been pre-installed around the mitral annulus and then passed through the valve sewing ring. The mitral position is such that the outflow end with commissure posts is the leading end as it advances toward the left ventricle during implantation, and thus the holder is attached to the inflow (i.e., trailing) end of the valve. The difficulty of the delivery task is compounded by the small access pathway into the left atrium. Suture looping sometimes occurs when one or more of the sutures in the parachute array inadvertently wraps around the inside of one or more of the commissure post tips. If this occurs, the looped suture(s) may slow down the implant procedure, damage one of the tissue leaflets when tightly tied down, or interfere with valve operation and prevent maximum coaptation of the valve leaflets, resulting in a deficiency in the prosthetic mitral valve. These issued can be resolved inter-operatively if the surgeon is aware of the suture looping, but because the loops occur on the blind side of a mitral or tricuspid valve the surgeon might not be aware of a suture loop. If the surgeon does not eliminate the suture loop and leaves a valve implanted with a suture looped over the leaflet it is very likely to result in leaflet tearing forcing what can be an emergency surgery. If after tearing initiates, it is not correctly diagnosed and treated the consequences can be fatal for the valve recipient.
Existing mitral valve holders on the market attempt to mitigate the potential for suture looping of the commissure posts during implantation by moving the posts toward the central axis of the valve (post constriction). For example, U.S. Pat. No. 4,865,600 to Carpentier, et al., provides a holder having a mechanism that constricts the commissure posts inwardly just prior to implantation. The Carpentier device provides an elongate handle to both hold the valve/valve holder combination during implantation, as well as to cause the commissure posts to constrict inwardly. More recently, U.S. Pat. Nos. 6,409,758, 6,702,852, 6,964,682, 6,966,925, and 7,033,390 disclose heart valve holder systems that resist suture looping.
Bioprosthetic heart valves configured for implanting in the aortic or pulmonic position also can benefit from constriction of the commissure posts. That is, although the holder attaches to the outflow side of the valve, the lower radial profile of the commissure posts eases implantation, such as through an aortotomy.
Bioprosthetic heart valves are conventionally packaged in jars filled with preserving solution for shipping and storage prior to use in the operating theater. Glutaraldehyde is widely used as a storage solution due to its sterilant properties. Because glutaraldehyde is a fixative, or cross-linking agent, and the fixing process is ongoing, bioprosthetic valves are stored in the jars with their leaflets in the closed or coapting position and the commissure posts relaxed, not constricted. This is to ensure that the leaflets fix in the shape they are supposed to have when closed. Otherwise the leaflets may assume a distorted shape which could detrimentally affect functioning, such as regurgitation upon implant. As a consequence, prior art devices that constrict the commissures are actuated in the operating room, just prior to implant of the valve. Various designs are available, each of which require an affirmative action which creates a risk that the operating room staff will not completely constrict the commissure posts, possibly leading to suture looping. To compound the problem, the devices sometimes require several precise steps, which can be confusing in the pressured environment of a heart surgery with the patient on bypass.
Despite a number of advances, there is still a need in the art for a holder and associated packaging for tissue-type prosthetic mitral valves that helps prevent suture looping and is more intuitive to use.