The mitral or bicuspid valve is the two-leafed valve between the left atrium and left ventricle of the heart. This valve closes the opening between the left atrium and left ventricle when the ventricle contracts to pump blood through the aorta to the body. Mitral regurgitation (MR) is backflow of blood from the left ventricle to the left atrium due to failure of the valve to close completely. MR is a fairly common abnormality, with some degree of physiologic mitral insufficiency seen in up to 80% of the adult population. Although usually well-tolerated if mild, higher grades of MR can result in significant decrease in cardiac function and increase in patient symptoms. MR is progressive, generally increasing in prevalence and severity with age, and can result in left ventricular failure, arrhythmias, and pulmonary hypertension. As disability progresses or cardiomegaly increases, surgical correction may be indicated. Valve repair can involve a prosthetic ring that reduces the size of the annulus, or tethered leaflets that correct the incompetence by immobilization. When the valve cannot be repaired, valve replacement may be performed. Currently, mitral valve repair requires an open-heart surgical procedure with cardiopulmonary bypass, hospital stay of three to five days, and extended recovery period at home.
Several companies are developing products that allow for percutaneous mitral valve treatment. Evalve, Inc. has developed catheter-based technology in which the cardiologist guides a percutaneous catheter to the mitral valve using a venous access and a transseptal approach. The Evalve MitraClip™ is introduced through the catheter and is placed on the center of the valve leaflets clipping them together. Alignment and residual MR is assessed using fluoroscopy and echocardiography. This approach is based on an open-heart surgical method known as edge-to-edge repair (Alfieri technique) in which the surgeon sutures the valve leaflets together to reduce regurgitation. Human trials are currently underway to evaluate the safety and efficacy of this procedure; at this time the U.S. Food and Drug Administration (FDA) limits this device to investigational use only. Placement of a self-compressing ring device in the coronary sinus along the region of the posterior mitral annulus (annuloplasty) is another type of percutaneous approach that has reduced MR in canine models.
In the Evalve trials, the procedure is performed under general anesthesia, and involves return home within 48 hours, no surgical wound, and very little recovery/rehabilitation period at home.