Replacement cardiac valves are implanted when the patient's native cardiac valve exhibits abnormal anatomy and function due to congenital or acquired valve disease. Congenital abnormalities can be tolerated for years, only to develop into life-threatening problems later. Acquired valve disease may result from various causes such as rheumatic fever, degenerative disorders of the valve tissue, and bacterial or fungal infections.
Valve dysfunction can be classified as either stenosis, in which the valve does not open properly, or insufficiency, in which the valve does not close properly. Stenosis and insufficiency can occur concurrently and both abnormalities increase the workload on the heart in pumping blood through the body. The ability of the heart to function with the increased workload is a major factor in determining whether the valve should be replaced.
When the valve must be replaced using conventional methods, the patient must undergo an invasive, traumatic surgical procedure. The patient's chest is opened with a median sternotomy or major thoracotomy to provide direct access to the heart through a large opening in the chest. The heart is then stopped and the patient is placed on cardiopulmonary bypass using catheters and cannulae inserted directly into the heart and into major blood vessels. The heart, or a blood vessel leading to the heart, is then cut open to access and remove the malfunctioning valve. After removing the valve, the replacement valve is then sewn into place. After the new valve has been implanted, the chest is then closed and the patient is weaned off cardiopulmonary bypass support.
The aforementioned drawbacks to conventional open-chest surgery prevent some patients from undergoing a valve implantation procedure even though a new cardiac valve is needed. Consequently, endovascular valve repair and/or valve replacement procedures that can be performed under local anesthesia in the cardiac catheterization lab, rather than in cardiac surgery, have been developed as they offer tremendous benefits to these patients. Such endovascular procedures for valve replacement often require the removal of the native valve using a minimally invasive, endovascular approach. Hence, a need exists for additional endovascular devices and methods for quickly and accurately removing cardiac valves.