don't cause blood clots). blood clots can be hazardous because they can lodge in, and block, downstream arteries (e.g. coronary arteries, leading to heart attack ; or cerebral arteries, leading to stroke). a desirable characteristic of artificial heart valves is that they are non- or minimally thrombogenic. self-repairing – valve leaflets retain some capacity for repair thanks to regenerative cells (e.g. fibroblasts) in the connective tissue from which the leaflets are composed. as the human heart beats approximately 3.4×109 times during a typical human lifespan, this limited but nevertheless present repair capacity is critically important. no heart valve prostheses can currently self-repair, but tissue-engineered valves may eventually offer such capabilities. artificial heart valve repair artificial heart valves are expected to last from 10 to 30 years. the most common problems with artificial heart valves are various forms of degeneration, including gross billowing of leaflets, ischemic mitral valve pathology, and minor chordal lengthening. the repairing process of the artificial heart valve regurgitation and stenosis usually requires an open-heart surgery, and a repair or partial replacement of regurgitant valves is usually preferred. researchers are investigating catheter-based surgery that allows repair of an artificial heart valve without large incisions. researchers are investigating interchangeable prosthetic heart valve that allows redo and fast-track repair of an artificial heart valve. additional images 3d rendering of mechanical valve 3d rendering of mechanical valve (st. francis model)