vegetation

In cardiology a vegetation is an abnormal mass that grows on a heart valve, made of a tangle of microorganisms, blood-clot material (platelets and fibrin), and inflammatory cells. The name comes from its lumpy, cauliflower-like appearance, as if something were growing on the valve surface.

Vegetations form where the valve lining has been disturbed: bacteria or other microbes from the bloodstream lodge there, get coated in clot, and a self-perpetuating mass develops that the immune system struggles to reach. They are the hallmark lesion of infective endocarditis and are typically seen on echocardiography as mobile masses attached to a valve.

These masses cause harm in two main ways. They damage and erode the valve, leading to leakage or other dysfunction, and pieces can break off as emboli that lodge in the brain, lungs, kidneys, spleen, or limbs. Not all vegetations are infected, however: sterile vegetations occur in conditions such as Libman-Sacks endocarditis and in advanced cancer.