William Walker, president of HemoSonics LLC, believes his Charlottesville-based medical device startup could bring substantial improvements to the way physicians analyze the balance between bleeding and clotting. When it goes awry, that balance can result in such leading causes of death as heart attack, stroke, pulmonary embolism or excessive bleeding. ... HemoSonics was founded in 2004 by Walker and fellow UVa biomedical engineering professors Francesco Viola and Michael Lawrence. The company’s original prototype was developed in-house at UVa.