Although he is renowned in medical circles as "the father of Viagra," the discoveries of Louis Ignarro have profound implications for all circulatory conditions, not least heart disease, the leading cause of death around the world. Nitroglycerin has been used in treating heart disease since the 1870s, but for over a century no one knew what property of the chemical causes constricted blood vessels to dilate. Ignarro determined that nitroglycerin, and other nitrates and nitrites, are metabolized as nitric oxide, relaxing the smooth muscle surface of the blood vessels, and inhibiting...