Aortopulmonary fistula

Watson's water hammer pulse, also known as Corrigan's pulse or collapsing pulse, is the medical sign (seen in aortic regurgitation) which describes a pulse that is bounding and forceful, rapidly increasing and subsequently collapsing, as if it were the sound of a waterhammer that was causing the pulse. A water hammer was a Victorian toy in which a tube was half filled with fluid, the remainder being a vacuum. [Source: Wikipedia ]