Aortic insufficiency (AI), also known as aortic regurgitation (AR), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle.
Definition of echidna. : a spiny-coated toothless burrowing nocturnal monotreme mammal (Tachyglossus aculeatus) of Australia, Tasmania, and New Guinea that has a long extensible tongue and long heavy claws and that feeds chiefly on ants; also : a related mammal (Zaglossus bruijni) of New Guinea having a longer snout and shorter spines.
The echidna is a small mammal and the echidna has a long snout that acts as both the mouth and nose of the echidna. The echidna has no teeth and the echidna feeds by tearing soft logs apart and then using its long, sticky tongue to feed on the ants and termites that inhabit the log.