title: Letter: Mitral valve closure and first heart sound.
mesh_terms: D000790:Angiocardiography; D000818:Animals; D002932:Cineangiography; D004285:Dogs; D004452:Echocardiography; D006326:Heart Auscultation; D006347:Heart Sounds; D006801:Humans; D008943:Mitral Valve / Q000502:physiology*; D010701:Phonocardiography