title: Letter: Significance of fourth heart sound and split first heart sound.
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D006326:Heart Auscultation; D006331:Heart Diseases / Q000175:diagnosis*; D006347:Heart Sounds; D006801:Humans; D008875:Middle Aged; D010701:Phonocardiography