Critical evaluation of atrial presystolic murmur.

A crescendo-decrescendo pattern of atrial presystolic murmur has long been considered highly specific for atrial septal defect. Atrial presystolic murmur was observed in 67 or 460 consecutive cases. Of these 67 cases, there were only six with atrial septal defect and four with mitral valvular diseases. The occurrence of atrial presystolic murmur was observed over a broad spectrum of clinical entities. Although the precise pathogeneis of atrial presystolic murmur is not clearly defined, certain conclusions can be drawn from the present study, as follows: (1) atrial presystolic murmur is observed in a variety of clinical situations; (2) atrial presystolic murmur is not infrequently observed in normal subjects; (3) atrial presystolic murmur is not a specific phonocardiographic finding for atrial septal defect; and (4) atrial presystolic murmur may be caused by a multiplicity of factors.