The use of amyl nitrite in differentiating mitral and aortic systolic murmurs.

The clinical differentiation of the apical systolic murmurs arising at the mitral and aortic valves may be difficult. This is especially so when the murmur of aortic origin is audible only at the apex or is loudest at this site. Phonocardiography gives further help in that the murmur of aortic stenosis is diamond shaped and ends before the aortic second sound while that of mitral regurgitation is pansystolic and often includes the second heart sound (Leatham, 1951; Besterman, 1955). Where phonocardiography is not available the distinction has to be made on clinical auscultation alone. The purpose of this paper is to show that the inhalation of amyl nitrite has a different effect on these two murmurs and is therefore useful in their differentiation.