[Differentiation of ejection systolic and regurgitant murmurs with inhaled isoproterenol]

A common clinical problem is the differentiation among ejection and regurgitant murmurs. Inhalation of amyl nitrite is useful for this purpose because it increases the intensity of ejection murmurs while decreases that of regurgitant ones. Because amyl nitrite is not easily available, inhaled isoproterenol was tested in seventeen patients with ejection murmurs and eighteen with regurgitant ones. Isoproterenol was administered at doses of 480-640 mcg, according to age and corpulence. The changes in murmur amplitude and heart rate were phonocardiographically registered immediately and then every 15'' up to a minute and a half after the inhalation, and were expressed as percent of change with respect to basal values. Heart rate increased in both groups. The intensity of ejection murmurs increased immediately and maximally 45'' after inhalation; on the contrary, the intensity of regurgitant murmurs decreased immediately and maximally 15'' after inhalation. It is concluded that isoproterenol, whose effects are similar to those of amyl nitrite, can substitute the latter in the clinical and phonocardiographically differentiation of systolic murmurs.