Innocent murmurs: a suspect diagnosis in non-pregnant adults.

The physics of turbulence include Reynolds numbers, but they argued that these do not apply for biomedical applications. However, the 2 key variables, viscosity and flow velocity, are conceptually useful. They also warned that turbulence and murmurs are not equivalent, obvious from Doppler studies of children with innocent murmurs who demonstrate no turbulence or abnormal velocities. The musical Still's murmur contrasts with the noise generated by abnormalities of heart valves. McKusick compared the Still's murmur with the Aeolian harp's strings set into vibration by the wind. He looked for analogues in the heart and suggested false chords, but he failed to acknowledge that these become flaccid during systole. McKusick did not suggest the normal chords of the septal leaflet of the tricuspid valve that are tightened in systole by papillary muscles and traverse the pulmonary outflow, nor has anyone else, to the author's knowledge. The location of the Still's murmur was found in the pulmonary outflow by microphonic catheterization. The innocent ejection murmurs in children and pregnant women are not musical but are associated with decreased hematocrit and increased ejection velocity compared to nonpregnant adults. The aorta has been suggested as the origin of Still's murmur, but that study was done in older adults with angina who presumably had aortic valvular sclerosis. In conclusion, innocent murmurs in childhood are not normally found in adults, except for pregnant women whose blood viscosity and velocity resemble children's. When murmurs are found in nonpregnant adults, echocardiography is prudent.