AJP - Heart and Circulatory Physiology, Vol 235, Issue 6 664-H669, Copyright © 1978 by American Physiological Society
Accentuation of heart sounds in anemia: an effect of blood viscosity
P. D. Stein and H. N. Sabbah
The effect of blood viscosity on the intensity of heart sounds was
investigated in 25 anemic patients and 41 control subjects. Calibrated
phonocardiograms showed that in anemic patients, the aortic component of
the second sound was of greater amplitude (54 +/- 3 vs. 33 +/- 3 dyn/cm2)
(P less than 0.001). The pulmonary component of the second sound and the
first sound were also of higher amplitude in anemic patients (both P less
than 0.001). The viscosity of blood of anemic patients was lower (0.029 +/-
0.001 vs. 0.045 +/- 0.001 poise) (P less than 0.001). Blood pressure was
comparable among the two groups. Sound produced by closure of a normal
porcine valve in an in vitro flow system also showed an accentuated sound
with liquids of lower viscosity. Augmented diastolic vibrations of the
closed valve, shown by high-speed motion pictures, accompanied the
accentuated sound. These observations suggest that the accentuated second
sound in anemic patients results from the lower blood viscosity, which
reduces the damping forces that act upon the semilunar valve as it vibrates
after closure. The reduced damping would allow augmented vibrations that
result in an accentuated sound.
