Influence of heart rate on the echocardiographic evaluation of mitral stenosis

Abstract

Circulatory changes in normal pregnancy include a fall in peripheral resistance (Bader, Bader, Rose & Braunward, 1955) and blood pressure (Hytten & Leitch, 1971) and an increase in blood volume (Hytten & Paintin, 1963). Human studies have shown that ganglion blockade during normal pregnancy causes a significant fall in blood pressure (Assali, Vergon, Tada & Garber, 1952). This effect is not observed in non-pregnant women, in pre-eclamptics or post partum (Assali et al. 1952). These observations imply that in normal pregnancy there may be a substance produced that reduces the effectiveness of the sympathetic system and the vasoconstrictors in the circulation. The same substance could account for the reduced responsiveness to angiotensin found in pregnancy by Chesley, Wynn &