Maternal left ventricular transverse and long-axis systolic function during pregnancy

Circumferential fiber shortening has been the dominant basis for conventional analysis by echocardiography of left ventricular systolic function during pregnancy. Results in the literature have been conflicting due mainly to the fact that geometric assumptions for the calculation of these indices are made that may not be valid due to changes in left ventricular shape during pregnancy. Left ventricular long-axis displacement is expected to be a useful index of systolic function, independent of the changes in left ventricular geometry. The aim of this study was to compare circumferential to long-axis shortening during left ventricular contraction in pregnant women.

This was a cross-sectional study of 125 pregnant women at 9-42 weeks of gestation and 19 non-pregnant female controls. Two-dimensional and M-mode echocardiography of the left ventricle was performed including measurement of left ventricular long-axis displacement and activation time on the lateral, septal, anterior and inferior sides of the mitral annulus. Activation time was assessed as the time from the start of the Q-wave of the electrocardiogram to the onset of left ventricular long-axis shortening.

Mean arterial pressure and activation time decreased during pregnancy, reaching a nadir at about 19 weeks' gestational age of 4% and 13%, respectively, below non-pregnant values; they subsequently increased towards term. Left ventricular long-axis displacement mirrored the changes in mean arterial pressure and activation time and increased with gestational age at all four sites of the atrioventricular plane reaching a peak at about 23 weeks (+ 12% compared to non-pregnant levels). The ejection fraction and fractional shortening remained stable until 30 and 32 weeks, respectively, and then decreased towards term.

Changes in left ventricular long-axis performance during pregnancy occur earlier than do measures of transverse function.