Factors Influencing the Twisting and Untwisting Properties of the Left Ventricle during Normal Pregnancy

Abstract

During pregnancy, important hemodynamic changes occur, consistent with an increase in preload and decrease in afterload and systemic vascular resistance. The aim of the present study was to investigate the changes in left ventricular (LV) strain and rotational properties during the 3 trimesters of normal pregnancy and to examine the factors that drive these changes. Twenty-seven pregnant women (29.7 ± 6.9 years) and 11 age-matched nonpregnant controls (29.9 ± 5.4 years) were evaluated. Conventional echocardiography and two-dimensional speckle tracking imaging were performed at 8-12 (1st trimester), 21-28 (2nd trimester), and 33-36 (3rd trimester) weeks of pregnancy. LV rotation, twist, untwisting rate, and circumferential strain were measured using the parasternal short-axis views at basal and apical levels. Global longitudinal strain was calculated from the LV apical views. Peak LV twist and peak untwisting rate increased significantly in the 3rd trimester of normal pregnancy (13.48 ± 2.90°, 13.12 ± 3.30°, 16.83 ± 3.61°, P < 0.001; and -111.52 ± 23.54°/sec, -107.40 ± 26.58°/sec, -144.30 ± 45.14°/sec, P < 0.001; in the 1st, 2nd, and 3rd trimester, respectively). Global longitudinal and circumferential strain of the apex decreased significantly from the 2nd trimester. An independent association was found between the change in LV twist and the change in LV end-systolic volume between the 1st and 3rd trimester. Peak untwisting rate at the 3rd trimester correlated significantly with peak twist and LV end-diastolic volume. During normal pregnancy, LV twist and peak untwisting rate increase in the 3rd trimester and correlate with end-systolic and end-diastolic volume, respectively. Circumferential strain of the apex and global longitudinal strain decrease from the 2nd trimester.