[Non-invasive estimates of hemodynamics in normal pregnancy]

Abstract

Pregnancy provides excellent opportunities for observing the hemodynamic alterations in cardiac function occurring during the physiologic stress imposed on the normal myocardium. Hemodynamically, the most important change in the maternal circulation during pregnancy is an increase in the circulating blood volume and cardiac output. In the average woman, the cardiac output at rest rises 30-50% above the normal non-gestational resting value. Echocardiography was performed for 25 normal pregnant women, ranging in age from 21 to 36 years (mean age of 28.7 years). Echocardiography was performed periodically through out pregnancy, at the gestational ages of the 10th, 24th, 32nd, 36th, and the 3rd postpartal weeks. Tracings were obtained in the left lateral and supine positions. All pregnancies were uncomplicated, and there was no twin pregnancy. The heart rate increased throughout gestation. However, the systolic and diastolic blood pressures did not change significantly throughout pregnancy. End-diastolic left ventricular dimension (LVDd) increased throughout gestation, with the peak at the 36th week of gestation. Left atrial dimension (LAD) and mVCF increased at the 36th week of gestation. Throughout gestation, the ejection fraction (EF) showed no significant change. There were no measurable differences in the cardiac size and function in the left lateral and supine positions. Increased LVDd and LAD throughout gestation were thought the reflexion of the increased blood volume and venous return which had its peak in the 36th week of gestation. The slightly larger cardiac size and end-diastolic volume seemed to induce the increased myocardial fiber stretch and, in turn, the increased mVCF. Our results indicated that chronic volume overload with increased circulating blood volume occurs in normal pregnancy, resulting in the large cardiac size and increased contractility of myocardial fiber.