Capeless E L, Clapp J F
Department of Obstetrics and Gynecology, University of Vermont College of Medicine, Burlington.
Am J Obstet Gynecol. 1989 Dec;161(6 Pt 1):1449-53. doi: 10.1016/0002-9378(89)90902-2.
To assess the magnitude and timing of cardiovascular changes in pregnancy, eight subjects were serially studied before conception and at 8, 16, and 24 weeks' gestation. With the use of M-mode echocardiography, cardiac output, ejection fraction, stroke volume, and end-diastolic volume were calculated from left ventricular dimensions with subjects in the left lateral position. Systemic vascular resistance was calculated with the use of cardiac output and simultaneously obtained measurements of arterial pressure. Cardiac output increased 1 L/min at 8 weeks' gestation, which represented greater than 50% of the total change seen. Cardiac output increased primarily because of stroke volume rather than heart rate. By 8 weeks' gestation, systemic vascular resistance had fallen to 70% of its preconceptional value. Thus when subjects are studied before conception and during the early phase of pregnancy, the majority of the pregnancy-induced changes in these parameters occur during the embryonic period.
为评估孕期心血管变化的程度和时间，对8名受试者在受孕前以及妊娠8周、16周和24周时进行了系列研究。使用M型超声心动图，让受试者处于左侧卧位，根据左心室尺寸计算心输出量、射血分数、每搏输出量和舒张末期容积。利用心输出量和同时获得的动脉压测量值计算全身血管阻力。妊娠8周时心输出量增加1升/分钟，这占所见总变化的50%以上。心输出量增加主要是由于每搏输出量而非心率。到妊娠8周时，全身血管阻力已降至孕前值的70%。因此，当在受孕前和妊娠早期对受试者进行研究时，这些参数中大多数由妊娠引起的变化发生在胚胎期。
