Poppas A, Shroff S G, Korcarz C E, Hibbard J U, Berger D S, Lindheimer M D, Lang R M
Department of Medicine, University of Chicago Medical Center, IL 60637, USA.
Circulation. 1997 May 20;95(10):2407-15. doi: 10.1161/01.cir.95.10.2407.
Temporal changes in systemic arterial compliance and wave propagation properties (pulsatile arterial load) and their role in ventricular-systemic arterial coupling during gestation have not been explored. Noninvasive methods combined with recently developed mathematical modeling techniques were used to characterize vascular and left ventricular (LV) mechanical adaptations during normal gestation.
Fourteen healthy women were studied at each trimester of pregnancy and again postpartum. Experimental measurements included instantaneous aortic pressure (subclavian pulse tracings) and flow (aortic Doppler velocities) and echocardiographic imaging of the LV. A small increase in LV muscle mass and end-diastolic chamber dimension occurred by late gestation, with no significant alterations in myocardial contractility. Cardiac output increased and the steady component of arterial load (total vascular resistance) decreased during pregnancy. Several changes in pulsatile arterial load were noted: Global arterial compliance increased (approximately 30%) during the first trimester and remained elevated thereafter. The magnitude of peripheral wave reflections at the aorta was reduced. The mathematical model-based analysis revealed that peripheral wave reflections at the aorta were delayed and that both conduit and peripheral vessels contributed to the increased arterial compliance. Finally, coordinated changes in the pulsatile arterial load and LV properties were responsible for maintaining the efficiency of LV-to-arterial system energy transfer.
The rapid time course of compliance changes and the involvement of both conduit and peripheral vessels are consistent with reduced vascular tone as being the main underlying mechanism. The pulsatile arterial load alterations during normal pregnancy are adaptive in that they help to accommodate the increased intravascular volume while maintaining the efficiency of ventricular-arterial coupling and diastolic perfusion pressure.
尚未探讨妊娠期全身动脉顺应性和波传播特性（脉动性动脉负荷）的时间变化及其在心室 - 全身动脉耦合中的作用。采用非侵入性方法结合最近开发的数学建模技术来表征正常妊娠期间血管和左心室（LV）的机械适应性。
对14名健康女性在妊娠各期及产后再次进行研究。实验测量包括瞬时主动脉压力（锁骨下脉搏描记）、流量（主动脉多普勒速度）以及左心室的超声心动图成像。到妊娠晚期，左心室肌肉质量和舒张末期腔室尺寸略有增加，心肌收缩性无显著改变。妊娠期间心输出量增加，动脉负荷的稳定成分（总血管阻力）降低。注意到脉动性动脉负荷有几个变化：妊娠早期全身动脉顺应性增加（约30%），此后一直保持升高。主动脉处外周波反射的幅度减小。基于数学模型的分析表明，主动脉处外周波反射延迟，且传导血管和外周血管均导致动脉顺应性增加。最后，脉动性动脉负荷和左心室特性的协调变化负责维持左心室到动脉系统能量传递的效率。
顺应性变化的快速时间进程以及传导血管和外周血管的参与与血管张力降低作为主要潜在机制是一致的。正常妊娠期间脉动性动脉负荷的改变具有适应性，因为它们有助于在维持心室 - 动脉耦合效率和舒张期灌注压的同时，适应血管内容量的增加。
