摘要：Doppler studies on haemodynamics of the cardio- vascular system and intra-abdominal organ perfusion in non-pregnant individuals are usually performed by cardiologists and radiologists. Specialists in Maternal-Fetal Medicine are also familiar with cardiovascular Doppler sonography, however, they mostly focus on the fetal (Malcus, 2004) or utero- placental circulation (Abramowicz and Sheiner, 2008; Papageorghiou and Leslie, 2007; Cnossen et al., 2008). Recently, several studies have been reported using Doppler assessment to explore the dynamics of the maternal venous compartment, illustrating its feasibility and reproducibility (Karabulut et al., 2003; Bateman et al., 2004; Roobottom et al., 1995; Gyselaers et al., 2009b; Gyselaers et al., 2008; Gyselaers et al., 2009a). These studies have shown that the venous compart- ment is also subject to maternal cardiovascular adap- tation during uneventful pregnancy (Gyselaers et al., 2009b; Gyselaers et al., 2009a). In gestational diseases , such as preeclampsia, some of the obser- vations show promising results with respect to detecting maternal cardiovascular maladaptation (Gyselaers et al., 2009b; Gyselaers et al., 2009a) and predicting the development of subsequent disease (Gyselaers and Mesens, 2009). Therefore, the maternal venous compartment is a new area to be explored in obstetric ultrasound imaging (Gyselaers, 2008), in order to link Doppler observations to known features of gestational (patho)physiology (Gyselaers et al., 2009b; Gyselaers et al., 2009a) and to the information obtained from other techniques (Carty et al., 2008).
关键词：Cardiovascular adaptation; doppler; gestational physiology; maternal veins; venous hemodynamics. ; var currentpos;timer; function initialize() { timer=setInterval("scrollwindow()";10);} function sc(){clearInterval(timer); }function scrollwindow() { currentpos=document.body.scrollTop; window.scroll(0;++currentpos); if (currentpos != document.body.scrollTop) sc();} document.onmousedown=scdocument.ondblclick=initialize 172 ; F; V & V ; IN ; O ; B ; G ; YN ; the renal veins. The blood in the central veins flows ; undisturbed into the right atrium; as there is no ; ; interposition of an anatomical or functional valve. ; The anatomical structure known as the valve of the ; inferior vena cava (VCI); first described by ; ; Eustachius (Hickie; 1956); is a non-occlusive semi- ; lunar endocardial fold at the anterior site of the ; entrance ; ; of the VCI in the right atrium; which directs ; the oxygenated blood towards the open foramen ; ovale during foetal life; but degenerates after birth ; (Hickie; 1956). As a result; intravascular measure- ; ments of venous pressure; flow velocities and ; ; volumes in the central veins mirror the function ; of the right heart (Boulpaep; 2005b; Berne and ; Levy; 2001a). In clinical practice; this principle is ; ; commonly used to estimate central venous pressure ; at the level of the jugular veins using both non- ; invasive and invasive methods (Magder; 2006). ; As illustrated in Figure 1A; the liver drains blood ; into the VCI through the hepatic venous tree; which ; consists of three main branches: the left; middle and ; right hepatic veins (HV). Sometimes; an accessory ; inferior right HV is found (Neumann et al.; 2006). ; Right and left HV; respectively; drain the largest and ; smallest liver volumes (Neumann et al.; 2006). ; ; Hepatic veins are the sole exit of blood from the ; liver; and drain blood originating from both the ; ; portal vein and hepatic arteries (Grant et al.; 1992). ; As illustrated in Figure 1B; the right Renal Vein ; (RV) is located more caudally and is half as long as ; the left RV; which is the one crossing the midline and ; draining blood from the left ovarian vein. The left ; RV is squeezed between the aorta and the Superior ; Mesenteric Artery; and sometimes this may provoke ; orthostatic haematuria (Ahmed et al.; 2006). This ; so-called Nutcracker phenomenon may aggravate ; during pregnancy (Itoh et al.; 1997). Compared to ; the left side; accessory renal veins are more frequent ; on the right side and the proximal RV diameter is ; larger (Satyapal et al.; 1995a; Satyapal et al.; 1995b). ; The anatomy of the lower central venous system ; differs widely between individuals; not only because ; of a high frequency of accessory veins as mentioned ; above; but also because of asymptomatic congenital ; variations. These congenital anomalies are found in ; all segments of the VCI (Fernandez-Cuadrado et al.; ; 2005) and have to be taken into account in the pre- ; operative work-up of liver- or kidney transplantation ; (Mathews et al.; 1999; Pannu et al.; 2001). Next to ; this; different types of congenital intrahepatic vascu- ; lar shunts have been observed; such as arteriovenous ; connections; arterioportal shunts and portosystemic ; fistulas (Gallego et al.; 2004). Both congenital aber- ; rations and intrahepatic vascular shunts are respon- ; sible for a wide inter-individual variation in hepatic ; vein Doppler patterns in healthy subjects (Pedersen ; et al.; 2005). ; Physiology of venous hemodynamics ; The venous compartment had an important role in ; human physiology. It is a large capacitance reservoir; ; containing 65-75% of the total blood volume; 75% ; of which residing in small veins and venules (Pang; ; Fig. 1. ¡ª Anatomy of the lower central venous compartment from liver to kidneys. As is shown in the left panel; there are 3 hepatic ; veins (HV): left; middle and right; which are often accompanied by additional branches. Usually; left and middle HV fuse before ; draining into the vena cava inferior (VCI) at a few centimeters caudal from the right cardiac atrium. The right panel shows that the ; right renal vein (RV) is shorter and inserts more caudally into VCI then the left RV. Next to this; the right RV has more accessory ; branches and a wider proximal diameter than the left RV. Also; the left LV is sometimes sandwiched between Aorta and Superior ; Mesenteric Artery (Nutcracker Syndrome) and drains blood from the left ovarian vein. ; A ; B
