Department of Radiology, Hospital for Sick Children, 555 University Ave., Toronto, Canada.
Pediatr Radiol. 2012 Feb;42(2):211-4. doi: 10.1007/s00247-011-2227-8. Epub 2011 Aug 24.
Typical flow velocity profiles in the extraparenchymal pulmonary veins (PVs) demonstrate two major antegrade flow waves: a biphasic systolic wave (S), with S1 and S2 peaks and a monophasic early diastolic wave (D). Flow reversal during atrial systole (A) is common. There is agreement that the forward diastolic PV flow wave is caused by left ventricular relaxation with opening of the mitral valve. The origin of the PV systolic wave, however, remains a topic of debate. Some studies have suggested that the S wave is created by the relaxation of the left atrium and descent of the mitral valve plane. These studies have concluded that forces generated by the right ventricle (RV) have no effect on the S wave. Others suggest that the forward propagation of the right ventricular systolic pressure pulse is the major contributor to the S wave.
To determine whether any part of the systolic wave of PV flow is dependent on forces created by the right ventricle.
We assessed PV flow pattern, as obtained by cardiac MRI in 12 cases (39 pulmonary veins) with RV-independent pulmonary circulation (bidirectional cavopulmonary connection or Fontan circulation). Phase-contrast imaging of the PVs was performed on a 1.5-T MR scanner with velocity encoding set at 120 cm/s. We compared these flow patterns with those of a control group of ten children (15 pulmonary veins) who had RV-dependent pulmonary circulation and underwent CMR for other indications.
In all PVs of children with RV-independent pulmonary circulation the flow curves showed a single systolic peak in early systole (S1) with the S2 peak consistently absent. PV flow pattern in the control group consistently showed distinct early and late systolic peaks.
This study supports the concept that S2 is caused by forward propagation of the right ventricular systolic pressure pulse. It also demonstrates that the S1 is independent of the right ventricle.
肺静脉（PV）外膜中的典型流速曲线表现为两个主要的前向血流波：双相收缩波（S），具有 S1 和 S2 波峰以及单相早期舒张波（D）。心房收缩期（A）的血流反转很常见。人们普遍认为，左心室舒张导致二尖瓣开放，从而产生向前的舒张期 PV 血流波。然而，PV 收缩波的起源仍然是一个有争议的话题。一些研究表明，S 波是由左心房舒张和二尖瓣瓣平面下降引起的。这些研究得出的结论是，右心室（RV）产生的力对 S 波没有影响。其他人则认为，右心室收缩压脉冲的向前传播是 S 波的主要贡献者。
确定 PV 血流的收缩波的任何部分是否依赖于右心室产生的力。
我们评估了 12 例（39 条肺静脉）RV 独立肺循环（双向腔肺连接或 Fontan 循环）患者的心脏 MRI 获得的 PV 血流模式。使用 Velocity Encoding 设置为 120 cm/s 的 1.5-T MR 扫描仪对 PV 进行相位对比成像。我们将这些血流模式与因其他原因接受 CMR 的 10 名儿童（15 条肺静脉）的对照组进行比较。
在所有 RV 独立肺循环的 PV 中，血流曲线在早期收缩期显示单个收缩峰（S1），S2 波峰始终不存在。对照组的 PV 血流模式始终显示出明显的早期和晚期收缩峰。
这项研究支持 S2 是由右心室收缩压脉冲的向前传播引起的概念。它还表明 S1 与右心室无关。
