DETERMINANTS OF PULMONARY ARTERY BLOOD VELOCITY PROFILE

先天性心脏病患者的最佳管理通常 取决于监测肺血流动力学和评估 肺血管受损。对改进技术的需求促使人们 肺循环异常与临床关系的探讨 和肺血流速度模式，可以观察到 用脉冲多普勒超声无创检查。常见功能 与肺动脉高压相关的是血流倒流增加 主肺动脉和减速时间(起病时间 收缩速度到峰值速度)。然而，最近的研究表明， 加速时间主要是动脉顺应性的函数；流量 反转与肺流出道曲率直接相关。 束和/或外周血管阻力。这些发现意味着 理想化的压力关系可能只存在于 预期中的、但不能保证的结构性变化。肺血管 损伤通常与对血管扩张剂缺乏反应有关： 然而，血流速度曲线和相关的肺输入的变化 阻抗谱可能是更好的响应性指标。本研究 将通过实验来解决这些问题，这些实验旨在识别和 在动物模型中量化速度分布的决定因素 发展为产生与以下相关的肺血管变化 压力升高或从婴儿期到儿童期的流动。新生儿 羔羊将被长期测量肺压力， 从出生到6月龄的速度分布和轴向尺寸。 肺动脉压力或血流的升高会通过 分别采用野百合碱、吡咯注射或动静脉分流术。 旨在评估血管反应性变化的急性干预措施 将在数据收集会议期间进行。在自然历史被 确定的，长期药物干预的能力 更改高压模型的历史将被评估。收集的数据 将被用来确定二维和三维速度分布， 电阻、柔度和形状变化以及输入阻抗谱。 在末期血流动力学检查后，右室和右室的管型 在血流动力学条件下原位制作近端肺动脉 匹配的收缩压。演员们将接受CT扫描，他们的 提交给计算机内存的结构，从该结构可以 图像是可以重建的。将开发算法来量化 主干的曲率和扭矩、分流板偏移量、锥度、 分叉角度和管段尺寸。旨在测试 并确定外周设备变化的影响 选择性栓塞术对个体血管阻力的影响 肺将在急性准备中进行。测量技术 肺输入阻抗谱及其显著特征提取 将使用简单的肺血管模型来开发功能 床。最后，将在动物模型中获得的结果与 可获得的临床数据，从而检验了这样一种信念 对速度剖面的决定因素的理解将导致 改善了患者的诊断和护理。

Optimal management of patients with congenital heart disease often depends on the ability to monitor pulmonary hemodynamics and assess pulmonary vascular impairment. Need for improved techniques has prompted investigations of relationships between abnormal pulmonary circulations and pulmonary blood velocity patterns, which can be observed noninvasively with pulsed Doppler ultrasound. Features commonly associated with pulmonary hypertension are increased flow reversal in the main pulmonary artery and decreased acceleration time (time from onset of systole to peak velocity). However, recent studies indicate that acceleration time is primarily a function of arterial compliance; flow reversal is directly related to the curvature in the pulmonary outflow tract and/or peripheral vascular resistance. These findings imply that idealized relationships with pressure may exist only in the presence of expected, but not guaranteed, structural changes. Pulmonary vascular impairment is commonly associated with lack of response to vasodilators: however, changes in velocity profiles and the associated pulmonary input impedance spectra may be better indicators of responsiveness. This study will address these issues through experiments designed to identify and quantitate the determinants of the velocity profiles in animal models developed to produce the pulmonary vascular changes associated with either elevated pressure or flow from infancy through childhood. Newborn lambs will be chronically instrumented to measure pulmonary pressures, velocity profiles and axial dimensions from birth to 6 months of age. Elevated pulmonary artery pressure or blood flow will be produced via monocrotaline pyrrole injections or arteriovenous shunts, respectively. Acute interventions designed to assess changes in vascular reactivity will be made during data collection sessions. After natural histories are determined, the ability of long-term pharmacological interventions to alter the high pressure model history will be assessed. Data collected will be used to determine 2- and 3- dimensional velocity profiles, resistance, compliance and shape changes and input impedance spectra. After the terminal hemodynamic study, casts of the right ventricle and proximal pulmonary arteries will be made in situ under hemodynamically matched systolic pressure. The casts will be CT scanned and their structure committed to computer memory, from which 2- and 3-dimensional images can be reconstructed. Algorithms will be developed for quantifying curvature and torque of the main trunk, flow divider offset, taper, bifurcation angles, and segment dimensions. Experiments designed to test instrumentation and to determine the effects of changes in peripheral vascular resistance as a result of selective embolization of individual lungs will be conducted in acute preparations. Techniques for measuring the pulmonary input impedance spectrum and extracting its salient features will be developed using simple models of the pulmonary vascular bed. Finally, results obtained in the animal models will be compared to available clinical data, thus testing the belief that better understanding of the determinants of the velocity profile will lead to improved patient diagnosis and care.