右室舒张功能无创定量新方法的建立及评价

Evaluation of right ventricular function is always difficult for clinical investigation, and diastolic dysfunction is the early performance of cardiac dysfunction. As the key index of assessment of right ventricular diastolic function, the noninvasive measurement of right ventricular end-diastolic pressure (RVEDP) has become an active demand for clinical diagnosis. In diastole, right ventricle is connected with right atrium. Thus the RVEDP is equal to right atrial pressure, i.e. the vertical blood column pressure from the central point of right atrium to the collapse point in internal jugular vein (IJV). However, the top point in most patients is in the chest, which makes it difficult to measure accurately. Based on our previous study, the increase of intrathoracic pressure (ITP) could cause pressure increase of the cardiovascular system in the chest in almost the same amplitude. Therefore, we hypothesized that we could noninvasively measure RVEDP by increasing the top point using Valsalva maneuver. We have initially confirmed our hypothesis by pre-experiment. In this project, we will further investigate the quantitative relationship between ITP and the intracardiac pressure and its influencing factor, by in vivo and in vitro experiments. Through quantitative Valsalva maneuver, the collapse point in IJV could be elevated to a level easy to show. Thus we could acquire the RVEDP by measurement. By contrast with the pressure measured by catheter, we will establish a novel noninvasive method of RVEDP measurement for clinic.

右室功能评价一直是临床研究的难点，而舒张功能异常又是心脏功能异常的最早表现。右室舒张末压作为评价右室舒张功能的核心指标，其无创测定方法成为临床迫切需要。心脏舒张期右室与右房相通，右室舒张末压等同于右房压，相当于端坐位从右房中心至颈内静脉塌陷点段血柱的垂直高度，但大多数患者顶点位置较低，位于胸腔内，通过传统方法尚无法准确判定。本课题组前期研究发现，胸内压升高可以引起胸腔内心血管压力产生几乎同等程度的升高。据此我们推测，通过乏氏动作可将血柱顶点上移，可实现无创右室舒张末压测定，并通过预实验进行了初步证实。本项目拟通过模拟实验和导管测压进一步明确胸压变化和右心压力变化的定量关系及其影响因素；在此基础上，通过定量乏氏动作使顶点提升到颈内静脉易显示水平从而得到右房压；并以导管测压为金标准，进行大样本临床对照实验，进一步验证该方法的准确性和敏感性，为临床无创右室舒张功能评价提供无创定量检测新方法。

项目背景.一直以来，由于右室形态结构复杂，影响因素较多，其舒张功能一直是心脏功能评价的难点。超声心动图是无创评价右室舒张功能的主要手段，但现有超声指标均为定性或半定量指标，尚无法准确反映右室舒张功能。右室舒张末压是右室舒张功能评价的核心指标，在临床上与右心相关疾病的发病率及病死率密切相关，是评价右心功能、指导临床决策的重要依据。然而，目前仍无法直接无创定量测定右室舒张末压。根据流体力学原理，在心脏舒张期右室与右房相通，右室舒张末压等同于右房压，因此若能无创测定右房压，也就得到了右室舒张末压。因此本项目对无创右房压（中心静脉压）的超声测量方法进行了研究。.主要研究内容.1. 通过模拟实验验证了胸压变化与右房压变化的关系及影响因素，确认了颈内静脉塌陷段顶点为右房压压力代表点。.2. 依靠空间几何原理，建立了右房中心体表投影的定位方法，结合颈部血管超声定位颈内静脉塌陷顶点，成功实现了右房压的无创定量测量。.3. 根据广义帕斯卡定律，对肘部浅表静脉加压，通过在血管探头前方加装测压水囊的方法，实现了压迫法右房压测定。.4. 进一步结合超声无创测定肺动脉舒张期跨瓣压，初步建立了无创心内压测定体系。.重要结果.1. 依靠空间几何原理，我们精确定位了右房中心的体表投影，同三维CT对照，两方法间绝对距离和垂直距离为0.77厘米和0.04厘米，几乎定位在冠状面同一水平。平均操作时间为42.52秒。.2. 空间定位法无创右房压测定与有创测压对照结果一致性和准确性很高。术前线性相关系数r=0.898，P<0.001，Bland-Altman分析显示二者的平均差为0.22 mmHg。术后线性相关系数r=0.928，P<0.001，Bland-Altman分析显示二者的平均差为-0.09 mmHg。.3. 压迫法无创右房压测定与有创法也具有很好的相关性和一致性（r=0.83， P＜0.01；平均差异为-0.33mmHg）.科学意义.本研究成功的建立了超声无创右房压定量新方法，将右室舒张功能无创评价真正达到了临床实用水平。