Eichenberger A C, Schwitter J, McKinnon G C, Debatin J F, von Schulthess G K
Department of Medical Radiology, University Hospital, Zürich, Switzerland.
J Magn Reson Imaging. 1995 Nov-Dec;5(6):648-55. doi: 10.1002/jmri.1880050606.
Although the clinical manifestations of Valsalva's maneuver are well known, the associated hemodynamic changes in the great vessels have not been extensively studied and documented. In each of six healthy subjects, we evaluated three "quasi-steady-state" phases of Valsalva's maneuver: (1) during normal respiration, (2) during late strain, and (3) 4 seconds after strain release. Continuous flow, velocity, and cross-sectional area measurements were obtained in the superior vena cava, pulmonary trunk, and thoracic aorta with single-shot echo-planar MR imaging (EPI) with velocity-encoded gradients, which provided 256 images in 5 seconds, yielding 26 velocity-encoded images per second. In the superior vena cava, Valsalva's maneuver induced an 11% decrease in average flow volume, a 102% increase in peak flow velocity, a 156% increase in the time velocity integral, and a 37% decrease in cross-sectional area. MR velocity measurements agreed with echocardiographic data and supplied additional information on flow and morphology. EPI showed a reduction in venous return during Valsalva's maneuver by simultaneously assessing flow, velocity, and vessel morphology; this technique appears to be useful in the analysis of flow dynamics of the great vessels.
虽然瓦尔萨尔瓦动作的临床表现广为人知，但大血管中相关的血流动力学变化尚未得到广泛研究和记录。在6名健康受试者中，我们评估了瓦尔萨尔瓦动作的三个“准稳态”阶段：(1)正常呼吸期间，(2)用力后期，(3)用力解除后4秒。使用具有速度编码梯度的单次激发回波平面磁共振成像(EPI)在上腔静脉、肺动脉干和胸主动脉中进行连续血流、速度和横截面积测量，该成像在5秒内提供256幅图像，每秒产生26幅速度编码图像。在上腔静脉中，瓦尔萨尔瓦动作导致平均血流量减少11%，峰值流速增加102%，时间速度积分增加156%，横截面积减少37%。磁共振速度测量结果与超声心动图数据一致，并提供了有关血流和形态的额外信息。EPI通过同时评估血流、速度和血管形态，显示了瓦尔萨尔瓦动作期间静脉回流的减少；该技术似乎对分析大血管的血流动力学有用。
