Porter T R, Ornato J P, Guard C S, Roy V G, Burns C A, Nixon J V
Department of Internal Medicine, Medical College of Virginia, Richmond.
Am J Cardiol. 1992 Oct 15;70(11):1056-60. doi: 10.1016/0002-9149(92)90360-b.
This study further defines the mechanism of blood flow during closed-chest compression using transesophageal Doppler echocardiography. Although the echocardiographic demonstration of mitral valve closure during closed-chest compression has been used as evidence of direct cardiac compression, mitral valve closure has also been documented to occur during resuscitation by selectively increasing intrathoracic pressure. Transesophageal Doppler echocardiography was used to assess mitral valve position and flow in 17 adult patients undergoing cardiopulmonary resuscitation with a mechanical piston compression device. Left and right ventricular fractional shortening, mitral valve position with chest compression, timing and magnitude of transmitral flow, and anteroposterior chest diameter were recorded. In 12 patients (group I), the mitral valve closed during the down-stroke of chest compression; in the remaining 5 (group II), it opened further. Peak transmitral flow occurred during the release phase and was significantly higher (p < 0.05) in group I (39.5 +/- 9.3 cm/s) than the peak flow in group II (21.3 +/- 5.9 cm/s), which occurred during the downstroke of chest compression. Left ventricular fractional shortening inversely correlated (r = -0.68; p = 0.02) with the anteroposterior chest diameter, but did not correlate with peak transmitral flow (r = 0.34; p = not significant). It is concluded that the mitral valve closes during the downstroke of chest compression in most adult patients during resuscitation. The absence of a relation between mitral valve flow and left ventricular fractional shortening supports the hypothesis that other factors such as nonuniform increases in intrathoracic pressure cause the mitral valve to open or close during chest compression.
本研究使用经食管多普勒超声心动图进一步明确了闭胸按压期间的血流机制。尽管闭胸按压期间二尖瓣关闭的超声心动图表现已被用作直接心脏按压的证据，但在复苏过程中，通过选择性增加胸内压也可出现二尖瓣关闭。使用经食管多普勒超声心动图评估了17例接受机械活塞按压装置进行心肺复苏的成年患者的二尖瓣位置和血流情况。记录左、右心室缩短分数、按压时二尖瓣位置、跨二尖瓣血流的时间和幅度以及前后胸径。12例患者（I组）在胸外按压的下行冲程中二尖瓣关闭；其余5例（II组）二尖瓣进一步打开。跨二尖瓣血流峰值出现在释放期，I组（39.5±9.3 cm/s）显著高于II组（21.3±5.9 cm/s），II组的峰值血流出现在胸外按压的下行冲程中。左心室缩短分数与前后胸径呈负相关（r = -0.68；p = 0.02），但与跨二尖瓣血流峰值无相关性（r = 0.34；p = 无显著性差异）。得出的结论是，在复苏过程中，大多数成年患者在胸外按压的下行冲程中二尖瓣关闭。二尖瓣血流与左心室缩短分数之间缺乏相关性支持了以下假设，即其他因素（如胸内压的不均匀增加）导致二尖瓣在胸外按压期间打开或关闭。
