Evaluation of Left Atrial and Left Ventricular Function by Velocity Vector Imaging in Patients on Mechanical Ventilation

在使用呼吸器的患者以心臟超音波速率向量影像評估左心房及左心室功能

蔡慶宏(Chin-Hung Tsai) ； 殷明昌(Ming-Cheng Yin) ； 鄭啟清(Kee-Ching Jeng) ； 陳穎從(Ying-Tsung Chen)

《童綜合醫學雜誌》 10卷1期 (2016/06) Pp. 16-25

摘要

背景及目的：於呼吸器上常使用的吐氣末正壓（PEEP）對於左心房及左心室功能造成的影響及評估方法目前仍待解決。本研究主要藉以左心房及左心室扭轉的速率向量影像變化來評估吐氣末正壓對左心房及左心室造成之影響。方法：本研究收錄18位腦部損傷接受呼吸器且以吐氣末正壓5釐米汞柱支持之患者，並在使用與未使用吐氣末正壓間測量三個相位的左心房容積，包括最大左心房容積（LAVmax）、最小左心房容積（LAVmin）、及左心房收縮前容積（LAVpreA），用來計算一次心臟收縮的排空容積及比例。並測量左心室十六個區域的收縮情況包括拉伸、扭轉及差異用以進一步評估呼吸器吐氣末正壓對心臟所造成的影響。結果：左心房三個相位的容積及其他指數皆無變化。左心室方面，在使用與未使用吐氣末正壓呼吸器間量測到的心室扭曲（twist: 22.47 ± 32.62 vs. -8.82 ± 14.01 degrees, p ＜ 0.05）及旋轉（torsion: 3.54 ± 4.86 vs.-1.49 ± 2.27 degrees/cm, p ＜ 0.05）都有顯著意義的降低。但在左心室的變形參數上包括長度、半徑、圓周伸張及伸張率等都沒有顯著的變化。結論：呼吸器若使用較低的吐氣末正壓（PEEP）並不足以改變左心房的相位容積，故臨床上不易以傳統心臟超音波偵測其對心臟的影響。而若以速率向量影像（VVI）測量左心房及左心室的扭曲與旋轉則是個非侵襲性、且敏感度高的方式。

關鍵字

機械性通氣 ； 吐氣末正壓 ； 速率向量影像

並列摘要

Purpose: The reported effects of mechanical ventilation, with and without positive end-expiratory pressure (PEEP), on left ventricular (LV) and left atrial (LA) function are controversial. The aim of this study was to evaluate phasic volume changes in LA and LV torsion in patients receiving mechanical ventilation with or without PEEP by vector velocity imaging. Methods: This study enrolled 18 patients who sustained head injury and were placed under ventilatory support with and without PEEP (5 cm H_2O). Three phasic LA volumes (LAVs), including maximal LAV, minimal LAV, and LAV before atrial contraction, were measured by echocardiography. These phasic LAVs were used to calculate the emptying volume and fraction at different phases of one heart cycle. The LV contractile properties were analyzed in 16 segments of the LV wall, including strain and strain rate. LV torsion was calculated as the net difference between the apical and basal mean values of rotation. Results: The three phasic volumes and indices of LA, including filling volume, expansion index, emptying index, passive emptying index, and active emptying index, did not change. Comparing on-PEEP and off-PEEP ventilation, there were significant decreases in LV twist (22.47° ± 32.62° vs. -8.82° ± 14.01°, respectively; p ＜ 0.05) and LV torsion (3.54 ± 4.86 vs. -1.49 ± 2.27 degrees/cm, respectively; p ＜ 0.05). There was no significant change in LV deformation, including longitudinal, radial, circumferential strain and strain rate, and displacement. Conclusion: Mechanical ventilation with low PEEP did not cause changes in the LA phasic volume. Velocity vector imaging was a practical and noninvasive technique for evaluation of LV contractile properties. LV twist and torsion were more sensitive to change in airway pressure compared with conventional echocardiographic indices.

並列關鍵字

Mechanical ventilation ； PEEP ； Velocity vector imaging