將杜卜勒組織超音波心圖影像的變異率應用在冠狀動脈繞道手術左心室功能變化的評估

Evaluation of the Longitudinal Contraction of the Ventricle Septum in Patients Undergoing Off-pump Coronary Artery Bypass Graft Surgery by Strain Rate Imaging

背景：變異率影像是一種評估心臟收縮及舒張功能的新方法。暫時性的心臟延遲收縮是一種心肌缺氧的表現；永久性的心臟延遲收縮是一種心肌壞死的表現。這種新方式可以比用肉眼觀測心臟的收縮及舒張早期偵測到心肌缺氧壞死。方法：九位計畫進行冠狀動脈繞道手術的病人被囊括本試驗中。全身麻醉下，經食道超音波完成後，應變率成像經由康柏電腦離線完成。試驗分成為（1）T1：完成全身麻醉後30分鐘（2）T2：在打開胸骨及心包膜後（3）T3：綁住左前降支冠狀動脈後（4）T4：左內乳動脈接上左前降支冠狀動脈後（5）T5：在關上胸骨及心包膜前（6）T6：在關上胸骨及心包膜後。結果：九位病人術後血管攝影追蹤都有良好功能的新接血管。綁住左前降支冠狀動脈後，變異率數值在左前降支冠狀動脈支配區域明顯下降，且在收縮和舒張期有相反的結果。左內乳動脈接在接上左前降支冠狀動脈後，左前降支冠狀動脈支配區域變異率數值在收縮及舒張期都有明顯的上升。本試驗呈現的是一種暫時性的心臟延遲收縮；肉眼觀測心臟的收縮卻沒有 偵測到心肌的缺氧或明顯的改善。結論：杜卜勒組織超音波心圖影像的變異率能夠精確的評估心臟收縮及舒張功能和外科醫師來說，可以成為冠狀動脈繞道手術監視所接血管功能的工具。

Background : Strain rate (SR) imaging is an emerging technique for assessing myocardial systolic and diastolic functions. This technique can provide assessment in real time and color mapping; it also can detect ischemia at its earlier stages in comparison with visual estimation of wall motion with other techniques. Methods: This study group consisted of 9 patients undergoing elective coronary artery bypass graft (CABG) surgery. After general anesthesia with sevoflurane (end-tidal 1.8%) in air/oxygen mixture, a complete transesophageal echocardiography (TEE) study was performed with an ultrasound machine. Myocardial wall strain rate imaging was then preformed off-line using a customized computer software (Echopac, Windows 2000 version 2.1, General Electric) running on a Compaq P4 computer. The experimental protocol was divided into 6 parts: (1) Tl: 30 minutes after general anesthesia completed, (2) T2: after opening the sternum and pericardium, (3) T3: left anterior descending coronary artery (LAD) snared for the preparation of ischemic pre-conditioning (SLAD), (4) T4: after anastomosing left internal mammary artery (LIMA) on LAD, (5) T5: before closing the sternum and pericardium and (6) T6: after closing the sternum and pericardium. Results: From strain rate imaging, peak systolic SRs were reduced or inverted over LAD perfused area during the SLAD period. In apical segments, peak systolic SR changed from -0.45 ± 0.48 to 0.42 ± 0.63 (P < 0.05), whereas peak diastolic SR changed from 0.34 ± 0.61 to -0.80 ± 1.08 (P < 0.05). In the middle septum, peak systolic SR changed from -0.67 ± 0.51 to -0.43 ± 0.50 (P < 0.05), while peak diastolic SR changed from 0.47 ± 0.44 to -0.64 ± 0.84 (P< 0.05). After LIMA grafting, peak systolic SR changed from 0.42 ± 0.63 to -0.61 ± 0.40 (P<0.05), as against peak diastolic SR which changed from -0.80 ± 1.08 to 0.21 ± 0.44 (P < 0.05) in the apical septum. Peak systolic SR changed from -0.43 ± 0.50 to -0.75 ± 0.46 (P < 0.05), whereas peak diastolic SR changed from -0.64 ± 0.84 to 0.64 ± 0.88 (P < 0.05) in the middle septum. Conclusions: Postsystolic shortening is a marker for both ischemia and successful myocardial reperfusion. By strain rate imaging, we could detect ischemia with a more sensitive and specific method. For anesthesiologists and surgeons, it can be an intraoperative tool for assessing ventricular function after reperfusion.