Evaluation of the longitudinal contraction of the ventricle septum in patients undergoing off-pump coronary artery bypass graft surgery by strain rate imaging.

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) T1: 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.