Background: Quantitative evaluation of Regional Wall Motion Abnormalities (RWMAs) induced by myocardial ischemia can be performed using Transesophageal Echocardiography (TEE). However, this relies on a subjective visual assessment of wall segments. A key advantage of RT3DE is a fast and automated analysis of Left Ventricle (LV) function while accounting for errors in geometric assumptions. We present a case report which illustrates the intraoperative use of RT3DE during coronary artery bypass surgery to objectively assess LV volumes, LV systolic function, RWMAs, and cardiac synchronization following coronary reperfusion.
Case Report: A 50-year-old female presented to Harbor-UCLA Medical Center (Torrance, California, USA) with unstable angina. Cardiac catheterization revealed an occlusion of the proximal Left Anterior Descending (LAD) Artery with collateral filling of the distal LAD. Preoperative Transthoracic Echocardiography (TTE) showed a mildly reduced Left Ventricular Ejection Fraction (LVEF) of 40-45% and RWMAs involving basal to mid-anterior and anteroseptal walls. She underwent an uneventful single vessel off-pump Left Internal Mammary Artery (LIMA) to LAD bypass. An intraoperative TEE was performed after induction and 30 minutes after coronary reperfusion. A multiplane phased array TEE probe (X7-2t transducer) was used and images were acquired using a Phillips iE33 xMatrix Ultrasound Imaging System (Phillips Medical Systems, Bothell, Washington). Digital RT3DE images were analyzed using prototype software (QLAB, 3DQ-Advance, Philips Medical Systems). Two-chamber and four-chamber views were selected and 5 individual points were placed along endocardial border and the automate software traced the endocardial border inside the LV cavity during end diastole and determined the voxel count inside the LV cast to derive the End-Diastolic Volume (EDV). The same process was repeated for the end-systolic frame deriving the End-Systolic Volume (ESV). The software generated baseline ejection fraction was calculated at 41.8% based on these measurements. Pre-reperfusion parametrics also revealed dyssynchrony of the anterior wall segments in the LAD territory (segments 1, 7, and 13). Similar LV data was performed post-reperfusion and analysis was carried out in a similar fashion using the software. Improvement in anterior wall motion, synchronization, and LVEF (49%) was seen post-reperfusion in the LAD territory.
Discussion: RT3DE can a beneficial and objective intraoperative tool for quantitative assessments of LV volumes, LV systolic function, and RWMAs before and after coronary reperfusion. Parametric imaging also revealed abnormal timing and the extent of segmental contraction in the anterior wall. Evaluation of LV systolic function and LVEF is more reproducible and accurate with RT3DE as compared with two-dimensional and M-mode techniques. Therefore, RT3DE may provide a useful standard for quantification. Further studies are needed to validate the utility of intraoperative RT3D TEE to directly and objectively assess the effects of coronary reperfusion on LV dynamics.
