Introduction
Right ventricular (RV) function strongly predicts outcome after cardiac surgery.1, 2 Echocardiography remains a cornerstone in detecting perioperative RV dysfunction, but the complex geometry of the right ventricle makes echocardiographic assessment still challenging.3, 4 Conventional echocardiographic parameters for RV function assessment have numerous limitations including incomplete imaging of the complex crescent-shaped right ventricle and angle dependency of Doppler and M-mode technique.5 Strain analysis with speckle-tracking echocardiography (STE) becomes an advancing technique to measure myocardial function. Myocardial strain analysis is less dependent on loading conditions, does not rely on geometric assumptions, has a smaller interobserver variability, is largely angle-independent and is an independent predictor of RV function.6-8 Therefore, strain analysis seems particularly suitable for the perioperative assessment of the right ventricle. Most data on RV strain analysis, however, comes from the evaluation of awake spontaneously breathing patients using transthoracic echocardiography (TTE).5, 9 Intraoperative evaluation of RV strain in anesthetized and ventilated patients using transesophageal echocardiography (TEE) is feasible and supports perioperative decision making, but there is only limited data.7, 10 In particular, this is true for three-dimensional derived right ventricular strain analysis.11, 12 Regardless of the possible benefit of three-dimensional derived RV strain, this technique is quite novel and is not well described in the intraoperative period. Evaluation is challenging by the fact that there are no established normal or reference values for the intraoperative setting. Therefore, by the present study we aim to close this gap by providing intraoperative values for three-dimensional derived right ventricular free-wall strain (3D-RV FWS) that can be expected in onpump coronary artery bypass grafting (CABG) patients with a complication-free, unremarkable intraoperative course.