Echocardiographic Assessment
We performed TEE after induction of anesthesia before sternotomy and any canulation of the patient. All measurements were done with Philips Epic 7 echocardiography machines and X8-2T-TEE probes. Examinations were performed by a board certified echocardiographer according to recent recommendations for TEE examination.13, 14
Real-time three-dimensional full-volume datasets, including the entire RV, were acquired from a mid-esophageal RV-focused four-chamber-view. Four-beat acquisition during apnea was performed. The settings of the ultrasound machine were adapted to a high temporal resolution. TomTec 4D-RV-Function-2.0 (TomTec Imaging Systems GmbH, Unterschleissheim, Germany) was used for estimation of three-dimensional derived RV-free-wall strain (3D-RV FWS) and RV ejection fraction (3D-RV EF). This software is based on speckle-tracking technology and provides a semi-automated quantification of RV size and function.15, 16 Therefore, RV borders needs mandatory adjustment by the operator after automatic extraction and tracking of the right ventricle out of the full-volume data set.16Figure 1 shows the assessment of 3D-RV EF and 3D-RV FWS by TEE.
For the evaluation of tissue velocity of the tricuspid annulus (RV S´), tricuspid annular systolic excursion (TAPSE), and RV fraction area change (RV FAC) we used Philips QLAB 10.8 software. TAPSE was assessed in the midesophageal RV-focused four-chamber-view by measuring the displacement of the tricuspid annulus in anatomic M-mode. Anatomic M-mode is an angle independent M-mode that allows the operator to position the cursor freely on the two-dimensional image. Therefore, the cursor was directed towards the RV apex. RV FAC was evaluated from midesophageal RV-focused four-chamber view. The change of RV area in relation to diastolic RV area was calculated and is shown in percent. RV S´ was assessed from the midesophageal RV-focused four-chamber view measuring the peak positive tissue velocity using pulsed wave tissue-Doppler imaging during ejection period in an angle-independent manner. Therefore, the cursor of the Doppler was directed towards the RV apex, which is available on all our Philips Epic 7 echocardiography machines. Settings of the ultrasound machine were adapted to high temporal resolution with a frame rate >100 frames/s. The sample volume of the pulsed-wave Doppler was set to 5-7 mm following recent suggestions of the European Association of Cardiovascular Imaging (EACVI).17