Discover the ESC Textbook of Cardiovascular Imaging 2nd edition
standardized data acquisition in transoesophageal echocardiography 23 Fig. 1.26 Holding of the actuator and the shaft of the transoesophageal probe at the beginning of the investigation. An assistant during the intubation is helpful to enable the most convenient mode of introduction of the probe (a). The user-operated actuator should be held by the assistant directly above the patient in a vertical direction with the shaft leading downwards (a). The shaft is touched by the operator with the right hand at the distal shaft near the movable tip (b). The distal ending of the unlocked probe is curved to adapt to the curvature of the oropharynx (c). Additional comments in the text. Fig. 1.27 Directly before introducing the probe the left hand of the operator is free for manipulating the tip of the probe during introduction to the oral cavity. The fingers of the left hand will guide the tip of the probe. If the bite guard has to be positioned between the teeth during insertion, the second finger should be laid across the tongue (a). Then, the probe can be fixed to the back of the pharynx, but positioned at the ridge in the middle of the tongue with the best possibility to introduce into the proximal oesophagus. If the patient can tolerate the introduction procedure without the bite guard, the second and third fingers can be used for introduction of the probe to fix the probe at the ridge in the middle of the tongue (b). Additional comments in the text. the best possibility of introduction into the proximal oesophagus ( Fig. 1.27a). If the patient tolerates the introduction procedure without the bite guard, the second and third finger can be used for introduction of the probe to fix the probe at the ridge in the middle of the tongue ( Fig. 1.27b). The bite guard, which during this manoeuvre was at the shaft of the probe, should be positioned between the teeth after insertion of the probe. Standardized data acquisition in transoesophageal echocardiography The sequence of the transoesophageal image acquisition and documentation depends on the individual situation. If there is no time limit due to emergency, cardiac or respiratory failure, cough or vomiting, agitation or high temperature, the transoesophageal investigation can be performed according to anatomical issues starting with the transgastric views followed by the oesophageal views with retraction of the probe. If there is a time limit, the investigation should focus on the target lesion and additional important findings. In conventional settings with high-quality transthoracic pre-investigations and sufficient acquisition of all necessary Doppler spectra by the transthoracic approach, documentation of the transgastric views can normally be spared with respect to the patient’s comfort. Important medical indications for a transoesophageal echocardiography are the accurate visualization of cardiac structures, which cannot be analysed by transthoracic echocardiography, and the clarification of issues which were the cause for
24 chapter 1 conventional echocardiography—basic principles the transoesophageal procedure. Then, depending on the patient’s tolerance and further circumstances, the transoesophageal study should be performed completely, if it is possible. Most of the transoesophageal cardiac views are characterized by the left atrium nearest to the transducer. All standard views should be documented as 2D grey-scale cineloops, as well as colour-coded 2D cineloops, to document flow phenomena at the valves or other special cardiac structures. Due to the higher frequencies used in transoesophageal echocardiography, the spatial resolution is normally better than in transthoracic echocardiography. The small layers of the oesophageal and left atrial wall result in an almost direct proximity to the heart. Thus, transoesophageal echocardiography is normally performed in the fundamental mode due to the absence of tissue interferences of the ultrasound. The transoesophageal study should normally start in the transverse position (0°) with a 5-chamber view or an oblique foreshortened 4-chamber view in the lower transoesophageal approach ( Fig. 1.28a–d). With a minimal deeper insertion of the probe, the longitudinal section of the coronary sinus can be visualized ( Fig. 1.28e–h). The standardized 4-chamber view is obtained by a rotation of the plane of about 0°–40° ( Fig. 1.29a–b), straightening the tip of the probe and retracting the probe to the midoesophageal window to get the apex into the centre of the scanning sector. The transoesophageal 2-chamber view is shown by rotating the plane a further 60° without any movement of the tip and/or the shaft (60°–100°) ( Fig. 1.29c–d). Then, the left ventricular apex is still in the centreline of the scanning sector. The transoesophageal long-axis view is obtained by further plane rotation of about 60° (120°–160°) ( Fig. 1.29e–f). The angle distance between the views is like in transthoracic echocardiography—60° if the left ventricular apex is in the centre of the scanning sector. If this is not possible and the left ventricular apex is rotating from the right side of the sector in the 4-chamber view to the left side of the sector in the long-axis view, which occurs if the correct position in the upper oesophagus cannot be achieved, the angle differences between the planes of the left ventricle will change. This is the reason why the 2-chamber view in transoesophageal echocardiography often seems to be perpendicular to the longaxis view. The normal 60°-angle difference between the standardized views of the left ventricle can be documented by the triplane approach, which will show exactly the standardized views with 60°-angle difference if the left ventricular apex is centred in the scanning sector ( Fig. 1.29g–h). An oblique 2-chamber view, which is obtained by deflecting the tip of the probe, normally enables the documentation of a longitudinal section of the left atrial appendage and the upper left pulmonary vein ( Fig. 1.30a–e). This view is used for acquisition of the pulsed wave Doppler spectra of the velocities of the left atrial appendage and the pulmonary venous inflow. The Doppler spectrum of the velocities of left atrial appendage is necessary for risk estimation of thromboembolic events and the Doppler spectrum of the pulmonary vein is necessary for analysis of diastolic function, as well as for estimation of the severity of mitral valve regurgitation. The left atrial appendage should be visualized at least in a second plane perpendicular to this view to detect possible thrombus formations. Using conventional echocardiography, the left atrial appendage has to be positioned in the centre of the sector by deflecting the probe ( Fig. 1.31a–c). Using multidimensional probes, this second plane can be achieved by the biplane scanning mode. Fig. 1.28 The mid-oesophageal 5-chamber view during systole (a) and diastole (b) and the corresponding colour-coded views during systole (c) and diastole (d). A slight deeper insertion of the probe at 0° displays the inflow of the coronary sinus. The following views of the right atrium and the right ventricular inflow tract are displayed in grey scale mode during systole (e) and diastole (f) and in colour-coded mode during systole (g) and diastole (h). Additional comments in the text.