and pulsed wave Doppler, which generally can be well aligned from this plane, it is possible to evaluate atrioventricular valvar regurgitation as well as stenosis This view is also suited to assess the ventricular septum FIG 19.30 Transesophageal four-chamber view obtained from a midesophageal position The left atrium (LA), left ventricle (LV), right atrium (RA) and right ventricle (RV) are all imaged in this projection Midesophageal Short- and Long-Axis Views From the midesophageal position, different short- and long-axis views can be obtained By slightly advancing and flexing the probe from a standard fourchamber view, a short-axis view at the level of the atrioventricular valves can be obtained (Fig 19.31) This is useful for assessing the leaflets after repair of an atrioventricular septal defect However, in most patients the transgastric shortaxis views are easier to obtain and are the ones most commonly used FIG 19.31 Transesophageal short-axis view at the level of the mitral valve showing both the left and right ventricles (LV, RV) The cut provides a nice image of the mitral valve, showing the aortic and mural leaflets seen in their open position From a standard apical four-chamber view, rotating the probe to between 0 and 60 degrees with slight flexion and pullback, produces an image of the aortic valve leaflets in their short axis (Fig 19.32) This usually permits the distinction of trileaflet from bileaflet valves The origins of the coronary arteries can also be assessed from this view The left coronary artery normally originates from the left coronary aortic sinus, whereas the right artery originates more anteriorly from the right coronary aortic sinus The proximal course of the coronary arteries can generally be identified Here, it can be extremely useful to use color Doppler with a low Nyquist limit, thus confirming normal flow in the arteries In addition, pulsed wave Doppler can be used to measure coronary velocities, which can be helpful after the arterial switch operation The same view permits identification of the membranous part of the ventricular septum and residual ventricular septal defects, if present The anterosuperior and septal leaflets of the tricuspid valves can be imaged It is often possible to obtain good alignment with a regurgitant jet across the tricuspid valve to estimate right ventricular pressure From the same plane, the right ventricular outflow tract, the pulmonary valve, and the pulmonary trunk can all be viewed (Fig 19.33) By pulling back the probe slightly, the proximal part of the right pulmonary artery, and its segment running behind the aorta, can usually be well imaged (Fig 19.34) Imaging the left pulmonary artery from the esophagus can be very challenging because of the loss of the image due to interference by air as it crosses the bronchus The distal parts can be seen from a midesophageal long-axis view, rotating the probe posteriorly to image both the descending aorta and the crossing left pulmonary artery FIG 19.32 Transesophageal short-axis view taken at the level of the aortic valve showing the leaflets of the aortic valve supported by their appropriate sinuses lcc, Left coronary; ncc, noncoronary sinus; PA, pulmonary trunk; rcc, right coronary sinus; RV, right ventricle