F. Goals of the Two-Dimensional Examination. A comprehensive evaluation is preferred with each cardiac chamber and valve imaged in at least two orthogonal planes. However, in an emergency situation, such examination may not be possible. In these cases, most echocardiographers focus the TEE examination to views that are most likely to provide a diagnosis, including the transgastric short axis view of the left ventricle (LV) for diagnosing hypovolemia, coronary ischemia, and acute heart failure (Table 26-3).
G. Three-Dimensional Echocardiography. This technology is capable of acquiring full volumes of the LV, visualizing heart valves in three dimensions, and assessing the synchrony of LV contraction.
III. DOPPLER ECHOCARDIOGRAPHY AND HEMODYNAMICS. Use of 2-D echocardiography captures high-fidelity motion images of cardiac structures but not blood flow. Blood flow indices, such as blood velocities, stroke volume, and pressure gradients, are the domain of Doppler echocardiography. The combination of 2-D images and quantitative Doppler measurements create a uniquely powerful diagnostic tool. The motion of an object causes a sound wave to be compressed in the direction of the motion and expanded in the direction opposite to the motion. This alteration in frequency and is known as the Doppler effect. By monitoring the frequency pattern of reflection of red blood cells, Doppler echocardiography can determine the speed, direction, and timing of blood flow.
A. Spectral Doppler. Two Doppler techniques, pulsed-wave (PW) and continuous-wave (CW) Doppler, are commonly used to evaluate blood flow.
1. PW Doppler offers the ability to sample blood flow from a particular location. Doppler data are frequently presented as a velocity–time plot known as the spectral display.
2. CW Doppler avoids the maximal velocity limitation of PW systems, and blood flows with very high velocities are recorded accurately (determining the high-velocity jet of aortic stenosis).
B. Color-flow Doppler (CFD) provides a dramatic display of both blood flow and cardiac anatomy by combining 2-D echocardiography and PW Doppler methods (Fig. 26-2). Red hues indicate flow toward the transducer, and blue hues indicate flow away from the transducer.
TABLE 26-3 MAIN USES OF VARIOUS TRANSESOPHAGEAL ECHOCARDIOGRAPHY VIEWS
Midesophageal Ascending Aorta Short-Axis View
Evaluate the ascending aorta for dissection flaps.
Evaluate the pulmonary artery (position of catheter, presence of thrombus).
Align the Doppler beam parallel to the blood flow in the main pulmonary artery.
Midesophageal Aortic Valve Short-Axis View
Evaluate the AV cusps.
Evaluate aortic stenosis and to measure the area of the AV orifice (planimetry).
Evaluate aortic insufficiency by applying CFD.
Evaluate the interatrial septum for PFO or ASD.
Midesophageal Aortic Valve Long-Axis View
Evaluate the AV annulus, sinus of Valsalva, sinotubular junction, and abdominal aorta dimensions.
Evaluate aortic insufficiency by using CFD.
Evaluate vegetations or masses attached to the AV.
Evaluate left ventricular outflow track pathology.
Evaluate the presence of calcification or dissection flaps in the proximal abdominal aorta.
Midesophageal Bicaval View
Evaluate the interatrial septum, including CFD, to detect a PFO or ASD.
Determine the passage of air across the interatrial septum.
Guide placement of catheters and cannulas (pulmonary artery catheter, pacemaker wires).
Detect the presence of thrombus or tumors.
Midesophageal Right Ventricular Inflow–Outflow View
Evaluate the pulmonic valve by measuring the pulmonary annulus (required for Ross procedure) and detect pulmonary insufficiency by applying CFD on top of the two-dimensional view.
Evaluate the structure and function of the RV and RVOT.
Evaluate the tricuspid valve.
Evaluate the location of the pulmonary artery.
Midesophageal Four-Chamber View
Evaluate the size and function of the LA, RA, RV, and LV (inferoseptal and anterolateral walls).
Evaluate tricuspid valve and mitral valve structure and function. (CFD detects valvular pathology.)
Evaluate diastolic function.
Midesophageal Two-Chamber View
Evaluate LV anterior and inferior wall function.
Evaluate the LV apex.
Diagnose apical thrombus.
Midesophageal Long-Axis View
Evaluate LV anteroseptal and posterior wall function.
Evaluate LV outflow tract pathology.
Evaluate the mitral valve.
Transgastric Midpapillary Short-Axis View (considered to be the most useful view in situations of intraoperative hemodynamic instability because it allows immediate diagnosis of hypovolemic state, pump failure, and coronary ischemia)
Evaluate LV size (enlargement, hypertrophy) and cavity volume.
Evaluate global ventricular systolic function and regional wall motion.
Transgastric Two-Chamber View
Evaluate function of the LV anterior and inferior walls.
Transgastric Long-Axis View
Evaluate the systolic function of the anteroseptal and posterior LV walls.
Deep Transgastric Long-Axis View
Perform Doppler assessment of the LV outflow tract and aortic blood velocities.
Aortic Short-Axis and Long-Axis Views
Identify pathology of the descending aorta (atheroma, dissection flaps, aneurysm).
Assist with placement of guidewires and cannulas (IABP, aortic cannula).
Upper Esophageal Aortic Arch Short-Axis View
Evaluate the presence of pathology in the distal aortic arch.
Perform Doppler assessment of the pulmonary arterial blood velocities.
ASD = atrial septal defect; AV = aortic valve; CFD = color-flow Doppler; IABP = intraaortic balloon pump; LA = left atrium; LV = left ventricle; PFO = patent foramen ovale; RA = right atrium; RV = right ventricle; RVOT = right ventricular outflow tract.
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