Basic Intraoperative Transesophageal Echocardiography

Color-Flow Doppler

Advances in electronics and computer technology have allowed the development of CFD ultrasound scanners capable of displaying real-time blood flow within the heart as colors while also showing 2D images in black and white. In addition to showing the location, direction, and velocity of cardiac blood flow, the images produced by these devices allow the estimation of flow acceleration and differentiation of laminar from turbulent blood flow. CFD echocardiography is based on the principle of multigated PWD in which blood-flow velocities are sampled at many locations along many lines covering the entire imaging sector. At the same time, the sector is also scanned to generate a 2D image.

A location in the heart where the scanner has detected flow toward the transducer (the top of the image sector) is assigned the color red. Flow away from the direction of the top is assigned the color blue. This color assignment is arbitrary and determined by the equipment's manufacturer and the user's color mapping. In the most common color-flow coding scheme, the faster the velocity (up to a limit), the more intense the color. Flow velocities that change by more than a preset value within a brief time interval (flow variance) may have an additional hue added to either the red or the blue. Both rapidly accelerating laminar flow (change in flow speed) and turbulent flow (change in flow direction) satisfy the criteria for rapid changes in velocity. In summary, the brightness of the red or blue colors at any location and time is usually proportional to the corresponding flow velocity, whereas the hue is proportional to the temporal rate of change of the velocity.

Left and Right Ventricles

The left ventricle should be examined carefully for global and regional function using multiple transducer planes, depths, and rotational and angular orientations ( Fig. 11.2 ). Analysis of segmental function is based on a qualitative visual assessment that includes the following grading system of both LV wall thickness and motion (endocardial border excursion) during systole: 1 = normal (>30% thickening); 2 = mild hypokinesis (between 10% and 30% thickening); 3 = severe hypokinesis (<10% thickening); 4 = akinesis (no thickening); 5 = dyskinesis (paradoxic motion). The recently recommended ME five-chamber view enables visualization of the septal and lateral walls (slightly anterior) of the left ventricle at 0 to 20 degrees from its base to the apex, along with the left ventricular outflow tract (LVOT), right ventricle and both atria (see Fig. 11.2 ). Slight TEE probe advancement eliminates the LVOT from the image window and permits the development of the ME four-chamber view (see Fig. 11.2 ), demonstrating a slightly more mid-to-inferior plane. TEE probe rotation to approximately 80 to 100 degrees develops the ME two-chamber view (see Fig. 11.2 ), which removes the right-sided chambers from the imaging window but enables visualization of the inferior and anterior LV walls at the basal, mid, and apical levels segments. The ME long-axis (LAX) view at 120 to 160 degrees (see Fig. 11.2 ) allows evaluation of the remaining anteroseptal and inferolateral (posterior) LV segments. Because the left ventricle is usually oriented inferiorly to the true horizontal plane, slight retroflexion of the probe tip may be required to minimize LV foreshortening. The TG midpapillary SAX view (TG mid-SAX) at 0 to 20 degrees (see Fig. 11.2 ) is the most commonly used view for monitoring LV function, because it allows a midpapillary assessment of the LV segments supplied by the corresponding coronary arteries (right coronary artery, left circumflex, and left anterior descending [LAD]). This view also enables qualitative and quantitative evaluation of pericardial effusions. Advancing or withdrawing the probe at the TG depth enables LV evaluation at the respective newly recommended TG apical SAX and basal levels ( TG basal SAX ) (see Fig. 11.2 ), respectively. Further evaluation of the left ventricle can be obtained at the midpapillary TG depth by rotating the probe forward to the TG two-chamber view (80 to 100 degrees) ( Fig. 11.2 ) and TG LAX (90 to 120 degrees) (see Fig. 11.2 ).

Right ventricular (RV) regional and global function can be assessed from the ME five-chamber and four-chamber views (see Fig. 11.2 ), which allows visualization of the septal and free walls. Although a formal segmental scheme has not been developed for the RV free wall, regional assessment of the septum can be performed. Turning the probe to the right and advancing slightly from the ME depth allows visualization of the tricuspid valve (TV), coronary sinus (CS), and RV apex. Rotating the probe between 60 and 90 degrees reveals the ME RV inflow-outflow view (see Fig. 11.2 ), in which the right atrium (RA), TV, inferior RV free wall, right ventricular outflow tract (RVOT), pulmonic valve (PV), and main pulmonary artery (PA) can be viewed wrapping around the centrally oriented aortic valve (AV). This view often allows optimal Doppler beam alignment to evaluate the TV and can also be helpful for directing PA catheter floating and positioning. The same right-sided structures can also be visualized from a different perspective by advancing the probe to the TG depth to obtain the newly recommended TG RV inflow-outflow view (see Fig. 11.2 ). The TG midpapillary SAX view (see Fig. 11.2 ) displays the crescent-shaped, thinner-walled right ventricle to the left of the left ventricle. Slightly withdrawing the probe reveals the right ventricle at a more basal level along with the PV in the newly recommended TG RV basal view (see Fig. 11.2 ). The TG RV inflow view (see Fig. 11.2 ) is developed by turning the probe to the right to center the right ventricle at this depth and rotating the multiplane angle forward to 100 to 120 degrees, thereby revealing the inferior RV free wall.

Mitral Valve

The echocardiographic evaluation of the MV requires a thorough assessment of its leaflets (anterior and posterior), annulus, and the subvalvular apparatus (chordae tendineae, papillary muscles, and adjacent LV walls) to locate lesions and to define the cause and severity of the pathophysiologic condition. The mitral leaflets can be further divided into posterior leaflet scallops: lateral (P1), middle (P2), and medial (P3), which correspond with respective anterior leaflet sections: lateral third (A1), middle third (A2), and medial third (A3). The leaflets are united at the anterolateral and posteromedial commissures. The ME four-chamber view (see Fig. 11.2 ) displays the larger appearing anterior leaflet (A2,3) to the left of the posterior leaflet (P2,1), whereas the ME five-chamber view reveals more of A1 and P1. Anteflexing the probe provides imaging of the anterolateral aspect of the MV, whereas gradual advancement of the probe and retroflexion shift the image plane to the posteromedial aspect of MV. Maintaining the probe at the ME depth and rotating the multiplane angle forward to 60 to 70 degrees develops the ME mitral commissural view (see Fig. 11.2 ), in which A2 is flanked by P1 on the right and P3 on the left, giving A2 the appearance of a “trap-door” as it moves in and out of the imaging plane throughout the cardiac cycle. Farther forward rotation of the probe to 80 to 100 degrees develops the ME two-chamber view (see Fig. 11.2 ), revealing P3 to the left and A1 on the right. Final forward probe rotation to 120 to 160 degrees reveals the ME LAX view (see Fig. 11.2 ), which images P2 on the left and A2 on the right. The TG basal SAX view (see Fig. 11.2 ) enables visualization of both MV leaflets (“fish-mouth view”) if the probe is anteflexed and withdrawn slightly from the midpapillary level of the left ventricle. In this view, the posteromedial commissure is in the upper left, the anterolateral commissure is in the lower right, the posterior leaflet is to the right, and the anterior leaflet is to the left of the displayed image. Rotation of the probe to 80 to 100 degrees develops the TG two-chamber view (see Fig. 11.2 ) that is especially useful for evaluating the chordae tendineae and corresponding papillary muscles.

Aortic Valve, Aortic Root, and Left Ventricular Outflow

The three cusps of the semilunar AV are best visualized simultaneously in the ME AV SAX view (see Fig. 11.2 ), which is obtained by rotating the probe forward to 30 to 60 degrees. The noncoronary cusp is superior, lying adjacent to the atrial septum; the right cusp is inferior; and the left cusp lies to the right, pointing in the direction of the left atrial appendage (LAA). This view permits planimetry of the AV orifice, evaluation of congenital anomalies of the AV (eg, bicuspid AV), and qualitative assessment of aortic insufficiency (AI) when CFD is used. The ME AV LAX view (see Fig. 11.2 ) can be obtained at the same depth while rotating the probe to 120 to 160 degrees, allowing for visualization of the LVOT, AV annulus, and leaflets (right and either noncoronary or left), sinuses of Valsalva, sinotubular junction, and proximal ascending aorta. This view is particularly useful for evaluating AI with CFD, systolic anterior motion of the MV, and proximal aortic pathologic conditions (eg, dissections, aneurysms). Rotating the probe back to 90 to 120 degrees and advancing into the stomach to TG level develops the TG LAX view (see Fig. 11.2 ). In this view, the LVOT and AV are oriented to the right and inferiorly in the displayed image, thereby providing an optimal window for parallel Doppler beam alignment for the assessment of flows and pressure gradients (aortic stenosis [AS], hypertrophic obstructive cardiomyopathy). Rotating the probe back farther to 0 to 20 degrees, advancing deep into the stomach, and anteflexing the tip so that it lies adjacent to the LV apex, allows for the development of the deep TG LAX view, now referred to as the deep TG five-chamber view (see Fig. 11.2 ), which also provides optimal Doppler beam alignment for measuring transaortic valve and LVOT flow velocities and may provide an additional window for assessing flows through muscular ventricular septal defects and LV apical pathologic conditions (thrombus, aneurysms).

Tricuspid Valve

The echocardiographic evaluation of the TV requires a thorough assessment of its three leaflets (anterior, posterior, and septal), annulus, chordae tendineae, papillary muscles, and the corresponding RV walls. In the ME five-chamber view, the septal TV leaflet is displayed on the right side, and the anterior leaflet is usually on the left side of the annulus. Advancing the probe slightly reveals the ME four-chamber view (see Fig. 11.2 ), with the septal TV leaflet on the right side and the posterior TV leaflet usually on the left side of the annulus. Rotating the multiplane angle to 50 to 70 degrees develops the ME RV inflow-outflow view (see Fig. 11.2 ), which displays the posterior TV leaflet on the left side of the image and the anterior TV leaflet on the right side of the image adjacent to the AV. Slightly turning the probe rightward from the ME bicaval view permits the development of the newly recommended ME-modified bicaval TV view (see Fig. 11.2 ) with the anterior leaflet on the right and the posterior leaflet on the left. The ME-modified bicaval view often provides better alignment of a CWD beam with a tricuspid regurgitation (TR) jet for estimating PA pressures. The TG RV inflow view (see Fig. 11.2 ) is obtained by advancing the probe into the stomach and rotating to 100 to 120 degrees. This view is ideal for visualizing the chordae tendineae and papillary muscles in the right ventricle. Rotating back to the TG mid-SAX at 0 to 20 degrees and slightly withdrawing the probe to obtain the TG RV basal view provides a cross-sectional, SAX view of the TV, displaying the anterior leaflet in the far field, the posterior leaflet to the left in the near field, and the septal leaflet on the right side of the image.

Pulmonic Valve and Pulmonary Artery

The PV is a trileaflet, semilunar valve. The ME AV SAX view (see Fig. 11.2 ) displays the transition between the RVOT and PV. Rotating the probe back toward 0 degrees and withdrawing slightly develops the ME ascending aortic SAX view (see Fig. 11.2 ) displaying the transition between the PV and the main PA and its bifurcation. Although the right PA is usually easy to visualize by turning the probe to the right, the left PA is often obscured by the interposing, air-filled, left mainstem bronchus. The ME RV inflow-outflow view (see Fig. 11.2 ) can also be used to assess the PV and main PA, which lie on the right side of the image adjacent to the AV. However, the newly recommended TG RV inflow-outflow view (see Fig. 11.2 ), with the PV on the right side of the screen and the more reliable UE aortic arch SAX view (see Fig. 11.2 ), displays the PV oriented to the left of the cross-sectional view of the aortic arch and usually provides a more parallel Doppler beam orientation through for the evaluation of pulmonic regurgitation or stenosis.

Left Atrium, Left Atrial Appendage, Pulmonary Veins, and Atrial Septum

The left atrium is the closest cardiac structure to the TEE probe when positioned in the esophagus. Consequently, the left atrium is usually easily displayed in the superior aspect of the 2D image sector. The ME five-chamber and four-chamber views (see Fig. 11.2 ) display the left atrium almost in its entirety with the LAA oriented to its superior and lateral aspects when the probe is slightly withdrawn. The muscular ridges of the pectinate muscles within the LAA should not be confused with thrombi. A slightly farther withdrawal of the probe, turning it to the left, and rotating the array to approximately 90 degrees, develops the newly defined UE left pulmonary vein view (see Fig. 11.2 ), which allows the left upper pulmonary vein (LUPV) to be imaged as it enters the left atrium from the anterior-to-posterior direction and separated from the lateral border of the LAA by the warfarin ridge . Turning the probe to the right at this depth reveals the newly defined UE right pulmonary view (see Fig. 11.2 ), and a slight advancement and rotation of the array to 0 degrees permits visualization of the newly defined ME right pulmonary vein view (see Fig. 11.2 ), which both reveal the right upper pulmonary vein (RUPV) entering the left atrium in an anterior-to-posterior direction and the right PA or superior vena cava (SVC), respectively.

The interatrial septum (IAS), consisting of thicker limbus regions flanking the thin fossa ovalis, can also be imaged in the ME four-chamber view (see Fig. 11.2 ). Benign lipomatous hypertrophy of the IAS must be distinguished from pathologic lesions such as atrial myxomas. The patency of the IAS and the presence of a patent foramen ovale (PFO) or congenital atrial septal defects should be assessed with Doppler echocardiography and intravenous injections of agitated saline. Advancing and rotating the probe to 80 to 100 degrees develops the ME two-chamber view (see Fig. 11.2 ), which allows for further imaging of the left atrium from left to right. The LAA and LUPV can be seen by turning the probe slightly to the left to develop the newly defined ME LAA view (see Fig. 11.2 ). Rotating the probe to the right at this level and adjusting the multiplane angle to 80 to 110 degrees will develop the ME bicaval view (see Fig. 11.2 ), which delineates the SVC entering the RA to the right of the image and the inferior vena cava (IVC) entering from the left. The IAS can be seen in the middle of the image separating the left and right atria.

Right Atrium and Coronary Sinus

The RA can be most easily visualized in the ME five-chamber and ME four-chamber views (see Fig. 11.2 ) by turning the probe to the patient's right side, as well as in the ME RV inflow-outflow view (see Fig. 11.2 ). In these views, the entire RA can be visualized for size, overall function, and the presence of masses (thrombi, tumors). Rotating the multiplane angle to 80 to 110 degrees develops the ME bicaval view (see Fig. 11.2 ), which displays the RA and its internal structures (Eustachian valve, Chiari network, crista terminalis). The SVC can be imaged entering the RA on the right, superior to the right atrial appendage, and the IVC enters the RA on the left of the display. Advancing and turning the probe to the right will allow for a qualitative evaluation of the intrahepatic segment of the IVC and hepatic veins. At the TG depth, both the TG RV inflow-outflow and TG RV inflow views may provide more optimal imaging windows for visualizing the RA and collateral structures. Pacemaker electrodes and central venous catheters for hemodynamic monitoring or cardiopulmonary bypass (CPB) can be easily imaged in this view.

The CS lies posteriorly in the atrioventricular groove, emptying into the RA at the inferior extent of the atrial septum. The CS can be viewed in LAX entering the RA just superior to the tricuspid annulus by advancing and slightly retroflexing the probe from ME four-chamber view (see Fig. 11.2 ). The CS can be imaged cross-sectionally in the SAX in the ME two-chamber view (see Fig. 11.2 ) in the upper left of the display. The CS and Thebesian valve can also be visualized in the ME-modified bicaval view (see Fig. 11.2 ) on the upper left of the image as it enters the RA at an obtuse angle. Echocardiographic visualization of the CS can be useful for directing the placement of CS catheters used for CPB.

Thoracic Aorta

The proximal and midascending thoracic aorta can be visualized in the SAX in the ME ascending aortic SAX view (see Fig. 11.2 ). Advancing and withdrawing the probe should enable visualization of the thoracic aorta from the sinotubular junction to a point 4- to 6-cm superior to the AV and allow an inspection for aneurysms and dissections. Rotating the multiplane angle to 100 to 150 degrees develops the ME ascending aortic LAX view (see Fig. 11.2 ), which optimally displays the parallel anterior and posterior walls for measuring proximal and midascending aortic diameters. This display can also be obtained from the ME AV LAX view (see Fig. 11.2 ) by slightly withdrawing and turning the probe to the left.

TEE imaging of the aortic arch is often obscured by the interposing, air-filled trachea. The most optimal views of the aortic arch are obtained by withdrawing the probe from the ME ascending aortic SAX view at 0 degrees and rotating to the left to obtain the UE aortic arch LAX view (see Fig. 11.2 ), which displays the proximal arch followed by the mid-arch, the great vessels (brachiocephalic, left carotid artery, and left subclavian artery), and the distal arch before it joins the proximal descending thoracic aorta imaged in cross-section. Alternatively, rotating the probe to 90 degrees develops the UE aortic arch SAX view (see Fig. 11.2 ). Turning the probe to the left in this view delineates the transition of the distal arch with the proximal descending thoracic aorta. Turning the probe to the right and slightly withdrawing it will allow for the mid-arch and great vessels to be imaged on the right side of the screen, followed by the distal ascending aorta when the probe is subsequently advanced and rotated forward to the 120-degree ME ascending aortic LAX view (see Fig. 11.2 ). Epiaortic aortic scanning may be particularly useful for assessing the extent of ascending aortic and arch pathologic conditions (ie, aneurysms, dissection, atherosclerosis) to determine cross-clamping and cannulation sites for CPB.

A SAX image of the descending thoracic aorta is obtained by turning the probe leftward from the ME four-chamber view to produce the descending aortic SAX view (see Fig. 11.2 ). Rotating the multiplane angle of the probe from 0 to 90 to 110 degrees produces an LAX image, the descending aortic LAX view (see Fig. 11.2 ). The descending thoracic aorta should be interrogated in its entirety, beginning at the distal aortic arch, by continually advancing the probe and turning slightly to the left until the celiac and superior mesenteric arteries are visualized branching tangentially from the anterior surface of abdominal aorta when the probe is in the stomach. A thorough examination of the descending thoracic aorta may be necessary to evaluate the distal extent of an aneurysm or dissection. In addition, the descending aortic SAX and LAX views can be useful for confirming appropriate intraaortic balloon positioning.