1 Transesophageal Echocardiography
The role of transesophageal echocardiography (TEE) in the diagnosis and management of patients with suspected and overt cardiac disease has evolved with time as a result of refinements in technology and the addition of three-dimensional (3D) TEE.1,2 The portable nature of the technique allows the examination to be performed in a diverse array of clinical settings that include the outpatient ambulatory clinic, intensive care unit, catheterization laboratory, and operating room. Currently, TEE accounts for approximately 5% to 10% of all echocardiography studies performed.
Performance of Transesophageal Echocardiography
Transesophageal echocardiography is a semi-invasive procedure that should be performed only by a properly trained physician who understands the indications and potential complications of the procedure. Both technical and cognitive skills are required for the competent performance and interpretation of TEE studies (Box 1-1), and guidelines on training have been published.2 The physician should be assisted by an experienced sonographer whose tasks are to ensure that optimal images are obtained by adjusting the controls of the echocardiographic system and to ensure safety by monitoring the responses of the patient during the procedure. Although family members or friends are usually not allowed in the room when the procedure is being performed, there are situations in which their presence can be helpful. The presence of a parent can have a calming effect when one is dealing with an apprehensive teenager. A friend or relative who speaks the same language can relieve anxiety when dealing with an anxious patient who is not fluent in English.
Box 1-1
Cognitive And Technical Skills Required For The Performance Of Transesophageal Echocardiography
Cognitive Skills
Knowledge of appropriate indications, contraindications, and risks of TEE
Understanding of differential diagnostic considerations in each clinical case
Knowledge of physical principles of echocardiographic image formation and blood flow velocity measurement
Familiarity with the operation of the ultrasonographic instrument, including the function of all controls affecting the quality of the data displayed
Knowledge of normal cardiovascular anatomy, as visualized tomographically
Knowledge of alterations in cardiovascular anatomy resulting from acquired and congenital heart diseases
Knowledge of normal cardiovascular hemodynamics and fluid dynamics
Knowledge of alterations in cardiovascular hemodynamics and blood flow resulting from acquired and congenital heart diseases
Understanding of component techniques for general echocardiography and TEE, including when to use these methods to investigate specific clinical questions
Ability to distinguish adequate from inadequate echocardiographic data and to distinguish an adequate from an inadequate TEE examination
Knowledge of other cardiovascular diagnostic methods for correlation with TEE findings
Ability to communicate examination results to patient, other health care professionals, and medical record
Technical Skills
Proficiency in performing a complete standard echocardiographic examination, using all echocardiographic modalities relevant to the case
Proficiency in safely passing the TEE transducer into the esophagus and stomach and in adjusting probe position to obtain the necessary tomographic images and Doppler data
Proficiency in correctly operating the ultrasonographic instrument, including all controls affecting the quality of the data displayed
Proficiency in recognizing abnormalities of cardiac structure and function as detected from the transesophageal and transgastric windows, in distinguishing normal from abnormal findings, and in recognizing artifacts
Proficiency in performing qualitative and quantitative analysis of the echocardiographic data
From Pearlman AS, Gardin JM, Martin RP, et al: Guidelines for physician training in transesophageal echocardiography: recommendations of the American Society of Echocardiography Committee for Physician Training in Echocardiography. J Am Soc Echocardiogr 5:187-194, 1992.
Transesophageal echocardiography should be performed in a spacious room that can comfortably accommodate a stretcher. The room should be equipped with an oxygen outlet and suction facilities. A pulse oximeter should be available, to be used mainly in cyanotic patients and patients with severe lung disease. The TEE probe should be carefully examined before each use. In addition to visual inspection, it is important to palpate the probe, particularly the flexion portion, to ensure that there is no unusual wear and tear of the probe.3 Stretching of the steering cables may result in increased flexibility and mobility of the probe tip with buckling of the probe tip within the esophagus.4 This phenomenon is associated with a poor TEE image and resistance to probe withdrawal. The probe should be advanced into the stomach and straightened by retroflexion of the extreme antiflexed probe tip. We have also detected perforation of the TEE probe sheath by a ruptured steering cable and recommend inspection of the casing for any protruding wires before probe insertion.3 The flexion controls need to be tested on a regular basis. Anterior flexion should exceed 90°, and right and left flexion should approach 90°.
Preparation Of Patient
Patients should be contacted at least 12 hours before the procedure and instructed to fast for at least 4 hours before the procedure. They are informed that they should be accompanied, because they will not be able to drive or return to work for several hours owing to the lingering effect of sedation. On the day of the study, the procedure is explained in detail, and informed consent is obtained. Patients are told to expect mild abdominal discomfort and gagging following the insertion of the probe and are reassured that these responses are transient. A 20-gauge intravenous cannula is then inserted for administration of medications and contrast agents, if necessary. Lidocaine hydrochloride spray is routinely used for topical anesthesia, which should cover the posterior pharynx and tongue. We usually use diazepam 2 to 10 mg intravenously for sedation.5 Midazolam at 0.05 mg/kg, with a total dose between 1 and 5 mg, can also be used.
Sedation is used in about 85% of our patients and should be more sparingly used in elderly patients, because they tend to be more stoic and the effect of sedation tends to be more prolonged. On the other hand, sedation is essential in young, anxious patients and when the study is expected to be protracted. We aim for light sedation so that at the end of the procedure the patients are awake and can leave with an escort. Heavy sedation is needed in situations in which blunting the hemodynamic responses to the procedure is desirable, as with a patient undergoing TEE for suspected aortic dissection.6
It has not been our practice to use anticholinergic agents such as glycopyrrolate to decrease salivation. In rare circumstances in which there is excessive salivation, it is usually adequate to simply instruct the patient to let the saliva dribble onto a towel placed under the chin, or remove the saliva by intermittent suction. Bacteremia is not a significant risk in TEE, and we do not use antibiotic prophylaxis to prevent endocarditis even in patients with prosthetic valves.7,8
Esophageal Intubation
We perform the TEE study with the patient in the left decubitus position. The physician, sonographer, and echocardiographic system are all positioned on the left-hand side of the patient.5 Artificial teeth or dentures are routinely removed. The flexion controls should be unlocked to allow for maximum flexibility of the probe when it is being inserted. The patient’s head should be in a flexed position. The tip of the probe is kept relatively straight and gently advanced to the back of the throat. It should be maintained in a central position, because deviation to either side increases the likelihood that it may become lodged in the piriform fossa. (See Fig. 2-2) The operator can facilitate this process by inserting one or two fingers into the patient’s oropharynx to direct the path of the probe. Gentle pressure is exerted, and the patient is instructed to swallow. The swallowing mechanism helps guide the probe into the esophagus. In older patients, cervical spondylosis with prominent protrusion into the posterior pharynx can create difficulty with passage of the probe.5 Manually depressing the back of the tongue provides more room, allowing the TEE probe to assume a less acute angle and facilitating intubation of the esophagus. If significant resistance is encountered when the probe is advanced, it is prudent to withdraw the probe and then initiate a new attempt. In experienced hands, the rate of failure of esophageal intubation should be less than 2%.5,9
Inadvertent passage of the probe into the trachea can occur, particularly in deeply sedated patients. The development of stridor and incessant cough should alert the operator of this possibility. Furthermore, it would be difficult to advance the probe beyond 30 cm from the teeth, and the image quality is usually poor.5
Image Format
There is no general agreement on how the imaging planes should be displayed. Our preference is to orient the images such that the right-sided structures are on the left side of the screen and the left-sided on the right. The apex of the imaging plane with the electronic artifact is at the top of the screen. Thus, in longitudinal views, superior structures are to the right of the screen and the inferior to the left.10
Standard Imaging Planes
The TEE probe should be capable of multiplane imaging and preferably also real-time 3D imaging. The imaging plane is steered electronically from 0° to 180° by means of a pressure-sensitive switch, providing views that are unobtainable using monoplane and biplane probes. The following discussion focuses only on standard imaging views routinely performed at the University of Ottawa Heart Institute using multiplane TEE (Table 1-1). These views are considered “standard” because they have important clinical relevance and can be obtained in most patients with specific imaging planes. Further advances in image quality and image analysis of 3D TEE will likely facilitate the rapid acquisition of these imaging planes.
Four basic maneuvers are used to obtain specific tomographic views with TEE.11 The first relates to the positioning of the probe by advancement or withdrawal of the probe. Although this is a simple maneuver, it is the most crucial, and the imaging views can be conveniently categorized according to the location of the TEE probe within the esophagus or stomach into four groups: basal, four-chamber, transgastric, and aortic views (Fig. 1-1). The second maneuver involves rotation of the probe from side to side. This is particularly useful when using longitudinal imaging planes, which provide a better demonstration of the continuity between vertically aligned structures such as the superior vena cava and the arch vessels (Fig. 1-2).10,11 Steering the imaging plane using the pressure-sensitive switch is the third maneuver to obtain different tomographic views (Fig. 1-3). The accompanying images in Figures 1-1, 1-2, and 1-3 represent the typical images obtained with one of the basic maneuvers and provide the starting points for further adjustment of the imaging plane to obtain optimal long- or short-axis views of specific structures. This may be achieved using the fourth maneuver, which involves manipulation of the anterior-posterior and right-left flexion control knobs. The availability of a steerable imaging plane has drastically reduced the need to use the flexion knobs, but there are situations in which these knobs play a crucial role in obtaining proper tomographic views.11 These maneuvers provide an almost infinite number of imaging planes. Table 1-1 summarizes the standard imaging planes and the cardiac structures evaluated in these four groups of views.
Basal Views
Aortic Valve
A short-axis view of the aortic valve can be obtained with the probe at about 30 to 35 cm from the teeth. The left coronary cusp often appears to have nodular thickening if the aortic valve is cut obliquely, which is often the case at 0°.10 Steering the imaging plane to 30° to 60° should eliminate this artifact by providing an optimal short-axis view of the aortic valve (see Fig. 1-3, A).11 A slight pull-back of the transducer should allow visualization of both the left and right coronary arteries (Fig. 1-4). The left coronary artery can be followed to its bifurcation into the left anterior descending and circumflex arteries. The right coronary artery is more difficult to display, and only the proximal 2 to 3 cm is usually seen. Other structures well seen in this view are the left atrial appendage and left pulmonary veins. The partition between these structures can be quite bulbous and should not be confused with an abnormal intracardiac mass (Fig. 1-5).12 Rotating the probe to the right should reveal the right pulmonary veins.
We like the horizontal plane in imaging the four pulmonary veins. The left and right pulmonary veins are imaged separately. When one pulmonary vein is identified, a slight translational movement of the probe should bring out the other, because the orifices of the superior and inferior pulmonary veins are in close proximity. The inferior pulmonary veins run horizontal to the imaging plane, whereas the superior veins are more anterior and at an obtuse angle, making them more suitable for Doppler assessment. It is feasible to image the superior and inferior pulmonary veins, left or right, in the same view using the vertical plane and imaging can be facilitated with the use of color flow imaging (Figs. 1-6 and 1-7). The right and left atrial appendages wrap around the great arteries anteriorly. The left atrial appendage is more prominent and can consist of multiple lobes (Fig. 1-8).13
A comprehensive interrogation using multiple imaging planes should be performed to exclude left atrial appendage thrombus in the appropriate clinical setting. The right atrial appendage is smaller and triangular in shape (see Fig. 1-3, B). The endocardial surfaces of both appendages are corrugated and should not be confused with small thrombi.12 A long-axis view of the aorta can be achieved with the imaging plane at about 120° (Fig. 1-9). A more rightward imaging plane, such as 150°, may be needed if the ascending aorta is dilated and tortuous. This view allows the visualization of a longer length of the ascending aorta and thus significantly reduces the blind spot caused by the interposing trachea.
Atrial Septum
We prefer to image the atrial septum using the longitudinal plane at 90° to 120°. The fossa ovalis, which is the thinnest part of the atrial septum, and the continuity of the superior vena cava with the RA are very well demonstrated in this view (see Fig. 1-3, B). This view is particularly valuable in demonstrating the sinus venosus atrial septal defect, which is usually located just inferior to the entrance of the superior vena cava.14,15 The foramen ovale, if present, is located at the superior aspect of the fossa ovalis and is readily seen in this view. It is important to advance the probe to the level of the inferior vena cava so as not to neglect the inferior aspect of the atrial septum.16 Careful sweep of the atrial septum with left-right rotation is needed to visualize the entire atrial septum. Continuous rotation from right to left will sequentially demonstrate the left ventricular (LV) outflow tract and the right ventricular (RV) outflow tract (see Fig. 1-2, B).
Pulmonary Bifurcation
The pulmonary bifurcation view is achieved by withdrawal of the probe with the imaging plane at 0°. The pulmonic valve and main pulmonary artery are best seen slightly superior to the aortic valve (Fig. 1-10). The pulmonic valve is thinner than the aortic valve and is usually difficult to image in true cross section. Further slight withdrawal allows imaging of the pulmonary bifurcation. The entire length of the right pulmonary artery, but only the very proximal portion of the left pulmonary artery, can be seen. The right pulmonary artery can usually be followed to its first bifurcation by rotation of the probe rightward, but this maneuver is better performed with the longitudinal plane at 90°. Gradual rotation from left to right provides good visualization in cross section of the entire right pulmonary artery and its first bifurcation. This is an important view in the detection of proximal pulmonary emboli.17,18
Four-Chamber Views
Four-chamber views are obtained with the transducer within the middle to lower esophagus (see Fig. 1-1, B). It is difficult to image the left ventricle in its true long axis. Excessive anterior flexion should be avoided to prevent foreshortening of the ventricles. Indeed, to optimize visualization of the left ventricle, it is advisable to withdraw the probe slightly and at the same time attempt gentle retroflexion while maintaining adequate contact between the imaging surface and the esophagus. In the setting of a dilated and unfolded aorta, rotating the imaging plane to about 20° to 30° may be necessary to obtain the four-chamber view without the aorta obscuring the tricuspid valve and part of the RV.
Left Ventricle
The inferior septum and anterolateral wall are usually seen in the four-chamber view (see Fig. 1-1, B). The LV apex is difficult to visualize, particularly in patients with a dilated LV. In addition to retroflexion, rightward flexion can often be helpful to minimize foreshortening of the LV. Far-field imaging can be improved by decreasing the transmission frequency or by using harmonic imaging. A continuous sweep from 0° to 180° should be performed to examine the different left ventricular segments so as to have a comprehensive assessment of left ventricular global and regional function (see Fig. 1-2, C).
Mitral Valve
The mitral valve is well seen using the four-chamber view, but the depth of the imaging plane should be reduced to enhance the resolution of the image (see Figs. 1-1, B, and 1-2, C). To identify the individual scallops of the anterior and posterior mitral leaflets, a careful sweep from 0° to 180° should be made. The technique of visualizing specific scallops of the mitral leaflets has been published,19 but patient-to-patient variation should be kept in mind. The presence of a good long-axis view of the aortic valve and proximal ascending aorta, usually at 120°, is a good indication that the middle scallops of both the anterior and the posterior mitral leaflets are imaged and provides the internal reference for the analysis of the other imaging planes. Both papillary muscles can be imaged, but usually not in the same plane. The subvalvular chords are seldom completely imaged because they are frequently obscured by the mitral leaflets. The morphologic information obtained from this view should be corroborated by the short-axis view of the mitral valve obtained from the transgastric view, which also allows a better assessment of the subvalvular structures, including the papillary muscles and chords. Four-chamber views are ideal for the assessment of mitral regurgitation in relation to the number of regurgitant jets, the direction of the jets, and the severity of regurgitation.20,21
Left Ventricular Outflow Tract
We like to image the left ventricular outflow tract at 120° to 160°, because the outflow tract has a horizontal alignment in this plane that may allow optimal imaging even in the setting of a prosthetic aortic valve (see Fig. 1-3, C). The opening and closing of the aortic valve as well as the presence or absence of aortic regurgitation can be well visualized. The proximal ascending aorta is present in this view. A slight withdrawal of the probe will allow more of the ascending aorta to be visualized (see Fig. 1-9). A slight rotation to the left will show the RV outflow tract with the thin pulmonic valve. The motion of the pulmonic valve and the presence or absence of pulmonic regurgitation can be adequately assessed using this view.
Transgastric Views
Left Ventricle
Multiple cross sections of the LV can usually be obtained using the transgastric approach (see Fig. 1-1, C, and Fig. 1-11). These are the views commonly used in the intraoperative assessment of LV function.19 Optimization of the short-axis views of the left ventricle can be achieved with leftward rotation accompanied by leftward flexion. To visualize the LV apex, gentle advancement of the probe is required together with slight retroflexion. In our experience, the short-axis view of the LV apex can be obtained in about 60% of cases. Another way to visualize the LV apex is to use the longitudinal plane at about 90° (see Fig. 1-11). Careful lateral rotation can be used to obtain comprehensive regional assessment of the LV. Leftward rotation of this imaging plane can yield a good alignment with the LV outflow tract and aortic valve to allow accurate measurement of the transaortic pressure gradients in the setting of aortic stenosis (Fig. 1-12).22 The RV can be seen with rightward rotation of the probe. Both short- and long-axis views of the tricuspid valve are achievable, although the tricuspid valve and its papillary muscles are better assessed with the long-axis plane.
Mitral Valve
The mitral valve can be best assessed using the horizontal imaging plane with the transducer brought up to near the gastroesophageal junction (Fig. 1-13). Anterior flexion and leftward flexion are usually required to optimize this view. Adjusting the imaging plane to about 20° will help to bring out the lateral commissure. This view provides unambiguous assessment of the individual scallops of both the anterior and posterior mitral leaflets and thus should be attempted in all patients with myxomatous mitral valve degeneration. In our experience, this view is achievable in about 70% of patients. Both papillary muscles and chords can be demonstrated, and the continuity between these structures and the mitral leaflets is best seen in the long-axis plane.
Coronary Sinus
The coronary sinus comes into view when the probe is withdrawn to near the gastroesophageal junction and the flexion knobs are in relatively neutral positions (Fig. 1-14). This view can also be achieved by retroflexion with the probe in the lower esophagus. The coronary sinus is seen as a vascular structure located posterior to the LV at the atrioventricular groove draining into the RA. The tricuspid valve can be visualized to the right and anterior. A dilated coronary sinus should raise the possibility of the presence of a persistent left superior vena cava, which is the most common cause. Leftward rotation while following the coronary sinus may sometimes demonstrate this anomalous vein.23 In the esophageal views, the left superior vena cava is usually sandwiched between the left atrial (LA) appendage and left superior pulmonary vein.24
Aortic Views
The thoracic aorta is well assessed by TEE because of its close proximity to the esophagus.
Descending Thoracic Aorta
The best way to assess the descending thoracic aorta is to use the horizontal imaging plane with the transducer rotated leftward and posterior, followed by slow withdrawal from the level of the diaphragm to the aortic arch (see Fig. 1-1, D).12 Because of the relationship between the esophagus and aorta, slight rotational adjustment is required to visualize the entire circumference of the aortic wall as the probe is slowly withdrawn.24 If the aorta is dilated or tortuous, proper short-axis views of the descending aorta will require adjustment of the imaging plane by 0° to 90°.
Aortic Arch
The longitudinal imaging plane at 90° is preferred in imaging the aortic arch because it allows visualization of the entire circumference of the aorta (Fig. 1-15).24 Anterior rotation of the longitudinal plane should visualize the entire aortic arch, but the proximal aortic arch may not be visualized when the aortic arch is unfolded. The transducer will need to be withdrawn slightly to image the arch vessels, which course superiorly. In one third of patients, all three arch vessels can be imaged, but in the other two thirds of patients, only the two distal arch vessels can be imaged. It is rare not to be able to image at least one arch vessel. As a rule, the brachiocephalic artery, which is anterior and more rightward, is the most difficult to image because of the interposing trachea. The transverse plane in a more superior location may sometimes show the three arch vessels in their short axis. Advancing the probe by 1 to 2 cm so that the imaging plane is just inferior to the aortic arch can frequently image the proximal left pulmonary artery. It is sometimes possible to follow it to the first bifurcation. This view should be sought in patients suspected of having pulmonary embolism.
Three-Dimensional Imaging
Advances in transducer technology have enabled the incorporation of real-time 3D-imaging capacity into the commercially available TEE probe, such that 3D imaging can be readily performed during a conventional two-dimensional (2D) TEE study providing unique anatomic perspectives in a number of clinical situations.25–32 (See Chapter 4.) The current clinical indications of 3D TEE are summarized in Table 1-2, and the indications are likely to increase with time. In our opinion, 3D TEE imaging should be routinely performed in patients with mitral valve disease and congenital heart disease (Fig. 1-16).
TABLE 1-2 Common Indications for Using Real-time Three-Dimensional Transesophageal Echocardiography
| Cardiac Structure | Information from 3D TEE | Clinical Situations |
|---|---|---|
| Mitral valve | En-face view of mitral valve | Assessment of the location of prolapsing or flail mitral leaflet scallops for potential mitral valve repair; intraoperative assessment of mitral valve clip repair. |
| Prosthetic valve | Number, size, and location of perivalvular regurgitant jets | Preoperative and intraoperative assessment for device closure of perivalvular regurgitation |
| Atrial septum | Number, size, and location of atrial septal defect | Preoperative and intraoperative assessment for device closure of atrial septal defect |
| Intracardiac baffle or conduit | Better anatomic perspective of intracardiac abnormalities | Assessment of naïve and postoperative complex congenital heart disease |
The currently available 3D TEE probe can perform 3D imaging in several modes: 3D full volume, 3D zoom, 3D live, 3D color-flow imaging, and X-plane imaging. We find 3D zoom and X-plane imaging to be the most useful. To acquire 3D full volume, the full pyramidal volume is obtained by stitching together four subvolumes gated to the R-wave of the electrocardiogram. To minimize the stitch artifact between the subvolumes, it is best to acquire the images during a breath hold (Fig. 1-17). In this mode, frame rates are relatively low. Although analysis of the volumetric data set can be performed online, it is frequently performed offline so as not to prolong the study. In the full-volume mode, the semiautomatic multiple parallel slice display can be a quick and useful format in the assessment of LV topography, such as in patients with regional wall motion abnormalities or ventricular aneurysms.
In the real-time live 3D mode, the 3D data set is displayed in real time. It is important to minimize the sector angle so as to increase the frame rate, which is considerably reduced compared to 2D imaging. We find the 3D zoom mode to be the most versatile. In the 3D zoom mode, the area of interest is identified and encompassed by the zoom box, generally in two orthogonal planes. The height and width of the zoom box are adjusted to include the entire area of interest and at the same time streamlined as much as possible in order to enhance the frame rate. Indeed, the 3D zoom mode is our preferred display format when using the 3D live mode. The availability of the X-plane is a very welcome addition to TEE imaging. It allows the simultaneous display of an additional plane during standard 2D imaging. The orientation of the additional plane is usually orthogonal but can be easily adjusted to any specific orientation. The availability of the X-plane provides a quick and comprehensive assessment of complex structures. One example is the LA appendage, which frequently has multiple lobes (see Fig. 1-8). The use of the X-plane allows rapid assessment of the multiple lobes. Similarly, when multiple mitral regurgitant jets are present, X-plane imaging can readily identify the number and orientations of the regurgitant jets.
Real-time 3D color flow imaging can also be performed to provide a 3D assessment of the color flow jet, but the volume of interest is small, and the frame rate is quite limited in this mode.33,34 In vitro and early clinical studies have suggested that 3D color flow imaging gives a more accurate assessment of the shape and size of the vena contracta and flow convergence, both of which are important measures of mitral regurgitation severity. Its clinical usefulness, however, remains unclear.
In order to obtain a high-quality 3D image, the 2D image needs to be optimized in terms of gain and compression settings. A slightly higher gain setting generally provides better 3D images. In both the 3D zoom and 3D live modes, the zoom box should be streamlined to focus on the area of interest to maximize the frame rate. Because the best 3D imaging is obtained with the structure close to the transducer and orthogonal to the ultrasound beam, the TEE transducer should be manipulated to achieve these two objectives. For instance, the transgastric window is superior to the transesophageal window in 3D imaging of the LV papillary muscles. The mitral valve is well suited for 3D TEE imaging precisely for these reasons (see Fig. 1-16). On the other hand, it is much more difficult to obtain a good 3D image of the aortic valve because the valve plane is frequently parallel to the ultrasound beam.
Doppler Examination
Transesophageal echocardiography can be used to assess the flow patterns across the four cardiac valves, but it does not provide additional information to transthoracic echocardiography (TTE). Furthermore, good ultrasound beam alignment with the transvalvular flow may not be feasible because of the anatomic confines of the esophagus. However, accurate Doppler assessment of aortic stenosis can often be obtained from the transgastric window (see Fig. 1-12).22 On the other hand, intracardiac flows such as pulmonary vein flow and LA appendage flow are better and more consistently obtained by TEE and provide important insight into intracardiac hemodynamics.
Left Atrial Appendage Flow
The pattern of LA appendage flow is dependent on cardiac rhythm.35,36 In atrial fibrillation, a regular atrial contraction wave is absent. (See Chapter 42.) In atrial flutter, the velocity waves are more regular and tend to be of greater velocity because of the slower atrial rate. The normal LA appendage velocities are as follows: contraction, 60 ± 14 cm/s; filling, 52 ± 13 cm/s; and early diastolic filling, 20 ± 11 cm/s.35,37
The potential clinical utility of measuring LA appendage velocities relates to their association with LA spontaneous echo contrast and LA thrombus.35,36,38,39
