Download The TEE imaging planes

TEE Probe Placement and Manipulation,
Comprehensive Examination
Gregg S. Hartman, M.D.
Professor of Anesthesiology
Dartmouth Medical School
Vice Chair and Clinical Director
Director of Cardiac Anesthesia
Dartmouth Hitchcock Medical Center
Lebanon, NH 03756
[email protected]
Conflicts and Disclosures:
I have no conflicts of interest and I have no disclosures
Objectives: - to understand the relevant anatomical relationships involved in TEE
- to understand TEE probe manipulations and their impact on scan planes
-to gain an understanding of the contraindications of TEE
Anatomical Relationships of the Heart, Esophagus, and Surrounding Structures
Because of the proximity of the esophagus to the heart, it is an excellent
“window” for obtaining detailed echocardiographic images of the heart. The esophagus
extends from the posterior pharynx through the mediastinum and finally to the level of
the diaphragm where it joins the stomach. Within the mediastinum it courses behind the
trachea and left mainstem bronchus and continues caudally to become immediately
adjacent to the anteriorly positioned LA and LV. It also runs next to the thoracic aorta
and both lung cavities. The narrowest portion of the esophagus is at its origin at the level
of the pharynx.
ASE Guidelines for Performing Multiplane TEE poster
www.asecho.org
TEE Probe Insertion:
Prior to insertion, the TEE probe should be carefully examined for structural
defects. Correct mechanical functioning should be confirmed by manipulation of the
controls and finally the TEE probe should be attached to the TEE console and the proper
electrical performance established. In addition to these pre-insertion checks, the probes
should have frequent testing by biomedical personnel.
TEE Probe manipulation and anatomical scan planes. GS Hartman
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The probe is then thoroughly lubricated and carefully placed in the posterior
pharynx. A bite block may be used to prevent any damage to or from the teeth. The
probe is then carefully advanced into the esophagus. At some centers, routine direct
visualization of the probe passage is aided by direct laryngoscopy. Passage of the TEE
probe beyond the laryngeal structures may be facilitated by anterior lift/thrust of the
mandible, flexion of the head and or manual – digital guidance. Slight anteflexion of the
probe tip is often helpful. There should be little or no resistance to probe passage.
Marked resistance to TEE advancement should alert the operator to the possibility of
unappreciated esophageal stricture. Typically there is a noticeable loss of resistance as
the probe passes the glottic structures and constrictor muscles. In a small subset of
patients (usually < 2%) significant difficulty to probe passage is encountered. It is
usually best to terminate further attempts at placement and utilize alternative imaging
modalities, (e.g. epicardial echocardiography).
from Konstadt, Shernan Oka, Clinical Transesophageal Echocardiography (2nd)2003
TEE Probe Manipulation:
There are five possible manipulations of the TEE probe and corresponding
terminology for such maneuvers. These include moving the probe up and down within
the esophagus to obtain different levels of imaging. This is called advancement or
withdrawal. The probe may be turned or rotated to the patient’s right (clockwise from the
anesthesiologist’s prospective at the head) or to the patient’s left (counterclockwise). The
control knobs permit further movement of the probe’s tip. It may be flexed anteriorly
(anteflexion), or posteriorly (retroflexion) and to the left or right (probe flexion). Finally
there is the capacity to rotate the transducer within the probe from 0 degrees or the
horizontal plane “forward” to 180 degrees or from 180 to 0 degrees (backward transducer
rotation).
University of Toronto Perioperative TEE Simulator
TEE Probe manipulation and anatomical scan planes. GS Hartman
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from Mathew & Ayoub. Clin Manual & Review of TEE. McGraw Hill 2005
The SCA and ASE have produced guidelines for performing and intraoperative TEE
examination and have standardized the nomenclature for such a study. This helps to
ensure common language and completeness of examinations. They have also defined 20
cross sectional views which are fundamental in the performance of a complete TEE
exam. These are reproduced elsewhere in the syllabus.
Several concepts need to be grasped. When moving from a transgastric SAX view (d) to
a TG 2 chamber view (e), the right side of the screen imaged by the left side of the
transducer (when viewed from behind the patient as in the typical intraoperative
orientation), moves from lateral to cephalad while the left side of the screen (right side of
the ultrasound array) moves caudally (see below)
⇒
TEE Probe manipulation and anatomical scan planes. GS Hartman
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⇒
In contrast, when moving from 0 degrees – 90 degrees from the ME long axis (a) to the
– ME long axis(b), the right side of screen changes from left lateral to anterior and left
side of screen changes from right lateral to inferior.
Transesophageal Echocardiographic Windows
There are four main positions within the esophagus from which the standard TEE
scan planes can be obtained. These four “windows” are 1) the upper esophageal (UE), 2)
the mid esophageal (ME), 3) the transgastric (TG) and 4) the deep transgastric (dTG).
From these four positions in combination with appropriate scan plane angulations, all of
the aforementioned “SCA-20” cross sectional views can be imaged. An alternative way
to organize the scan plane images is by structure of interest. For example, the mitral
valve can be imaged from the ME level from multiple scan angles, (sections a,b,c), from
the TG level (sections e,f,g).and from the dTG level (section k).
from Perrino & Reeves Transesophageal Echocardiography 2003
Virtual TEE: Computer simulation of scan planes vs. heart
In order to fully utilize transesophageal echocardiography (TEE), the
echocardiographer is required to have a 3-dimensional understanding of the heart and the
surrounding structures. Integrated into this concept, is a mental image of the ultrasound
scan plane. Unlike surface echocardiography, TEE requires placement of the probe in the
esophagus and thus while quite safe, it is somewhat "invasive." The student of TEE must
learn from such hands-on situations, limited typically to the operative setting with
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anesthetized patients. In addition, teachers of TEE are limited to static illustrations of the
image scan planes and their orientation to the heart. Lastly, the vantage point for these
illustrations is fixed, whereas the vantage-point for anesthesiologist is from the top of the
patient, and for cardiologists it is typically from the side, facing the patient. These
differences complicate an already difficult concept.
Computer technology has evolved the world of visual reality. In the virtual TEE
simulator, students have the ability to manipulate the flexible TEE probe, see the
resulting movement of the corresponding scan planes on a 3-dimensional heart model,
and view the ultrasound image obtained from that scanning location (acoustic "window").
The student is able to perform repetitive examinations and probe manipulations without
the added morbidity associated with similar probe movements as required for an actual
TEE examination.
Computer and video technology have evolved dramatically allowing virtual
reality simulators to be developed in many settings. Aviation for example has
demonstrated the utility of realistic simulators for safely and efficiently teaching complex
and dangerous skills like flying an airplane. Simulators have numerous medical
applications as well including fiberoptic intubation, pharmacokinetics and
pharmacodynamics, epidural and other regional anesthetic techniques, and recently
complete simulators for operating rooms and anesthetic delivery have been brought to the
public domain. The utility of these various systems has been demonstrated in improved
trainee success and patient safety.
Several self-tutorial programs have been developed for TEE utilizing numerous
media including video-tapes, computer-based tutorials and web-based interactive sites
(see end of handout for links and references). However, all suffer from the limitation of
having a predetermined set of scan planes and images. The presenter or student is not
able to independently manipulate the TEE probe and thus perform a "virtual" scan. Not
infrequently, students can understand the images when shown them, but are unable to
gain facility with obtaining the images themselves. These students often related their
difficulties to the lack of a clear grasp of the three dimensional relationships of the heart
and ultrasound scan planes.
Performing a comprehensive TEE examination:
There are two basic schemes for performing a comprehensive examination. The
underlying principle is to assure a complete and comprehensive study. This can be
achieved by either obtaining images from a given level within the esophagus (e.g. upper,
middle, transgastric or deep-transgastric) or by organizing the study based upon structure
of interest, (e.g. left ventricle, mitral valve, aortic valve etc.). Both systems work-each
with their advantages and limitations. “Esophageal level” focused examinations have the
advantage of limiting movement of the probe, can permit a global or 3D sequential
imaging strategy and may be best tolerated in the sedated but not completely anesthetized
patient. The structure focused examination can facilitate a more comprehensive study of
valves/chambers in question and permits the interrogation of a specific structure from
varying levels or vantage points.
Whatever system is used, most important is to document and communicate your
findings. This is essential to a complete examination. To follow are a series of
illustrations of with the esophageal-level or structure-directed TEE examination
sequence.
TEE Probe manipulation and anatomical scan planes. GS Hartman
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Organized by differing levels in the esophagus:
In this sequence the exam begins in the Upper Esophagus(UE) and proceeds distally from
the Middle Esophagus(ME), the Transgastric (TG), to the Deep Transgastric (dTG). In
this fashion, minimal probe movement up and down the esophagus occurs. This may be
better tolerated in the sedated patient but is of little consequence when the TEE exam is
performed under general anesthesia and tracheal intubation. It does require one to
integrate views of various structures across various scan levels.
Structures viewed from the Upper Esophagus (UE) are the aortic arch in short and long
axis.
Advancing the probe distally one arrives at the level of the left atrium and the middle
esophagus (ME) vantage point, usually starting at 0 degrees and retro-flexion and the
development of the ME 4 chamber (a). Typically the array is advanced form 0- 120+
degrees and full interrogation of the mitral valve, the aortic valve the inter-atrial septum,,
the left atrial appendage, the pulmonary veins is performed. At the same time, the walls
of the LV are examined as well. Images of the SCA 20 obtained at this level are
illustrated below.
Color Flow Doppler may be added for better interrogation of the MV and AV for stenosis
and regurgitation. Increased detail can be achieved by changing the depth setting to a
shallower area when examining the two valves when compared to imaging the more
distal ventricular walls. Right side examination of the tricuspid valve, the pulmonic
valve and the right atrium and RV outflow tract is performed by turning the probe to the
right side and similarly progressing through scan plane advancements. The proximal
ascending aorta is also imaged form this level in both short and long axis.
TEE Probe manipulation and anatomical scan planes. GS Hartman
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Upon completion of ME imaging, the probe is returned to 0 degrees and advanced more
distally to the transgastric (TG) level. Here, short and long axis imaging of both
ventricles is performed as well as visualization of the subvalvular apprarati of the MV
and TV.
The descending aorta is then imaged either from the ME or TG level but requires CCW
turning of the probe ~ 120 degrees.
Final views are completed by further advancement to the deep transgastric level and
retroflexion to obtain the dTG LAX. This view is most common for Doppler flow
interogation of the LVOT and AV as it affords parallel beam alignment to blood flow.
Structure Focused TEE examination sequence:
As previously mentioned, the disadvantage of an esophageal level examination sequence
is that views of structures must be integrated across different level scan sequences. As an
alternative strategy and one typically more easily understood by more inexperienced
echocardiographers, the examinations now proceed according to structure of interest.
Typically, the sequence will progress from evaluating the left ventricle from both the
transgastric and ME levels with scan planes optimized at these levels to image the
ventricular walls. Views include the TG SAX at the mid papillary, the basal and apical
level. Advancing the multiplane angle develops the TG 2 chamber and AV LAX as well.
TEE Probe manipulation and anatomical scan planes. GS Hartman
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Perform 2-D, Doppler color flow from 0 - 180°
Next the Mitral valve is imaged from the TG and then the ME level. Depth is usually
dropped when compared to that utilized for LV interrogation and sequential views with
and without CFD are obtained. Thus the sequence might be the ME 4 chamber,
commissural, 2 chamber and AV LAX. Spectral Doppler is applied to complete the MV
examination. The Aortic valve is next typically imaged in the ME AV SAX and LAX
views, complimented with CFD and finally spectral Doppler form the dTG position.
Next the Left atrial structures are viewed including the pulmonary veins. Turning the
probe to the right images the interatrial septum in the 4 chamber and bicaval views.
Right side examination of the TV and RA and RV are performed at both the ME and TG
level. Finally, the probe is returned to the ME and then rotated ~ 120 degrees CCW to
image the descending aorta in short and long axes and with drawn to complete the
examination of the aortic arch.
Descending aorta: Turn probe 120-140°CCW, Center display on Ao, Decrease depth,
maximize MHz
Aortic Arch: Withdraw probe until UE window (s, t)
TEE Probe manipulation and anatomical scan planes. GS Hartman
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Whatever system is used, most important is to document and communicate your
findings. This is essential to a complete examination.
Useful Websites:
http://pie.med.utoronto.ca/TEE/index.htm
http://www.e-echocardiography.com
References:
JP Mathew, CM Ayoub. Clinical Manual and Review of Transesophageal
Echocardiography. McGraw Hill New York 2005
AC Perrino, ST Reeves. A Practical Approach to Transesophageal Echocardiography.
Lippincott Williams & Wilkins. Philadelphia 2003
RM Savage, S Aronson. Comprehensive Textbook of Intraoperative Transesophageal
Echocardiography. Lippincott Williams & Wilkins. Philadelphia