Abstract
Transesophageal echocardiography (TEE) provides complementary and additional information regarding the anatomy and pathophysiology of the heart, great vessels, and thorax. It is a semiinvasive procedure that carries some risk to the patient, due to the invasive nature of the exam and associated need for sedation or general anesthesia to perform the exam. When the indications for a TEE exam are met and a risk/benefit analysis discussed, TEE adds vital information for patient diagnosis, planning, and guidance of surgical/interventional procedures and outcomes.
Keywords
complications, echocardiography, indications, interventional, transesophageal
Introduction
Transesophageal echocardiography (TEE) is an additional and complementary method of obtaining ultrasound images of the heart and surrounding structures. A flexible TEE probe is introduced, via the mouth, into the esophagus of the patient. The tip of the TEE probe contains a miniaturized phased array transducer capable of producing imaging planes in a full 180-degree spectrum (multiplane imaging; Fig. 4.1A ). TEE has all the imaging capabilities of transthoracic echocardiography (TTE), including two-dimensional (2D) and three-dimensional (3D) imaging, and color, spectral, and tissue Doppler. Most TEE images are obtained with the tip of the probe in the esophagus, with additional images obtained from the stomach (see Fig. 4.1B ). Given the proximity of the esophagus to the heart, TEE can use much higher transmission frequencies, resulting in better image quality and spatial resolution compared to standard TTE imaging. This is especially true for posterior structures adjacent to the esophagus such as the left atrium, left atrial appendage, pulmonary veins, atrial septum, and left-sided valves. TEE is generally used as an adjunct or follow-up test to an initial TTE exam if additional information is sought or the TTE images are inconclusive. Table 4.1 summarizes the advantages and disadvantages of TTE versus TEE.
| Advantages | Disadvantages |
|---|---|
| Useful in percutaneous and surgical procedures, as well as at the bedside | Semiinvasive—usually requires sedation, hence associated risks with probe intubation (gastrointestinal and pulmonary implications) and sedation effects (hypotension). Long procedures may necessitate general anesthesia. Generally a minimum of two staff members required: one operator and one person to monitor the sedation needed. |
| Higher resolution: better to definitively diagnose or characterize vegetations, thrombi, masses, intracardiac shunts. Superior imaging of valves, especially the mitral and aortic, left atrium, left ventricle, aorta and arch, and interatrial septum, as well as the pulmonary veins. | May not view the LV apex or right-sided structures well (structures that are further from probe, particularly in large patients). |
| “Continuous” acoustic window when compared with TTE (no ribs to cause shadowing). | “Blind spot” of acoustic shadowing where the trachea is interposed between the esophagus and heart. Much of the abdominal aorta is out of range. |
| Superior imaging of the mitral valve and mitral prostheses in general, with the ability to precisely localize valvular and paravalvular defects. | Mechanical aortic prostheses can cause excessive shadowing. May be technically difficult to achieve the best angle of insonation for interrogating aortic gradients (i.e., less reproducible for assessing aortic stenosis gradients). Maneuvers to increase or decrease preload may be more difficult (e.g., Valsalva maneuver), although most patients can cooperate. Real-time three-dimensional imaging and reconstruction dependent on a slow regular heart rate and “stable” window (i.e., still patient). |
In 1999, the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists published guidelines for a comprehensive intraoperative TEE examination that consisted of 20 2D views. In 2013, the TEE guidelines were updated to include 28 2D views. The initial 20 views from the 1999 paper focused primarily on intraoperative imaging and decision making. The updated 2013 guidelines included additional views, such as imaging the left atrial appendage, that are obtained regularly in the nonoperative application of TEE. In addition, the guidelines also added 3D imaging and use of biplane imaging. 3D echocardiography is a valuable imaging modality that is particularly suited for TEE.
Introduction
Transesophageal echocardiography (TEE) is an additional and complementary method of obtaining ultrasound images of the heart and surrounding structures. A flexible TEE probe is introduced, via the mouth, into the esophagus of the patient. The tip of the TEE probe contains a miniaturized phased array transducer capable of producing imaging planes in a full 180-degree spectrum (multiplane imaging; Fig. 4.1A ). TEE has all the imaging capabilities of transthoracic echocardiography (TTE), including two-dimensional (2D) and three-dimensional (3D) imaging, and color, spectral, and tissue Doppler. Most TEE images are obtained with the tip of the probe in the esophagus, with additional images obtained from the stomach (see Fig. 4.1B ). Given the proximity of the esophagus to the heart, TEE can use much higher transmission frequencies, resulting in better image quality and spatial resolution compared to standard TTE imaging. This is especially true for posterior structures adjacent to the esophagus such as the left atrium, left atrial appendage, pulmonary veins, atrial septum, and left-sided valves. TEE is generally used as an adjunct or follow-up test to an initial TTE exam if additional information is sought or the TTE images are inconclusive. Table 4.1 summarizes the advantages and disadvantages of TTE versus TEE.
| Advantages | Disadvantages |
|---|---|
| Useful in percutaneous and surgical procedures, as well as at the bedside | Semiinvasive—usually requires sedation, hence associated risks with probe intubation (gastrointestinal and pulmonary implications) and sedation effects (hypotension). Long procedures may necessitate general anesthesia. Generally a minimum of two staff members required: one operator and one person to monitor the sedation needed. |
| Higher resolution: better to definitively diagnose or characterize vegetations, thrombi, masses, intracardiac shunts. Superior imaging of valves, especially the mitral and aortic, left atrium, left ventricle, aorta and arch, and interatrial septum, as well as the pulmonary veins. | May not view the LV apex or right-sided structures well (structures that are further from probe, particularly in large patients). |
| “Continuous” acoustic window when compared with TTE (no ribs to cause shadowing). | “Blind spot” of acoustic shadowing where the trachea is interposed between the esophagus and heart. Much of the abdominal aorta is out of range. |
| Superior imaging of the mitral valve and mitral prostheses in general, with the ability to precisely localize valvular and paravalvular defects. | Mechanical aortic prostheses can cause excessive shadowing. May be technically difficult to achieve the best angle of insonation for interrogating aortic gradients (i.e., less reproducible for assessing aortic stenosis gradients). Maneuvers to increase or decrease preload may be more difficult (e.g., Valsalva maneuver), although most patients can cooperate. Real-time three-dimensional imaging and reconstruction dependent on a slow regular heart rate and “stable” window (i.e., still patient). |
In 1999, the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists published guidelines for a comprehensive intraoperative TEE examination that consisted of 20 2D views. In 2013, the TEE guidelines were updated to include 28 2D views. The initial 20 views from the 1999 paper focused primarily on intraoperative imaging and decision making. The updated 2013 guidelines included additional views, such as imaging the left atrial appendage, that are obtained regularly in the nonoperative application of TEE. In addition, the guidelines also added 3D imaging and use of biplane imaging. 3D echocardiography is a valuable imaging modality that is particularly suited for TEE.
Indications
Indications for TEE fall into two basic categories: diagnostic and procedural ( Table 4.2 ). Diagnostic indications for TEE include the evaluation of cardiac and surrounding structures, where TTE is either nondiagnostic or will likely be nondiagnostic. Commonly this includes the evaluation of far field TTE structures that are in the near field for TEE imaging, given the probe location in the esophagus. Examples of this include imaging the left atrial appendage to rule out thrombus or plan suitability for percutaneous left atrial occlusion device placement. In addition, TEE is used to evaluate cardiac valvular pathophysiology because its superior image quality often facilitates medical and surgical planning and decision making. Examples of this include planning of surgical or percutaneous valve interventions, evaluation of valve masses including infectious complications such as endocarditis, and evaluation of prosthetic valve dysfunction. It is not possible to review all the diagnostic indications for TEE, but given the invasive nature of the procedure, it is important that the findings sought should alter the medical or surgical management of the patient.
| Indication | Examples |
|---|---|
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Procedural indications for TEE include both surgical and interventional evaluation and guidance. The utility of TEE for the evaluation and guidance of cardiac surgical procedures is recognized by cardiologists, anesthesiologists, and surgeons. Recent practice guidelines describing the indications for perioperative imaging have been published by the American Society of Anesthesiologists and the Society of Cardiovascular Anesthesiologists. TEE should be used in all open heart and thoracic aortic surgical procedures and should be considered in coronary artery bypass procedures. The objectives of the TEE exam include confirmation and/or refinement of the preoperative diagnosis, detecting new or unsuspected pathology, and assessing the results of the surgical intervention. TEE should also be used for transcatheter intracardiac procedures. TEE is especially useful for structural heart interventions such as atrial septal defect or patent foramen ovale closure, atrial appendage occlusion, and catheter-based valve repair or replacement. The utilization of TEE is equivocal for dysrhythmia treatment. In noncardiac surgery, TEE may be indicated when the surgery or the patient’s condition might result in severe hemodynamic, pulmonary, or neurologic compromise. TEE is indicated during unexplained life-threatening circulatory instability that persists despite corrective therapy.
Appropriate use criteria for the ordering of echocardiographic examinations have been established to assist clinicians in determining when echocardiography is indicated for specific clinical scenarios. The writing taskforce developed 202 indications for echocardiographic imaging. The proposed list of indications was not meant to be exhaustive. Specifically they evaluated 15 clinical indications for TEE for appropriateness. The criteria did not include intraoperative indications for TEE. Table 4.3 lists the 15 clinical indications and their appropriateness for TEE as an initial or supplemental test.
| TEE as Initial or Supplemental Test | Indication for Exam | Appropriate Use |
|---|---|---|
| General use | Use of TEE when there is a high likelihood of a nondiagnostic TTE due to patient characteristics or inadequate visualization of relevant structures | Yes |
| General use | Routine use of TEE when a diagnostic TTE is reasonably anticipated to resolve all diagnostic and management concerns | No |
| General use | Reevaluation of prior TEE finding for interval change (e.g., resolution of thrombus after anticoagulation, resolution of vegetation after antibiotic therapy) when a change in therapy is anticipated | Yes |
| General use | Surveillance of prior TEE finding for interval change (e.g., resolution of thrombus after anticoagulation, resolution of vegetation after antibiotic therapy) when no change in therapy is anticipated | No |
| General use | Guidance during percutaneous noncoronary cardiac interventions including but not limited to closure device placement, radiofrequency ablation, and percutaneous valve procedures | Yes |
| General use | Suspected acute aortic pathology including but not limited to dissection/transsection | Yes |
| General use | Routine assessment of pulmonary veins in an asymptomatic patient status post pulmonary vein isolation | No |
| Valvular disease | Evaluation of valvular structure and function to assess suitability for, and assist in planning of, an intervention | Yes |
| Valvular disease | To diagnose infective endocarditis with a low pretest probability (e.g., transient fever, known alternative source of infection, or negative blood cultures/atypical pathogen for endocarditis) | No |
| Valvular disease | To diagnose infective endocarditis with a moderate or high pretest probability (e.g., staph bacteremia, fungemia, prosthetic heart valve, or intracardiac device) | Yes |
| Embolic event | Evaluation for cardiovascular source of embolus with no identified noncardiac source | Yes |
| Embolic event | Evaluation for cardiovascular source of embolus with a previously identified noncardiac source | Uncertain |
| Embolic event | Evaluation for cardiovascular source of embolus with a known cardiac source in which a TEE would not change management | No |
| Atrial fibrillation/flutter | Evaluation to facilitate clinical decision making regarding anticoagulation, cardioversion, and/or radiofrequency ablation | Yes |
| Atrial fibrillation/flutter | Evaluation when a decision has been made to anticoagulate and not to perform cardioversion | No |
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