Resuscitative Transesophageal Echocardiography in Critical Care

Abstract

The use of focused critical care echocardiography, diagnostic modality aimed to provide immediate and actionable information, represents a core competency of contemporary intensive care medicine. Resuscitative transesophageal echocardiography (TEE) is a focused, goal-directed examination performed at the point of care, for the rapid evaluation of critically ill patients in whom transthoracic images are either logistically untenable, inadequate, or unobtainable. Some of the applications of TEE in the management of critically ill patients include the evaluation of patients in shock and cardiac arrest, the assessment of trauma patients, and the guidance of several endovascular procedures. Due to the indwelling nature of the transducer, TEE can provide consistently high-quality images and allows for continuous monitoring during hemodynamic interventions, making it ideally suited for the evaluation of critically ill patients. In this article, we review the evolving landscape of resuscitative TEE, discuss the rationale, supporting evidence, safety, and training for the use of this modality in critical care settings. We address the transdisciplinary evolution of TEE and the practical aspects of its implementation in emergency and critical care settings.

Introduction

In recent years, transesophageal echocardiography (TEE) has emerged as a promising diagnostic and therapy-guiding modality in various critical care settings, including the Emergency Department (ED) and Intensive Care Units (ICU). Goal-directed, resuscitative TEE is increasingly used in the evaluation of critically ill patients with a framework similar to emergency and critical care point-of-care ultrasound.

In this narrative review, we present an overview of the rationale and evidence supporting the current applications, safety, and training for the use of TEE in resuscitative and critical care settings. We address the transdisciplinary evolution of TEE, the nomenclature used to describe the use of this modality and the practical aspects of its implementation in emergency and critical care settings.

Terminology

The field of echocardiography has become replete with terminology describing its myriad applications across clinical settings. Anesthesiologists, intensivists, emergency physicians, and others have taken to identifying their respective niches within transthoracic echocardiography (TTE) and TEE. Often the nomenclature differs with respect to the echocardiographer, setting, indication, and/or protocol, which can lead to confusion and inconsistency. There is currently no consensus on the terminology used to describe the use of focused TEE in acute care settings. However, there is increasing awareness of the need to find agreement in the terminology used to describe this practice to ensure unhindered communication and standardization of practice. In this review, we have chosen to use “Resuscitative TEE” to refer to the use of TEE with goal-directed protocols, at the point of care, in the ED, OR, PACU, ICU, or wherever a critically ill patient may be, for the management of patients in cardiac arrest, shock or otherwise critically ill, including guidance of procedures such as temporary mechanical circulatory support.

Focused Cardiac Ultrasound (FOCUS)

Predating the use of TEE in the emergency and critical care settings is the practice of focused cardiac ultrasound (FOCUS), a goal-directed application of TTE, performed by a clinician at the point-of-care.¹ Focused emergency and critical care echocardiography (CCE) differs from the traditional comprehensive TTE examination in its scope, operator, setting, and intent. In contrast to comprehensive TTE, FOCUS aims to answer one or more specific clinical questions, and to guide immediate therapeutic intervention in an emergent setting at the hands of an operator who is not necessarily trained to perform comprehensive echocardiography. The goals and scope of FOCUS have been previously defined in guidelines published by the American Society for Echocardiography (ASE).¹ Since then, FOCUS has been proposed to play a key role in cardiac arrest and non-arrest critical care settings.²

Limitations of FOCUS and Advantages of Resuscitative TEE

While recognized for its diagnostic yield, noninvasive nature, and ability to impact therapeutic decision-making, FOCUS has several limitations in critically ill patients. Among these are patient-specific anatomical barriers to obtaining adequate windows, such as body habitus, small intercostal spaces, and pulmonary pathology such as emphysema. Other anatomical barriers can be found in the setting of chest trauma, whether it’s the result of traumatic injuries in patients with penetrating or blunt thoracic trauma, or secondary to chest compressions (CCs) during cardiopulmonary resuscitation (CPR), chest wall hematomas, rib fractures, and subcutaneous emphysema, all limit surface echocardiography.³ Similarly, chest wall changes resulting from prior sternotomy or surgical dressings following cardiothoracic surgery, are other common limitations of TTE. Additional factors specific to the setting of cardiac arrest include the need to work around both defibrillator pads and ongoing CCs, as well as to minimize pauses of CPR, which limits the opportunity to obtain parasternal and apical views.² For these reasons, the transthoracic approach provides sub-optimal views in many resuscitative and critical care settings and does not allow continuous monitoring during cardiac arrest.

By contrast, the transesophageal approach overcomes these barriers and provides a more continuous scanning window during resuscitative settings. As the esophagus is directly posterior to the heart without intervening lung or subcutaneous tissue, higher-quality views are obtained without the interference of the lungs, excess subcutaneous tissue, or any other device or interventions taking place over the chest wall as described earlier. Furthermore, this approach provides additional views that are not traditionally achieved by TTE, potentially allowing more diagnostic information, as well as capturing interval changes over time. Besides it’s diagnostic potential, the possibility to obtain unique views with TEE make this modality ideally suited to provide real-time guidance for multiple endovascular procedures like extracorporeal membrane oxygenation (ECMO), commonly performed emergently during the care of critical-ill patients. Thus, TEE has attributes that improve upon the already clinically impactful role of TTE in the management of critical care patients.

Rationale and Evidence for TEE in Resuscitation

In the late 1990s and early 2000s, several studies demonstrated the feasibility and usefulness of focused, or goal-directed TEE as a tool to establish the etiology of arrest and circulatory failure in EDs, ICUs, hospital wards, and operating rooms (ORs).^4–9 In these reports, the application of TEE was often referred to as “rescue” TEE, a term describing the use of a limited number of views with the goal of answering a specific set of clinical questions in arresting or hemodynamically unstable patients.

Building on the experience of intraoperative TEE, the use of focused TEE protocols has emerged in ED and ICU settings.^10,11 Like current standards of intraoperative rescue TEE, resuscitative TEE describes an exam of narrow scope, intended to provide emergent and actionable clinical information regarding a predefined question. Resuscitative TEE is similar to FOCUS in that it is intended for use by emergency and other critical care physicians at the bedside, and it is intended to have immediate impact in decision making.^1,2,10 Current common applications of resuscitative TEE include the intra and post-arrest evaluation of patients in cardiac arrest, the use of TEE as a tool for hemodynamic monitoring, and evaluation of undifferentiated shock in patients with a definitive airway. In addition, resuscitative TEE has been described in trauma evaluation and resuscitation, as well as certain procedures involving intra-arterial or intravenous catheterization or cannulation.^12–15 Figure 1 describes the main applications of resuscitative TEE across the emergency, intensive care, and operative settings.

Figure 1.

Clinical applications of resuscitative TEE across the emergency, intensive care, and operative settings.

Brief History and Evolution of TEE

The origins of TEE date back to 1976, when Frazin and colleagues reported the first clinical use of what they called “esophageal cardiac ultrasound,” which at the time, was composed of only an M-mode image generated by a single plane transducer.¹⁶ Subsequent improvements in technology, only then formally called “transesophageal echocardiography,” were developed by Matsumoto et al and Hisanaga et al^17,18 Hisanaga et al was responsible for incorporating pulsed wave Doppler, and for the first description of a TEE probe that incorporated mechanical controls allowing for flexion of the probe’s tip and rotation of the transducer (omniplane).¹⁸ This allowed for the first-time cross-sectional images of the heart in B-mode. However, it wasn’t until the early 1980s that the groups of Matsuzaki and Schlüter mounted the transducer into gastrocameras, producing the “endoscope-type” TEE devices we are familiar with today, introducing the era of multiplane TEE.^19,20 It is noteworthy to mention that the invention of this novel technology that would later revolutionize cardiovascular care originated in the early days of cardiac anesthesiology, and was the product of the ingenuity, creativity, expertise, and collaborative work of cardiac surgeons, cardiologists, anesthesiologists and engineers.²¹ Multidisciplinary collaboration is what permitted the development and improvement of this ground-breaking technology.

Over the 1980s and 90 s, TEE devices continued to improve. Their use expanded rapidly to become a critical component of contemporary cardiac surgery and the echocardiography modality of choice in a number of clinical applications, including the guidance of interventional cardiac procedures and the evaluation of structural heart disease pathologies in the inpatient and outpatient settings.^10,11

While the adoption of comprehensive TEE examination by the fields of anesthesiology and cardiology in these settings is well known, less known is the vast amount of work incorporating this modality in emergency and critical care applications. In the five decades since the birth of TEE, this tool has been used repeatedly by cardiologists, anesthesiologists, and emergency physicians in the evaluation of patients in cardiac arrest. Indeed, the first report of TEE in resuscitation dates back to 1984, when Uenishi et al described in a research letter their initial experience using TEE to assess valvular motion in 3 patients undergoing cardiopulmonary resuscitation (CPR) at the Osaka University of Japan.²² In the early 1990s, studies performed by Kühn, Porter, and Redberg investigating CPR physiology with TEE confirmed the “cardiac pump model” theory. This concept of the generation of forward flow during closed chest CPR provides the basis for our current understanding of cardiac arrest resuscitation.^23–25

Resuscitative TEE in Emergency Settings

The first and most used application of resuscitative TEE in emergency settings has been the evaluation of cardiac arrest. In 2008, Blaivas described the first report of emergency-physician performed TEE in the ED.²⁶ In the following decade, studies provided additional observational data regarding the diagnostic and therapeutic impact of TEE in emergency settings. In addition to the same diagnostic and therapy-guidance framework of TEE described earlier, TEE has been used to evaluate the effect of optimization of the location where CCs are performed. In 2009, Hwang and colleagues showed that certain hand position used during external CCs results in compression of the left ventricular outflow tract (LVOT) and the aortic root, but not the left ventricle (LV), and found a correlation between the area of maximal compression (AMC) and the stroke volume (SV), where AMC closer to the LV produced higher SV.²⁷ Consistent evidence was reported in recent years by Cha et al, Teran et al, and Catena et al^28–30 These studies support the notion that TEE can be used by clinicians to optimize the quality of CCs in real time during CPR by identifying and correcting compression of the outflow tract, thereby potentially improving outcomes. Studies in the ED setting have also shown that TEE could shorten chest compression interruptions and guide resuscitative procedures such as ECMO.^29,31

The most recent guidelines on the use of resuscitative TEE by the American College of Emergency Physicians (ACEP), describe three specific clinical indications: 1. Evaluation of shock in the presence of inadequate TTE windows; 2. Evaluation of cardiac arrest; and 3. Guidance of emergency endovascular procedures. While these guidelines include a selection of 10 views, they provide a framework establishing that resuscitative TEE protocols “should aim to limit the complexity of the exam and to maximize the efficiency of the procedure and the information acquired”, highlighting that different subsets of views may be utilized during a study depending on the clinical application, purpose of the exam, and the focused question (s) being asked.¹⁵

Numerous studies have demonstrated the utility of these views in the intra-arrest setting for the purpose of identifying reversible pathology and shockable rhythms.³² Specifically, the use of TEE during cardiac arrest has been shown to identify cardiac tamponade, aortic dissection, severe hypovolemia, and signs concerning for massive pulmonary embolism – all of which have the capacity to lead to potentially life-saving changes in management if discovered in a timely manner.^{26,29,32–36} Additionally, TEE has been shown to identify the presence of shockable rhythms in patients thought to have pulseless electrical activity or asystole.^29,32,33 Given the demonstrated mortality benefit in early defibrillation for patients in cardiac arrest and shockable rhythms, one may hypothesize that the discovery of shockable rhythms via TEE may also lead to improved patient mortality. Table 1 provides a selection of studies and their key findings in the use of TEE in cardiac arrest resuscitation.

Table 1.

Selection of Studies Evaluating the Use of TEE in Cardiac Arrest Resuscitation.

Year, Author, Journal	N	Key Conclusions
1984, Uenishi, Anesthesiology	3	First report on the use of TEE in cardiac arrest resuscitation, covering TEE evaluation of valvular motion during CPR in 3 patients. Findings support Cardiac Pump Theory of CPR.
1991, Kühn, Resuscitation	18	Second report of TEE use in cardiac arrest resuscitation. Authors investigated the effect of external chest compressions on cardiac chambers, finding direct compression of all 4 chambers and consequent ejection of blood into aorta and pulmonary artery. This also supports the Cardiac Pump Theory of CPR.
1992, Porter, American Journal of Cardiology	17	TEE was used to characterize intracardiac hemodynamics.
1993, Redberg, Circulation	20	Third report of TEE use in cardiac arrest resuscitation, including B-mode images and Doppler through the mitral valve via the mid-esophageal 4 chamber view. Findings included mitral valve opening during cardiac release, reduction of ventricular cavity size with compression, and atrioventricular regurgitation; overall supported Cardiac Pump Theory of CPR.
1997, van der Wouw, Journal of the American College of Cardiology	48	TEE found to be useful in diagnosing structural causes of circulatory arrest in both in-hospital and out-of-hospital cardiac arrest patients. In a significant portion of these, TEE findings led to major therapeutic decisions.
1997, Varriale, Critical Care Medicine	4	Study assessed the utility of information and potential to guide management from both transthoracic and esophageal echocardiography during in-hospital CPR.
2000, Comess, American Journal of Medicine	36	Study used TEE to evaluate the prevalence of pulmonary embolism as the cause of unexplained sudden in- and out-of-hospital cardiac arrest with PEA as the presenting rhythm.
2004, Miyake, Journal of Cardiology	4	Study aimed to determine the utility of TEE in cases of cardiac arrest and shock and found to be useful in diagnosing and/or ruling out structural cardiac etiologies. In many cases, TEE-based diagnosis led to emergency surgery.
2006, Memtsoudis, Anesthesia & Analgesia	22	Authors evaluated utility of TEE during intraoperative cardiac arrest including diagnostic yield and impact on therapeutic management.
2006, Lin, British Journal of Anaesthesia	10	Study describing the diagnostic and management impact of TEE during intraoperative cardiac arrest for non-cardiac, elective surgical cases.
2008, Blaivas, Resuscitation	6	Case series describing the use of point-of-care TEE by an emergency physician in the evaluation of patients in out-of-hospital cardiac arrest and peri-arrest in the emergency department.
2009, Hwang, Academic Emergency Medicine	34	Hand placement during CPR affects LV outflow due to varying degrees of LVOT and/or aortic narrowing during compressions. This study showed that the hand position used during external chest compressions results in compression of the LVOT and the aortic root, but not the LV. The authors also describe a correlation between the area of maximal compression (AMC) and the stroke volume (SV), where AMC closer to the LV produced higher SV
2012, Shillcutt, Journal of Cardiothoracic and Vascular Anesthesia	4	This study investigated the utility of TEE to identify the etiology of hemodynamic collapse during intraoperative cardiac arrest. It is also the first study to refer to the term “rescue TEE” to describe the use of goal-directed TEE at the point-of-care in patients with circulatory collapse.
2013, Cha, Emergency Medicine Journal	114	Findings indicate that current CPR guidelines recommend hand positioning that results in sub-optimal ventricular compression, and that alteration of hand placement may result in greater ventricular compression.
2014, Hilberath, European Heart Journal – Cardiovascular Imaging	6	This study evaluated the utility of “rescue TEE” in patients who became unstable during extraction of malfunctioning transvenous leads in the operating room. TEE found to be useful in identifying and/or ruling out critical cardiovascular injuries.
2016, Arntfield, Journal of Emergency Medicine	54	This study described the indications, diagnostic ability, and therapeutic influence of TEE for cardiac arrest and undifferentiated hypotension patients in the first ED-based point-of-care TEE program. In this setting, TEE was diagnostically and therapeutically influential in most cases.
2016, Liu, International Journal of Cardiology	20	TEE used during peri-arrest management in patients with non-traumatic cardiac arrest to further characterize intracardiac hemodynamics. Findings indicated that over the course of prolonged CPR, hemodynamics evolve such that cardiac effect dominates early on and the thoracic pump mechanism drives hemodynamics later.
2019, Fair, Annals of Emergency Medicine	25	Study comparing the duration of chest compression pauses during cardiac arrest resuscitation in the emergency department with no echocardiography, TTE, or TEE. Findings demonstrate reduced duration of pauses with TEE use.
2019, Teran, Resuscitation	33	First prospective observational study demonstrating the feasibility of Emergency Physician-performed TEE in the intra-arrest and post-arrest evaluation of patients with OHCA in the ED, providing information on quality of chest compression and allowing the diagnosis of reversible pathologies.
2019, Catena, Resuscitation	19	Hemodynamic assessment of ongoing CPR may provide prognostic information to help predict resuscitation failure or success.
2019, Kim, Journal of Critical Care	20	TEE was used to assess intracardiac hemodynamics in the peri-arrest setting; high compression velocity was found to be associated with adequate compression depth.
2020, Kim, American Journal of Emergency Medicine	45	TEE demonstrated to be useful in identifying aortic dissection as the cause of cardiac arrest in the per-arrest setting.
2020, Jung, Resuscitation	158	Study investigated the correlation between specific intra-arrest TEE findings and prognosis, finding that certain echocardiographic findings may be predictive of poor outcomes.

Resuscitative TEE in Critical Care Settings

As defined a decade ago by an international consensus statement assessing the standards for CCE,³⁷ TEE is an established modality of advanced CCE and in the U.S. is formally part of the National Board of Echocardiography’s Critical Care Echocardiography certification.³⁸

One of the central uses for resuscitative TEE in the critical care settings is the evaluation of patients in shock. Due to the use of mechanical ventilation, body habitus, surgical dressings, and lung pathology, traditional FOCUS views are often impaired in patients suffering from cardiovascular failure. Several studies have now demonstrated resuscitative TEE by critical care physicians in the ICU to be feasible, of high diagnostic yield, and capable of guiding therapy in patients with undifferentiated states of shock.¹⁴ Furthermore, in patients with unexplained hypoxemia, TEE can unveil right-to-left intracardiac shunts,³⁹ and a novel extension of resuscitative TEE – transesophageal lung ultrasonography (TELUS) – has been described as an ideal modality to evaluate the lung and pleural space in critically ill patients.^40–42 Although a detailed description of TELUS lies beyond the scope of this review, it is worth noting that a key advantage of this modality is the ability to image the posterior (dependent) zones of the lungs, which are often difficult to reach with TTE in supine critically ill patients.⁴³

One need in critical care patients that TEE is uniquely situated to meet is that of continuous hemodynamic monitoring.^44–48 As best illustrated by the decades of experience of perioperative TEE during cardiothoracic surgery, the probe may remain indwelling for long periods of time without disrupting access to the patient’s vasculature, compromising the airway, or posing unnecessary risk of infection. TEE may be used to serially assess right and left ventricular function, stroke volume and cardiac output with measurement of LVOT VTI and area. Assessment of superior vena caval collapsibility with TEE has been developed as a means of determining volume status and predicting response to administration of intravenous fluids.⁴⁸ The use of TEE for hemodynamic monitoring has been documented in critical care patients with hypovolemia, vasoplegia, cardiac dysfunction or obstruction due to heart failure, sepsis, respiratory failure, pericardial effusion, and prosthetic valve dysfunction. In these states, TEE can provide vital information by monitoring progression of disease and response to therapeutic interventions such as addition or removal of inotropic or vasopressor medications, fluid challenges and other interventions.

A specific clinical scenario in which the role of TEE for ICU-based hemodynamic monitoring has become particularly prominent recently is in caring for the prone patient.^{11,14,43,49,50} For years it has been known that in some patients suffering from acute respiratory distress syndrome (ARDS), prone positioning can optimize ventilation-perfusion matching and ultimately improve patient survival.⁵¹ The use of TEE in this context is particularly useful because the prone position of the patient eliminates the ability of the physician to perform FOCUS, and TEE has been demonstrated as a feasible and efficacious alternative.^49,50

Another critical care setting in which TEE has been described as diagnostically informative and therapeutically influential is in the evaluation of trauma patients. Specifically, TEE can be useful in assessing patients for blunt aortic trauma.^13,52 For these patients, expedient diagnosis of aortic injury occurring simultaneously with resuscitative efforts may be lifesaving whereas instability might otherwise preclude transfer to CT scan.⁵³ A recent observational study by Prager et al involving resuscitative TEE performed during the critical care evaluation of trauma patients, described multiple cases with dynamic left ventricular outflow tract obstruction and systolic motion of the anterior leaflet of the mitral valve (SAM), highlighting that trauma patients are particularly susceptible to this physiology in the context of their hypotension and vasoplegia.¹³ Furthermore, given the evolving role of endovascular techniques for traumatic thoracic aortic injuries, as well as the current drive to tailor the management approach to the patient and type of injury, real time data provided by resuscitative TEE at the point of care regarding the injury grade can help deciding whether an endovascular or surgical approach is indicated. Table 2 provides a selection of studies and their key findings in the use of TEE in non-cardiac arrest applications.

Table 2.

Selection of Studies Evaluating the Use of TEE in Non-Arrest Critical Care Applications.

Year, Author, Journal	N	Key Conclusions
2004, Vieillard-Baron, Journal of Intensive Care Medicine	66	TEE found to be useful in evaluation of SVC collapsibility in critically ill patients as a means of predicting IV fluid responsiveness.
2005, Stawicki, Journal of the Royal Society of Medicine	24	Transesophageal Doppler indwelling monitors found to be diagnostically useful and therapeutically impactful, as well as safe, in several resuscitative settings.
2011, Mekontso, Journal of Intensive Care Medicine	34	Hemodynamic monitoring via TEE in prone positioned patients with ARDS demonstrated to be both feasible and safe
2013, Vieillard-Baron, Journal of Intensive Care Medicine	94	Indwelling TEE probe placement feasible and clinically influential in ventilated, critically ill patients suffering from hemodynamic failure
2017, Garcia, Chest	152	TEE performance by critical care fellows in the medical ICU found to be feasible and without complications in all attempted studies. TEE also found to be diagnostically and therapeutically influential in many patients.
2017, Cronin, Journal of Cardiothoracic and Vascular Anesthesia	20	TEE use as an adjunct method for monitoring pulmonary artery catheterization is feasible
2018, Arntfield, Journal of Intensive Care Medicine	274	Intensivist-performed TEE studies in the ICU were evaluated for indications, resultant change in management, and complications. Most common indications included undifferentiated shock, infective endocarditis, and cardiac arrest. Most studies led to a change in management, and no mechanical complications were observed. Overall, study supports feasibility and efficacy of focused TEE in the ICU performed by critical care physicians.

Resuscitative TEE Guiding Endovascular Procedures

In addition to its diagnostic, therapy-guiding, and monitoring roles, resuscitative TEE has also been used for bedside procedural guidance. Both during cardiac arrest and non-arrest critical care, studies have demonstrated the efficacy of resuscitative TEE in guiding ECMO cannulation.^54–56 Using the midesophageal bicaval view, TEE provides the physician with a clear view of the transvenous catheter as it is placed near the right atrium-IVC junction, while the midesophageal long axis and transgastric short axis views provide imaging of the arterial cannula in the descending aorta. The use of TEE when providers would otherwise place ECMO cannulae blindly has the potential to decrease the need for repositioning and the complications associated with this procedure. Similarly, the use of TEE has been described in the bedside placement of pulmonary artery catheters and IV pacemaker wires.^57,58 The same advantages apply to these procedures as stated above with regard to ECMO cannulation –the ability to visualize guidewires, catheters, and cannulae as they are positioned decreases the risk of misplacement and complications. In addition, TEE has recently been reported to aid in catheter-directed thromboembolectomy of atrial-caval thrombus.⁵⁹ Figure 1 provides a conceptual map of the overlapping applications of resuscitative TEE across the emergency, intensive care, and operative settings.

Safety

The safety of comprehensive TEE has been studied extensively across clinical settings including perioperative, ambulatory, and critical care environments. An important distinction between resuscitative and comprehensive (eg, cardiology-performed) TEE, is that resuscitative TEE studies are performed in critically ill patients with a protected airway (endotracheal tube or tracheostomy in place). Therefore, respiratory complications of the procedure, including aspiration and sedation-related issues, can be obviated. The safety profile of resuscitative TEE has not been studied as extensively as ambulatory TEE. In large studies of primary ambulatory exams, major complications such as serious oropharyngeal trauma, esophageal perforation and major bleeding are rare with incidence rates between 0.01 and 0.08%.^60–62 In the largest available study of TEE in the intensive care setting, Hüttemann et al reported on 2508 cases of TEE performed in critically ill patients with no deaths and or serious mechanical injury.⁶³

The largest theoretical safety concern regarding resuscitative TEE is the risk of oropharyngeal and gastroesophageal injury upon probe insertion and manipulation. To that end, studies performed during elective TEE procedures have identified risk factors that allow for stratification of patients at risk for esophageal complications with length of procedure and preexisting patient-specific risk factors associated with a higher risk of injury.⁶⁴ It may be sensible, therefore, to consider preexisting esophageal abnormality as a contraindication to TEE use in any given patient. With that said, in the context of resuscitative TEE studies, particularly those performed emergently, the physician may not be aware of preexisting esophageal abnormalities, and therefore studies in this setting need to be approached with a risk-benefit analysis that considers both the potential risks associated with resuscitative TEE as well as the opportunity to obtain time-sensitive, lifesaving information which can have an impact in the patient’s care and clinical outcomes.

Regarding the impact of the probe insertion technique and complications, studies in the perioperative setting have identified the jaw thrust technique and insertion with the use of direct or video-assisted laryngoscopy (VL) as protective practices associated with decreased incidence of oropharyngeal injury during probe insertion.^65,66 A randomized clinical trial by Borde et al showed that the use of VL was associated with a lower incidence of oropharyngeal injuries compared to conventional technique, and that use of VL for probe insertion resulted in fewer attempts compared with the conventional technique.⁶⁶ These results were consistent with prior studies from patients undergoing cardiac surgery summarized in a meta-analysis by Namekawa et al demonstrating that probe insertion using VL was associated with a significant reduction in the number of insertion attempts and complications rate, compared to the conventional blind insertion or a direct laryngoscopy-assisted insertion.⁶⁷ Practically speaking, these findings may be applied to the nonoperative setting easily. Laryngoscopy and jaw thrust are commonplace techniques for airway management in ED and ICU settings and therefore should be reasonable for the operator to accommodate.

Another potential concern in the context of resuscitative TEE are injuries that could result from performing TEE while delivering CCs during CPR. While studies specifically evaluating these complications are lacking, a case report of an intramural atrial hematoma developing during intra-arrest TEE has been described.⁶⁸

With the goal to produce multicenter data that are specific to the critical care setting, the Resuscitative TEE Collaborative Registry (rTEECoRe), is an ongoing prospective multicenter study currently investigating the safety, and clinical impact of resuscitative TEE across acute care environments (NCT04972526).⁶⁹

Training and Competency

Although resuscitative TEE shares some similarities with comprehensive TEE, the difference in setting, scope of the exam, and background of the operator are important to consider when defining the optimal training model for physicians using this modality. To that end, several studies have reported the feasibility in training emergency and critical care physicians with prior training in FOCUS to practice resuscitative TEE.^70–75 These studies, which included both didactic and hands-on simulation-based training, collectively demonstrate acquired competency in both image acquisition and interpretation of focused, resuscitative TEE studies.

A structured practical training using high fidelity simulators to teach a focused TEE protocol designed to mimic the scope of FOCUS established as the standard of care, has been successfully used to train emergency physicians with evidence of adequate 6-week retention.⁷⁰ In the ICU setting, with higher sophistication that included additional views and quantitative hemodynamic measurements, a minimum number of 31 supervised studies over a period of 6 months was shown to be necessary before competence was achieved.⁷²

While the studies all reported high levels of competency among physicians with prior competency in TTE (FOCUS), they lack a unifying method for evaluating competency. One study sought to create a metric for evaluation of proficiency among critical care physicians training in FOCUS, which led to the development of the Rapid Assessment of Competency in Echocardiography (RACE).⁷⁶ Given that a similar evaluation tool for resuscitative TEE is currently lacking, this may prove a worthwhile pursuit as the field continues to further incorporate resuscitative TEE into clinical care. As of now, the ACEP has published guidelines recommending that all physicians undergoing resuscitative TEE training have prior training in TTE, undergo at least 4–6 h of structured practical TEE education, aimed to develop both motor and cognitive skills, at least 10 proctored TEE exams on live patients and simulations, and a standardized assessment by a credentialed provider.¹⁵

Implementation Barriers

A recent cross-sectional survey study by Teran et al reported that financial barriers were the single most reported item preventing the use of TEE in the ED, followed by maintenance of equipment, and difficulty establishing credentialing and privileges to perform TEE.¹⁰ This study found that adoption of resuscitative TEE is predominantly seen in academic centers with ultrasound fellowship programs, typically with more critically ill patients. In those centers where TEE has not yet been adopted, data suggests this is due to operational barriers rather than lack of interest.¹⁰

A recognized barrier is access to high-fidelity simulators used for developing competency in TEE. Unlike TTE which can be practiced with human models, TEE is not suitable for practice using patients solely for educational purposes.

Another potential barrier to adoption of TEE in critical care units is the need for resources to credential and privilege users, and to ensure maintenance of skills. In our experience, most ICUs that have successfully implemented resuscitative TEE have had a group of physician champions who have undergone training first and then helped train additional physicians in their department. This foundational training is most often achieved through mentorship and interdisciplinary collaboration with local TEE experts in cardiac anesthesia, emergency medicine, or cardiology. If physicians seeking to implement an ICU-based TEE programs do not have the opportunity or access to acquire foundational skills for probe insertion, image acquisition, and interpretation with TEE within their institution, structured courses in resuscitative TEE can help overcome this gap.

Lastly, studies comparing FOCUS to resuscitative TEE are needed to determine the advantages, disadvantages, and appropriate use of both modalities. This will allow for the delineation of indications, contraindications, and superiority of either across a variety of clinical settings and patient demographics.

Conclusion

Resuscitative TEE has the potential to not only supplement the practice of FOCUS in patients who are not appropriate for TTE in the setting of resuscitation, but also to advance our diagnostic and management capabilities in the critically ill patient population. Further work will need to elucidate which patients would most likely benefit from resuscitative TEE, what terminology and protocols to adopt to standardize care, and how to implement resuscitative TEE safely and efficiently across diverse critical care settings.