Introduction

Cardiac arrest is one of the most demanding presentations for emergency physicians. The use of point-of-care ultrasonography during cardiopulmonary resuscitation (CPR) is increasing and is recommended in guidelines [1]. Focused transthoracic echocardiography (TTE) can identify critical and reversible pathologies during cardiac arrest. However, TTE may be impractical during active chest compressions or inadequate in some cases, such as with morbidly obese patients or when imaging the ascending aorta [2][3][4]. High-quality CPR is vital for improving survival and neurological outcomes, and minimizing interruptions in chest compressions is crucial [5]. Since TTE can cause prolonged pauses during CPR, especially for inexperienced users [2], transesophageal echocardiography (TEE) has emerged as a valuable alternative [2]. TEE provides continuous imaging without interfering with CPR and is gaining recognition in emergency departments (EDs) worldwide [4].

Participants practicing TEE

Demonstration by instructor

Demonstration of TEE Probe

TEE simulator screen

Preconference Workshop on Shock and Resuscitative Ultrasound Workshop, ICEM 2024

Role and advantages

The TEE transducer is inserted into the esophagus, allowing for continuous, high-quality imaging of the heart without disrupting CPR. TEE has four key roles during CPR:

1. Chest Compression Quality Feedback: TEE optimizes chest compression quality by visualizing cardiac anatomy in real time. Studies show that compressions are often applied over critical structures like the left ventricular outflow tract (LVOT), leading to suboptimal CPR. TEE helps adjust hand placement to ensure effective compressions [2][8]. This can increase the chance of return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest (OHCA) [9].

2. Rhythm Characterization: TEE can distinguish between true pulseless electrical activity (PEA) and pseudo-PEA, aiding in rhythm interpretation during pulse checks. It can also identify fine ventricular fibrillation (VF) that may be misinterpreted as asystole on cardiac monitors [7].

3. Diagnosis of Reversible Causes: TEE helps identify reversible causes of cardiac arrest, such as pericardial effusion, pulmonary embolism, and aortic dissection. It offers a detailed evaluation of cardiac and extracardiac structures, guiding treatment [16][7].

4. Procedural Guidance: TEE provides guidance during procedures like cannula placement for extracorporeal CPR or temporary pacemaker insertion [2].

Limitations and risks

The risks associated with TEE, such as oropharyngeal trauma or esophageal perforation, are rare, with an incidence of less than 1% [2]. Most data on TEE complications come from non-resuscitative settings, but since TEE allows continuous imaging without interrupting CPR, its benefits during cardiac arrest outweigh the potential risks [2].

Practicality and Value

TEE is typically performed after endotracheal intubation, as both procedures share similar physician positioning [2]. A study showed that TEE was feasible and had a therapeutic or prognostic impact in 97% of cases during CPR [3][12][13]. Proper storage and accessibility of TEE equipment are essential for timely use in emergency situations [2].

Imaging Protocol

The American College of Emergency Physicians (ACEP) has established a goal-directed framework for focused TEE in the ED. The key TEE views include:

• Mid-esophageal 4-chamber (ME 4C)

• Mid-esophageal long-axis (ME LAX)

• Transgastric short-axis (TG SAX)

These views provide essential information for managing cardiac arrest [4]. Extended views can be used for more detailed assessments when needed [7].

Table: Basic TEE views [7]

AMC, area of maximal compression; 4C, 4-chamber; DescAo, descending aorta; IAS, interatrial septum; LAX, long axis; LVOT, left ventricular outflow tract; ME, midesophageal; r/o, rule out; RV, right ventricle; SAX, short axis; TG, transgastric

Participants practicing TEE

Group discussion

Lectures before hands-on

The ResusTEE Workshop Amsterdam 2023

Future Work in Hong Kong

TEE is a relatively new technique in Hong Kong’s EDs. A few emergency physicians have attended training courses, with the most recent being at the ICEM 2024 conference [14]. For successful implementation of a TEE program, factors such as budget, equipment acquisition, and standardized training need to be addressed. Adequate planning is essential to ensure the program's long-term success.