The Use of Point-of-Care Ultrasound (POCUS), Transthoracic Echocardiography (TTE), and Transesophageal Echocardiography (TEE) in Cardiac Arrest and Acute Coronary Syndrome Patients

Studies have shown that POCUS can rapidly change the management in nearly 80% of cases in emergency settings, particularly in environments such as war zones and disaster relief. TTE is highly sensitive in diagnosing acute coronary syndromes and can effectively rule out myocardial infarction. In cardiac arrest patients, TTE assists in determining cardiac activity and identifying reversible causes, such as pericardial tamponade and pneumothorax. However, TTE can be affected by suboptimal image quality due to factors like chest compression in out-of-hospital cardiac arrest (OHCA) patients.

In Taiwan's emergency medical system, EMT-Ps (paramedics) undergo approximately one year of training, which enables them to provide emergency care, including ultrasound examinations, before hospital arrival. Research on pre-hospital cardiac arrest has shown that most ultrasound applications can be completed within 3 minutes and do not significantly increase on-scene time.

TEE, though advantageous for its high-quality imaging and ability to reduce interruptions during chest compressions, faces challenges in pre-hospital emergency applications due to specialized training and equipment requirements. However, a study in Vienna, Austria, demonstrated that TEE could be performed and yield high-quality images in most pre-hospital cases, with an average examination time of 5.1 minutes.

Several hospitals in Taiwan have begun training personnel in TEE, emphasizing the importance of establishing TEE image registries for large-scale, effective research analysis. However, these efforts also face challenges related to resources and collaboration. The research team has over three years of experience using TEE in the emergency department to examine OHCA patients, and a three-year study will be conducted to validate the efficacy of pre-hospital TEE in cardiac arrest patients.

Background:

The application of Point-of-Care Ultrasound (POCUS), Transthoracic Echocardiography (TTE), and Transesophageal Echocardiography (TEE) in cardiac arrest and acute coronary syndrome has evolved with technological advancements. POCUS, in particular, has been recognized for its ability to change clinical management in nearly 80% of emergency cases, such as war and disaster scenarios. TTE is highly sensitive in diagnosing acute coronary syndromes and can effectively rule out myocardial infarction. It also plays a crucial role in identifying reversible causes in cardiac arrest patients, like pericardial tamponade and pneumothorax, but its image quality can be compromised during chest compressions in out-of-hospital cardiac arrest (OHCA) patients. TEE, on the other hand, offers superior image quality and reduces interruptions during chest compressions but requires specialized training and equipment.

Currently, Taiwan's emergency medical system allows EMT-P personnel, after a year of training, to perform pre-hospital ultrasounds, including POCUS, for OHCA patients. Research has shown that most ultrasound applications can be completed in under 3 minutes without significantly increasing on-scene time. TEE's use in pre-hospital emergencies has also been validated in international studies, such as those from Vienna, which demonstrated TEE's feasibility in providing clear diagnostic images during pre-hospital cardiac arrest care.

Research Methods:

This study aims to assess the feasibility and efficacy of TEE in pre-hospital cardiac arrest care through a randomized controlled trial over three years.

Study Design:

The study will be conducted in two phases:

Phase 1: A prospective observational feasibility study involving 60 patients to assess the practical application of TEE in pre-hospital settings.

Patients aged 18 or older. Non-traumatic OHCA patients.

Exclusion Criteria:

Signs of obvious death. Patients with DNR orders. Patients for whom TEE is contraindicated (e.g., esophageal tumors). Patients requiring ECPR.

Training and Implementation:

Emergency department staff and EMT teams will undergo specialized training, including TEE workshops and simulations. The TEE procedure will be performed after establishing the airway and during mechanical chest compressions using a LUCAS device.

Data Collection:

Data will include patient demographics, emergency response times, CPR parameters, and TEE imaging results. Outcomes such as return of spontaneous circulation (ROSC) and neurological recovery will be tracked.

Randomization:

The RCT phase will utilize cluster randomization based on bi-weekly intervals, ensuring random and balanced patient groupings for intervention and control.

Sample Size Estimation:

Based on prior studies and statistical analysis, each group will require 93 patients to detect significant differences, with a total of 186 patients over the course of 24 months.

Expected Results:

The study anticipates that the use of TEE in pre-hospital cardiac arrest care will:

Provide high-quality cardiac images during CPR. Facilitate accurate identification of reversible causes of cardiac arrest. Improve the overall effectiveness of CPR through real-time feedback. Demonstrate the feasibility of integrating TEE into pre-hospital emergency protocols without significantly delaying patient transport.

The primary outcome is the proportion of cases where TEE ensures optimal chest compression. Secondary outcomes include the rate of sustained ROSC, time to ROSC, and neurological outcomes.

Conclusion:

This study will provide valuable insights into the feasibility and impact of TEE in pre-hospital cardiac arrest management. It will serve as the foundation for future large-scale research and contribute to improving survival rates and neurological outcomes in OHCA patients.

Inclusion Criteria:

1. Age ≥ 18 years
2. Patients with out-of-hospital cardiac arrest (OHCA)
3. Non-traumatic cause of cardiac arrest

Exclusion Criteria:

1. Presence of obvious signs of death, such as decapitation, rigor mortis, livor mortis, or decomposition.
2. Family explicitly expresses a Do Not Attempt Resuscitation (DNR) order, or the patient has a documented refusal of resuscitation.
3. Any condition that contraindicates the use of transesophageal echocardiography (TEE), such as esophageal tumors, preventing probe insertion.
4. Patients eligible for ECPR (Extracorporeal Cardiopulmonary Resuscitation) treatment.
5. Spontaneous circulation has already been stabilized before performing TEE.

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