Transthoracic echocardiography (TTE) has been endorsed by international guidelines as a potentially useful diagnostic modality for the evaluation of patients in cardiac arrest.1,2 Echocardiography can identify organized cardiac activity vs. standstill, predict the likelihood of survival,3—5 and may be used to establish the cause of the arrest and guide treatment, such as in the case of pericardial tamponade or massive pulmonary embolus.
However, the process of TTE image acquisition has been observed to cause prolonged pauses in the delivery of vital chest compressions and reduce hands-on time.6,7 A structured protocol and quality assurance process may reduce these times.8
Nonetheless, TTE remains particularly challenging in patients who are obese, have gastric distention from air insufflation, or are barrel chested. In approximately one-third of patients, an adequate cardiac window cannot be obtained for interpretation during resuscitation.9
Transesophageal echocardiography (TEE), by contrast, offers several advantages over TTE in the setting of cardiac arrest. Cardiac windows can be obtained once the probe has been correctly positioned during CPR, offering continuous images during CPR. Image quality is superior to TTE as the transducer is placed directly behind the heart without significant intervening tissue.
In our own ED, pauses in CPR were shorter with TEE vs. TTE, when performed by emergency physicians, since image acquisition was continuous. Mean pauses were 9 seconds (95% CI 9—12) for TEE and 19 seconds (95% CI 16—22) for TTE, a difference that was statistically significant. By comparison, the use of manual palpation to check for a pulse while a verbal countdown was performed resulted in an average pause of 11 (95% CI 8—14) seconds. (This data was presented at AHA 2017 and is unpublished data under review.)
Emergency physicians are able to obtain adequate images 98% of the time and findings impacted therapeutic decisions in 31—67% of cases.6,10 TEE can be used to identify the cause of arrest with sensitivity of 93% and specificity of 50%.10 It’s also been used to assess the adequacy of chest compressions, as well as direct the positioning of hands (or mechanical piston) to improve subjective assessment of flow.
There are known limitations of TEE. The modality requires that the patient be endotracheally intubated for airway protection before examination. Supraglottic airways create an obstruction to passage of the probe into the esophagus and, thus, can’t be in place during placement. TEE probes have come down in cost over time, but they remain relatively expensive. Additionally, probes require the same level of decontamination and cleaning as endoscopes before reuse.
Finally, no study has demonstrated superior outcomes using TTE or TEE to guide resuscitation. The existing evidence arises from case reports and case series, making it difficult to determine whether a patient-oriented benefit exists. When trained personnel are available, TEE can play an important role in the overall bundle of care by facilitating more accurate diagnosis of a number of disease states that can cause cardiac arrest.
References
1. Link MS, Berkow LC, Kudenchuk PJ, et al. Part 7: Adult Advanced Cardiovascular Life Support: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2015;132(18 Suppl 2):S444—S464.
2. Soar J, Nolan JP, Bà¶ttiger BW, et al. European Resuscitation Council Guidelines for Resuscitation 2015: Section 3. Adult advanced life support. Resuscitation. 2015;95:100—147.
3. Wu C, Zheng Z, Jiang L, et al. The predictive value of bedside ultrasound to restore spontaneous circulation in patients with pulseless electrical activity: A systematic review and meta-analysis. PloS One. 2018;13(1):e0191636.
4. Gaspari R, Weekes A, Adhikari S, et al. A retrospective study of pulseless electrical activity, bedside ultrasound identifies interventions during resuscitation associated with improved survival to hospital admission. A REASON Study. Resuscitation. 2017;120:103—107.
5. Gaspari R, Weekes A, Adhikari S, et al. Emergency department point-of-care ultrasound in out-of-hospital and in-ED cardiac arrest. Resuscitation. 2016;109:33—39.
6. Arntfield R, Pace J, Hewak M, et al. Focused transesophageal echocardiography by emergency physicians is feasible and clinically influential: observational results from a novel ultrasound program. J Emerg Med. 2016;50(2):286—294.
7. Clattenburg EJ, Wroe P, Brown S, et al. Point-of-care ultrasound use in patients with cardiac arrest is associated prolonged cardiopulmonary resuscitation pauses: A prospective cohort study. Resuscitation. 2018;122:65—68.
8. Clattenburg EJ, Wroe PC, Gardner K, et al. Implementation of the Cardiac Arrest Sonographic Assessment (CASA) protocol for patients with cardiac arrest is associated with shorter CPR pulse checks. Resuscitation. 2018;131:69—73.
9. Reed MJ, Gibson L, Dewar A, et al. Introduction of paramedic led Echo in Life Support into the pre-hospital environment: The PUCA study. Resuscitation. 2017;112:65—69.
10. van der Wouw PA, Koster RW, Delemarre BJ, et al. Diagnostic accuracy of transesophageal echocardiography during cardiopulmonary resuscitation. J Am Coll Cardiol. 1997;30(3):780—783.
