Team Sono: TEE in Cardiac Arrest

The Ultrasound Mini-Fellowship (Team Sono) met last month to discuss TransEsophageal Echocardiography (TEE) in cardiac arrest. We specifically discussed two major papers in the TEE literature discussing TEE during cardiac arrest. First, thank you to all of our amazing faculty (Drs. Maurelus, Ozaki, Aherne, Mahalingham, Balakrishnan, Kim, Cutright, Reisman, Beyda, and Ko) for joining us in our amazing discussion. Here is an overview of the two papers we discussed:

TEE reduces pulse check times during CPR

TEE may be useful to assess reversible underlying conditions during cardiac arrest and useful in assessing adequacy of chest compression during resuscitation. We already know that high-quality CPR during cardiac arrest is an important intervention (after defibrillation, if indicated) and keeping your pauses in CPR < 10 seconds is key.

Fair et al. assessed whether TEE is associated with shorter or longer pulse check interruptions during CPR compared to transthoracic echocardiography (TTE) or no bedside ultrasound. [1] This was a retrospective case series of 25 patients that included 139 CPR pauses for analysis. The authors excluded pauses for procedures or other resuscitation actions such as intubation and arterial access. Two trained researchers who were blinded to the study hypothesis reviewed video recordings of the resuscitations and recorded the timing and duration of all pauses and activities during the pauses in CPR.

Resuscitations guided by TEE were associated with a mean pulse check time of 9 seconds, whereas resuscitations guided by TTE had a mean pulse check time of 19 seconds. Furthermore, resuscitations guided by manual pulse checks had a mean pulse check time of 11 seconds. Therefore, TEE was associated with the least amount of CPR interruption time for pulse checks and the only modality below the acceptable 10 seconds of pulse check as recommended by the AHA. [2]

There were a few important limitations to this study, including the small sample, retrospective nature, and digital recording review process. Also, only four emergency medicine attendings were competent and used TEE in this study, making it less generalizable. These TEE-trained attendings may have been prone to bias if they knew they were being recorded. There was also no mention about how they were assessing ROSC using the different modalities. Lastly, it was a single small study from one academic center. The group discussed that a larger, multi-center prospective study needs to be conducted to see if these findings are reproducible.

Association of LVOT opening and successful resuscitation in cardiac arrest using TEE

Catena et al. assessed whether TEE during CPR can be used to predict a successful resuscitation in cardiac arrest. [3] This was a retrospective cohort study including 19 non-traumatic out-of-hospital cardiac arrests. The inclusion criteria were purposely strict to target patients who would have the best-predicted outcomes at baseline. The inclusion criteria included: CPR started within six minutes, absence of major comorbidities or terminal illness, intubation in the field, unsuccessful ACLS treatment for at least 20 min, and arrest to door time less than 65 minutes. TEE was placed, on average, within 8 min of arrival times. The sonographer recorded multiple measurements during CPR including right ventricular outflow tract fractional shortening, right ventricular fractional area change, left ventricular outflow tract (LVOT) diameter, aortic root diameter, and left ventricular volumes and ejection fraction (EF). CPR continued until there was either return of spontaneous circulation during mechanical compressions or return of electro-mechanical activity during ECMO. Of note, 15 out of 19 patients were treated with venous-arterial ECMO during cardiac arrest.

This study compared two groups – those who had successful resuscitation (Group-SUXX) and those with failed resuscitations (Group-FAIL). Successful resuscitation was defined as return of spontaneous circulation for patients undergoing CPR or return of electro-mechanical activity for ECMO patients. Only seven of the 19 patients had successful resuscitations, while only one patient survived to hospital discharge. The main finding of the study was that LVOT opening during CPR was significantly associated with the probability of successful resuscitation. Only one patient in Group-FAIL had an open LVOT, while all seven patients in Group-SUXX had open LVOTs identified with TEE. Group-SUXX also had statistically significant higher EFs during CPR, compared to Group-FAIL, however that is intuitive given they had open LVOT with assumed less obstruction to cardiac output.

This was a small study in which most patients were treated with ECMO, making it less generalizable. Hand placement was not recorded, and changing placement may have affected LVOT opening. This study did find an association between successful resuscitation and an open LVOT using TEE, which is difficult to assess using TTE. However, it is difficult to extrapolate whether there is a patient-centered benefit of TEE from this study. There was no mention of the neurological status of the patient who survived to discharge. Our group discussed how we do not know how to use the findings from this study in a resuscitation, such as whether or not to terminate a resuscitation earlier based on LVOT opening or use TEE to change hand position to allow for LVOT opening. Our group also discussed how there were alternative methods to evaluate adequate CPR quality including end-tidal capnography and invasive arterial diastolic blood pressure. We discussed how there should be further larger, multi-center studies evaluating LVOT opening using TEE and the other above modalities.

We do not have a TEE probe at our hospital yet, so discussing these papers cited by the pro-TEE community was the first step in one day incorporating this advanced imaging modality into our cardiac resuscitations.