Physician Interpretation of Cardiac Standstill on US

Background

Point of Care Ultrasound (POCUS) has gained wider use in resuscitation of patients presenting with cardiac arrest. POCUS can play an important role in determining the etiology of arrest as well as being used to determine the presence or absence of mechanical activity. The REASON study demonstrated that patients with PEA or asystole without cardiac activity on POCUS are extremely unlikely to survive to hospital discharge though this study did not investigate the more important question of a survival with a good neurologic outcome. (Gaspari 2016). In light of this as well as other evidence, some have proposed that the absence of cardiac activity may be adequate to declare resuscitation futility and stop resuscitative efforts. However, there is a lack of agreement on what defines cardiac activity (see table 1). Due to this, and other factors, the level of agreement between physicians in interpretation of cardiac standstill is unknown.

Primary Results

Primary Results

• Physician sonogrphers included: 127
  • Emergency Medicine: 94 (74%)
  • Critical Care: 15 (12%)
  • Cardiology: 4 (3%)
• Training Level
  • Resident: 80 (63%)
  • Fellow: 11 (9%)
  • Attending: 24 (19%)
• POCUS Skill Level
  • Basic: 68 (54%)
  • Advanced: 37 (29%)
  • Expert: 7 (6%)

Critical Findings

• Interrater Agreement (Primary Outcome)
  • Overall: moderate agreement (alpha = 0.47)
  • Variable agreement across US clips
• Interrater Agreement by Subgroup
  • Moderate agreement seen across specialty, training level and US experience
  • Fair agreement among critical care physicians

Definitions:

Krippendorff’s alpha = assessment of interrater reliability among physicians, similar to Fleiss’s kappa but thought to be more reliable in situations with missing data points

• Range of 0 to 1
• Score of 0: Poor agreement
• Score of 1: Perfect agreement
• Customary to require alpha ≥0.80 for agreement, but tentative conclusions can be drawn at alpha ≥0.667

Strengths

• Study asks an important diagnostic question that has not been previously addressed
• Majority of respondents self-reported “basic skill level” which may make study more generalizable (in comparison to just having expert level operators)

Limitations

• Non-random, convenience sample of participants
• Majority of respondents self-reported “basic skill level” which may skew analysis towards disagreement

Author's Conclusions

“According to the results of our study, there appears to be considerable variability in interpretation of cardiac standstill among physician sonographers. Consensus definitions of cardiac activity and standstill would improve the quality of cardiac arrest ultrasonographic research and standardize the use of this technology at the bedside.”

Our Conclusions

We agree with the authors that this study, though limited by it’s methodology and convenience sample, demonstrates significant disagreement between providers as to the interpretation of cardiac standstill on POCUS.

Potential Impact To Current Practice

This study cannot be used to impact clinical practice but should cause some pause for thought for providers who are currently using POCUS in cardiac arrest as part of their protocol for termination based on cardiac standstill.

Bottom Line

The use of POCUS to declare death and stop resuscitation is predicated on a clear ability to establish the presence of cardiac standstill. The low level of agreement of providers likely reflects the absence of a single definition of standstill as well as calls for increased training and assessment. A unified definition of standstill would be extremely helpful not only in future research but in cardiac arrest care as well.

Read More

Core EM: ED POCUS in OHCA – The REASON Study

Gaspari R et al. Emergency Department Point-Of-Care Ultrasound in Out-Of-Hospital  and in-ED Cardiac Arrest. Resuscitation 2016; 109: 33 – 39. PMID: 27693280