Question 8

Compare and contrast a focused cardiac ultrasound with a formal diagnostic transthoracic echocardiogram (TTE), using the following headings in your answer:
a) Indications (20% marks)
b) Assessments made (40% marks)
c) Limitations (40% marks)

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College answer

Most candidates described the indications for a focused cardiac ultrasound, however, the indications for formal diagnostic TTE were less well described (very few candidates included stroke, arrhythmia, peripheral embolus). 
The assessments of a focused cardiac ultrasound were generally well described although the assessments of TTE were less well described, and the windows and modes were infrequently described. The limitations of each study could have been better answered with only a few candidates including TTE cannot exclude IE, left atrial appendage clot, and PFO)

Discussion

The difference between "indications" and "assessments made" is subtle, i.e. the candidates may not have appreciated that "windows and modes" were expected. Is a pericardial effusion an indication, or is it an assessment made of the pericardial space, and in that case, which window should you be mentioning (subxiphoid, parasternal, apical?) In short it is not clear what was expected from the answer, and this appears to be reflected in the marks, where 45% of the candidates scored poorly. It seems from the distribution of marks that the examiners probably did not want a lot of indications to be listed. Thus, in the suggested model answer below, for "indications" only pathologies or broad scenarios are listed, whereas "assessments made" include the specific game-changing findings or answered questions. 

  Focused bedside TTE Formal TTE
Indications

Cardiac arrest

Pulmonary embolism

Suspected tamponade

Undifferentiated shock

Stroke

Cardiac ischaemia

Heart failure

Investigations for murmurs

Stress testing

Investigation of syncope and arrhythmias

Assessments

Pericardial effusion

Cardiac tamponade

LV systolic function

Volume status

RV dilatation (PE)

Cardiac activity during cardiac arrest

LVOT obstruction

Valvular abnormalities

Aortic dissection

Myocardial ischemia (i.e. regional wall motion abnormalities)

RV systolic function

Pulmonary hypertension

Diastolic function assessment

Limitations

Specific, not sensitive

Usually done on smaller machines with poor resolution.

Windows and probe orientation are not always standardised.

Staff performing this assessment may be variably trained, increasing error.

Trained staff may be unfamiliar with the limitations of the technique, and may underestimate its accuracy.

Poor windows or views may result in inaccurate chamber size comparisons, leading to the wrong diagnosis.

Defined scope of practice, limited to specific views (i.e. not a diagnostic investigation)

Requires a skilled sonographer or TTE-trained accredited ICU staff.

Time-consuming; may not be suitable for rapidly making decisions

More difficult to perform serial assessments within a short timeframe. 

Otherwise static: a snapshot assessment in a dynamically changing ICU scenario.

For many ICU patients, all classic views may not be possible.

Not cost-effective (usually requires dedicated staff)

Limitations of both
  • cannot exclude IE, left atrial appendage clot, and PFO

References

Mitchell, Carol, et al. "Guidelines for performing a comprehensive transthoracic echocardiographic examination in adults: recommendations from the American Society of Echocardiography." Journal of the American Society of Echocardiography 32.1 (2019): 1-64.

Spencer, Kirk T., et al. "Focused cardiac ultrasound: recommendations from the American Society of Echocardiography." Journal of the American Society of Echocardiography 26.6 (2013): 567-581.

Andrus, Phillip, and Anthony Dean. "Focused cardiac ultrasound." Global Heart 8.4 (2013): 299-303.

Price, Susanna, Shahana Uddin, and Tom Quinn. "Echocardiography in cardiac arrest." Current opinion in critical care 16.3 (2010): 211-215.

Zafiropoulos, Andreas, et al. "Critical Care Echo Rounds: Echo in cardiac arrest." Echo Research and Practice 1.2 (2014): D15-D21.