Compare and contrast transthoracic and transoesophageal echocardiography in the evaluation of cardiac disease in the critically ill patient. (You may tabulate your answer)

 TTE TOE Time lag to diagnosis Instantaneous A certain degree of delay Need for sedation None May need sedation Invasive No Minimally invasive Morbidity None Minimal Mortality None Minimal Image quality Good/excellent in non- vent, reduced in ventilated patients Excellent in all patients Infection control Stricter infectious control procedures Cost More expensive probes Native and prosthetic valve endocarditis TOE is superior Aortic dissection TOE is superior Aortic trauma TOE is superior LA appendage clot TOE is superior Pericardial effusion Good Good Localised tamponade (post surgery) Occasionally useful Very useful

## Discussion

The recommendations for the use of TTE or TOE have been updated in 2003. The update statement, though the "summary" of a much larger statement, is in fact an unwieldy document many pages long. A much better summary of echosonography in the ICU is presented in a review article from 2008.  Thre massive 2007 Appropriateness Criteria for Transthoracic and Transesophageal Echocardiography statement was used to construct the suggested non-college answer below.

 Category TTE TOE Equipment Small scale devices available Bedside apparatus ranges from cheap hand-held probes (sub-$10K ) to professional equipment (ranging$70K- $150K) Probes are easily replaceable when they break, as their cost is small There is no cheap bedside option Bedside apparatus is portable but still large and expensive (ranging$70K- \$150K) Expensive probes need to be carefully protected from such threats as patient's teeth Time lag to diagnosis Instant diagnosis Slight delay Need for sedation Usually unnecessay Frequently necessary Invasiveness Non-invasive Minimally invasive Absolute contraindications None Severe left-sided rib fractures could be viewed as a relative contraindication Oral or oesophageal surgery, anastomosis Oesophageal stricture or diverticulum Severe coagulopathy could be viewed as a relative contraindication Factors affecting image quality Body habitus Mechanical ventilation Patient position Exposure of chest wall (eg. severe burn, or open chest in cardiothoracic theatre) Most of the time image quality is good; most important factor affecting it is the experience of the operator Infection control Probe needs to be disinfected with surface-acting disinfectant agents (similar to any other patient contact instrument); it is usually not exposed to patient body fluids. It cannot be subjected to autoclaving. Disposable sleeves are available. The probe must be disinfected thoroughly in a manner similar to the disinfection of endoscopy probes, as it is exposed to patient body fluids. Protective sleeves are inappropriate. Most probe designs factor in the need to be subjected to automated cleaning, and tolerate high temperatures. The usual probe turnaround time is 20 minutes under ideal circumstances Mortality and morbidity Essentially, a benign and consequence-free procedure. The greatest risks are misinterpretation of data (leading to inappropriate management) and inaccurate findings (due to operator inexperience). No formal consent process is usually required (verbal / implied consent is sufficient) Each procedure has a small but non-zero risk of major complications, including oesophageal perforation, endotracheal tube dislodgement, and death. The nasogastric tube is often in the way, and ends up being removed. It then needs to be reinserted, with attendent complications. In the non-intubated patient, the use of sedation carries its own risks. Focused assessment of the cardiac arrest patient The subcostal view does not interfere with CPR, but is a sub-optimal view. Information derived from peri-arrest TTE is frequently useful and tends to change the management Some prognostic interest: patients with absent LV wall movement are highly unlikely to succeed at ROSC (only ~2.4% will go on to ROSC). Also does not interfere with CPR, but offers much better quality of images. Likely to be the only option in perioperative cardiac arrest Same as TTE, changes management in arrest and can offer some prognostic information. Assessment of ventricular function TTE is a better modality for assessment of LV and RV function as it includes the true cardiac apex Multiple window directions enhance the ability to assess flow with Doppler The cardiac apex is poorly seen with TOE. There are fewer windows, and Doppler assessment of flow is incomplete Assessment of aortic dissection Descending and thoracic aorta is either impossible or difficult to image. TOE is the US modiality of choice for aortic dissection Assessment of valve function Valve function can be assessed to a high degree of accuracy provided image quality is satisfactory. Small vegetations cannot be excluded Valve function can be assessed to a high degree of accuracy Valve images are of sufficiently high quality to appreciate small vegetations This is the modality of choice for infective endocarditis Assessment of septal defects Grossly, large defects and intracardiac shunts can be appreciated, but their quantitative assessment usually cannot be carried out Intracardiac shunts and septal defects are well imaged. This is the modality of choice for such pathology. Identification of intracardiac thrombi Large LA and LV thrombi can be identified; small thrombi cannot be excluded. All sorts of intracardiac thrombi can be identified; particularly the left atrial appendage is well visualised. This is the modality of choice for pre-cardioversion assessment of embolic risk.

### References

References

Cheitlin, Melvin D., et al. "ACC/AHA/ASE 2003 guideline update for the clinical application of echocardiography." A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASE Committee to Update the 1997 Guidelines for the Clinical Application of Echocardiography). American College of Cardiology Foundation and American Heart Association (2003).

Roscoe, Andrew, and Tim Strang. "Echocardiography in intensive care."Continuing Education in Anaesthesia, Critical Care & Pain 8.2 (2008): 46-49.

Douglas, Pamela S., et al. "ACCF/ASE/ACEP/ASNC/SCAI/SCCT/SCMR 2007 Appropriateness Criteria for Transthoracic and Transesophageal Echocardiography⁎: A Report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group, American Society of Echocardiography, American College of Emergency Physicians, American Society of Nuclear Cardiology, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, and the Society for ...." Journal of the American College of Cardiology 50.2 (2007): 187-204.