Question 24

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

• 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

• Instant diagnosis

• Slight delay

• Usually unnecessay

• Frequently necessary

• Non-invasive

• Minimally invasive

• 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

• 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

• 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

• 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.

• 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.

• 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

• Descending and thoracic aorta is either impossible or difficult to image.

• TOE is the US modiality of choice for aortic dissection

• 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

• 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.

• 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.