Transthoracic Echocardiography in Anaesthesia

Veltman, Michael
Departments of Anaesthesia
Sir Charles Gairdner Hospital &
Royal Perth Hospital

Summary

Echocardiography has progressed rapidly in anaesthesia over the last decade. In the late 1990's anaesthetists adopted transoesophageal echocardiography(TOE) in cardiac surgery in increasing numbers. Even as TOE was accepted as a standard tool for the cardiac anaesthetist, its utility was being seen in other areas of critical care. Intensive care rapidly saw not only the value of TOE, but also that transthoracic echocardiography (TTE) had increasing relevance to their practice. In the last few years TTE has been adopted by anaesthetists in both cardiac and non cardiac work.

Compared to TOE, TTE is the superior imaging modality for most purposes. With the exception of a few special indications, TTE can provide answers to clinically important questions in a faster, safer and often more accurate manner than TOE. In particular, TTE offers an imaging modality that can be repeated at no direct risk to the person being imaged.

TTE capable machines have become portable, robust and remarkably cheap, and as the price continues to fall the uptake will increase.

The biggest limitation for uptake relates to training and credentialing. Options for formal training are growing, from workshops run by equipment manufacturers and various educational institutions. The number of anaesthetists undertaking training in echocardiography is increasing rapidly.

The traditional full echocardiography examination is also not always the appropriate examination in the critical care setting. Cardiologists do occasionally undertake limited examinations and a similar rationale applies in other areas of ultrasound, such as a FAST examination. One major difference between the traditional use in cardiology and in critical care is the need to frequently repeat the echo examination to watch for changes in haemodynamic state, which can be quite rapid.

A similar concept is needed in critical care for a rapid assessment of haemodynamic state. Such an examination would not be a full echo study, but would aim to provide a haemodynamic echo assessment in real time(HEART).

The details of what comprises a HEART scan will be outlined at the ANZCA ASM, but it essence it is the functional equivalent of a FAST scan, but for cardiac assessment. It would provide a rapid screen for valve abnormalities important to acute critical care management (particularly aortic stenosis) and allow both initial and repeat assessment of haemodynamic state. Unlike echocardiography, formal quantification of most lesions would not be a part of the study, nor would be the diagnosis of all possible conditions that are detectable using ultrasound.

The concept of a limited monitor and screening examination which requires training, but to a much lesser extent than for echocardiography, is now possible due to improved technology. The information that even limited examinations will provide will justify the use of transthoracic echo for a large number of anaesthetists and other critical care physicians.