100 QUESTIONS IN CARDIOLOGY

72 How sensitive are transthoracic and

transoesophageal echocardiography for the

detection of thrombus in the left atrium?

Suzanna Hardman and Martin Cowie

The ability of echocardiography to detect left atrial clot is

determined by the sophistication of the equipment, the ease with

which the left atrium and left atrial appendage can be scanned

and the skill and experience of the operator. Historically, at best,

the sensitivity of two dimensional transthoracic echo-

cardiography for detecting left atrial thrombus has been of the

order of 40–65%, with the left atrial appendage visualised in

under 20% of patients even in experienced hands. This

compared with a reported sensitivity of 75–95% for visualising

left ventricular thrombi from the transthoracic approach. More

recent data, from a tertiary referral centre using the new gener-

ation transthoracic echocardiography, suggest the left atrial

appendage can be adequately imaged in 75% of patients and that

within this group 91% of thrombi identified by trans-

oesophageal echocardiography will also be visualised from the

transthoracic approach. Although encouraging, the extent to

which these figures can be reproduced using similar equipment

by the generality of units remains to be established.

Available data for the sensitivity of transoesophageal echo-

cardiography in detecting left atrial and left atrial appendage

thrombus consistently report a high positive predictive value. The

largest series of 231 patients identified thrombus ranging from 3 to

80mm in 14 patients: compared with findings at surgery this

produced a sensitivity of 100%. But these findings need to be

interpreted with considerable caution and are unlikely to be ap-

plicable to all users of the technique. The study was carried out in a

tertiary referral centre with a particular interest and long-standing

investment in the technique and the nine observers involved in

reporting the data all had extensive experience. Nonetheless,

transoesophageal echocardiography is undoubtedly the investi-

gation of choice for imaging the left atrium and left atrial

appendage.