Abstract
We systematically assessed the utility of diagnostic data and the accuracy of haemodynamic data obtained by transthoracic echocardiography in critically ill adults, by examination of prospective studies in unselected adult intensive care patients. Of the ten studies identified, three examined the diagnostic utility of transthoracic echocardiography. Thirty-eight percent of clinical questions were answered by a single transthoracic echocardiogram. The weighted mean percentage of clinical findings yielded by transoesophageal echocardiography not found by the transthoracic approach was 33% (range 28–50%).
Four studies examined the correlation between transthoracic echocardiographic estimation of pulmonary artery occlusion pressure and pulmonary artery catheter-derived measurement. Correlation was strong in all studies: for example in one study r=0.98, p<0.001, with a mean difference of 0.0 (2.5) mm Hg by the Bland-Altman technique.
Three studies examined the correlation between transthoracic echocardiography and thermodilution-derived cardiac output measurement. Correlation varied with the echocardiographic technique used and correlated best with Dopplerderived measurement: r=0.93, p<0.0001, mean difference of 0.2 (0.82) litres per minute.
The diagnostic utility of transthoracic echocardiography compared with transoesophageal echocardiography in the critically ill cannot be reliably assessed from the available studies. More relevantly designed studies are required. Transthoracic echocardiography can accurately estimate pulmonary artery occlusion pressure, but the technique requires the patient to be in sinus rhythm. Transthoracic echocardiography can also accurately estimate cardiac output in the critically ill. Further studies should concentrate on Doppler-based assessments. The scene is now set for the development of this valuable non-invasive tool.