ONLINE ESTIMATION OF LEFT-VENTRICULAR STROKE VOLUME USING TRANSESOPHAGEAL ECHOCARDIOGRAPHY AND ACOUSTIC QUANTIFICATION

We have examined the usefulness of transoesophageal echocardiography ( TOE) and automated endocardium detection for on-line calculation of le ft ventricular stroke volume. In 12 of 15 patients undergoing abdomina l surgery, stroke volume was derived continuously from the multiple di scs (MD) and area-length (AL) methods and compared with stroke volume calculated by thermodilution. In 10 patients (80%), more than three ma nipulations of the ultrasound transducer were required before measurem ents. Linear regression analysis of automated TOE methods and thermodi lution revealed weak correlations (r < 0.75) for stroke volume (114 ma tched pairs) and its changes (105 matched pairs). Correlation of perce ntage changes in stroke volume calculated by thermodilution with those derived from MD (r = 0.85) and AL (r = 0.79) was better. Changes in M D (AL) derived stroke volume by more than 20% identified changes in th ermodilution-derived stroke volume greater than 20% (n = 57) with a se nsitivity of 74% (70%) and a specificity of 82% (79%). Signal instabil ity, lack of accuracy and only a moderate trend capability currently l imit the intraoperative usefulness of automated TOE techniques for con tinuous estimation of stroke volume from a single long-axis plane.