We appreciate the interest in our article  and certainly would agree with a conclusion that the TEI-index may be a useful variable in certain clinical settings. However, over-interpretation of data as well as speculation should be avoided.
First, we agree that the TEI-index may be superior to ejection fraction in assessing global myocardial performance. However, our study was neither designed to address this issue nor to clarify whether the degree of coronary stenosis correlated to TEI-index values at baseline in the patients studied. In fact, this has already been shown previously and would not come as a surprise since its sensitivity has been demonstrated both in patients with chronic ischaemic heart disease and those with idiopathic dilated cardiomyopathy .
Second, besides an increase in coronary artery perfusion pressure, an increase in cardiac output is (by definition) an unlikely explanation for the improved TEI-index seen with the head-down tilt manoeuvre. In fact, this peculiar consideration somewhat resembles the odd problem of ‘the hen and the egg’. Our understanding of circulatory physiology is that cardiac output is determined by overall myocardial performance and loading conditions. If an index of cardiac performance would be the sequel, rather than the determinant, of cardiac output and thus be affected by cardiac output, this would be a rather strange variable indeed. Accordingly, we feel that this notion is beside the point. Therefore, the only hypothesis that could be put forward is that head-down tilt, by increasing left ventricular end-diastolic volume and cardiac output, resulted in adaptive neurohumoral changes, which by their feed-back on the heart in turn altered the TEI-index.
Finally, we doubt that the TEI-index is an intelligent indicator of the potential benefit of a volume challenge. All our patients suffering from coronary artery disease of varying degrees and having a left ventricular ejection fraction between 39% and 75%, improved with regard to the TEI-index after an increase in left ventricular preload although seven had previous myocardial infarctions. By the same token, hypovolaemia prior to tilt was excluded by normal left ventricular end-diastolic area.
Thus, for the purpose of considering acute changes in cardiac performance occurring during anaesthesia and surgery, the TEI-index appears to have no ‘added value’ beyond standard variables. Furthermore, as we have shown, it is certainly not a pure variable of myocardial contractile performance (‘contractility’), independent of left ventricular loading conditions, a claim that has been made by others. Accordingly, we avoided both over-interpretation as well as misinterpretation and would prefer stick to our data rather than to speculate.
J. T. Lutz
*Klinik für Anästhesiologie und Intensivmedizin, Universitätskliniken Uni Essen, Essen, Germany
1. Lutz JT, Giebler R, Peters J. The ‘TEI-index’ is preload dependent and can be measured by transoesophageal echocardiography during mechanical ventilation. Eur J Anaesthesiol
2. Tei C, Nishimura RA, Seward JB, Tajik AJ. Noninvasive Doppler-derived myocardial performance index: correlation with simultaneous measurements of cardiac catheterization measurements. J Am Soc Echocardiogr