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Myocardial performance index or Tei index: valuable in research but doubtful in clinical practice.

P hysicians have a burning desire to express the distinction between normal and abnormal as a number. Cardiologists—and the informed patient, too—have accepted that left ventricular systolic function is expressed in terms of the ejection fraction, even though it is not unusual to find a lack of correspondence between the value of this parameter and the clinical manifestations of the disease or cases where the ejection fraction shows pseudo-normal behaviour (e.g. mitral regurgitation). But while the ejection fraction is considered an index of left ventricular systolic performance, the absence of any reliable, non-invasive and easy to use index for the evaluation of diastolic function is plain. The index of myocardial performance, or Tei index, celebrates its tenth birthday this year. It belongs to the category of indexes for the measurement and calculation of cardiac time intervals for the evaluation of cardiac function. Its inventors maintain that the sum of the isovolumic contraction and relaxation times divided by the ejection time is an index for the overall estimation of left ventricular function, including both the systolic and the diastolic phase. The temporal precision of the sequence of events in the cardiac cycle (isovolumic relaxation → mitral valve opening → left ventricular filling → isovolumic contraction → aortic valve opening → ejection of blood from the left ventricle) is a prerequisite for normal cardiac function. Temporal disturbances, even of thousandths of a second, are in some cases indicative of specific cardiac dysfunction. Clinical physicians suspect the existence of an atrial septal defect from a fixed splitting of the second sound, or the severity of mitral stenosis from the timing of the opening snap. The diagnostic use of cardiac time intervals started many years ago with the electrocardiogram and continued with phonocardiography, carotid pulse recording and apexcardiography. Since the nineteen sixties the duration of isovolumic contraction and the pre-ejection period have been used as indexes of left ventricular systolic function and the ejection fraction as a measure of stroke volume. Weissler et al introduced the term “systolic time interval,” which was expressed by the ratio of preejection period to left ventricular ejection time and had normal values 0.34 ± 0.04. That index was destined to rule for many years as a measure of left ventricular systolic function. It had the advantage of being relatively unaffected by changes in heart rate and its increase denoted a deterioration of systolic function. However, over time it was proved to show significant variability in various forms of systolic dysfunction and it became progressively much less Myocardial Performance Index or Tei Index: Valuable in Research but Doubtful in Clinical Practice