To the Editor

Abstract

The article by Lax and colleagues1Lax JA Bermann AM Cianciulli TF Morita LA Masoli O Prezioso HA Estimation of the ejection fraction in patients with myocardial infarction obtained from the combined index of systolic and diastolic left ventricular function: a new method.J Am Soc Echocardiogr. 2000; 13: 116-123Google Scholar proposes a new formula to convert the myocardial performance index (MPI) into a more recognizable measure of ventricular function, namely ejection fraction (EF). In this study, the authors measured the MPI in adults with a previous myocardial infarction and compared this index value to the EF obtained with radionuclide angiography. The authors then derived a formula to “convert” the index to the more recognizable EF. The premise of this report is that the MPI is a relatively new measurement of ventricular performance that the medical community is unable to use because its values are different from other more established measures of ventricular function. Consequently, the index must be converted to an EF to gain wide acceptance. This premise is flawed in many respects. First, EF is a measure of systolic performance, whereas the index measures both systolic and diastolic components of function. In patients with ventricular dysfunction in whom the index is increased primarily because of diastolic dysfunction while systolic function is relatively normal, expressing the index as an EF would be very confusing, not to mention inaccurate. Second, this new formula is not applicable to children or adults with normal ventricular function and normal index values. In normal controls, the left ventricular MPI ranges between 0.35 and 0.39 ± 0.05. 2Tei C Ling LH Hodge DO Bailey KR Oh JK Rodeheffer RJ et al.New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function-a study in normals and dilated cardiomyopathy.J Cardiol. 1995; 26: 357-366Google Scholar, 3Tei C Dujardin KS Hodge DO Bailey KR McGoon MD Tajik AJ et al.Doppler echocardiographic index for assessment of global right ventricular function.J Am Soc Echocardiogr. 1996; 9: 838-847Google Scholar, 4Eidem BW Tel C O'Leary PW Cetta F Seward JB Nongeometric quantitative assessment of right and left ventricular function: myocardial performance index in normal children and patients with Ebstein anomaly.J Am Soc Echocardiogr. 1998; 11: 849-856Google Scholar If we use the formula proposed by the authors, EF = 60 − (34 × Index), we would predict the EF in these normal controls to be between 0.45 and 0.50. This is clearly an underestimation of their EFs (0.60 to 0.65 in both studies). Third, one of the most important reasons that the MPI is useful in the quantitative assessment of ventricular function is that it is nongeometric and can be readily applied to both the left and right ventricles. To convert this index to a measure that classically represents left ventricular systolic performance, yet is not applicable to quantitative measurement of right ventricular function, is not practical. Finally, in numerous studies, the MPI has been shown to be a much better predictor of outcome than are conventional measures of ventricular performance, including EF. 2Tei C Ling LH Hodge DO Bailey KR Oh JK Rodeheffer RJ et al.New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function-a study in normals and dilated cardiomyopathy.J Cardiol. 1995; 26: 357-366Google Scholar, 3Tei C Dujardin KS Hodge DO Bailey KR McGoon MD Tajik AJ et al.Doppler echocardiographic index for assessment of global right ventricular function.J Am Soc Echocardiogr. 1996; 9: 838-847Google Scholar, 4Eidem BW Tel C O'Leary PW Cetta F Seward JB Nongeometric quantitative assessment of right and left ventricular function: myocardial performance index in normal children and patients with Ebstein anomaly.J Am Soc Echocardiogr. 1998; 11: 849-856Google Scholar, 5Tei C Dujardin KS Hodge DO Kyle RA Tajik AJ Seward JB Doppler index combining systolic and diastolic myocardial performance: clinical value in cardiac amyloidosis.J Am Coll Cardiol. 1996; 27: 658-664Google Scholar, 6Poulsen SH Jensen SE Nielsen JC Moller JE Egstrup K. Serial changes and prognostic implications of a Doppler-derived index of combined left ventricular systolic and diastolic myocardial performance in acute myocardial infarction.Am J Cardiol. 2000; 85: 19-25Google Scholar To convert this index to a less predictive measure and then try to clinically use the EF to affect management or address outcome is incorrect. In summary, although the overall premise of this report underscores an important dilemma in the clinical use of data obtained with novel techniques, care should be exercised in attempting to convert these data to a more “user-friendly” form that may sacrifice many of the unique benefits of the newer technique.