Technical Considerations for Measurement of the Fetal Left Modified Myocardial Performance Index

late debate into technical issues which will ultimately allow research teams to work towards a methodological consensus. The imaging plane for the left ModMPI has been clearly described by Hernandez-Andrade et al. [4] . Isovolumetric contraction time (ICT) is measured from mitral valve (MV) closure to aortic valve (AoV) opening. Isovolumetric relaxation time (IRT) is measured from AoV closure to MV opening. Ejection time (ET) is measured from AoV opening to AoV closure. Left Mod-MPI = (ICT + IRT)/ET. Lowering Doppler gain allows clear visualization of valve clicks and increasing the wall motion filter allows clear demarcation of time intervals. For consistency in our figures we kept the mitral inflow below the Doppler baseline and the aortic outflow above the baseline. Figure 1 shows the morphological characteristics of MV and AoV closure and opening that may influence the measurement of time intervals. As cardiac Dear Editors, In one of our recent publications regarding the Fetal Modified Myocardial Performance Index (Mod-MPI) [1–3] we highlighted the broad range of quoted ‘normal’ values for the left Mod-MPI and described how this has precluded its translation into clinical practice [2] . We concluded that systematic technical variations could be responsible for such differing normal ranges and that alterations in measurement by only a matter of milliseconds could significantly influence final ModMPI. Considering that pathological states may be expected to alter a Doppler measurement by an order of this magnitude, there could be considerable overlap between the ‘normal’ range from one group and a ‘pathological’ value from another. We wish to present some of our findings regarding the idiosyncrasies of valve opening and closing ‘click’ Doppler morphol ogy for Mod-MPI measurement, which have been uncovered during PhD studies by one of the authors (N.M.). Our aim is to stimuReceived: September 15, 2011 Accepted: October 5, 2011 Published online: January 6, 2012