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Lee et al in trying to define the accuracy of one method illustrate the huge weakness in echo vs MRI comparative data. First and foremost neither FAC or TAPSE correlated that well with RVEF ( FAC only slightly better) although statistically significant this difference is clinically of negligible importance. Secondly in assuming that MRI provides a gold standard for RVEF. As with echo there are strengths and weaknesses of MRI. On is the rather lower sensitivity to long axis abnormalities because ventricular volumes are usually defined using the short axis plane. So a reduced correlation between a purely long axis technique, a moderate correlation with a technique that has both long and short axis components and one which is defined using predominantly radial function is entirely to be expected. Long axis dysfunction is usually the first sign of ventricular deterioration with short axis hyperactivity to compensate - exactly the example cited post cardiac surgery. Finally in their conclusions they state that FAC provides a better guide to RV systolic function. This is not justified - what it does do is provide a slightly better estimate of RVEF -these two are not synonymous. So as there are no clinical correlates - prognosis, symptoms, exercise performance, hospitalisations , the comparison between the techniques tells us nothing we did not already know - all methods of defining systolic function are different - we have not answered which one is best.