Echocardiographic Tests of Left Ventricular Function in Pediatric Cardiology: Are We Searching for the Holy Grail?

In this article the utility of echocardiographic tests of left ventricular (LV) function in pediatric cardiology is reviewed. These indices are derived from the basic concepts of cardiac physiology, namely the Frank-Starling curve, pressure volume loops, and the force frequency relation and, to some extent, are all governed by these general principles. Thus, they are prone to be load-dependent and their utility variable. Methods that use formulas for calculating LV volume are a problem in congenital heart disease in which LV geometry is frequently abnormal. New indices, such as the TEI index, continue to be developed but they are still load-dependent. The utility of more complex LV function tests such as mean velocity of circumferential fibre shortening corrected for heart rate, mean velocity of circumferential fibre shortening corrected for heart rate/wall stress, end-systolic, and arterial elastance also have limitations. Tissue Doppler and its functional derivatives which test myocardial mechanics are being intensively applied to patients with acquired and congenital heart disease. To apply these tests appropriately, knowledge of the strengths, limitations, and variability of each of these tests is required. Resting echocardiograms may mask limited myocardial reserve. Our experience with semisupine cycle ergometry has unmasked limited myocardial reserve and helped in clinical decision-making. Thus, there is no single echocardiographic test that is perfect for all clinical questions. Clinicians must use the appropriate combination of tests to answer the question relevant to individual patients.