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Quantitative left ventricular systolic function: from chamber to myocardium.

One of the most common indications for obtaining a Doppler echocardiographic study is to ascertain left ventricular (LV) systolic function. There are many ways in which LV function can be determined, but an important assumption that is often overlooked is that every measure that we commonly use is only a surrogate marker of LV function due to the fact that it is impossible to characterize the complex geometric and volumetric function of the ventricle (or myocyte) in a single number. Stated in another way, there is no one perfect measure of LV function. The ejection fraction has emerged as the preeminent method to express LV performance, but although ejection fraction is universally accepted, there are a number of other techniques that can assess LV function and, when taken together, provide a more comprehensive picture both of global and regional LV function. Each of these measures (including ejection fraction) has variable dependence on loading conditions, heart rate, and geometric position that limits its accuracy. Understanding the limitations of each measure will allow the physician to more intelligently understand the true status of the myocardium.