Quantitative left ventricular systolic function: From chamber to myocardium

Abstract

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.

Maternal cardiac function in preeclampsia

“…Some studies included women with comorbidities, in early labour or on vasoactive medication [8] disregarding that all these factors independently affect cardiovascular system. Finally, systolic and diastolic indices have also been interpreted in isolation, even though no single index is representative of the global function [6,7,9]. Such data can only be reliably interpreted using multiple indices assessed with a validated diagnostic algorithm [6,7,9].…”

“…The major limitations of older publications on cardiovascular effects in preeclampsia include the use of reference ranges constructed from mixed populations and the reliance on ejection-phase indices that are dependent on loading conditions which are altered in pregnancy [1,2]. Furthermore, these indices only reflect radial function which changes late in chronic cardiovascular disease [6,7] and are unlikely to reflect early changes or subtle impairment of systolic function in the acute condition of preeclampsia. Some studies included women with comorbidities, in early labour or on vasoactive medication [8] disregarding that all these factors independently affect cardiovascular system.…”

Echocardiographic evaluation during weaning from mechanical ventilation

“…It permits direct observation of all cardiac structures and the patient's hemodynamic status, allowing immediate intervention related to volume replacement and the use of inotropic agents 6,7. In patients on MV, its use can explain some cardiac morphological and functional analyses that may influence weaning from MV, particularly when weaning is difficult or there is refractory hypoxemia that cannot be explained by lung disease alone 8.…”

Evaluation of contractility and postloading in the intensive care unit

“…: 0.30---0.38), and requires placing the echocardiographic sample volume in the left ventricle between the mitral valve and the aortic valve (apical 5-chambers), in order to obtain the aortic ejection flow and the mitral filling flow. 24,26 …”