Non-invasive evaluation of left ventricular filling pressure (LVFP) by echocardiography is critical for diagnosis and management of heart failure. Conventional echocardiographic parameters employed for assessment of LVFP have poor correlation and predictive value for assessing LVFP. To overcome this, complex, multi-parametric diagnostic algorithms have been developed for clinical assessment of LVFP. There are numerous limitations to the current guideline algorithms and refinement of echocardiographic assessment of LVFP is necessary to improve patient care. Left atrial reservoir strain (LASr) derived by speckle tracking echocardiography is a novel parameter that may improve echocardiographic assessment of LVFP. By reflecting dynamic changes in left atrial wall stiffness induced by alterations in left atrial volume and pressure, LASr more accurately predicts LVFP than any conventional echocardiographic parameter. Currently, however, due to unresolved technical limitations, and the absence of a clearly defined framework for clinical implementation, LASr is not routinely employed in clinical assessment. Through conducting a large-scale prospective trial examining LASr in relation to invasively assessed LVFP, this thesis intends to resolve these limitations and develop a framework for clinical application of LVFP. [...]