Assessment of Myocardial Structure, Function and Mechanics by 3D and 3D-Speckle Tracking Echocardiography and its Associations with Morbidity and Mortality in Older People

Abstract

Introduction: 3D-echocardiography(3DE) is a recommended method for assessing left ventricular(LV) structure/function. 3D speckle-tracking echocardiography(3DSTE) is an emerging tool for assessing LV mechanics, evidence of its prognostic utility is limited. While 3DE and 3D-STE have theoretical advantages over other methods, their utility may be compromised by image quality(IQ). This could be an important source of bias as sicker/frailer individuals often have suboptimal IQ. Aims: To investigate: • The prognostic utility of 3DE- and 3D-STE-derived indices of LV structure/function/mechanics with morbidity/mortality in a multi-ethnic general population sample of older individuals. • The feasibility of 3D-STE derived LV indices and the impact of IQ on these indices. Methods: This thesis comprises 1)a systematic review to summarise existing data and establish knowledge gaps on the prognostic significance of 3D-STE, 2)an analysis of the prognostic value of 3DE and 3D-STE in a multi-ethnic UK longitudinal population cohort(SABRE), and 3)additional work assessing the impact of suboptimal IQ on 3D-STE LV indices. Results: A systematic review showed limited evidence regarding LV strains as prognostic markers of cardiovascular morbidity/mortality in community-dwelling individuals. Associations between 3DE LV measures and adverse outcomes in SABRE differed by sex. This difference was partially explained by higher ventricular and arterial stiffness in women. 3D-STE LV myocardial strains were found to predict adverse cardiovascular events in SABRE, strengths of v association were similar or slightly better than 3D-EF, and 3D-strain showed some evidence of being a slightly better predictor than conventional indices of LV function(3D-GLS and 3D-EF), although it is questionable whether the improvement would be useful in a community setting. Suboptimal IQ caused a systematic underestimation-bias of 3D-STE-derived LV indices. Conclusions: Altered cardiac structure, function and mechanics assessed by 3DE and 3DSTE predict the risk of morbidity/mortality, but sex-specific LV remodelling patterns may influence mortality risk in the general population. 3DE/STE is sensitive to IQ, which has the potential to be a neglected source of bias in clinical and epidemiological studies.