Abstract
Abstract Introduction Speckle-tracking echocardiography has gained widespread use, and strain parameters such as global longitudinal strain (GLS) and strain rates are strongly associated with risk of heart failure and cardiovascular death. Such strain measures, however, only represent limited features of the complete longitudinal strain (LS) curve. Thus, interpretation of entire curves might provide additional insight. Purpose To establish normal standardized LS curves over an entire heart cycle for healthy subjects stratified by age and sex. Furthermore, to assess how these curves vary with age and to compare this with conventional strain measures. Methods The study population consisted of 1790 healthy subjects free of cardiovascular disease and risk factors including diabetes mellitus and hypertension at baseline. Subjects were stratified by sex and further by age in groups as defined in the SCORE risk chart. Subjects underwent echocardiography, and LS curves from the apical four-chamber view were derived and standardized in length using linear interpolation. Terms to describe qualitative findings in the standardized strain curves were established (Figure 1). Early diastolic strain (EDS) was defined as the difference in strain from peak LS to maximal curvature after early diastolic filling, while late diastolic strain (LDS) was defined as the difference in strain from the plateau phase in late passive diastole to maximal curvature in active diastole. Conventional strain measures included GLS, systolic strain rate (SRS), early diastolic strain rate (SRE), and late diastolic strain rates (SRA). The association between these and age group were investigated using univariable linear regression for each sex. Results In the study population, 1101 (61.5%) subjects were female. The standardized strain curves (Figure 2) showed that aging primarily manifested in the diastolic part of the strain curve. Decreasing EDS was associated with increasing age group, while the opposite was true for LDS. In linear regression, both SRE (female: beta=-0.13; p<0.001, male: beta=-0.1; p<0.001) and SRA (female: beta=0.09; p<0.001, male: beta=0.09; p<0.001) were associated with age group for both sexes. Peak LS did not change notably with age, and in linear regression, GLS and SRS were only significantly associated with age for women (GLS: beta=0.12; p<0.001, SRS: beta=0.01; p<0.001). Conclusion We derived normal standardized LS curves for healthy individuals stratified by age and sex, which can serve as normal values in future studies. In addition, these showed that age was primarily associated with changes in the diastolic part of the strain curve in both sexes, which was consistent with conventional strain measures.Figure 1:Overview of termsFigure 2Standardized longitudinal strai
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