During the cardiac cycle the LA plays the functions of reservoir, conduit and atrial pump; the different phases are influenced by changes at the atrial chamber and the left ventricular chamber (6,21).
With normal aging cell remodeling occurs, with loss of cardiomyocytes and compensatory development of hypertrophy; changes in the extracellular matrix were also described, with greater presence of fibrosis and deposits of amyloid protein (22). At the molecular level, mitochondrial dysfunction and oxidative stress occur, as well as alterations in the entrance of calcium to the sarcoplasmic reticulum, which determine changes in cell elasticity with decreased relaxation and lower suction force by the LV, decrease in passive ventricular filling, and compensatory increase of the contribution of the atrial systole to LV filling to maintain an adequate stroke volume (23–25). These events were associated with greater predisposition to suffer AF, and heart failure with preserved systolic function (26), entities that are becoming more prevalent in Argentina and the rest of the world (27–31), given the increase in longevity that the world population is experiencing (14,22).
Different authors found an association between cardiovascular events and alteration in LA function evaluated by Strain and SRI. Inaba et al. found that SRS, SRE and SRA were lower in AF patients than in age-matched controls (32).Wang et al. found that LA SRE and LA dimension were independent predictors of CV failure (33).Mondillo et al.found that reservoir and conduit phaseswere lower in patients with hypertension or diabetes than in controls (34).
New technologies in medicine are important components of health care, which have the potential to save lives and improve quality of life and well-being. However, too many people around the world do not have access to affordable and high-quality health technology, and the problem is more serious in low and middle-income countries (35).
Many echo laboratories do not have the possibility of assessing LA by strain since it is necessary to incorporate additional and expensive software, a wide learning curve, also post-processing of the images is required to interpret them, and a high quality of images. Unlike the DTI, is a simple method, widely available, that allows analyzing the information at the time of the study and does not require an extensive learning curve, this leaded us to think it could be an alternative to LA SRI in low resource centers. As a previous instance for the study of LA function through this method in individuals with established cardiovascular pathology or at higher risk of presenting it, we need to understand how these parameters behave in normal population and stablish initial reference values according to age groups, which is the reason why we perform this sub-analysis.
In this study we described the age related changes observed in a population of adults without cardiovascular disease with TDI online, SRI and other diastolic function parameters. The variations in E'la and SRE waves, and E'la/A'la and SRE/SRA ratios identified earlier the increase in the atrial systole contribution to LV filling than others diastolic function parameter.
Comparison with previous studies
Similar to our work, Pérez Paredes et al. (36) studied the lateral wall of the LA, in that case with spectral pulsed TDI in mid segments, finding a decrease in the early diastole wave and an increase in late diastole wave in the age group over 45 years; no changes in the reservoir phase were reported. Similar results were obtained by Thomas et al. (37) with TDI color off line, when evaluating late diastole of lateral wall of the LA at the annular level and mid segments level. When comparing the results obtained in this study by TDI at the annular and auricular levels, we observed that the lateral wall of the LA has a speed profile different from the mitral annulus as shown in Fig. 2, which suggests that by directly assessing the atrial myocardium we can detect changes that are not evident at the level of the annulus.
Inaba et al. evaluated the LA by SRI in a subgroup of healthy patients; they could not find a significant correlation of late diastole with age, which according to the author could be due to the need of a high quality of images and to have analyzed only one of the walls (32). Boyd et al. also evaluated a population of healthy adults with atrial SRI and reported significant correlation of SRI with age at the different phases: reservoir, conduit and atrial systole (5). Similar findings reported by Sun et al.; this author analyzed the ratio between early and late diastole (SRe/a) finding a negative correlation with age. These authors also demonstrated changes in atrial SRI that would allow an earlier detection of altered diastolic function than with the parameters usually used (38).In a recent work Yoshida et al. evaluated the impact of age on cardiac function by speckle tracking echocardiography and serum B type natriuretic peptide and concluded that the decrease in the reservoir and conduit phase are the earliest markers of cardiac remodeling (39). Regarding the atrial contraction function and its changes with age, the information is still controversial; there are studies that show an increase in this function (22, 37) while others did not show significant changes (30, 37, 40).
In this study both TDI and SRI showed a decrease in the conduit phase in the age subgroups over 40 years old, at least a decade before the other methods analyzed.