468 effect of age on global kinetic energy dissipation within the left ventricle. an echocardiographic study.

Abstract Background The echocardiographic evaluation of the left ventricular function is traditionally based on parameters of cardiac mechanics and analysis of transvalvular blood flow, but recently the study of intracardiac fluid dynamics has been proposed as an integrative approach to the assessment of cardiac function. More precisely, dissipation of the kinetic energy of blood moving within the left ventricle (global kinetic energy dissipation, gKED) during the entire cardiac cycle (systole and diastole) can now be evaluated in a very practical way using the new non-contrast, color Doppler based HyperDoppler technique. Although feasibility of this technique and reproducibility of gKED have been demonstrated, the effect of age and its consequences have not been clarified. Objectives The purpose of this study was to evaluate: 1) the effect of age on gKED measures; and 2) whether this impacts on the ability of gKED to differentiate physiological and pathological hemodynamic models, expected to have different loss of kinetic energy within the left ventricle. Methods Two groups of individuals were considered for this study: 50 normal subjects (physiological model) and 50 patients with chronic heart failure in stable clinical and hemodynamic condition, with no signs of clinical and echocardiographic increase of left ventricular filling pressure (pathological model). Normal subjects were divided into 3 age groups: 17-32 years (group I), 33-48 years (group II) and 49-64 years (group III). All participants underwent both standard and HyperDoppler echocardiography using a Esaote MyLab X8 echo scanner. Results In normal subjects, gKED decreased with age (group I 0.8, group II 0.59, and group III 0.27; P=0.001). In particular, this reduction was statistically significant between group III (age >=49) and the other 2 age groups. At the multivariate analysis, gKED was associated with both age and peak of transmitral E-wave, while there was no association with left ventricular ejection fraction. Patients with heart failure showed lower gKED values (0.715 vs. 0.18, P<0.001). HF patients with age <49 years had a markdly different gKED compared with normals of the same age, while the difference in gKED between normals and HF patients with age >= 49 years was much less pronounced, although significant (P<0.003). HF patients were characterized by reduced left ventricular ejection fraction in addition to reduced peak E-wave and this may explain the low gKED values observed in these patients. Conclusions Our preliminary observations show that gKED depends on age but maintains the ability to differentiate two physiological and pathological hemodynamic and functional models. These results should be taken into account when applying the HyperDoppler technique in clinical practice for evaluation of gKED.