Impact of frailty on cardiac contractile function in an aging mouse model
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This study quantified frailty in a longitudinal study in the mouse model and investigated whether frailty was a better predictor of changes in cardiac morphology and function than chronological age. Frailty scores progressively increased as mice aged. Echocardiography showed in vivo that left ventricular internal diameter increased as frailty increased while contractile function declined. Individual ventricular myocytes hypertrophied with increasing age and especially frailty, while peak contractions declined in myocytes from moderately frail mice in comparison to the least frail mice. By contrast, calcium transient amplitudes declined slightly with age but not frailty. Interestingly, intracellular Ca2+ levels in myocytes were similar between all frailty groups, even when Ca2+ overload was induced by β-adrenergic agonist. These results suggest that age-associated changes in cardiac structure and function are more prominent in animals with high frailty scores and that frailty is a better predictor of these changes than chronological age.