Echocardiographic assessment of age-associated changes in systolic and diastolic function of the female F344 rat heart

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Abstract
Aging is associated with hypertrophy, dilatation, and fibrosis of the left ventricle (LV) of the heart. Advances in echocardiographic assessment have made it possible to follow changes in cardiac function in a serial, noninvasive manner. The purpose was to determine whether there is echocardiographic evidence of age-associated changes in chamber dimensions and systolic and diastolic properties of the female Fischer 344 (F344) rat heart. On the basis of previous invasive studies, it was predicted that echocardiographic assessment would detect age-associated changes in indexes of systolic and diastolic function. Rats were sedated with 1.5% isoflurane and placed in the supine position. Two-dimensional images and two-dimensionally guided M-mode, Doppler M mode, Doppler tissue, and pulsed-wave Doppler recordings were obtained from the parasternal long axis, parasternal short axis, and/or apical four-chamber views as per convention by using a 15-MHz linear array or 8-MHz phased-array transducer or a GE S10-MHz phased-array transducer. Compared with young adult 4-mo-old rats, there is a significant decrement in the resting systolic function of the LV in 30-mo-old female F344 rats as evidenced by declines in LV ejection fraction (80 ± 9 vs. 89 ± 5%; mean ± SD), fractional shortening (43 ± 9 vs. 54 ± 8%) and velocity of circumferential fiber shortening (2.43 ± 0.53 vs. 2.99 ± 0.50 circ/s). Evidence for age-associated differences in diastolic function included an increase in isovolumic relaxation time (25.0 ± 7.6 vs. 17.2 ± 4.4 ms) and decreases in the tissue Doppler peak E waves at the septal annulus and at the lateral annulus of the mitral valve. The modest changes in systolic and diastolic LV function that occur with advancing age in the female F344 rat are likely to reduce the capacity of the heart to respond to hemodynamic challenges.