REGULATION OF LEFT VENTRICULAR VOLUMES AT REST AND DURING STRESS

放射性核素心室造影可以准确地追踪左心室的变化 静息和剧烈有氧运动期间的心室（LV）容积 （EX）。尽管年龄相关的左心室容积和射血分数的变化 (EF)在以前的研究中，在EX期间已经显示，年龄变化的作用 在EX期间，这些LV参数的心血管适应性尚未得到 评估。确定年龄对EX LV容量的影响，不依赖于 身体健康水平，我们获得了门控心脏血池扫描， 95名23-86岁健康男性的分级最大直立周期EX。在 整个组的最大努力，左心室舒张末期容积指数（EDVI） 收缩末期容积指数（ESVI）随年龄增长而增加（r = 0.37，p<0.01 r = 0.46，p<0.001 re-sample），而LVEF随年龄增长而下降，r = - 0.46，p<0.001，每搏输出量指数（SVI）与年龄无关。中 49名健康状况均匀的男性组成的子集（最大工作量125-150瓦）， EDVI和ESVI随着年龄的增长而增加，LVEF随着年龄的增长而下降， 样本，但SVI随年龄增加（r = 0.39，p<.01），由于口音- EDVI的估计增加（r = 0.51，p<0.001）。心脏的年龄差异 对β-肾上腺素能刺激的反应可能是 心血管EX血流动力学。检验这一假设的一种方法是 给正常人服用β-肾上腺素能阻断药物， 广泛的年龄范围，并将EX反应与未阻断的 对剧烈有氧运动的反应在很大程度上是由 通过β-肾上腺素能激活，其效率随 年龄增长。为了确定急性β受体阻滞剂是否会减弱 这些心血管EX性能的标准年龄变化，我们进行了 BLSA男性静脉注射普萘洛尔后的最大周期EX。在 25名年龄在28-72岁的男性在峰值工作负荷时静脉注射普萘洛尔，EDVI 随着年龄的增长而下降（r= -0.20），导致与年龄相关的SVI下降（r= 0.48，p<0.05）。心脏的衰退 普萘洛尔治疗的男性年龄变钝（0.46次/分/年）， 对照组（1.09次/分/年）。最大左室射血分数随着年龄的增长而下降， 存在（r=-0.50，p<.01）和不存在（r=-0.45，p<.0001） β-肾上腺素能阻滞剂斜坡移动的主要原因是 在普萘洛尔存在下的年龄回归是一个很大的增加， EDVI和SVI以及年轻男性的HR大幅下降。因此， 年龄相关的最大LVEF下降不受影响，急性β受体阻滞剂 逆转直立周期中与年龄相关的心室扩张 并使最大HR的下降变钝。净效应是 最大CI随年龄增长而下降。

Radionuclide ventriculography can accurately track changes in left ventricular (LV) volumes at rest and during vigorous aerobic exercise (EX). Although age-associated changes in LV volumes and ejection fraction (EF) have been shown during EX in prior studies, the role of age changes in cardiovascular fitness on these LV parameters during EX has not been assessed. To determine the effect of age on EX LV volumes, independent of physical fitness level, we obtained gated cardiac blood pool scans during graded maximal upright cycle EX in 95 healthy men ages 23-86 yr. At maximal effort in the overall group, LV end-diastolic volume index (EDVI) and end-systolic volume index (ESVI) increased with age (r = 0.37, p<.01 and r = 0.46, p<.001 re-spectively) while LVEF declined with age, r = - 0.46, p<.001 and stroke volume index (SVI) was unrelated to age. In a subset of 49 men of homogeneous fitness (maximal workload 125-150 watts), EDVI and ESVI increased and LVEF decreased with age as in the overall sample, but SVI increased with age (r = 0.39, p<.01) due to an accent- uated increase in EDVI (r = 0.51, p<.001). Age differences in the cardiac response to beta-adrenergic stimulation may underlie aging changes in cardiovascular EX hemodynamics. One way to test this hypothesis is to administer a beta-adrenergic blocking drug to normal individuals across a broad age range and compare the EX re-sponse to that in the unblocked condition The response to strenuous aerobic EX is mediated in large part by beta-adrenergic activation, the efficiency of which de-clines with advancing age. To ascertain whether acute beta-blockade would attenu-ate these normative age changes in cardiovascular EX performance, we performed maximal cycle EX in a group of BLSA men after intravenous propranolol. In 25 men ages 28-72 yr given intravenous propranolol, EDVI at peak workload declined with age (r= -0.20) causing an age-associated decline in SVI (r= 0.48, p<0.05) not pre-sent in the unblocked men. The decline in heart with age in propranolol-treated men was blunted (0.46 beats/min/yr) compared to controls (1.09 beats/min/yr). Max-imal LVEF declined with age similarly in the presence (r= -0.50, p<.01) and the absence (r= -0.45, p<.0001) of beta-adrenergic blockade. The primary reason for the slope shifts in the age regressions in the presence of propranolol was a large increase in EDVI and SVI and a large decrease in HR in younger men. Thus, while the age-associated decline in maximal LVEF is unaffected, acute beta-blockade reverses the age-associated ventricular dilatation during upright cycle and blunts the de-cline in maximal HR. The net effect is an accentuated decline of maximal CI with age.