Nii T, Fouad-Tarazi F M, Ferrario C M, Bravo E L, Czerska B
Hypertension. 1987 Jun;9(6 Pt 2):III176-80. doi: 10.1161/01.hyp.9.6_pt_2.iii176.
Chronic sodium depletion has been reported to decrease ejection fraction in anesthetized dogs. We tested the hypothesis that this reduction in cardiac performance is due to either hemodynamic or humoral factors. Seven mongrel dogs were fed a low sodium diet (less than 2 mEq Na+ per day) for 5 weeks. Echocardiographic and radionuclide techniques were used to monitor cardiac function. There was a gradual but significant (p less than 0.01) decrease in ejection fraction from 61 +/- 7% (SD) at baseline to 47 +/- 8% after 5 weeks of sodium depletion in association with a fall in left ventricular end-diastolic volume. Ejection fraction did not change in five control dogs fed 55 mEq Na+ per day throughout the 5-week follow-up period. Myocardial contractility did not change in either salt-depleted or control dogs. Plasma norepinephrine levels in the coronary sinus were twice as high in salt-depleted as in control dogs, but there were no significant differences in arterial norepinephrine concentration between the two groups. Therefore, we concluded that reduced ejection fraction during sodium depletion resulted from hemodynamic changes (decreased preload). The excess available norepinephrine failed to increase myocardial contractility, suggesting a dysfunction at the cardiac adrenergic neuroeffector junction.
据报道，慢性钠缺乏会降低麻醉犬的射血分数。我们检验了这样一个假设，即心脏功能的这种降低是由于血流动力学因素或体液因素所致。七只杂种犬被给予低钠饮食（每天少于2毫当量钠），持续5周。采用超声心动图和放射性核素技术监测心脏功能。在钠缺乏5周后，射血分数从基线时的61±7%（标准差）逐渐但显著地（p<0.01）降至47±8%，同时左心室舒张末期容积下降。在整个5周的随访期内，每天喂食55毫当量钠的五只对照犬的射血分数没有变化。缺盐犬和对照犬的心肌收缩力均未改变。冠状窦血浆去甲肾上腺素水平在缺盐犬中是对照犬的两倍，但两组间动脉去甲肾上腺素浓度无显著差异。因此，我们得出结论，钠缺乏期间射血分数降低是由血流动力学变化（前负荷降低）所致。过量的去甲肾上腺素未能增加心肌收缩力，提示心脏肾上腺素能神经效应器连接处存在功能障碍。
