Affiliation:
1. Department of Internal Medicine, Veterans Administration Medical Center, Tucson 85723.
Abstract
The cardiovascular system of hypothyroid, normal, and hyperthyroid rats was studied by evaluation of the peripheral venous circulation and left ventricular (LV) systolic and diastolic performance in rats. Cardiac index (CI) and CI during a volume load were measured in open-chest rats. When compared with control, hypothyroid rats showed a decrease in heart rate, aortic pressure, LV systolic pressure, first derivative for LV pressure (LV dP/dt), CI, and CI during a volume load. LV pressure-volume relation was shifted to the right, muscle stiffness was unchanged, and LV relaxation was prolonged. There was a decrease in mean circulatory filling pressure (MCFP) to 6.3 +/- 0.2 from 7.6 +/- 0.2 mmHg in control rats. This was associated with an 11% decrease in unstressed vascular volume and 12% decrease in total blood volume but no change in venous compliance. In hyperthyroid rats there was an increase in heart rate, LV systolic pressure, LV dP/dt, CI, and CI during a volume load. LV chamber stiffness was increased, but muscle stiffness and LV relaxation were unchanged. There was an increase in MCFP to 9.5 +/- 0.3 mmHg and a decrease in venous compliance to 2.65 +/- 0.12 compared with 3.20 +/- 0.09 ml.mmHg-1.kg-1 in control rats. Unstressed vascular volume and total blood volume were unchanged. In conclusion, hyperthyroid rats have augmented LV systolic function and altered diastolic function which, combined with changes in the venous circulation, result in increased venous return and thus cardiac output. In hypothyroid rats both LV systolic and diastolic function are altered. When combined with changes of the venous circulation the changes result in a decrease in cardiac output.
Publisher
American Physiological Society
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine,Physiology
Cited by
46 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献