Can radiocardiography using I 131-albumin reliably estimate cardiac output in patients with mild heart failure?
Radiocardiography using wide angle counting is unreliable for directly estimating cardiac output due to interference from extracardiac tissue activity.
A scintillation counter permits the use of very low doses of I 131 -albumin in the recording of radiocardiograms. In the presence of mild heart failure there is a distinct widening of the interval between the humps derived from the right and left heart. Application of the principle of three-compartment serial dilution suggests that this prolongation may be due in large part to reduced cardiac output; however, cardiac dilatation may contribute significantly. Although radiocardiographic tracings represent time concentration curves, wide angle counting over the heart does not permit a reliable direct estimate of cardiac output. The chief source of error lies in the variable contribution of surrounding extracardiac tissue to the total activity which is recorded.
Shipley et al. (Tue,) studied this question.
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