Arterial Blood Flow Patterns in Human Subjects and Their Effect on Indicator Dilution Curves

Indicator dilution curves obtained from various systemic arterial sampling sites are commonly used for analysis of blood flow, cardiac shunts and valvular regurgitation, and for study of segments of the blood volume. It is generally assumed that the contour of such curves is largely determined by the passage and dilution of the indicator in the central circulation and that changes occurring during arterial passage are minor and predictable on the basis of the expected velocity of arterial blood flow and the distances of the commonly used sampling sites from the aortic root. Although it is accepted that quantification of blood flow is unaffected by changes in curve contour so long as the first circulation of indicator can be identified, the estimation of other parameters available from curve analysis may be significantly influenced by the validity of the above assumption. Beard, Wood and Clagett (1) and Fox, Sutterer and Wood (2) have demonstrated considerable differences in contour as well as appearance time of curves obtained from the femoral (FA), radial (RA) and dorsalis pedis arteries. The first study showed delay in the FA components in coarctation of the aorta as compared with the RA curve, whereas the latter study noted delay and skewing of the RA or pedal curve as compared with the FA curve. The FA curves were similar in contour to the abdominal aortic curves in normal subjects. During preliminary studies of an investigation which attempted to quantitate valvular regurgitation by comparison of indicator dilution curves recorded simultaneously from the pulmonary artery (PA) and a systemic artery, we noted that in normal subjects only FA curves consistently resembled the PA curve while those recorded from the