The two-catheter technique in indicator-dilution cardiovascular studies.

Indicator dilution technique is more widely used during cardiac catheterization for the diagnosis and rough estimate of the size of intracardiac shunts and valvular regurgitation (Korner and Shillingford, 1955; Fox and Wood, 1957; Swan and Wood, 1957; Woodward et al., 1957; Shillingford, 1958; Carter et al., 1959; Carleton et al., 1960; Jose et al., 1960). Evans blue dye (T-1824) has long been used to record dye dilution curves, being of special value in the diagnosis of right-to-left shunts (Falholt and Fabricius, 1958). However, this dye has the disadvantage of accumulation in human tissue and is influenced by the blood oxygen saturation; therefore, it cannot be used to record curves with venous blood. With the development of a new dye by Fox and Wood (1957) (tricarbocyanine dye II-cardiogreen)* it became possible to record indicator dilution curves from the right heart or venous circulation since this dye is not influenced by oxygen saturation of the blood. In the present study, we intend to report the usefulness of the dye dilution curve from the right side of the heart, using a two-catheter technique in patients with valvular regurgitation and left-to-right shunt in whom the blood oxygen saturation did not reveal an intracardiac shunt or adequately did not locate it. The dye dilution curve with injection into the right heart and sampling at the systemic artery does not provide information regarding location of a left-to-right shunt. It may but suggest the presence of a shunt; and in many cases it does not differentiate a curve due to valvular regurgitation from a curve of a patient with left-to-right shunt. In both circumstances, there is a prolonged disappearance curve with absence of a small recirculation curve. Thus, in order to make the indicator dilution technique useful in the diagnosis of a left-to-right shunt, injections and sampling sites have to be in the right heart.