Relationship between left ventricular systolic function and plasma clearance of ¹⁶⁹Yb-DTPA in normal and ischemic dogs

Plasma clearance of ¹⁶⁹Yb-DTPA, a heavy chelate metal excreted only by glomerular filtration, was measured serially in a canine model to determine whether the clearance of this substance correlates with left ventricular systolic function. Fourteen anesthetized open-chest dogs were studied. Six dogs (group I) were used to estimate the clearance of ¹⁶⁹Yb-DTPA in the setting of normal left ventricular function. Eight dogs (group II) were used to estimate clearance of ¹⁶⁹Yb-DTPA in the presence of ischemic left ventricular dysfunction. Cardiac output, mean arterial pressure, and plasma levels of ¹⁶⁹Yb-DTPA were measured serially. In group II dogs, area at risk for necrosis was defined using myocardial contrast echocardiography. The change in clearance of ¹⁶⁹Yb-DTPA in group II dogs correlated well with change in cardiac output and area at risk (rc = 0.80 and -0.93, respectively) and was significantly different from group I dogs (p < 0.01). However, changes in clearance of ¹⁶⁹Yb-DTPA in the group II dogs did not correlate well with change in mean arterial pressure (r = 0.26). In conclusion: (1) clearance of ¹⁶⁹Yb-DTPA is constant over time in the absence of ischemic left ventricular dysfunction and derangement of other hemodynamic parameters; (2) changes in clearance of ¹⁶⁹Yb-DTPA correlate well with changes in systolic pump function and left ventricular area at risk in the setting of ischemic left ventricular dysfunction, and (3) clearance of ¹⁶⁹Yb-DTPA is not related to mean arterial pressure.