On poststress images with 99mTc-sestamibi (MIBI), increased lung uptake of the radiotracer may reflect severe or multivessel coronary artery disease.
Methods: We measured pulmonary/myocardial ratios of MIBI at standardized times on immediate poststress acquisitions and on delayed tomographic acquisitions. In 1500 sequential patients referred for rest and stress myocardial tomography, ancillary planar images were obtained 4 min postinjection at peak stress with exercise, either alone (exercise, n = 674), or after intravenous dipyridamole (dipyridamole, n = 826).
Results: Based on 95% confidence limits in the angiographic normals, high values for immediate acquisitions were found in 17% of dipyridamole studies and 15% of exercise studies. High values for delayed acquisitions were found in 10% of dipyridamole studies and 9% of exercise studies. For both stress modes, increased values were related (p < 0.001) to ischemic perfusion defects for immediate images, to fixed defects for delayed images, and to ventricular dilation in both cases. By logistic regression analysis, body weight and history of infarction were also minor independent determinants (p < 0.01) of delayed acquisitions. In a subset of 250 cases with angiographic correlation (163 with dipyridamole; 87 with exercise), immediate lung uptake was highly correlated with ventricular dysfunction and with coronary stenoses (p < 0.0001). Relationships were similar to those in a historic control series imaged with 201TI. Values for delayed poststress images, and for corresponding rest images, showed strong relationships to ventricular dysfunction but not to stenosis severity.
Conclusion: The relationships of immediate lung uptake to scintigraphic and angiographic disease patterns suggest its possible diagnostic use as an indicator of stress-induced ventricular decompensation.