Pulmonary uptake of technetium-99m-sestamibi induced by dipyridamole-based stress or exercise.

UNLABELLED: 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.

Dynamic renal imaging with technetium-99m-sestamibi in hypertension: potential for assessment of renovascular disorders.

UNLABELLED: The myocardial perfusion agent, 99mTc-sestamibi (MIBI), offers the potential to combine renal and myocardial imaging because of high initial renal extraction and significant renal clearance. METHODS: Dynamic renal imaging was performed during rest MIBI injections in 3 normal subjects (NS) and 91 patients referred for cardiac assessment. Ten served as normal controls, and 81 were hypertensive. Renal activity of MIBI during the first transit, uptake and excretory phases of the study was quantified. These data were compared with the normal kinetics of 99mTc-diethylenetriaminepentaacetic acid (DTPA) in concurrent studies. RESULTS: With MIBI, clear definition of the kidneys was possible on all phases in most studies; occasionally, overlap with liver or spleen provided a minor problem. Renal MIBI activity reached levels 70% greater than DTPA during first transit and remained higher throughout the study; renal/background activity ratios were also higher on the MIBI study (p < 0.001). During the excretory phase with MIBI, hepatic and splenic activity did not decline, and gut activity increased. In NS, 40% of the total activity was excreted in the urine in 1 hr; urinary MIBI clearances approximated creatinine clearance. Asymmetry in initial renal uptake was seen in 14 of 81 hypertensive patients (17%); renal cysts and aortic dilatation could also be identified. CONCLUSION: These data suggest that ancillary renography during rest injection of MIBI could be a useful addition to the cardiovascular assessment of selected patients.