Kinetic analysis of 125I-iodorotenone as a deposited myocardial flow tracer: comparison with 99mTc-sestamibi.
The goal of this investigation was to assess the accuracy of 7'-Z-[125I]iodorotenone (125I-iodorotenone) as a new deposited myocardial flow tracer and compare the results with those for 99mTc-sestamibi.


METHODS
The kinetics of these two flow tracers were evaluated in 25 isolated, erythrocyte- and albumin-perfused rabbit hearts over a flow range relevant to patients. The two flow tracers and a vascular reference tracer (131I-albumin) were introduced simultaneously as a compact bolus through a port just above the aortic cannula in the absence of tracer recirculation. Myocardial extraction, retention, washout, and uptake parameters were computed from the venous outflow curves using the multiple-indicator dilution technique and spectral analysis.


RESULTS
The extraction of 125I-iodorotenone was much higher than the extraction of 99mTc-sestamibi (0.84 +/- 0.05 vs. 0.48 +/- 0.10, respectively, P < 0.001). 125I-iodorotenone extraction was also less affected by flow than was 99mTc-sestamibi (P < 0.001). Net retention of 125I-iodorotenone was significantly greater than 99mTc-sestamibi net retention at 1 min (0.77 +/- 0.08 vs. 0.41 +/- 0.11, respectively, P < 0.001) and 26 min (0.46 +/- 0.13 vs. 0.27 +/- 0.11, respectively, P < 0.001) after tracer injection. Flow had less effect on 125I-iodorotenone net retention than on 99mTc-sestamibi net retention 1 min after tracer injection (P < 0.04). However, at 26 min, flow had an equivalent effect on the retention of both flow tracers (P < 0.4). The relationship between 125I-iodorotenone and 99mTc-sestamibi washout was complex and depended on elapsed time after isotope introduction and perfusion rate. Reflecting the favorable extraction and retention characteristics of 125I-iodorotenone, both its maximum myocardial uptake and its 26-min uptake were more closely related to flow than were those of 99mTc-sestamibi (P < 0.001 for both comparisons).


CONCLUSIONS
The extraction and retention of 125I-iodorotenone were greater than those of 99mTc-sestamibi, making 125I-iodorotenone the superior flow tracer in the isolated rabbit heart.
Marshall
R C
RC
Center for Functional Imaging, E.O. Lawrence Berkeley National Laboratory, University of California, Berkeley 94720, USA.
Powers-Risius
P
P
Reutter
B W
BW
Taylor
S E
SE
VanBrocklin
H F
HF
Huesman
R H
RH
Budinger
T F
TF
D000818:Animals; D003326:Coronary Circulation; D066298:In Vitro Techniques; D008297:Male; D009206:Myocardium / Q000378:metabolism; D011817:Rabbits; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012402:Rotenone / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D012709:Serum Albumin / Q000378:metabolism; D012711:Serum Albumin, Radio-Iodinated; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon
C421170:7'-iodorotenone; D019275:Radiopharmaceuticals; D012709:Serum Albumin; D012711:Serum Albumin, Radio-Iodinated; D012402:Rotenone; D017256:Technetium Tc 99m Sestamibi