Limits...
Myocardial clearance of technetium-99m-teboroxime in reperfused injured canine myocardium.

Okada DR, Johnson G, Okada RD - EJNMMI Res (2014)

Bottom Line: During coronary occlusion, both the IR30 and IR120 groups demonstrated decreases in percent wall thickening in the ischemia-reperfusion zone (IRZ) as compared with the normal zone (NZ).Final Tc-99m-teboroxime myocardial IRZ/NZ activity ratio was 0.94 ± 0.01 for the IR30 group, compared to 0.80 ± 0.01 for the IR120 group (p < 0.05).Thus, Tc-99m-teboroxime clearance kinetics may be helpful in differentiating normal and minimally injured from severely injured myocardium.

View Article: PubMed Central - HTML - PubMed

Affiliation: Brigham and Women's Hospital, Harvard Medical School, Boston 02446, MA, USA.

ABSTRACT

Background: Recent technical developments using solid-state technology have enabled rapid image acquisition with single photon emission computed tomography (SPECT) and have led to a renewed interest in technetium-99m-teboroxime (Tc-99m-teboroxime) as a myocardial imaging agent. Tc-99m-teboroxime has demonstrated high myocardial extraction, linear myocardial uptake relative to flow even at high flow rates, rapid uptake and clearance kinetics, and differential clearance in the setting of ischemia. However, the myocardial clearance kinetics of Tc-99m-teboroxime in a model of myocardial injury has not been previously reported. Thus, the purposes of this study were to use a canine model of ischemia-reperfusion to (1) compare Tc-99m-teboroxime clearance kinetics in normal and ischemic-reperfused myocardium and (2) assess the utility of Tc-99m-teboroxime clearance kinetics in determining the severity of injury following ischemia-reperfusion.

Methods: Thirteen dogs underwent left circumflex coronary artery (LCx) occlusion for either 30 min (IR30, n = 6) or 120 min (IR120, n = 7), followed by reperfusion, and finally Tc-99m-teboroxime administration 120 min after reperfusion. Microsphere blood flows were determined at baseline, during occlusion, after reperfusion, and before euthanasia. Post-mortem, area at risk was determined using Evans blue dye, and viability was determined using triphenytetrazolium chloride (TTC) staining. The hearts were then subdivided into 24 pieces and Tc-99m activity was measured in a well counter.

Results: TTC-determined infarct area as a percentage of total left ventricular myocardium was 1.1% ± 0.3% for the IR30 group and 7.5% ± 2.9% for the IR120 group (p < 0.05). During coronary occlusion, both the IR30 and IR120 groups demonstrated decreases in percent wall thickening in the ischemia-reperfusion zone (IRZ) as compared with the normal zone (NZ). In the IR30 group, percent wall thickening in the IRZ recovered during the reperfusion phase as compared with the NZ. In the IR120 group, percent wall thickening in the IRZ remained depressed during the reperfusion phase and through the end of the experiment as compared with the NZ. Final Tc-99m-teboroxime myocardial IRZ/NZ activity ratio was 0.94 ± 0.01 for the IR30 group, compared to 0.80 ± 0.01 for the IR120 group (p < 0.05).

Conclusions: Tc-99m-teboroxime demonstrates moderate differential clearance in a model of severe injury with 120 min of ischemia-reperfusion, but only minimal differential clearance in a model of mild injury with 30 min of ischemia-reperfusion. Thus, Tc-99m-teboroxime clearance kinetics may be helpful in differentiating normal and minimally injured from severely injured myocardium.

No MeSH data available.


Related in: MedlinePlus

Myocardial blood flow and Tc-99m ratios. Myocardial blood flow ratios (IRZ/NZ) were determined by microspheres for both study groups at four time points. Gamma well counter-determined myocardial tissue Tc-99m ratios (IRZ/NZ) at the end of 1 h of clearance are also shown. *p < 0.05 as compared to IR30 final Tc ratio; †p < 0.05 as compared to IR120 Tc-99m flow ratio. End, 1 h after tracer administration; IR30, ischemia-reperfusion, 30-min occlusion group; IR120, ischemia reperfusion, 120-min occlusion group; IRZ, ischemia-reperfusion zone; NZ, normal zone; Occl, time of LCx occlusion; Tc-99m, time of Tc-99m-teboroxime administration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4233307&req=5

Figure 4: Myocardial blood flow and Tc-99m ratios. Myocardial blood flow ratios (IRZ/NZ) were determined by microspheres for both study groups at four time points. Gamma well counter-determined myocardial tissue Tc-99m ratios (IRZ/NZ) at the end of 1 h of clearance are also shown. *p < 0.05 as compared to IR30 final Tc ratio; †p < 0.05 as compared to IR120 Tc-99m flow ratio. End, 1 h after tracer administration; IR30, ischemia-reperfusion, 30-min occlusion group; IR120, ischemia reperfusion, 120-min occlusion group; IRZ, ischemia-reperfusion zone; NZ, normal zone; Occl, time of LCx occlusion; Tc-99m, time of Tc-99m-teboroxime administration.

Mentions: Regional myocardial blood flows were determined by the radiolabeled microsphere technique as described above, and flow ratios were calculated for the two experimental groups at four time points (Figure 4). During the control period, flow ratios (LCx/LAD) were near unity and were not significantly different between the two groups. Following LCx occlusion, both groups had significantly reduced flow ratios as compared to their respective baseline values. Following reperfusion and at the end of the study, both groups had flow ratios that were not significantly different as compared to their respective baseline values.


Myocardial clearance of technetium-99m-teboroxime in reperfused injured canine myocardium.

Okada DR, Johnson G, Okada RD - EJNMMI Res (2014)

Myocardial blood flow and Tc-99m ratios. Myocardial blood flow ratios (IRZ/NZ) were determined by microspheres for both study groups at four time points. Gamma well counter-determined myocardial tissue Tc-99m ratios (IRZ/NZ) at the end of 1 h of clearance are also shown. *p < 0.05 as compared to IR30 final Tc ratio; †p < 0.05 as compared to IR120 Tc-99m flow ratio. End, 1 h after tracer administration; IR30, ischemia-reperfusion, 30-min occlusion group; IR120, ischemia reperfusion, 120-min occlusion group; IRZ, ischemia-reperfusion zone; NZ, normal zone; Occl, time of LCx occlusion; Tc-99m, time of Tc-99m-teboroxime administration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4233307&req=5

Figure 4: Myocardial blood flow and Tc-99m ratios. Myocardial blood flow ratios (IRZ/NZ) were determined by microspheres for both study groups at four time points. Gamma well counter-determined myocardial tissue Tc-99m ratios (IRZ/NZ) at the end of 1 h of clearance are also shown. *p < 0.05 as compared to IR30 final Tc ratio; †p < 0.05 as compared to IR120 Tc-99m flow ratio. End, 1 h after tracer administration; IR30, ischemia-reperfusion, 30-min occlusion group; IR120, ischemia reperfusion, 120-min occlusion group; IRZ, ischemia-reperfusion zone; NZ, normal zone; Occl, time of LCx occlusion; Tc-99m, time of Tc-99m-teboroxime administration.
Mentions: Regional myocardial blood flows were determined by the radiolabeled microsphere technique as described above, and flow ratios were calculated for the two experimental groups at four time points (Figure 4). During the control period, flow ratios (LCx/LAD) were near unity and were not significantly different between the two groups. Following LCx occlusion, both groups had significantly reduced flow ratios as compared to their respective baseline values. Following reperfusion and at the end of the study, both groups had flow ratios that were not significantly different as compared to their respective baseline values.

Bottom Line: During coronary occlusion, both the IR30 and IR120 groups demonstrated decreases in percent wall thickening in the ischemia-reperfusion zone (IRZ) as compared with the normal zone (NZ).Final Tc-99m-teboroxime myocardial IRZ/NZ activity ratio was 0.94 ± 0.01 for the IR30 group, compared to 0.80 ± 0.01 for the IR120 group (p < 0.05).Thus, Tc-99m-teboroxime clearance kinetics may be helpful in differentiating normal and minimally injured from severely injured myocardium.

View Article: PubMed Central - HTML - PubMed

Affiliation: Brigham and Women's Hospital, Harvard Medical School, Boston 02446, MA, USA.

ABSTRACT

Background: Recent technical developments using solid-state technology have enabled rapid image acquisition with single photon emission computed tomography (SPECT) and have led to a renewed interest in technetium-99m-teboroxime (Tc-99m-teboroxime) as a myocardial imaging agent. Tc-99m-teboroxime has demonstrated high myocardial extraction, linear myocardial uptake relative to flow even at high flow rates, rapid uptake and clearance kinetics, and differential clearance in the setting of ischemia. However, the myocardial clearance kinetics of Tc-99m-teboroxime in a model of myocardial injury has not been previously reported. Thus, the purposes of this study were to use a canine model of ischemia-reperfusion to (1) compare Tc-99m-teboroxime clearance kinetics in normal and ischemic-reperfused myocardium and (2) assess the utility of Tc-99m-teboroxime clearance kinetics in determining the severity of injury following ischemia-reperfusion.

Methods: Thirteen dogs underwent left circumflex coronary artery (LCx) occlusion for either 30 min (IR30, n = 6) or 120 min (IR120, n = 7), followed by reperfusion, and finally Tc-99m-teboroxime administration 120 min after reperfusion. Microsphere blood flows were determined at baseline, during occlusion, after reperfusion, and before euthanasia. Post-mortem, area at risk was determined using Evans blue dye, and viability was determined using triphenytetrazolium chloride (TTC) staining. The hearts were then subdivided into 24 pieces and Tc-99m activity was measured in a well counter.

Results: TTC-determined infarct area as a percentage of total left ventricular myocardium was 1.1% ± 0.3% for the IR30 group and 7.5% ± 2.9% for the IR120 group (p < 0.05). During coronary occlusion, both the IR30 and IR120 groups demonstrated decreases in percent wall thickening in the ischemia-reperfusion zone (IRZ) as compared with the normal zone (NZ). In the IR30 group, percent wall thickening in the IRZ recovered during the reperfusion phase as compared with the NZ. In the IR120 group, percent wall thickening in the IRZ remained depressed during the reperfusion phase and through the end of the experiment as compared with the NZ. Final Tc-99m-teboroxime myocardial IRZ/NZ activity ratio was 0.94 ± 0.01 for the IR30 group, compared to 0.80 ± 0.01 for the IR120 group (p < 0.05).

Conclusions: Tc-99m-teboroxime demonstrates moderate differential clearance in a model of severe injury with 120 min of ischemia-reperfusion, but only minimal differential clearance in a model of mild injury with 30 min of ischemia-reperfusion. Thus, Tc-99m-teboroxime clearance kinetics may be helpful in differentiating normal and minimally injured from severely injured myocardium.

No MeSH data available.


Related in: MedlinePlus