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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 area at risk and infarcted area. This figure illustrates the percentage of the total left ventricle at risk as determined by Evans blue dye, the percentage of the area at risk that ultimately infarcted as determined by TTC staining, and the percentage of the total left ventricle that ultimately infarcted as determined by TTC staining. *p < 0.05 as compared to IR30. AAR, area at risk; INF, infarcted area; IR30, ischemia-reperfusion, 30-min occlusion group; IR120, ischemia-reperfusion, 120-min occlusion group; TLV, total left ventricle.
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Figure 2: Myocardial area at risk and infarcted area. This figure illustrates the percentage of the total left ventricle at risk as determined by Evans blue dye, the percentage of the area at risk that ultimately infarcted as determined by TTC staining, and the percentage of the total left ventricle that ultimately infarcted as determined by TTC staining. *p < 0.05 as compared to IR30. AAR, area at risk; INF, infarcted area; IR30, ischemia-reperfusion, 30-min occlusion group; IR120, ischemia-reperfusion, 120-min occlusion group; TLV, total left ventricle.

Mentions: Figure 2 shows the area at risk as determined by Evans blue staining and the percent infarcted myocardium as determined by TTC staining for the two experimental groups. The area at risk expressed as a percentage of total left ventricular myocardium was 32.7% ± 2.5% for the IR30 group and 34.2% ± 6.0% for the IR120 group (p = ns). The infarcted area as a percentage of the area at risk was 4.0% ± 0.9% for the IR30 group, compared with 23.5% ± 6.9% for the IR120 group (p < 0.05). The infarcted 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). Figure 3 shows the TTC/Evans blue images from representative dogs.


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

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

Myocardial area at risk and infarcted area. This figure illustrates the percentage of the total left ventricle at risk as determined by Evans blue dye, the percentage of the area at risk that ultimately infarcted as determined by TTC staining, and the percentage of the total left ventricle that ultimately infarcted as determined by TTC staining. *p < 0.05 as compared to IR30. AAR, area at risk; INF, infarcted area; IR30, ischemia-reperfusion, 30-min occlusion group; IR120, ischemia-reperfusion, 120-min occlusion group; TLV, total left ventricle.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Myocardial area at risk and infarcted area. This figure illustrates the percentage of the total left ventricle at risk as determined by Evans blue dye, the percentage of the area at risk that ultimately infarcted as determined by TTC staining, and the percentage of the total left ventricle that ultimately infarcted as determined by TTC staining. *p < 0.05 as compared to IR30. AAR, area at risk; INF, infarcted area; IR30, ischemia-reperfusion, 30-min occlusion group; IR120, ischemia-reperfusion, 120-min occlusion group; TLV, total left ventricle.
Mentions: Figure 2 shows the area at risk as determined by Evans blue staining and the percent infarcted myocardium as determined by TTC staining for the two experimental groups. The area at risk expressed as a percentage of total left ventricular myocardium was 32.7% ± 2.5% for the IR30 group and 34.2% ± 6.0% for the IR120 group (p = ns). The infarcted area as a percentage of the area at risk was 4.0% ± 0.9% for the IR30 group, compared with 23.5% ± 6.9% for the IR120 group (p < 0.05). The infarcted 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). Figure 3 shows the TTC/Evans blue images from representative dogs.

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