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Viable myocardium identified by reinjection thallium-201 imaging: comparison with regional wall motion and metabolic
N Tamaki1, H Ohtani, Y Yonekura
1Department of Radiology and Nuclear Medicine, Faculty of Medicine, Kyoto University.
Insights
Reinjection thallium-201 scans can identify ischemic but viable myocardium missed by standard scans. This method improves detection of myocardial viability in coronary artery disease patients.
Area of Science:
- Nuclear Cardiology
- Cardiovascular Imaging
- Myocardial Perfusion Imaging
Background:
- Coronary artery disease (CAD) diagnosis relies on assessing myocardial perfusion and viability.
- Standard stress-delayed thallium-201 scans may not detect all ischemic yet viable myocardium.
- Improved imaging techniques are needed for accurate assessment of myocardial viability.
Purpose of the Study:
- To evaluate the efficacy of reinjection thallium-201 scans in identifying ischemic but viable myocardium.
- To compare reinjection scan findings with regional wall motion and metabolic activity.
- To determine if reinjection improves the detection of viable myocardium in CAD patients.
Main Methods:
- 68 patients with CAD underwent routine stress-delayed thallium-201 SPECT scans.
- A reinjection scan with thallium-201 was performed 3 hours after the initial scan.
- Findings were correlated with radionuclide ventriculography (wall motion) and F-18 fluorodeoxyglucose Positron Emission Tomography (FDG-PET) for metabolic activity.
Main Results:
- Reinjection identified new thallium-201 "fill-in" in 27% of patients and 28% of segments not seen on stress-delayed scans.
- Segments with reinjection "fill-in" showed significantly better preserved regional wall motion (p < 0.01).
- All segments with "fill-in" demonstrated persistent FDG uptake on PET, indicating viability (p < 0.05).
Conclusions:
- Reinjection thallium-201 scans can detect ischemic but viable myocardium missed by routine imaging.
- This technique enhances the identification of myocardial viability in coronary artery disease.
- Reinjection thallium-201 SPECT is a valuable tool for assessing myocardial viability in select CAD patients.
Abstract:
Reinjection thallium-201 scans were performed in 68 patients with coronary artery disease after the routine stress-delayed scans for more accurate identification of new fill-in. Following the stress and 3 hour delayed thallium-201 SPECT scans, 40 MBq (1.1 mCi) was injected at rest, and 10 min later, the reinjection SPECT scan was obtained. To determine whether the reinjection method can aid in identifying ischemic but viable myocardium, the thallium-201 findings were compared with regional wall motion on radionuclide ventriculography in 61 patients and with metabolic activity on positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG) in 18 patients. The reinjection scan identified new fill-in which had not been shown on the stress-delayed scans in 6 of the 22 patients (27%) or in 29 of the 105 segments (28%). Regional wall motion was preserved more in the segments that exhibited new fill-in after reinjection (wall motion score = 1.64 +/- 1.29) than in those without new fill-in (score = 2.72 +/- 1.04) (p < 0.01). In the comparative study with FDG-PET, persistent FDG uptake was observed in all segments with new fill-in (20/20 segments: 100%); whereas, it was seen in only 7 of the 28 segments (25%) without new fill-in after reinjection (p < 0.05). We concluded that the segments having new fill-in after reinjection may represent ischemic but viable myocardium. Thus, the reinjection thallium-201 scan should be performed to identify ischemic myocardium which occasionally cannot be detected by the routine stress-delayed thallium-201 scans.