A different reading from the second scan
A second heart scan changed how many areas initially classified as fixed defects were read in adults who had already undergone routine rest and stress sestamibi imaging. Among 587 heart segments with uptake below 50% on both sestamibi scans, 282, or 48.0%, reached at least 50% uptake on the later thallium scan. At the patient level, 120 of 152 people, or 78.9%, had at least one segment reclassified. No confidence interval was reported for either headline proportion.
The study labeled uptake of at least 50% of maximum myocardial activity as viable and uptake below 50% as non-viable, but the authors describe a change between tracers as diagnostic reclassification, not evidence that the tissue is viable or will recover after revascularization. No independent reference standard for viability was used.
How the comparison was made
This was a single-center retrospective cross-sectional study with ethics approval and a waiver of informed consent because the work used retrospective records. It included adults aged 18 or older with known or suspected coronary artery disease who underwent both imaging protocols during 2013 to 2022. Studies more than three months apart or with significant artifacts were excluded.
The analyzed cohort contained 174 patients and 2,958 myocardial segments. Everyone underwent a one-day rest/stress adenosine sestamibi SPECT myocardial perfusion protocol. Thallium SPECT was performed after a fixed defect was identified, using two pathways chosen mainly according to camera availability and radiotracer procurement logistics.
Researchers compared uptake between the two scans using descriptive summaries, correlation and agreement measures, then used exploratory receiver operating characteristic, or ROC, analysis to examine possible cutoffs. The analysis assessed the added diagnostic information from thallium imaging and whether sestamibi uptake could help identify segments unlikely to be reclassified.
Rest images tracked thallium more closely
The two imaging methods generally agreed, but rest sestamibi uptake tracked thallium more closely than stress uptake. The Spearman correlation was 0.817 for rest and 0.790 for stress. The intraclass correlation coefficient, another agreement measure, was 0.812 for rest and 0.781 for stress.
The observed pattern was similar across the two thallium pathways. Conversion rates were 48.9% versus 46.9% at the segment level and 78.6% versus 79.6% at the patient level.
Rest uptake also performed somewhat better than stress uptake at distinguishing segments that later converted on thallium from those that remained below the thallium threshold. The ROC area under the curve, or AUC, was 0.779 for rest and 0.747 for stress. The study describes both as only fair discrimination, with rest numerically higher.
The search for a simple rule showed a tradeoff. Here, specificity reflects how well a cutoff avoids false alarms, while sensitivity reflects how many of the relevant segments it catches. A rest sestamibi cutoff at 20% of maximum uptake had 99% specificity but 12% sensitivity for persistent below-50% thallium uptake. At 30%, specificity fell to 93% and sensitivity rose to 36%. The lower cutoff was therefore more selective but missed more of the segments that stayed low on thallium.
The authors say these cutoffs are a cautious exploratory gatekeeping benchmark, not a rule for omitting further evaluation. The analysis was derived from one dataset and was not internally or externally validated.
A result with narrow limits
The study's narrow design is central to interpreting the numbers. Thallium SPECT was performed only in patients who already had fixed sestamibi defects. That creates structural selection bias and limits how confidently the conversion rates can be extended to a broader, unselected SPECT population.
Because the study was retrospective and cross-sectional, it can show how uptake classifications differed between the two tracers in this selected group, but it cannot establish whether reclassified segments are truly viable or will recover function after revascularization. The authors explicitly describe the finding as intertracer diagnostic reclassification rather than evidence of viability or functional recovery.
Paper data and sources
Original title: Incremental value of dedicated [201Tl] cadmium-zinc-telluride thallium SPECT over rest/stress [99mTc] technetium sestamibi SPECT MPI: a comparative analysis of fixed perfusion defects
Authors: Teungsang P, Laohamethanee M, Kitkhuandee N et al.
Journal/Repository: Frontiers in cardiovascular medicine
Status: Peer-reviewed
First online: 2026-10-19
DOI: Not available
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