Complexities of Atrial Fibrosis Imaging
Bibliographic record
Abstract
BACKGROUND: Atrial fibrillation is associated with abnormal synchronization of left atrial electrical activity and substantially increased risk of myocardial infarction, stroke and heart failure. OBJECTIVES: C-hydroxyephedrine positron emission tomography [PET]), extracellular volume (by magnetic resonance imaging [MRI]) and endocardial voltage (by voltage mapping), measured in vivo with the extent of left atrial (LA) tissue fibrosis measured post mortem with histology. METHODS: A total of 9 adult female canines were imaged with hybrid PET/MRI. The animals were then implanted with a dual chamber pacemaker, and 1 week later, 6 animals were paced at 220 to 240 beats/min for 5 weeks, whereas the other 3 had sham surgeries. After another week, the animals were again imaged with PET/MRI and had voltage maps taken. The animals were then euthanized, hearts were excised, and the extent and location of LA fibrosis was determined using Masson's trichrome stain. RESULTS: End-diastolic volume and end-systolic volume increased, sympathetic innervation (measured with PET) increased in the left ventricle and LA, interstitial fibrosis increased in the LA, and extracellular volume increased in the LV. There was no significant correlation of the extent of interstitial fibrosis with bipolar voltage, MRI, or fractional uptake rate. A weak, but significant, negative correlation was found between interstitial fibrosis and unipolar voltage. Delayed enhancement failed to detect LA interstitial fibrosis. CONCLUSIONS: Mild-to-moderate LA interstitial fibrosis may be present before affecting LA voltage maps. PET may be promising for detecting early atrial fibrillation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".