Abstract 12646: Cellular Mechanisms Underlying Post-operative Atrial Fibrillation in Patients
Bibliographic record
Abstract
Background: Post-operative atrial fibrillation (poAF) after cardiac surgery is a common condition. Although usually self-limiting, poAF increases length of hospital stay and can cause debilitating strokes. A multifactorial pathophysiology involving triggered activity has been hypothesized, but the underlying cellular and molecular mechanisms are unknown and were the subject of this study. Methods: Multicellular action potentials (APs) were recorded with sharp microelectrodes in right atrial trabeculae obtained from sinus-rhythm patients during open-heart surgery and correlated with subsequent non-poAF (Ctl) or poAF status. Membrane currents (whole-cell voltage clamp) and [Ca 2+ ] i (Fluo-3) were also measured in right atrial cardiomyocytes isolated from Ctl and poAF patient samples. Protein expression was quantified by immunoblot. Results: In poAF, AP duration at 90% repolarization (APD 90 ) was slightly prolonged (Fig A), whereas AP amplitude, upstroke velocity, APD 20 , APD 50, and resting membrane potential (RMP) were unchanged. I Ca,L -triggered [Ca 2+ ] i transient (CaT) amplitude was 37% lower in poAF despite greater Ca 2+ influx via L-type Ca 2+ current (integral I Ca,L ), pointing to sarcoplasmic reticulum (SR) dysfunction (Fig B). Na + -Ca 2+ exchange (NCX) activity was similar in both groups (Fig C). SR Ca 2+ content calculated by integrating NCX current (I NCX ) during caffeine-induced SR Ca 2+ release was decreased by 50% in poAF (Fig C), likely because of smaller expression of SR Ca 2+ -ATPase-2a (SERCA2a) and decreased Ser16-phosphorylation (stronger SERCA2a inhibition) of the SERCA2a regulator phospholamban (PLB, Fig D). Expression of cardiac SR ryanodine receptor (RyR2) was reduced by 56% (Fig D), consistent with the reduced CaT amplitude. Conclusions: PoAF is associated with prolonged APD and impaired SR function. These abnormalities likely result in the Ca 2+ mishandling that predisposes patients to triggered activity underlying poAF.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".