Potential Deleterious Effect of<i>ß</i>-Adrenergic Stimulation During Warm-Blood Cardioplegia in Rabbit Hearts
Bibliographic record
Abstract
We hypothesized that beta-adrenergic stimulation with isoproterenol during continuous normothermic cardioplegic arrest would enhance the regenerative and regulatory function of the myocardium, resulting in improved cardiac function. We studied isolated rabbit hearts paced at approximately 200 beats per minute (bpm) and perfused by a support rabbit. We measured ventricular pressure over a range of ventricular volumes to determine maximal elastance (Emax) at baseline and 20 and 45 min after discontinuation of cardioplegia. Myocardial oxygen consumption (MVO2) measurements were performed simultaneously and during cardioplegic arrest. Hearts were prospectively randomized to receive either isoproterenol at 0.1 M or control in blinded fashion for 10 min during a 1-h continuous warm-blood cardioplegic arrest. Compared to control hearts, isoproterenol-treated hearts had trends toward longer time to first spontaneous heartbeat (control 141 +/- 43 vs. isoproterenol 200 +/- 74 s, p = .07), and longer time to capture of atrial pacing (control 214 +/- 52 vs. isoproterenol 288 +/- 91 s, p = .06). There was no difference observed in the MVO2 between isoproterenol-treated and control groups of hearts. MVO2 decreased during cardioplegia (p < .01), but there was no significant change in MVO2 during isoproterenol infusion during cardioplegic arrest. There was a significant reduction in Emax compared to baseline 20 min after discontinuation of cardioplegic arrest in both groups (control 7.3 +/- 1.7 mm Hg/microL vs. 9.0 +/- 1.7 mm Hg/microL, p = .02, isoproterenol-treated 6.8 +/- 2.8 mm Hg/microL vs. 8.2 +/- 2.6 mm Hg/microL, p = .01, respectively), with recovery of Emax by 45 min in control hearts only. We conclude that exposure of hearts to isoproterenol during warm cardioplegic arrest has a deleterious effect that may be mediated through mechanisms independent of increased myocardial oxygen consumption.
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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) | 0.001 | 0.000 |
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".