Effects of chronic, rapid right atrial pacing on cardiac hemodynamics and myofibrillar ATPase activity in piglets.
Bibliographic record
Abstract
OBJECTIVES: To determine whether chronic, rapid right atrial pacing in newborn neonatal piglets has any effects on cardiac hemodynamics, and whether these changes are associated with intrinsic alterations in cardiac contractile potential as shown by cardiac myofibrillar calcium ATPase activity. BACKGROUND: Although many studies have examined aspects of heart function in models of supraventricular tachycardia, far less is known about its effects in neonatal animals. It is thought that rapid pacing induces a dilated cardiomyopathy in immature pigs. ANIMALS AND METHODS: Two-week-old piglets underwent rapid right atrial pacing (250 beats/min) for 10 days, and their cardiac hemodynamic response was monitored. To obtain subcellular mechanistic information regarding systolic dysfunction, cardiac myofibrils were isolated and calcium adenosine triphosphatase activity was measured. RESULTS: Control piglets had a heart rate of 185 beats/min at the end of the experimental period. Pulmonary artery flow, pulmonary artery flow index and left ventricular end-diastolic diameter were unchanged as a function of rapid, chronic right atrial pacing. Aortic pressure decreased in the paced piglets. Left atrial pressure increased approximately threefold in the paced animals. Left ventricular end-systolic diameter was also significantly higher after pacing, but left ventricular end-diastolic diameter was unchanged. Left ventricular shortening fraction was depressed approximately 50%. Myofibrillar calcium adenosine triphosphatase activity was significantly depressed as a function of pacing. CONCLUSIONS: Neonatal piglets undergoing chronic supraventricular tachycardia exhibit systolic dysfunction in the absence of dilation. The depression in contractile protein calcium adenosine triphosphatase activity provides information at a subcellular level regarding the mechanism responsible for this cardiomyopathy.
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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 | 0.001 |
| 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".