THE PRESSURE-VOLUME LOOP REVISITED
Bibliographic record
Abstract
UNLABELLED: Our previous studies indicate that left ventricular end-systolic pressure-volume relations (ESPVRs) or elastance (Ees) are not reduced in studies where expected reductions of contractility should be found (i.e., heart failure, stunning, and endotoxemia). The present study was done to assess whether this phenomenon is due to a particular load sensitivity of elastance, rendering this index inappropriate as a measurement of contractility in pathologic states in vivo. METHODS AND RESULTS: Analysis of previously generated data revealed an increased ESPVR in stunned hearts, in pigs made endotoxemic, and in hearts rapidly paced. After inducing acute heart failure by microembolization, the ESPVR was increased when assessed using linear relations but reduced when assessing ESPVR by a curvilinear algorithm. To further evaluate the effect of different load alterations on ESPVR, this relation was generated by (i) inferior vena caval occlusions (VCOs); (ii) gradually occluding the descending aorta (pressure interventions); and (iii) rapidly infusing blood (120 mL) into the left atrium (volume increments). The load protocol was applied in 5 pigs, before and after the left ventricle was stunned by 11 brief left main coronary artery occlusions/reperfusions (accumulated ischemia 20 min affecting 81% of the left ventricle). Correlation coefficients for left ventricular elastance ranged from 0.93 to 0.99 in all the 3 types of loading interventions. Despite significant reductions in stroke volume, stroke work, and dP/dtmax, VCO-calculated linear and curvilinear Ees increased 90 min after stunning (55% +/- 4% and 94% +/- 6%, respectively). Linear Ees during pressure interventions decreased 36% +/- 1%, whereas curvilinear Ees decreased 33% +/- 3%. During volume infusions, linear Ees decreased 27% +/- 2%. We achieved the same results after blocking the baroreceptor reflexes using hexamethonium. CONCLUSIONS: The Ees is particularly load dependent and will reflect load interventions more than the inotropic state of the cardiac muscle. A VCO-generated Ees increase could be an unmasking of a pronounced preload sensitivity in failing myocardium.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.006 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.003 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.006 | 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".