<b>V</b> alidity of Assessing <i>in vivo</i> Cardiac Contractility Using A “Less‐Invasive” Approach during Mechanical Ventilation: Insights from Small and Large Animal Models
Bibliographic record
Abstract
Background and Aims End‐systolic elastance (E es ) derived from sequential pressure‐volume (PV) loops acquired during inferior vena cava occlusion (IVCO) is the reference for quantification of in vivo left ventricular (LV) contractile performance. Given the challenges associated with midline laparotomy surgeries in animal models and the barriers of performing such measures in clinical practice, a number of single‐beat estimations of LV contractile function have been proposed. Here, we examined the agreement between two single‐beat estimates of E es obtained from basal LV and arterial hemodynamics in rats and pigs and the E es obtained from IVCO (E es(IVC) ). We also tested whether a novel approach of leveraging the respiratory‐induced oscillations in cardiac PV (i.e., changes in intrathoracic pressure) during mechanical ventilation enables a “naturally” occurring change in cardiac preload and the subsequent estimation of E es (E es(RES) ). Methods 38 Wistar rats (300‐350g; aged 10 wks) and 22 Yucatan mini‐pigs (20‐25 kg, aged 8‐12 wks) were used. Once anesthetized and ventilated, animals were instrumented with 1) a LV PV catheter for assessments of LV E es(IVC) during IVCO and LV hemodynamics, and 2) a femoral arterial catheter to record basal systemic hemodynamics. Basal LV and arterial indices, including end‐systolic volume (ESV), end‐systolic pressure (ESP), and arterial systolic blood pressure (SBP), were averaged over a 30s (rats) or 60s period (pigs). E es(IVC) was measured as the slope of end‐systolic PV relationship (ESPVR). From the basal LV and arterial data we then calculated single‐beat estimation of E es(IVC) , including the ESP and ESV ratio (E esSB1 ), and the ESP (SBP × 0.9) and EDV ratio (E esSB2 ). Estimation of E es(RES) was analogous to E es(IVC) however, respiratory‐induced oscillations in cardiac preload, rather than an IVCO, was used to calculate the slope of the ESPVR. Absolute agreement between metrics was examined using intra‐class correlation coefficients (ICC). Results In rats, while we found a moderate agreement between E es(SB1) (ICC = 0.685, P < 0.001), E es(SB2) (ICC = 0.685, P < 0.001) and E es(IVC), there was excellent agreement between E es(RES) and E es(IVC) (ICC = 0.934 P < 0.001). In pigs, although a moderate agreement was observed between E es(RES) and E es(IVC) (ICC = 0.572, P = 0.033), no agreements were noted between E es(SB1) (ICC = 0.352, P = 0.101), E es(SB2) (ICC = 0.320, P = 0.0741) and E es(IVC) . Conclusion Thesefindings demonstrate that the single‐beat estimates of E es show moderate agreement with E es(IVC) in rats. Utilizing the respiratory‐induced changes in cardiac preload during mechanical ventilation, however, may provide a better less‐invasive approach for estimation of cardiac contractile performance, especially in a small animal model.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".