Abstract 18262: Left Ventricle Strain Rate in Children Demonstrates Heart Rate Dependence and a Force-frequency Relationship
Bibliographic record
Abstract
Introduction: In adult pigs and human studies, strain rate (SR) is a valid and reproducible marker of contractility. It is also heart rate (HR) independent, hence lacks force-frequency relationship (FFR). Isovolumic acceleration (IVA) is a proven non-invasive load-independent measure of LV contractility used in research settings. This study sought to assess SR behavior during tachycardia and inotropic stimulation in children, compared to IVA. Methods: Twenty-four patients (median age, 13.9; range 7.8 - 22.5 years) with no structural or functional heart abnormalities were evaluated after a radiofrequency ablation procedure. Echocardiogram was performed at baseline, during atrial pacing and isoprenaline infusion to achieve 130% of baseline HR. Speckle tracking global LV longitudinal SR and tissue Doppler septal IVA were measured. Relationships between HR, SR and IVA were assessed. Percent (%) change and absolute differences between SR and IVA at baseline, pacing and isoprenaline were evaluated. Data are reported as median and interquartile ranges. Results: SR and IVA showed a moderate correlation with HR at baseline (SR: r=-0.68, p=0.0002; IVA: r=0.46, p=0.01), and during pacing (SR: r=-0.56, p=0.003; IVA: r=0.58, p=0.002). Both SR and IVA increased with pacing and isoprenaline (table 1), however the greatest % change was seen during isoprenaline infusion for IVA (p < 0.006) and SR (p < 0.0001). Conclusion: SR enhances with increasing HR in children, demonstrating a relative HR dependence and a FFR. This is contrary to findings in adult studies, thus this study highlights that children show a different LV mechanical response to chronotropic effects and therefore caution should be use when extrapolating of adult findings to children.
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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 | 0.001 |
| 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) | 0.004 | 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".