Cardiovascular Responses to the Exercise Pressor Reflex in Pediatric Heart Transplant Recipients
Bibliographic record
Abstract
Pediatric heart transplant recipients (HTR) have reduced exercise tolerance despite normal systolic ventricular function. A slower heart rate adaptation to exercise in HTR due to cardiac denervation is commonly observed in HTR patients, which explains, in part, the exercise intolerance. We tested the hypothesis that the cardiovascular response to exercise pressor reflex activation from handgrip exercise would be blunted in HTR. Methods Six pediatric HTR (3f/3m; mean±SD, 10±3 yrs) and five healthy‐matched controls (CTL; 3f/2m; 10±2 yrs) were studied. After 3 min of resting baseline, subjects performed 2 min of isometric handgrip (HG) exercise at 40% maximal voluntary contraction, followed by 3 min post‐exercise circulatory occlusion (PECO). Beat‐by‐beat mean arterial pressure, heart rate, and modelflow stroke volume and cardiac output were recorded. Data were analysed as the change (Δ) from rest using two‐way repeated measures ANOVA (2 × 3; group × condition) and Holm‐Sidak multiple comparisons analysis. Significance was accepted at P <0.05. Results Mean arterial pressure increased in HTR (Δ17±15 mmHg) and CTL (Δ13±16 mL) during HG ( P <0.001) and remained elevated above baseline during PECO (HTR: Δ10±10 mmHg; CTL: Δ11±9 mmHg; P <0.05), with no between group differences. Heart rate did not significantly increase during HG in HTR (Δ4±5 bpm, P =0.235) but did in CTL (Δ14±11 bpm, P <0.001), and was 9 bpm lower in HTR vs CTL ( P =0.005). Heart rate was not different during PECO from rest in HTR and CTL. Stroke volume increased in HTR (Δ3±1 mL) and CTL (Δ3±3 mL) during HG ( P <0.001) and remained elevated above baseline during PECO (HTR: Δ3±2 mL; CTL: Δ4±3 mL; P <0.001), with no between group differences. Cardiac output did not significantly increase during HG in HTR (Δ0.34±0.21 L/min, P =0.074) but did in CTL (Δ0.71±0.54 L/min, P <0.001), and was 0.37 L/min lower in HTR vs CTL ( P =0.035). Cardiac output was not different during PECO from rest in HTR and CTL. Conclusions Owing to the impaired heart rate response during handgrip exercise, cardiac output was lower in pediatric HTR compared to healthy‐matched controls in response to exercise pressor reflex activation. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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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) | 0.001 | 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".