Ischemic Heart Failure Etiology Affects Phase II VO2 Kinetics in Heart Transplant Recipients
Bibliographic record
Abstract
Heart transplant recipients (HTR) have severely reduced peak aerobic power (VO2peak) and delayed oxygen (VO2) kinetics. The role that pre-transplant heart failure etiology has on VO2peak and VO2 kinetics in HTR has not been well studied. PURPOSE: The objective of this study was to examine the role that heart failure etiology has on VO2peak and phase II VO2 kinetics in HTR. We hypothesized that HTR with pre-transplant ischemic heart failure (I-HTR) would have a reduced VO2peak and attenuated phase II VO2 kinetics compared with HTR with pre-transplant non-ischemic heart failure (NI-HTR). METHODS: 11 clinically stable I-HTR (mean ± SD, age: 65 ± 5 years; 9 males and 2 females) and 6 NI-HTR (age, 46 ±11 years; 4 males and 2 females) were included in this study. All participants performed an incremental exercise test on a cycle ergometer during which time expired gases were collected. On a separate day, participants completed step-transition exercise to 25% VO2peak that lasted ∼5 minutes. This intensity was below the ventilatory threshold. Phase II VO2 kinetics was estimated with a monoexponential model that included a time delay, amplitude term, and a time constant. Data were analyzed using analysis of variance. The alpha level was set “a priori” at p <0.05. RESULTS: No significant difference was found for VO2peak between the groups (I-HTR: 1.8 ± 0.6 L/min versus NI-HTR: 1.8 ± 0.7 L/min, p> 0.05). The phase II VO2 time constant was 45 ± 18 seconds for I-HTR and 25 ± 11 seconds for NI-HTR (p <0.05). The time delay was 52 ± 23 seconds and 61 ± 23 seconds (p >0.05) for I-HTR and NI-HTR, respectively. Finally, the amplitude response was 0.34 ± 0.15 L/min (I-HTR) and 0.41 ± 0.26 L/min (NI-HTR, p >0.05). CONCLUSION: I-HTR have a slower phase II VO2 time constant compared to NI-HTR despite no differences in VO2peak. The delayed response may be related to pre- and post-transplant abnormalities in cardiovascular and skeletal muscle function that result in reduced oxygen delivery and/or skeletal muscle oxygen utilization. Future studies are required to determine if exercise training can reverse the abnormal VO kinetics found in I-HTR.
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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".