Peak Exercise and Post‐Exercise Recovery Oxygen Uptake and Muscle Oxygenation in Patients with Heart Failure and Preserved Ejection Fraction and Healthy Matched Adults
Bibliographic record
Abstract
Background Exercise intolerance and muscle dysfunction characterize heart failure with preserved ejection fraction (HFpEF). Exercise intolerance, as measured by low peak oxygen uptake (VO 2 ), and slow post‐exercise VO 2 recovery are predictors of mortality. The relationship between peak exercise and recovery VO 2 and muscle oxygenation is unknown in this population. Purpose We tested the hypothesis that post‐exercise VO 2 recovery would be slower in patients with HFpEF compared to controls, and that slower post‐exercise VO 2 recovery would be related to slower muscle oxygenation recovery in patients with HFpEF. Methods Eight patients with HFpEF and 8 healthy age‐and sex‐matched controls completed a stationary cycling peak exercise test to volition fatigue followed by 5‐min of passive recovery. Pulmonary VO 2 (gas exchange via metabolic cart) and muscle oxygenation (tissue muscle oxygenation index, TOI) and deoxygenated hemoglobin (HHb via near infrared spectroscopy) were sampled continuously during the exercise test and recovery. Breath‐by‐breath VO 2 data were linearly interpolated to 1‐s intervals, and both VO 2 and NIRS data were averaged into 5‐s time bins. VO 2 recovery data were mono‐exponentially curve‐fitted (OriginPro, 2017) to yield a recovery time constant (tau) and amplitude change. TOI and HHb at end‐exercise, end‐recovery, and the amplitude change were calculated as 10‐s averages. Statistical analyses included independent t ‐tests and stepwise multiple regression. Significance was accepted at P <0.05. Results Peak VO 2 (15.8 ± 5.9 vs. 24.6 ± 6.6 mL/kg/min, P = 0.011) and VO 2 recovery amplitude (−10.0 ± 4.9 vs. −15.1 ± 4.2 mL/kg/min, P = 0.041) were significantly lower in patients with HFpEF compared to matched controls. However, there were no differences between groups in VO 2 recovery tau (98 ± 43 vs. 71 ± 16 s, P = 0.122) nor in any TOI or HHb parameter (all P >0.05). Stepwise regression by group to predict peak VO 2 yielded a positive regression using both peak‐exercise HHb and VO 2 recovery amplitude in HFpEF ( R 2 = 0.957, P <0.001) but only VO 2 recovery amplitude in controls ( R 2 = 0.947, P <0.001). The same parameters predicted VO 2 recovery tau in HFpEF ( R 2 = 0.940, P = 0.001) with no significant finding in controls ( P >0.05). Conclusions Slower post‐exercise VO 2 recovery in patients with HFpEF compared to their healthy counterparts was not confirmed with these data, although this may be largely influenced by the elevated variance in the HFpEF group, or the mild‐moderate HFpEF severity. Regression analyses suggest that the level of muscle deoxygenation, i.e. , the level of O 2 extraction, during peak exercise may be a more important contributor to peak VO 2 in patients with HFpEF compared to their healthy counterparts. The latter may suggest a muscle‐based limitation in HFpEF not observed in healthy controls. 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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".