Sympathetic Response to 1-Leg Cycling Exercise Predicts Exercise Capacity in Patients With Heart Failure With Preserved Ejection Fraction
Bibliographic record
Abstract
BACKGROUND: In heart failure, sympathetic excess and exercise intolerance impair quality of life. In heart failure with reduced ejection fraction, exercise stimulates a reflex increase in muscle sympathetic nerve activity (MSNA) that relates inversely to peak oxygen uptake (V̇O 2peak ). Whether similar sympathoexcitatory responses are present in heart failure with preserved EF (HFpEF) and relate to V̇O 2peak are unknown. METHODS: In 13 patients with HFpEF (70±6 years), 17 comorbidity-matched controls (CMC; 67±8 years), and 18 healthy controls (65±8 years), we measured heart rate, blood pressure, and MSNA (microneurography) during (1) 7-minute baseline; (2) 2-minute isometric handgrip (40% maximal voluntary contraction) or rhythmic handgrip (50% and 30% maximal voluntary contraction) exercise, followed by 2-minute postexercise circulatory occlusion; and (3) 4-minute 1-leg cycling (2 minutes each at mild and moderate intensity). V̇O 2peak was obtained by open-circuit spirometry. RESULTS: Resting MSNA was higher and V̇O 2peak was lower in HFpEF versus CMCs and healthy controls (all P <0.05). During handgrip, MSNA increased in all groups (all P <0.05); in HFpEF, MSNA was greater than CMCs and healthy controls during HG and postexercise circulatory occlusion at 40% isometric handgrip (all P <0.05) and HG only at 50% and 30% rhythmic handgrip (all P <0.05). During cycling, MSNA (bursts·min −1 ) decreased during mild (−4±4; P =0.01) and moderate (−8±6; P <0.001) cycling in healthy controls, was unchanged during mild (+1±7; P =0.42) and moderate (+2±8; P =0.28) cycling in CMCs, yet increased in HFpEF during mild (+8±8; P <0.001) and moderate (+9±10; P <0.001) cycling. In HFpEF, the change in MSNA during moderate cycling related inversely to relative ( r =−0.72; R 2 =0.51; P <0.01) and percent-predicted ( r =−0.63; R 2 =0.39; P =0.03) V̇O 2peak . No statistically significant relationships were detected in controls ( P >0.05). CONCLUSIONS: In contrast to CMCs, patients with HFpEF exhibit augmented MSNA at rest and during exercise. The magnitude of such paradoxical sympathoexcitation during dynamic cycling relates inversely to V̇O 2peak , consistent with a neurogenic, vasoconstrictor limit on exercise capacity in HFpEF.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".