BLUNTED SKELETAL MUSCLE MICROVASCULAR BLOOD FLOW IS A POTENTIAL UNDERLYING MECHANISM FOR EXERCISE INTOLERANCE IN ADULTS WITH ATRIAL FIBRILLATION
Bibliographic record
Abstract
INTRODUCTION & AIMS Approximately 45% of adults living with atrial fibrillation (AF) experience exercise intolerance (EI). However, the mechanisms of EI in AF are not well understood. We aimed to determine whether impaired skeletal muscle microvascular blood flow (MBF), not macrovascular, responses to peak exercise is a plausible explanation for EI in adults with AF. METHODS Adults with AF and healthy controls completed a Modified Bruce treadmill protocol to obtain peak oxygen uptake (V̇O2peak). Skeletal muscle microvascular blood volume, velocity, and flow in the vastus lateralis muscle was assessed using contrast enhanced ultrasound. Superficial femoral artery diameter, blood velocity and flow were assessed using 2D and Doppler ultrasound. Vascular measurements were collected at rest, immediately post-exercise, and 30 minutes post-exercise. RESULTS Nine adults with AF (age: 62±5 years, 66% females, BMI: 29.7±4.2 kg/m2, V̇O2peak: 24.3±6.1 mL/kg/min) and seven controls (age: 63±10 years, 57% females, BMI: 26.7±1.7 kg/m2, V̇O2peak: 31.0±7.5 mL/kg/min) participated. One participant was in AF during testing. A significant group x time interaction in skeletal muscle MBF (p=0.04) and near significant interaction in blood volume (capillary recruitment, p=0.08) was observed. Post-hoc analysis revealed adults with AF had a significantly blunted MBF at 30 minutes post-exercise (-1.3 fold versus control, p=0.01) and reduced microvascular blood volume (i.e. capillary recruitment) pre- and 30 minutes post-exercise (-6.6 fold [p=0.01] and -9.4 fold [p=0.01] versus controls). No differences were observed for changes in skeletal muscle microvascular blood velocity, or femoral artery diameter, blood velocity or flow. CONCLUSION Despite similar femoral artery blood flow responses, adults with AF have lower skeletal muscle MBF responses to peak exercise which may be driven by a reduced capillary recruitment in the skeletal muscle. Our findings provide new insight into vascular complications which may partially explain EI in those with AF.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.003 |
| 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 | 0.001 | 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".