Attenuation of Cardiovagal Baroreflex Gain Resetting During Isometric Handgrip Exercise in Patients With Fontan Circulation
Bibliographic record
Abstract
Exercise intolerance is hallmark in patients with Fontan (FTN) circulation and may be attributed to low baroreflex sensitivity and thus, a low heart rate response for a given exercise intensity. Whether resetting of the cardiovagal baroreflex gain during exercise in FTN is attenuated remains unknown. Accordingly, we tested the hypothesis that the increase in heart rate from rest to exercise would be lower and cardiovagal baroreflex gain resetting attenuated in FTN. 23 patients with FTN (F = 11, M = 12; 14(4) yrs; BMI = 20(6)) were age- and sex-matched to 20 healthy controls (CTL; F = 7, M = 13; 14(4) yrs; BMI = 20(4)) who performed 2-min of isometric handgrip (IHG) exercise at 30-40% maximal voluntary contraction following 2-min of rest. Heart rate (electrocardiogram) and blood pressure (finger cuff photoplethysmography) were measured throughout. Cardiovagal baroreflex gain was determined using the spontaneous sequence method at rest and during IHG exercise. Sequences of 3 or more successive increases or decreases in SBP and heart rate (R-R interval) using a lag of 0, 1, or 2 cardiac cycles when r ≥ 0.7 were included. Comparisons were made using mixed-designs ANOVA or unpaired t-tests and the threshold for significance was set to P < 0.05. In FTN, 36(21) sequences/participant at rest and 35(12) sequences/participant during IHG exercise were analyzed. In CTL, 26(9) sequences/participant at rest and 39(13) sequences/participant during IHG exercise were analyzed. Resting heart rate (FTN = 76(13) vs CTL = 70(8) bpm , P = 0.2208) and SBP (FTN = 109(13) vs CTL = 106(14) mmHg, P = 0.7188) did not differ between groups. Despite similar increase of SBP from rest to IHG exercise (FTN = 5(6) vs. CTL = 8(8) ∆, P = 0.2014), the heart rate increase was attenuated in FTN relative to CTL (3(5) vs 15(10) ∆, P < 0.0001). At rest, cardiovagal baroreflex gain was lower in FTN relative to CTL (14.0(9.8) vs 24.4(6.3) ms/mmHg, P = 0.0001). Further, the baroreflex gain from rest to IHG exercise was attenuated in FTN compared to CTL (-0.2±5 vs. -9±8 ∆, P = 0.0001). The cardiovagal baroreflex gain and heart rate responses were negatively correlated in FTN (r = -0.68, P = 0.0003). Attenuated resetting of the cardiovagal baroreflex gain during exercise contributes to a blunted exercise heart rate in FTN. Heart and Stroke Foundation This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
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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 | 0.000 | 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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".