Systolic Function in the Fontan Circulation Is Exercise, but Not Preload, Recruitable
Bibliographic record
Abstract
Background Fontan circulatory failure with impaired systolic function is well documented; however, its mechanisms are not fully understood. The aim of this study was to explore myocardial functional reserve in adolescent patients with Fontan circulation in response to exercise or acute preload increase. Methods The study included 32 patients (median age, 16.7 years; range, 15.4–17.9 years; 12 female patients) with Fontan circulation. Echocardiographic imaging was performed during exercise using a recumbent cycle ergometer and during heart catheterization with a rapid infusion of 0.9% saline infusion at 5 mL/kg body weight. Myocardial peak longitudinal strain (LS) was measured in a four-chamber view during specific time intervals before, during, and after exercise (LS stress ) and volume load (LS cath ). During catheterization, central venous pressure and ventricular end-diastolic pressure were simultaneously recorded. A control group of 16 healthy individuals participated in the exercise test. Results Mean LS stress was less negative for patients than for control subjects ( P ≤ .001 at all stages); however, it significantly improved from −18.4 ± 5.5% at baseline to −22.0 ± 6.5% ( P = .004) at maximal loading. LS stress at maximal loading did not correlate with changes in heart rate. During catheterization, mean LS cath was −19.6 ± 6.0% at baseline and did not improve significantly at 1.00 to 2.00 minutes and at 4.00 to 6.00 minutes after saline infusion. In more than half of the patients, LS cath worsened or improved by less than −2% after saline infusion. Worsening of LS cath correlated with central venous pressure and ventricular end-diastolic pressure in all conditions ( P ≤ .017). There was no difference in LS stress or LS cath between the morphologic right ventricle and the morphologic left ventricle. Conclusions Patients with Fontan circulation demonstrate systolic myocardial functional reserve that can be recruited with exercise stress but not with an acute increase in preload.
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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".