A randomized study of tilt test angle in patients with undiagnosed syncope.
Bibliographic record
Abstract
BACKGROUND: A widely used tilt test protocol involves passive head-up tilt followed by tilt with isoproterenol infusion if necessary. Little is known about the effects of passive tilt angle and duration, duration of isoproterenol infusion or hemodynamic diagnostic criteria. OBJECTIVES: To assess whether tilt angle and duration of isoproterenol infusion affected test outcomes in patients with undiagnosed syncope. PATIENTS AND METHODS: Two hundred one syncope patients (87 men, age 45+/-20 years, median five faints) were randomly assigned to undergo 60 degrees versus 80 degrees tilt for 45 min, then, if necessary, to receive isoproterenol 30 ng/kg/min for 20 min or less. Positive tests ended in presyncope or syncope. RESULTS: Overall, 49% and 71% of patients fainted at 60 degrees and 80 degrees, respectively (P=0.002). In the drug-free stage, 27% and 50% of patients fainted at 60 degrees and 80 degrees, respectively (P=0.0005). In the 119 patients who received isoproterenol, there was no significant difference in the probability of a positive isoproterenol test at 60 degrees and 80 degrees, respectively (31% compared with 43% of exposed patients, P=0.25). Symptoms developed in adults during drug-free tilt linearly with time at both 60 degrees and 80 degrees at 0.6% and 1.1%/min, respectively, while symptoms during isoproterenol tilt reached an asymptote after about 10 min. Rate-systolic pressure products of 7000 mmHg/min and 9000 mmHg/min best distinguished positive from negative passive and isoproterenol stages, respectively. CONCLUSIONS: The positive yield of passive tilt tests is higher at 80 degrees and increases linearly with the duration of tilt. A subsequent 10 min isoproterenol infusion maximizes positive yield. Evidence-based outcome criteria accurately distinguish negative from positive tilt tests.
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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 | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.003 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".