Marked respiratory-related fluctuations in left ventricular outflow tract gradients in hypertrophic obstructive cardiomyopathy: an observational study
Bibliographic record
Abstract
Aims: Left ventricular outflow (LVOT) obstruction in patients with hypertrophic cardiomyopathy (HCM) is dynamic and sensitive to many variables that affect left ventricular preload, afterload, and contractility. The haemodynamic effect of normal respiration on LVOT obstruction has not been described. Methods and results: We examined 20 patients with HCM who were noted to have phasic respiratory variation of LVOT obstruction on initial transthoracic 2D echocardiogram and Doppler examination. LVOT gradients were re-examined with simultaneous recording of a respirometer. LVOT gradients varied widely during the respiratory cycle; peak gradients were uniformly lowest during inspiration (50.8 mmHg + 25.6) and highest during expiration (90.1 mmHg + 41.8). On average, there was 82.4% ± 39.1 (P ≤ 0.0001) incremental change from inspiration to expiration, in the severity of LVOT obstruction. In 11 patients with mitral annulus inflow, LV inflow (preload) was decreased during inspiration. In 16 patients with isovolumic relaxation time and ejection time measurements, decreased left atrial filling pressure was noted during inspiration, consistent with decreased LVOT obstruction. When compared with a control group of 20 HCM patients who did not have respiratory variation, the study group patients were more overweight (mean body mass index cases 35.1 ± 7.3 vs. control group 29.1 ± 5.1, P = 0.0045) and more likely to have sleep-disordered breathing (n = 15 study group, n = 5 control group). Conclusions: Counterintuitive respiratory-related fluctuations in LVOT gradients were observed in this case series of 20 HCM patients. These findings challenge traditional haemodynamic teaching and demonstrate the contribution of LV transmural pressure to LVOT obstruction in certain HCM patients.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".