P6484Invasive and non-invasive characterisation of low gradient aortic stenosis
Bibliographic record
Abstract
Abstract Background Low gradient severe aortic stenosis (LGAS) is associated with unfavourable outcomes when compared to high gradient aortic stenosis (HGAS), yet the contributing pathophysiology is poorly understood. Methods Symptomatic LGAS and HGAS patients undergoing trans-catheter aortic valve implantation (TAVI) underwent 3T stress perfusion cardiac magnetic resonance imaging (CMR) pre-(within 24 hours) and post-(4–6 months) TAVI. Left ventricular (LV) contractility and coronary flow/pressure were measured during hyperaemia and rapid pacing, immediately before and after TAVI, using a conductance LV catheter and dual-pressure and Doppler sensor–tipped guidewire in the mid-left anterior descending coronary artery. Results 24 patients were recruited resulting in 19 suitable datasets (LGAS N=9, HGAS N=10, equally matched for comorbidities and B-natriuretic peptide level). LGAS patients had a smaller LV end diastolic volume index (p=0.035) and lower LV mass index (LVMI) (p=0.037). Pre-TAVI stress global endocardium-epicardium gradient was 0.88±0.09 and global myocardial perfusion reserve (MPR) 2.0±0.48 in 14 patients (6 LGAS and 8 HGAS patients, no difference between groups). Pre-TAVI, baseline coronary data demonstrated lower augmentation pressure (AP, p=0.035) and augmentation index (AIx, p=0.02) in the LGAS group. LGAS patients also exhibited a shorter ejection time (p=0.015), larger forward compression waves during rest, hyperaemia and rapid pacing, and smaller backward expansion waves (BEW) (p=0.001). Lower baseline end systolic pressure (p=0.004), inotropy (dP/dt+, p=0.045), lusitropy (dP/dt-, p=0.069), and stroke work (p=0.019) were observed in the LGAS group. Whilst LV size was smaller the LGAS group, rapid pacing induced a more significant drop in end systolic volume (p=0.045) and ejection fraction (p=0.015) in patients with HGAS. Post-TAVI, the hyperaemic BEW fell sharply (p<0.001), along with coronary VTI (p=0.02), and average pulse velocity (p=0.028), and AP and AIx remained lower (p=0.034 and p=0.031, respectively). The forward expansion wave was reduced in LGAS during rapid pacing. The HGAS group displayed a more profound drop in dP/dt+ (p=0.011) and dP/dt- p=0.014) at rest following intervention. Repeat CMR demonstrated statistically significant reduction in LV size and LVMI (p=0.012 and p<0.001, respectively) with significant increase in 3D global peak radial, circumferential and longitudinal strain (p=0.004, p=0.001 and p=0.018, respectively). Post-TAVI stress global endocardium-epicardium gradient was 0.88±0.13 and MPR 2.46±0.59 (improved from pre-TAVI, p=0.05). There was no difference in remodelling patterns or perfusion between the two groups. Conclusion This is the first study detailing the combined invasive and CMR pathophysiological changes in LGAS. Despite invasive parameters indicating a disease of less severe AS, the level of perfusion abnormality is disproportionate which may in part, relate to their adverse prognosis. Acknowledgement/Funding This research is funded by a Clinical Research Training Fellowship grant from the British Heart Foundation (FS/16/51/32365).
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".