Third Heart Rhythm Congress, Birmingham, 19th-22nd October 2008
Bibliographic record
Abstract
Aims: Animal studies have shown an improvement in haemodynamics with LV endocardial (EN) pacing.This may be more effective than conventional biventricular (BIV) pacing alone.We examined the cumulative effect of simultaneous LV EN and BIV pacing on haemodynamics (HD) and LV total activation time (LVTAT) using non-contact mapping (NCM).Methods and results: Eight patients (five with non-ischaemic dilated cardiomyopathy and three with ischaemic cardiomyopathy) and indications for cardiac resynchronization therapy (CRT) underwent invasive electrophysiological (EP) study using NCM of the left ventricle (LV) with a multi-electrode array passed retrogradely via the femoral artery.Electrophysiological catheters were positioned (via the femoral vein) in the high right atrium (HRA), right ventricular apex, and coronary sinus (CS) and (via the femoral artery) to the LV endocardium.The haemodynamic response to pacing was assessed using a pressure wire in the LV to give real-time mean peak dP/dt.A pacing protocol was performed to include AAI pacing, DDD LV EN pacing with 100 ms AV delay, DDD BIV EN (BIV EN) LV pacing (RV apical and LV EN 100 ms post-HRA), DDD BIV epicardial (BIV EPI) pacing (RV apical and CS 100 ms post-HRA), and simultaneous LVEN and BIV EPI pacing (termed 'TRIV'), at heart rate 100 bpm.The LV EN activation pattern was acquired by NCM and the LVTAT was calculated from the virtual unipolar electrograms.Mean baseline dP/ dtmax was 754 + 153 mmHg/s in sinus rhythm, compared with 881 + 85 mmHg/s for LVEN, 880 + 163 mmHg in BIV EN mode, 920 + 166 in BIV EPI mode, and 968 + 210 mmHg in TRIV mode (P ¼ NS).Incremental haemodynamic benefits were evaluated as per cent improvement compared with baseline sinus rhythm (Figure 1).There was an improvement compared with sinus rhythm of 12.4 + 11.7%, 7.1 + 15%, 13.9 + 12%, and 20.4 + 11.5% with LVEN, BIV EN, BIV EPI, and TRIV pacing, respectively.TRIV pacing compared with BIV EN conferred a 13% improvement (P ¼ 0.02).There were trends but no significant change in mean LVTAT (88 + 32 vs. 76 + 23 vs. 75 + 25 vs. 71 + 25 ms) or QRS duration (165 + 38 vs. 140 + 32 vs. 161 + 36 vs. 133 + 34 ms) between LVEN, BIV EN, BIV EPI, and TRIV pacing, respectively.Conclusion: (i) Endocardial TRIV compared with BIV pacing results in additional acute haemodynamic benefit, but this is not solely dependent on the LVTAT.(ii) Mechanical recruitment rather electrical activation may be responsible for this benefit.(iii) Additional endocardial pacing may improve HD in non-responders to CRT.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.192 | 0.115 |
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".