Third Heart Rhythm Congress, Birmingham, 19th-22nd October 2008
Bibliographic record
Abstract
The pathophysiological basis of Brugada syndrome (BS) remains contentious. Characterized by a triad of right bundle branch block pattern in V1 -V3, coved ST elevation in right precordial leads, and sudden cardiac death, it remains one of the leading causes of sudden cardiac death in the young. Two principal mechanisms are thought to be responsible for BS: (i) right ventricular (RV) conduction delay and (ii) RV subepicardial action potential shortening. To date, there has been no report of in vivo high-density mapping of the Brugada heart in man. We set out to characterize the electrophysiological arrhythmogenic substrate in human RV in BS using high-density endocardial mapping. This study evaluated the conduction and repolarization properties of the RV in BS subjects. Methods and results: Thirty patients (BS n 18; controls n 12) were studied using non-contact mapping. A non-contact mapping array was deployed in the RV of BS subjects and controls. A detailed geometry of the chamber was created by a 5 kHz locator signal emitted by the drag catheter and received by two ring electrodes on the array. Right ventricular pacing was established using a pacing lead placed in the RV apex. Right ventricular pacing was established at a constant coupling interval of 600 and 400 ms. After a steady state had been reached following 3 min of pacing, an extrastimulus (S2) was introduced after a train of 10 beats. The coupling interval of S1 -S2 was decremented by 40 ms every cycle from steady state to 400 ms, by 20 ms every cycle to 300 ms and by 5 ms every cycle from 300 ms until the ventricular effective refractory period (ERP) was encountered. Conduction and restitution curves were generated from multiple sites within the RV, RV outflow tract (RVOT), and RV apex. Significant regional conduction delays in the anterolateral free wall of the RVOT of Brugada patients were identified. The mean increase in delay was 67% greater in this region compared with the body and apex (P 0.027). Local conduction velocity was also maximally reduced in this area: 0.33 + 0.02 mm/ms in BS vs. 0.52 + 0.04 mm/ms (P , 0.001) in controls. The uniformity of wavefront propagation as measured by the coefficient of linear regression r 2 was 0.94 + 0.01 for BS vs. 0.84 + 0.03 for controls (P , 0.001) (Figure The odds ratio of BS hearts having any RV segment with S max . 1 was 3.79 vs. controls (P , 0.05). Five episodes of provoked VT arose from wavebreaks originating from RVOT slow conduction zones in five separate patients. Conclusion: Marked regional endocardial conduction delay and heterogeneities in repolarization exist in BS. Wavebreak in areas of maximal conduction delay appears to be critical in the initiation and maintenance of VT with degeneration into VF in this condition. Mapping to identify and direct therapies to these RVOT sites may enable the prevention of lethal arrhythmia in BS.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.002 |
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 teacher head, 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".