19 * Prognostic utility of microvolt T wave alternans in hypertrophic cardiomyopathy improves when assessed with QRS fractionation
Bibliographic record
Abstract
Introduction: Microvolt T wave alternans (TWA) can be arrhythmogenic in patients with cardiomyopathy, particularly when discordant TWA develops from delayed conduction. We hypothesized that QRS fractionation, as a measure of delayed conduction, will improve the accuracy of TWA in predicting ventricular arrhythmias (VA) in patients with hypertrophic cardiomyopathy (HCM). Methods: We prospectively evaluated 97 HCM patients with a preexisting ICD (age 51±15 yrs, 62 male). High resolution (1kHz sampling) 12-lead Holter recordings were made during sinus rhythm and ventricular pacing at 100, 110 and 120 bpm for 3 minutes at each rate. TWA was measured during ventricular pacing using the spectral method that quantifies the maximum alternans magnitude (Valt) and a noise threshold (k). +TWA was defined as Valt >0 µV with k >3. QRS fractionation was measured in each precordial QRS complex during sinus rhythm using custom software that quantifies the number of low amplitude peaks of <25ms duration (QRSp). Ventricular arrhythmia (VA) was assessed as cardiac arrest or appropriate ICD therapy during followup after ICD implant. Results: Over a median follow-up period of 41 (22-98) months, 20% of patients had VA. +TWA was found in 77% of patients. +TWA (21 vs 19%, p=0.54) and Valt (8.4 [2.5-18.6] vs 6.4 [2.5-10.5] µV, p=0.39) were similar between +VA and –VA patients. Sensitivity of +TWA for distinguishing +VA vs –VA was 79%, but specificity and accuracy were poor at 24 and 35%, respectively. QRSp was greater in +VA vs -VA patients (2 [1-3] vs 1[0-2], p=0.024). ROC curve analysis (area under curve 0.66, p=0.03) showed that a QRSp ≥ 2 was the optimal cutpoint for distinguishing +VA vs –VA (sensitivity 58%, specificity 65%, accuracy 64%). The proportion of patients with both QRSp ≥ 2 and +TWA was 31%. QRSp ≥2 and +TWA together achieved higher specificity (74%) and accuracy (70%) with similar sensitivity (53%) when compared to QRSp ≥ 2 alone. Patients with both QRSp ≥ 2 and +TWA had greater VA events compared to those without (33 vs 13%, p=0.03). Conclusions: In HCM, the presence of both QRS fractionation and +TWA identifies patients at risk of VA more accurately than either measure alone. The conduction delay causing QRS fractionation may promote more arrhythmogenic discordant TWA; thereby increasing arrhythmia vulnerability.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 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".