Cardiac Restitution, Ion Channels, and Racehorses: A Naturally Occurring Model of Sudden Cardiac Death in Athletes
Notice bibliographique
Résumé
Sudden cardiac death is the second most common cause of athletic mortality in both elite human and equine athletes. Racehorses perform at extremely high exercise intensities with maximal heart rates and aerobic capacities exceeding those of human athletes. A predisposition to life-threatening arrhythmias unmasked by athletic activity, is suspected to underlie sudden cardiac death in both species and predicting risk is critical for the health and safety of athletes. Cardiac restitution ratio (CRR) is used as a measure of arrhythmia risk at rest in humans and represents the ability of cardiomyocytes to recover between successive action potentials. CRR can be calculated as QT/TQ on an electrocardiogram (ECG) and has never been investigated during high intensity exercise. The objectives are to characterize changes in the QT interval and CRR in normal racehorses to establish a risk threshold and to identify unique ion channels in the equine myocardium that may be involved in accommodation of the cardiac action potential to changes in heart rate. It is hypothesized that CRR will be highest during exercise periods when sudden cardiac death most frequently occurs, and that the horse will exhibit differences in myocardial ion channel expression. Over 3800 cardiac cycles obtained from ECGs of 42 racehorses were analysed using custom software to calculate RR interval, QT interval, and CRR. Instantaneous heart rate ranged from 26 beats per minute at rest to 293 during racing. Interquartile ranges (median) of QT interval and CRR during maximal effort were 176-198 ms (186 ms) and 2.1-3.3 (2.5), respectively. CRR was highest during race exercise; the first 30 seconds of cardiac deceleration following the race; and sporadically during non-race exercise, corresponding to periods when sudden death most frequently occurs. Preliminary multivariable regression analyses revealed numerous significant associations for both QT interval and CRR, including with exercise period, RR interval, racing gait, sex, and age. Apparently healthy horses during exercise routinely displayed CRRs exceeding the described arrhythmogenic threshold of 1, established in humans. Left ventricular free wall myocardium was obtained from horses of typical racing breeds. A combined proteomic approach using mass spectrometry and immunoblotting revealed presence of several ion channels not known or not known to be significant to the ventricular action potential in humans, including Kv1.5 and Kir6.2, and different primary isoforms of sodium and calcium channels. These findings identify unique aspects of myocardial electrophysiology in horses with potential implications for sudden cardiac death in human athletes. Funding graciously provided by Equine Guelph. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».