Effect of coronary artery disease on myocardial blood flow during passive heat stress
Notice bibliographique
Résumé
INTRODUCTION. Extreme heat is associated with a greater risk of cardiovascular mortality in older adults. However, the pathophysiology that links extreme heat and cardiovascular mortality remains unknown. One possibility is that myocardial oxygen requirements during heat exposure surpass the capacity for myocardial oxygen delivery, thereby predisposing to myocardial ischemia. This may notably occur in individuals with coronary artery disease (CAD), because it reduces the capacity of the coronary arteries to dilate (i.e., coronary flow reserve). However, it is unknown to what extent myocardial blood flow (MBF) increases during heat exposure and whether this increase is altered by CAD. OBJECTIVE. This study tested the hypothesis that passive heat stress increases myocardial blood flow in older adults and that this increase is attenuated in older adults with CAD. METHODS. Healthy older adults (n=19, 68 ± 7 years) and older adults with CAD (n=12, 72 ± 6 years) were passively heated (water-perfused suit) until rectal temperature increased 1.5°C above baseline values. Myocardial blood flow was measured at baseline and at each 0.5°C increment in rectal temperature during heating by positron emission tomography following intravenous infusion of 82-Rubidium. Heart rate (ECG) and blood pressure (automated auscultation) were also measured to calculate rate pressure product (heart rate × systolic blood pressure). MBF reserve (MFR) was calculated by dividing the MBF at 1.5°C by baseline MBF. Adults with CAD were asked to withhold β-blockers, calcium channel blockers and nitroglycerin for 24h prior to the study. RESULTS. At a 1.5°C increase in core temperature, myocardial blood flow increased from 0.85 ± 0.20 to 1.51 ± 0.40 mL/min/g in healthy older adults and from 0.87 ± 0.19 to 1.37 ± 0.48 mL/min/g in adults with CAD. The change in myocardial blood flow at a 1.5°C increase in rectal temperature did not differ between groups (healthy: 0.66 ± 0.31 mL/g/min, CAD: 0.49 ± 0.42 mL/g/min, p=0.25. Furthermore, healthy adults and adults with CAD displayed a similar MFR at an increase in rectal temperature of 1.5°C (healthy: 1.8 ± 0.4 vs. CAD: 1.6 ± 0.6, p=0.25). CONCLUSION. These results demonstrate that passive heat stress increases myocardial blood flow nearly 1.6 times in older adults, and that this increase is not affected by CAD. These results will help determine if the increase in myocardial blood flow during passive heat exposure is sufficient to predispose to myocardial ischemia in individuals with low coronary flow reserve. Canadian Institutes for Health Research, Montreal Heart Institute Foundation. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology 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 ».