Foster Josh, McKenna Zachary J, Sarma Satyam, MacNamara James P, Belval Luke N, Watso Joseph C, Atkins Whitley C, Jarrard Caitlin P, Crandall Craig G
Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.
Centre for Human and Applied Physiological Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK.
J Appl Physiol (1985). 2025 Jul 28. doi: 10.1152/japplphysiol.00917.2024.
Older individuals are at a greater risk for adverse cardiovascular events during extreme heat exposure. However, detailed characterization of their cardiac responses to environmental heat exposure are lacking. In 20 young (18 to 39 years) and 20 older (> 65 years) adults (50% male in both groups), we document the echocardiography assessed left-ventricular responses to a very hot and dry (DRY, 47°C and 15% RH) and hot humid (HUMID, 41°C and 40% RH) 3-hour heat exposure, with intermittent bouts of light physical activity throughout. In both climates and in both age groups, heat stress increased cardiac output by ~0.7 ± 0.8 L/min, decreased stroke volume by ~7 ± 10 mL and augmented diastolic function through increased atrial contribution to filling by 5 ± 5%. In the DRY climate, mitral annual systolic velocity (s') increased to a greater extent in older subjects (Δ3.3 ± 2.1 vs Δ1.5 ± 1.5 cm/s, = 0.002), with less difference in HUMID (Δ2.1 ± 1.3 cm/s vs 1.4 ± 1.3 cm/s, = 0.096). Despite these adjustments, systolic blood pressure was only maintained in the younger group and fell consistently in older individuals (0 ± 8 mmHg) in DRY (Δ-11 ± 14 mmHg vs 1 ± 8 mmHg, = 0.001) and HUMID (Δ-9 ± 15 mmHg vs -1 ± 8 mmHg, = 0.030). In summary, older adults rely on a greater augmentation of systolic function during extreme heat exposure, but the magnitude of depends on the heat stress severity.
在极端高温暴露期间，老年人发生不良心血管事件的风险更高。然而，目前缺乏对他们心脏对环境热暴露反应的详细描述。我们招募了20名年轻人（18至39岁）和20名老年人（>65岁）（两组男性均占50%），记录了他们在3小时的炎热干燥（DRY，47°C，相对湿度15%）和炎热潮湿（HUMID，41°C，相对湿度40%）环境中暴露时，经超声心动图评估的左心室反应，期间伴有间歇性轻度体力活动。在两种气候条件下以及两个年龄组中，热应激使心输出量增加约0.7±0.8升/分钟，使每搏输出量减少约7±10毫升，并通过增加心房对充盈的贡献5±5%增强舒张功能。在干燥气候下，老年受试者的二尖瓣环收缩期速度（s'）增加幅度更大（分别为Δ3.3±2.1与Δ1.5±1.5厘米/秒，P = 0.002），在潮湿气候下差异较小（分别为Δ2.1±1.3厘米/秒与1.4±1.3厘米/秒，P = 0.096）。尽管有这些调整，收缩压仅在年轻组中得以维持，而在老年个体中持续下降（干燥环境中为0±8毫米汞柱）（分别为Δ-11±14毫米汞柱与1±8毫米汞柱，P = 0.001）以及在潮湿环境中（分别为Δ-9±15毫米汞柱与-1±8毫米汞柱，P = 0.030）。总之，老年人在极端高温暴露期间依赖更大程度的收缩功能增强，但增强幅度取决于热应激的严重程度。
