Effect of aging on cardiac function during cold stress in humans

Abstract

determine whether skin surface cooling increases left ventricular preload and contractility to a greater extent in older compared with young adults we studied 11 young (28 Ϯ 2 yr; means Ϯ SE) and 11 older (64 Ϯ 3 yr) adults during normothermia (35°C water perfused through a tube-lined suit) and cooling (15°C water perfused for 20 min) using standard and tissue Doppler echocardiography. Cooling significantly decreased skin surface temperature in young (⌬2.8 Ϯ 0.3°C) and older (⌬3.0 Ϯ 0.3°C) adults and increased rate-pressure product, an index of myocardial oxygen demand, in older (6,932 Ϯ 445 to 7,622 Ϯ 499 mmHg · beats/ min for normothermia and cooling, respectively), but not young (7,085 Ϯ 438 to 7,297 Ϯ 438 mmHg · beats/min) adults. Increases in blood pressure (systolic and mean blood pressure) during cooling were greater (P Ͻ 0.05) in older than in young adults. Cooling increased preload in older (left ventricular end-diastolic volume from 106 Ϯ 7 to 126 Ϯ 9 ml and left ventricular internal diameter in diastole from 4.69 Ϯ 0.12 to 4.95 Ϯ 0.14 cm; both P Ͻ 0.01), but not young adults (left ventricular end-diastolic volume from 107 Ϯ 7 to 111 Ϯ 7 ml and left ventricular internal diameter in diastole from 4.70 Ϯ 0.10 to 4.78 Ϯ 0.10 cm). Indices of left ventricular contractility (ejection fraction, myocardial acceleration during isovolumic contraction, and peak systolic mitral annulus velocity) were unchanged during cooling in both young and older adults. Collectively, these data indicate that cooling increases left ventricular preload, without affecting left ventricular contractility in older but not young adults. Greater increases in preload and afterload during cooling in older adults contribute to greater increases in indices of myocardial oxygen demand and may help explain the increased risk of cardiovascular events in cold weather.tissue Doppler imaging; echocardiography; age CARDIOVASCULAR-RELATED MORTALITY increases in the cold winter months, particularly in older adults (10,12,23,24,28,40). Associations between increased cardiovascular-related mortality and cold temperatures may be mediated, in part, by acute physiological responses to cold, which include peripheral and visceral vasoconstriction, elevated plasma norepinephrine, and diuresis (33, 38). Recently, we reported an augmented increase in arterial blood pressure during acute cold exposure (nonpainful and noninternal temperature lowering) in older adults (15). This augmented pressor response to cold stress in older adults was strongly associated with increased levels of central arterial stiffness before cooling and an increase in rate-pressure product during cooling (15). This effect appears to be confined to older adults as neither rate-pressure product nor cardiac minute work increase during similar cold exposure in young adults (36,38).Myocardial oxygen demand is affected by a number of factors (17) that may be altered by acute (i.e., cold stress) and chronic processes (i.e., aging). For instance, cold stress that does not induce shivering or d...

Muscle sympathetic nerve activity during cold stress and isometric exercise in healthy older adults

“…Whole body cold stress elicits a robust systemic pressor response (3,4,9,23,62) that is exaggerated in aged adults, evidenced by this and other (23,60) studies. The augmented pressor response to skin surface cooling in older adults is likely not mediated by an increase in cardiac output, as cardiac output derived via transthoracic echocardiography remains unchanged throughout cooling in older adults (60).…”

“…The augmented pressor response to skin surface cooling in older adults is likely not mediated by an increase in cardiac output, as cardiac output derived via transthoracic echocardiography remains unchanged throughout cooling in older adults (60). The results of the present study indicate that pronounced increases in MSNA during cold stress in older adults may contribute to the greater pressor response.…”

“…Reflex cutaneous vasoconstriction is markedly attenuated in healthy older adults, likely mediated by impairments in both end-organ responsiveness (30,51,55) and the thermoregulatory control of skin sympathetic nerve activity (19). In young adults, whole body cold stress elicits a pronounced systemic pressor response (3,4,9,23,62), and this pressor response to mild cold stress (i.e., with no reduction in core body temperature) is exaggerated in aged humans (23,60). The age-related augmentation in the pressor response to acute cold stress is associated with increased central arterial stiffness (23) and increased left ventricular preload (60).…”

“…In young adults, whole body cold stress elicits a pronounced systemic pressor response (3,4,9,23,62), and this pressor response to mild cold stress (i.e., with no reduction in core body temperature) is exaggerated in aged humans (23,60). The age-related augmentation in the pressor response to acute cold stress is associated with increased central arterial stiffness (23) and increased left ventricular preload (60). In addition, sympathetic nervous system activation likely contributes to the cold-induced increase in BP.…”

Effect of cold air inhalation and isometric exercise on coronary blood flow and myocardial function in humans

“…Cardiac death is highest in the winter months, even in people who spend little time outdoors (45,54). While the effects of lowered skin temperature on cardiovascular function have been extensively studied (10,29,59,60), other mechanisms likely play a role in this process.Physical perturbation of the oropharynx and larynx elevates blood pressure in clinical settings (18,34), and laryngeal cold receptors have been identified in animals (38, 51). Previous studies (26,28,35,37) have shown that blood pressure, heart rate, and/or muscle sympathetic nerve activity are increased with cold air breathing in healthy humans.…”