Heart Failure and Thermoregulatory Control: Can Patients With Heart Failure Handle the Heat?

The difference in core-surface temperature indicates the prognosis of heart failure patients

Aim: To evaluate the difference between core temperature and surface temperature (ΔT) as an index for the prognosis of heart failure (HF). Patients & methods: Core temperature and surface temperature were measured in 253 patients with HF. The association of ΔT with prognostic indicators of HF was analyzed. Results: Patients with ΔT ≥2°C were more likely to have lower left ventricular ejection fraction and lower estimated glomerular filtration rate, higher levels of troponin T, brain natriuretic peptide and procalcitonin, and high blood urea nitrogen/creatinine ratio. The risk of death increased by 32% for a 1°C increase in ΔT and was 4.36-times higher in the ΔT ≥2°C group than in the ΔT <2°C group. Conclusion: ΔT may be used to predict the prognosis of patients with HF.

Experimental research in environmentally induced hyperthermic older persons: A systematic quantitative literature review mapping the available evidence

The heat-related health burden is expected to persist and worsen in the coming years due to an aging global population and climate change. Defining the breadth and depth of our understanding of age-related changes in thermoregulation can identify underlying causes and strategies to protect vulnerable individuals from heat. We conducted the first systematic quantitative literature review to provide context to the historical experimental research of healthy older adults - compared to younger adults or unhealthy age matched cases - during exogenous heat strain, focusing on factors that influence thermoregulatory function (e.g. co-morbidities). We identified 4,455 articles, with 147 meeting eligibility criteria. Most studies were conducted in the US (39%), Canada (29%), or Japan (12%), with 71% of the 3,411 participants being male. About 71% of the studies compared younger and older adults, while 34% compared two groups of older adults with and without factors influencing thermoregulation. Key factors included age combined with another factor (23%), underlying biological mechanisms (18%), age independently (15%), influencing health conditions (15%), adaptation potential (12%), environmental conditions (9%), and therapeutic/pharmacological interventions (7%). Our results suggest that controlled experimental research should focus on the age-related changes in thermoregulation in the very old, females, those with overlooked chronic heat-sensitive health conditions (e.g. pulmonary, renal, mental disorders), the impact of multimorbidity, prolonged and cumulative effects of extreme heat, evidence-based policy of control measures (e.g. personal cooling strategies), pharmaceutical interactions, and interventions stimulating protective physiological adaptation. These controlled studies will inform the directions and use of limited resources in ecologically valid fieldwork studies.

Projected Change in the Burden of Excess Cardiovascular Deaths Associated With Extreme Heat by Midcentury (2036-2065) in the Contiguous United States

BACKGROUND

Climate change is causing an increase in extreme heat. Individuals with cardiovascular disease are at high risk of heat-related adverse health effects. How the burden of extreme heat-associated cardiovascular deaths in the United States will change with the projected rise in extreme heat is unknown.

METHODS

We obtained data on cardiovascular deaths among adults and the number of extreme heat days (maximum heat index ≥90 °F [32.2 °C]) in each county in the contiguous United States from 2008 to 2019. Based on representative concentration pathway trajectories that model greenhouse gas emissions and shared socioeconomic pathways (SSP) that model future socioeconomic scenarios and demographic projections, we obtained county-level projected numbers of extreme heat days and populations under 2 scenarios for the midcentury period 2036 to 2065: SSP2-4.5 (representing demographic projections from a "middle-of-the-road" socioeconomic scenario and an intermediate increase in emissions) and SSP5-8.5 (demographic projections in an economy based on "fossil-fueled development" and a large increase in emissions). The association of cardiovascular mortality with extreme heat was estimated with a Poisson fixed-effects model. Using estimates from this model, the projected number of excess cardiovascular deaths associated with extreme heat was calculated.

RESULTS

Extreme heat was associated with 1651 (95% CI, 921-2381) excess cardiovascular deaths per year from 2008 to 2019. By midcentury, extreme heat is projected to be associated with 4320 (95% CI, 2369-6272) excess deaths annually, which is an increase of 162% (95% CI, 142-182) under SSP2-4.5, and 5491 (95% CI, 3011-7972) annual excess deaths, which is an increase of 233% (95% CI, 206-259) under SSP5-8.5. Elderly adults are projected to have a 3.5 (95% CI, 3.2-3.8) times greater increase in deaths in the SSP2-4.5 scenario compared with nonelderly adults. Non-Hispanic Black adults are projected to have a 4.6 (95% CI, 2.8-6.4) times greater increase compared with non-Hispanic White adults. The projected change in deaths was not statistically significantly different for other race and ethnicity groups or between men and women.

CONCLUSIONS

By midcentury, extreme heat is projected to be associated with a significantly greater burden of excess cardiovascular deaths in the contiguous United States.

The Importance of Optimal Hydration in Patients with Heart Failure-Not Always Too Much Fluid

Heart failure (HF) is a leading cause of morbidity and mortality and a major public health problem. Both overhydration and dehydration are non-physiological states of the body that can adversely affect human health. Congestion and residual congestion are common in patients hospitalized for HF and are associated with poor prognosis and high rates of rehospitalization. However, the clinical problem of dehydration is also prevalent in healthcare and community settings and is associated with increased morbidity and mortality. This article provides a comprehensive review of the issue of congestion and dehydration in HF, including HF guidelines, possible causes of dehydration in HF, confirmed and potential new diagnostic methods. In particular, a full database search on the relationship between dehydration and HF was performed and all available evidence in the literature was reviewed. The novel hypothesis of chronic subclinical hypohydration as a modifiable risk factor for HF is also discussed. It is concluded that maintaining euvolemia is the cornerstone of HF management. Physicians have to find a balance between decongestion therapy and the risk of dehydration.

Association of Extreme Heat and Cardiovascular Mortality in the United States: A County-Level Longitudinal Analysis From 2008 to 2017

BACKGROUND

Extreme-heat events are increasing as a result of climate change. Prior studies, typically limited to urban settings, suggest an association between extreme heat and cardiovascular mortality. However, the extent of the burden of cardiovascular deaths associated with extreme heat across the United States and in different age, sex, or race and ethnicity subgroups is unclear.

METHODS

County-level daily maximum heat index levels for all counties in the contiguous United States in summer months (May-September) and monthly cardiovascular mortality rates for adults ≥20 years of age were obtained. For each county, an extreme-heat day was identified if the maximum heat index was ≥90 °F (32.2 °C) and in the 99th percentile of the maximum heat index in the baseline period (1979-2007) for that day. Spatial empirical Bayes smoothed monthly cardiovascular mortality rates from 2008 to 2017 were the primary outcome. A Poisson fixed-effects regression model was estimated with the monthly number of extreme-heat days as the independent variable of interest. The model included time-fixed effects and time-varying environmental, economic, demographic, and health care-related variables.

RESULTS

Across 3108 counties, from 2008 to 2017, each additional extreme-heat day was associated with a 0.12% (95% CI, 0.04%-0.21%; P=0.004) higher monthly cardiovascular mortality rate. Extreme heat was associated with an estimated 5958 (95% CI, 1847-10 069) additional deaths resulting from cardiovascular disease over the study period. In subgroup analyses, extreme heat was associated with a greater relative increase in mortality rates among men compared with women (0.20% [95% CI, 0.07%-0.33%]) and non-Hispanic Black compared with non-Hispanic White adults (0.19% [95% CI, 0.01%-0.37%]). There was a greater absolute increase among elderly adults compared with nonelderly adults (16.6 [95% CI, 14.6-31.8] additional deaths per 10 million individuals per month).

CONCLUSIONS

Extreme-heat days were associated with higher adult cardiovascular mortality rates in the contiguous United States between 2008 and 2017. This association was heterogeneous among age, sex, race, and ethnicity subgroups. As extreme-heat events increase, the burden of cardiovascular mortality may continue to increase, and the disparities between demographic subgroups may widen.

Autonomic symptoms and associated factors in patients with chronic heart failure

OBJECTIVE

Autonomic disorders are common in chronic illness, and their symptoms may restrict the daily functioning of patients. However, in chronic heart failure, extensive knowledge about autonomic symptoms is still lacking. This study aims to explore self-perceived autonomic symptoms, associated factors, and their relationship with health-related quality of life in chronic heart failure.

METHODS

One hundred and twenty-four patients with documented chronic heart failure (men and women; 50-86 years) and 124 sex and age-matched controls participated in this study. The participants filled validated questionnaires about autonomic symptom profile (COMPASS 31), fatigue (CIS, Checklist for individual strength), anxiety and depression (HADS, Hospital Anxiety and Depression), and health-related quality of life (SF36). Non-parametric statistics were performed to analyse the data.

RESULTS

Total score for autonomic symptoms was higher in chronic heart failure compared to controls [Median: 14.9; IQR: 6.2-25.1 vs. 7.3; 0-18; p < 0.001], especially for orthostatic hypotension [Median: 8; IQR: 0-16 vs. 0; 0-12; p < 0.001], vasomotor [Median: 0; IQR: 0-0 vs. 0; 0-0; p < 0.001] and secretomotor function [Median: 0; IQR: 0-4.2 vs. 0; 0-2.1; p = 0.013]. High scores for autonomic symptoms were moderate correlated with higher scores of fatigue, anxiety and depression (0.343 ≤ rs ≥ 0.420; p < 0.001) and with decreased health-related quality of life (-0.454; p < 0.01).

CONCLUSION

Autonomic symptoms, especially for orthostatic intolerance, vasomotor and secretomotor subdomains, are prevalent and are associated with fatigue complaints and poor health-related quality of life in CHF.

Global warming, heat-related illnesses, and the dermatologist

Global warming, provoked by the greenhouse effect of high levels of atmospheric gases (most notably carbon dioxide and methane), directly threatens human health and survival. Individuals vary in their capacity to tolerate episodes of extreme heat. Because skin is the organ tasked with heat dissipation, it is important for dermatologists to be versed in the physiology of cutaneous heat dissipation and cognizant of clinical settings in which the skin’s thermoregulatory responses may be impaired. When the external temperature is lower than that of the skin, the skin releases internal heat through direct thermal exchange with the environment, a process that is aided by an expansion of cutaneous blood flow and eccrine sweating. Cooling through the evaporation of sweat is effective even when the external temperature exceeds that of skin. Many factors, including environmental and physiological (e.g., age and sex), and pathological (e.g., preexisting illnesses, disorders of eccrine function, and medications) considerations, affect the skin’s capacity to thermoregulate. Identification of individuals at increased risk for heat-related morbidity and mortality will become increasingly important in the care of patients.

Pediatric Thermoregulation: Considerations in the Face of Global Climate Change

Predicted global climate change, including rising average temperatures, increasing airborne pollution, and ultraviolet radiation exposure, presents multiple environmental stressors contributing to increased morbidity and mortality. Extreme temperatures and more frequent and severe heat events will increase the risk of heat-related illness and associated complications in vulnerable populations, including infants and children. Historically, children have been viewed to possess inferior thermoregulatory capabilities, owing to lower sweat rates and higher core temperature responses compared to adults. Accumulating evidence counters this notion, with limited child-adult differences in thermoregulation evident during mild and moderate heat exposure, with increased risk of heat illness only at environmental extremes. In the context of predicted global climate change, extreme environmental temperatures will be encountered more frequently, placing children at increased risk. Thermoregulatory and overall physiological strain in high temperatures may be further exacerbated by exposure to/presence of physiological and environmental stressors including pollution, ultraviolet radiation, obesity, diabetes, associated comorbidities, and polypharmacy that are more commonly occurring at younger ages. The aim of this review is to revisit fundamental differences in child-adult thermoregulation in the face of these multifaceted climate challenges, address emerging concerns, and emphasize risk reduction strategies for the health and performance of children in the heat.

Activity modification in heat: critical assessment of guidelines across athletic, occupational, and military settings in the USA

Exertional heat illness (EHI) risk is a serious concern among athletes, laborers, and warfighters. US Governing organizations have established various activity modification guidelines (AMGs) and other risk mitigation plans to help ensure the health and safety of their workers. The extent of metabolic heat production and heat gain that ensue from their work are the core reasons for EHI in the aforementioned population. Therefore, the major focus of AMGs in all settings is to modulate the work intensity and duration with additional modification in adjustable extrinsic risk factors (e.g., clothing, equipment) and intrinsic risk factors (e.g., heat acclimatization, fitness, hydration status). Future studies should continue to integrate more physiological (e.g., valid body fluid balance, internal body temperature) and biometeorological factors (e.g., cumulative heat stress) to the existing heat risk assessment models to reduce the assumptions and limitations in them. Future interagency collaboration to advance heat mitigation plans among physically active population is desired to maximize the existing resources and data to facilitate advancement in AMGs for environmental heat.

Thermoeffector Responses at a Fixed Rate of Heat Production in Heart Failure Patients

PURPOSE

Heart failure (HF) patients seem to exhibit altered thermoregulatory responses during exercise in the heat. However, the extent to which these responses are altered due to physiological impairments independently of biophysical factors associated with differences in metabolic heat production (Hprod), evaporative heat balance requirements (Ereq), and/or body size is presently unclear. Therefore, we examined thermoregulatory responses in 10 HF patients and 10 age-matched controls (CON) similar in body size during exercise at a fixed rate of Hprod and therefore Ereq in a 30°C environment.

METHODS

Rectal temperature, local sweat rate, and cutaneous vascular conductance were measured throughout 60 min of cycle ergometry. Whole-body sweat rate was estimated from pre-post nude body weight corrected for fluid intake.

RESULTS

Despite exercising at the same rate of Hprod (HF, 338 ± 43 W; CON, 323 ± 31 W; P = 0.25), the rise in rectal temperature was greater (P < 0.01) in HF (0.81°C ± 0.16°C) than in CON (0.49°C ± 0.27°C). In keeping with a similar Ereq (HF, 285 ± 40 W; CON, 274 ± 28 W; P = 0.35), no differences in whole-body sweat rate (HF, 0.45 ± 0.11 L·h; CON, 0.41 ± 0.07 L·h; P = 0.38) or local sweat rate (HF, 0.96 ± 0.17 mg·cm·min; CON, 0.79 ± 0.15 mg·cm·min; P = 0.50) were observed between groups. However, the rise in cutaneous vascular conductance was lower in HF than in CON (HF, 0.83 ± 0.42 au·mm Hg; CON, 2.10 ± 0.79 au·mm Hg; P < 0.01). In addition, the cumulative body heat storage estimated from partitional calorimetry was similar between groups (HF, 154 ± 106 kJ; CON, 196 ± 174 kJ; P = 0.44).

CONCLUSIONS

Collectively, these findings demonstrate that HF patients exhibit a blunted skin blood flow response, but no differences in sweating. Given that HF patients had similar body heat storage to that of CON at the same Hprod, their greater rise in core temperature can be attributed to a less uniform internal distribution of heat between the body core and periphery.

Aging and Thermoregulatory Control: The Clinical Implications of Exercising under Heat Stress in Older Individuals

Climate change is predicted to bring about a greater variability in weather patterns with an increase in extreme weather events such as sustained heat waves. This change may have a direct impact on population health since heat waves can exceed the physiological limit of compensability of vulnerable individuals. Indeed, many clinical reports suggest that individuals over the age of 60 years are consistently the most vulnerable, experiencing significantly greater adverse heat-related health outcomes than any other age cohort during environmental heat exposure. There is now evidence that aging is associated with an attenuated physiological ability to dissipate heat and that the risk of heat-related illness in these individuals is elevated, particularly when performing physical activity in the heat. The purpose of this review is to discuss mechanisms of thermoregulatory control and the factors that may increase the risk of heat-related illness in older individuals. An understanding of the mechanisms responsible for impaired thermoregulation in this population is of particular importance, given the current and projected increase in frequency and intensity of heat waves, as well as the promotion of regular exercise as a means of improving health-related quality of life and morbidity and mortality. As such, the clinical implications of this work in this population will be discussed.

Folic acid supplementation improves vascular endothelial function, yet not skin blood flow during exercise in the heat, in patients with heart failure

Heart failure (HF) patients are susceptible to heat strain during exercise, secondary to blunted skin blood flow (SkBF) responses, which may be explained by impaired nitric oxide (NO)-dependent vasodilation. Folic acid improves vascular endothelial function and SkBF through NO-dependent mechanisms in healthy older individuals and patients with cardiovascular disease. We examined the effect of folic acid supplementation (5 mg/day for 6 wk) on vascular function [brachial artery flow-mediated dilation (FMD)] and SkBF responses [cutaneous vascular conductance (CVC)] during 60 min of exercise at a fixed metabolic heat production (300 Ẇ_Hprod) in a 30°C environment in 10 patients with HF (New York Heart Association Class I-II) and 10 healthy controls (CON). Serum folic acid concentration increased in HF [preintervention (pre): 1.4 ± 0.2; postintervention (post): 8.9 ± 6.7 ng/ml, P = 0.01] and CON (pre: 1.3 ± 0.6; post: 5.2 ± 4.9 ng/ml, P = 0.03). FMD improved by 2.1 ± 1.3% in HF ( P < 0.01), but no change was observed in CON postintervention ( P = 0.20). During exercise, the external workload performed on the cycle ergometer to attain the fixed level of heat production for exercise was similar between groups (HF: 60 ± 13; CON: 65 ± 20 external workload, P = 0.52). Increases in CVC during exercise were similar in HF (pre: 0.89 ± 0.43; post: 0.83 ± 0.45 au/mmHg, P = 0.80) and CON (pre: 2.01 ± 0.79; post: 2.03 ± 0.72 au/mmHg, P = 0.73), although the values were consistently lower in HF for both pre- and postintervention measurement intervals ( P < 0.05). These findings demonstrate that folic acid improves vascular endothelial function in patients with HF but does not enhance SkBF during exercise at a fixed metabolic heat production in a warm environment.

Mining telemonitored physiological data and patient-reported outcomes of congestive heart failure patients

This paper addresses patient-reported outcomes (PROs) and telemonitoring in congestive heart failure (CHF), both increasingly important topics. The interest in CHF trials is shifting from hard end-points such as hospitalization and mortality, to softer end-points such health-related quality of life. However, the relation of these softer end-points to objective parameters is not well studied. Telemonitoring is suitable for collecting both patient-reported outcomes and objective parameters. Most telemonitoring studies, however, do not take full advantage of the available sensor technology and intelligent data analysis. The Chiron clinical observational study was performed among 24 CHF patients (17 men and 7 women, age 62.9 ± 9.4 years, 15 NYHA class II and 9 class III, 10 of ishaemic, aetiology, 6 dilated, 2 valvular, and 6 of multiple aetiologies or cardiomyopathy) in Italy and UK. A large number of physiological and ambient parameters were collected by wearable and other devices, together with PROs describing how well the patients felt, over 1,086 days of observation. The resulting data were mined for relations between the objective parameters and the PROs. The objective parameters (humidity, ambient temperature, blood pressure, SpO2, and sweeting intensity) could predict the PROs with accuracies up to 86% and AUC up to 0.83, making this the first report providing evidence for ambient and physiological parameters to be objectively related to PROs in CHF patients. We also analyzed the relations in the predictive models, gaining some insights into what affects the feeling of health, which was also generally not attempted in previous investigations. The paper strongly points to the possibility of using PROs as primary end-points in future trials.