Ambient temperature affects thrombotic potential at rest and following exercise

Low ambient temperature exposure increases the risk of ischemic stroke by promoting platelet activation

BACKGROUND

Accumulating epidemiological evidence suggests the association between low ambient temperature exposure and the risk of ischemic stroke, but the underlying mechanisms remain unclear.

OBJECTIVE

Given the crucial role of platelet activation and thrombosis in ischemic stroke, this study aims to investigate the effect of ambient temperature on platelet activation through multi-center clinical data in Tianjin as well as animal experiments.

METHODS

From 2018 to 2020, nearly 3000 ischemic stroke patients from three stroke centers in Tianjin were included in the analysis, among them the ADP induced platelet aggregation rate was available. Meteorological data from the same period had also been collected. After controlling for confounding factors, the generalized additive mixed model (GAMM) was used to evaluate the correlation between environmental temperature and platelet aggregation rate. In further animal experiments, platelet function assessments were conducted on mice from the cold exposure group and the normal temperature group, including platelet aggregation, spreading, and clot retraction. Additionally, tail bleeding and mesentery thrombosis were also tested to monitor hemostasis and thrombosis in vivo.

RESULT

A nonlinear "S" shaped relationship between outdoor temperature and platelet aggregation was found. Each 1 °C decrease of mean temperature was associated with an increase of 7.77 % (95 % CI: 2.06 % - 13.48 %) in platelet aggregation. The ambient temperature is not related to other platelet parameters. Subgroup analysis found that males, people aged ≥65 years, and hypertensive individuals are more susceptible to temperature changes. Furthermore, animal experiments demonstrated that the increased CIRBP levels and subsequent activation of p-AKT/p-ERK may be one of the reasons for cold exposure induced platelets activation.

CONCLUSION

Both clinical data and basic research support that low ambient temperature exposure has the potential to increase platelet activation. These results provide a basis for understanding the potential mechanism of temperature variations on the pathogenesis of cerebrovascular diseases.

Global, regional, and national burden of mortality associated with cold spells during 2000-19: a three-stage modelling study

BACKGROUND

Exposure to cold spells is associated with mortality. However, little is known about the global mortality burden of cold spells.

METHODS

A three-stage meta-analytical method was used to estimate the global mortality burden associated with cold spells by means of a time series dataset of 1960 locations across 59 countries (or regions). First, we fitted the location-specific, cold spell-related mortality associations using a quasi-Poisson regression with a distributed lag non-linear model with a lag period of up to 21 days. Second, we built a multivariate meta-regression model between location-specific associations and seven predictors. Finally, we predicted the global grid-specific cold spell-related mortality associations during 2000-19 using the fitted meta-regression model and the yearly grid-specific meta-predictors. We calculated the annual excess deaths, excess death ratio (excess deaths per 1000 deaths), and excess death rate (excess deaths per 100 000 population) due to cold spells for each grid across the world.

FINDINGS

Globally, 205 932 (95% empirical CI [eCI] 162 692-250 337) excess deaths, representing 3·81 (95% eCI 2·93-4·71) excess deaths per 1000 deaths (excess death ratio), and 3·03 (2·33-3·75) excess deaths per 100 000 population (excess death rate) were associated with cold spells per year between 2000 and 2019. The annual average global excess death ratio in 2016-19 increased by 0·12 percentage points and the excess death rate in 2016-19 increased by 0·18 percentage points, compared with those in 2000-03. The mortality burden varied geographically. The excess death ratio and rate were highest in Europe, whereas these indicators were lowest in Africa. Temperate climates had higher excess death ratio and rate associated with cold spells than other climate zones.

INTERPRETATION

Cold spells are associated with substantial mortality burden around the world with geographically varying patterns. Although the number of cold spells has on average been decreasing since year 2000, the public health threat of cold spells remains substantial. The findings indicate an urgency of taking local and regional measures to protect the public from the mortality burdens of cold spells.

FUNDING

Australian Research Council, Australian National Health and Medical Research Council, EU's Horizon 2020 Project Exhaustion.

Short-term effects of cold spells on plasma viscosity: Results from the KORA cohort study in Augsburg, Germany

As the underlying mechanisms of the adverse effects of cold spells on cardiac events are not well understood, we explored the effects of cold spells on plasma viscosity, a blood parameter linked to cardiovascular disease. This cross-sectional study involved 3622 participants from the KORA S1 Study (1984-1985), performed in Augsburg, Germany. Exposure data was obtained from the Bavarian State Office for the Environment. Cold spells were defined as two or more consecutive days with daily mean temperatures below the 3^rd, 5^th, or 10^th percentile of the distribution. The effects of cold spells on plasma viscosity were explored by generalized additive models with distributed lag nonlinear models (DLNM). We estimated cumulative effects at lags 0-1, 0-6, 0-13, 0-20, and 0-27 days separately. Cold spells (mean temperature <3^rd, <5^th or <10^th percentile) were significantly associated with an increase in plasma viscosity with a lag of 0-1 days [%change of geometric mean (95% confidence interval): 1.35 (0.06-2.68), 1.35 (0.06-2.68), and 2.49 (0.34-4.69), respectively], and a lag of 0-27 days [18.81 (8.97-29.54), 17.85 (8.29-28.25), and 7.41 (3.35-11.0), respectively]. For the analysis with mean temperature <3^rd or 10^th percentile, we also observed significant associations at lag 0-20 days [8.34 (0.43-16.88), and 4.96 (1.68, 8.35), respectively]. We found that cold spells had significant immediate and longer lagged effects on plasma viscosity. This finding supports the complex interplay of multiple mechanisms of cold on adverse cardiac events and enriches the knowledge about how cold exposure acts on the human body.

Association between El Niño-Southern Oscillation events and stroke: a case-crossover study in Kaunas city, Lithuania, 2000-2015

The aim of this study was to determine the association between the daily number of cases of ischemic stroke (IS) and hemorrhagic stroke (HS) in patients aged 25-64 years and the El Niño-Southern Oscillation (ENSO) events during 2000-2015. As an indicator of the effect of the ENSO, the monthly NIÑO 3.4 index (Equatorial Pacific Sea Surface Temperature) was used. During the 5844-day study period, 5600 cases of stroke (3170 (56.61%) in men and 2430 (43.39%) in women) were analyzed. Of these, 4354 (77.8%) cases were IS, and 1041 (18.6%) cases were HS. In 3496 (62.2%) cases, stroke occurred in the age group of 55-64 years. In the analysis, we used the following categories of the ENSO events: strong La Niña, moderate La Niña, moderate El Niño, and strong El Niño. The effect of the ENSO was examined by using the multivariate Poisson regression adjusting for weather variables. The highest risk of both strokes (BS) was observed on days of strong and moderate La Niña (rate ratio (RR) 1.27, 95% CI 1.13-1.42) and RR = 1.15 (1.07-1.23), respectively), while the risk for IS was the highest on days of moderate El Niño (RR = 1.11(1.02-1.20)). A lower risk for BS was found on days of strong El Niño (RR = 0.77(0.62-0.97)). We found that ENSO events affected the occurrence of BS and IS in all age groups, and the strongest effect was observed among females. The results of this study provide new evidence that ENSO events may affect the risk of stroke, especially the risk of IS.

Hemostatic Responses to Multiple Bouts of Firefighting Activity: Female vs. Male Differences in a High Demand, High Performance Occupation

While the fire service has long been a male-dominated occupation, women's participation in this strenuous, high risk, high performance activity has increased in recent years. Firefighting induces significant cardiovascular strain, including hemostatic disruption; however, the effect of sex on hemostatic responses has not been investigated despite evidence that there are sex-related differences in hemostatic variables at rest and following exercise. Thus, we investigated hemostatic responses in age- and BMI-matched male and female firefighters who performed 3-4 evolutions of firefighting drills over a 3 h period. Venous blood samples were collected before and after the firefighting training drills and hemostatic variables were assessed. Firefighting significantly increased platelet count and factor VIII, tissue plasminogen activator (t-PA) antigen, and t-PA activity, and decreased activated partial thromboplastin time and plasminogen activator inhibitor (PAI-1) activity. Females had lower values for epinephrine-induced platelet closure time, antithrombin III, PAI-1 activity, and PAI-1 antigen. There were no interactions between sex and time for any variables assessed. In conclusion, multiple bouts of firefighting activity resulted in a procoagulatory state. Although there were sex differences for several hemostatic variables, male and female firefighters did not differ in their hemostatic response to multiple bouts of firefighting.

Cold Weather and Cardiac Arrest in 4 Seasons: Helsinki, Finland, 1997‒2018

Objectives. To test the a priori hypothesis that out-of-hospital cardiac arrest (OHCA) is associated with cold weather during all seasons, not only during the winter. Methods. We applied a case‒crossover design to all cases of nontraumatic OHCA in Helsinki, Finland, over 22 years: 1997 to 2018. We statistically defined cold weather for each case and season, and applied conditional logistic regression with 2 complementary models a priori according to the season of death. Results. There was an association between cold weather and OHCA during all seasons, not only during the winter. Each additional cold day increased the odds of OHCA by 7% (95% confidence interval [CI] = 4%, 10%), with similar strength of association during the autumn (6%; 95% CI = 0%, 12%), winter (6%; 95% CI = 1%, 12%), spring (8%; 95% CI = 2%, 14%), and summer (7%; 95% CI = 0%, 15%). Conclusions. Cold weather, defined according to season, increased the odds of OHCA during all seasons in similar quantity. Public Health Implications. Early warning systems and cold weather plans focus implicitly on the winter season. This may lead to incomplete measures in reducing excess mortality related to cold weather. (Am J Public Health. 2022;112(1):107-115. https://doi.org/10.2105/AJPH.2021.306549).

Association between winter cold spells and acute myocardial infarction in Lithuania 2000-2015

Acute myocardial infarction (AMI) is a major public health problem. Cold winter weather increases the risk of AMI, but factors influencing susceptibility are poorly known. We conducted an individual-level case-crossover study of the associations between winter cold spells and the risk of AMI, with special focus on survival at 28 days and effect modification by age and sex. All 16,071 adult cases of AMI among the residents of the city of Kaunas in Lithuania in 2000-2015 were included in the study. Cold weather was statistically defined using the 5th percentile of frequency distribution of daily mean temperatures over the winter months. According to conditional logistic regression controlling for time-varying and time-invariant confounders, each additional cold spell day during the week preceding AMI increased the risk of AMI by 5% (95% CI 1-9%). For nonfatal and fatal cases, the risk increase per each additional cold spell day was 5% (95% CI 1-9%) and 6% (95% CI - 2-13%), respectively. The effect estimate was greater for men (OR 1.07, 95% CI 1.02-1.12) than for women (OR 1.02, 95% CI 0.97-1.08), but there was no evidence of effect modification by age. Evidence on factors increasing susceptibility is critical for targeted cold weather planning.

The effects of submaximal exercise and cold exposure on blood coagulation parameters in coronary artery disease patients

BACKGROUND

Both exercise and cold exposure increase blood coagulation potential but their combined effects are not known. The purpose of the present study was to assess blood coagulation factors in response to submaximal exercise in the cold environment among patients with stable coronary artery disease (CAD).

METHODS

Sixteen men (61.1 ± 7.1 years) with stable CAD participated in three 30-min experimental conditions (seated rest in - 15 °C and exercise in both + 22 °C and - 15 °C) in random order. The employed exercise consisted of brisk walking (66-69% of maximal heart rate). Factor VII (FVII), fibrinogen, D-dimer and von Willebrand factor (vWF) were analyzed from blood samples obtained before, immediately and one hour after each experiment.

RESULTS

On average, FVII activity (95% confidence interval, CI) was 123 (108-143) %, 123 (106-140) %, 121 (103-139) % (baseline, recovery 1, recovery 2), fibrinogen concentration (95% CI) 3.81 (3.49-4.12) g/l, 3.71 (3.34-4.08) g/l, 3.65 (3.26-4.05) g/l, D-dimer concentration (95% CI) 0.42 (0.28-0.56) µg/ml, 0.42 (0.29-.55) µg/ml and 0.39 (0.29-0.49) µg/ml, and vWF activity (95% CI) 184 (135-232) %, 170 (128-212) % and 173 (129-217) % after exercise in the cold. Average FVII activity varied from 122 to 123%, fibrinogen concentration from 3.71 to 3.75 g/l, D-dimer concentration from 0.35 to 0.51 µg/ml and von Willebrand factor activity from 168 to 175% immediately after each three experimental condition.

CONCLUSIONS

Our findings suggest that submaximal lower body exercise carried out in a cold environment does not significantly affect blood coagulation parameters among patients with stable CAD.

Laboratory medicine: health evaluation in elite athletes

The need to evaluate the health status of an athlete represents a crucial aim in preventive and protective sports science in order to identify the best diagnostic strategy to improve performance and reduce risks related to physical exercise. In the present review we aim to define the main biochemical and haematological markers that vary significantly during and after sports training to identify risk factors, at competitive and professional levels and to highlight the set up of a specific parameter's panel for elite athletes. Moreover, we also intend to consider additional biomarkers, still under investigation, which could further contribute to laboratory sports medicine and provide reliable data that can be used by athlete's competent staff in order to establish personal attitudes and prevent sports injuries.

Post-operative of bleeding, haemolysis and coagulation in mechanical circulatory support patients

There are unique complications arising from mechanical support devices but some of the long-term systemic haematological complications are indistinguishable from management problems affecting the care of other patients receiving intermediate to long term care in the cardiac ICU. The field of mechanical cardiac assist device (MCAD) is evolving. Despite major changes in design of these devices the most feared haematological complications have remained unchanged, namely haemolysis, pump thrombosis or thromboembolism. This review article gives an overview over the pathophysiology of MCAD related haematological complications, their management and where possible an outlook on future strategies to prevent such complications. The impact of MCAD on blood is discussed, starting with rheology, common pump mechanisms, current and future pump surface coating materials, anatomical considerations of the connection of the circuit and design of the circuit itself. Moreover, the duration of the cardiovascular support, impact of bleeding complications and other patient factors. This article also covers the impact of long term mechanical cardiac support on the properties of platelets, the anticoagulation strategies and a basic guide to the differential diagnosis of haemolysis is reviewed. The section on anaemia considers anaemia in the wider perioperative setting for patients in critical care having undergone cardiac surgery and also discusses transfusion alternatives.

Venous Thromboembolism at High Altitude: Our Approach to Patients at Risk

Venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism, is a prevalent disorder that confers substantial cardiovascular morbidity and, in serious cases, death. VTE has a complex and incompletely understood etiopathogenesis with genetic, acquired, and environmental risk factors. As the focus of this review, one environmental risk factor, which may interact with other risk factors such as hereditary and/or acquired thrombophilias, is travel to high altitude (HA), although current evidence is limited. As guidelines do not directly address this topic, we will discuss the epidemiology of HA-VTE, review the putative mechanisms for thrombosis at HA, and discuss our clinical approach to both risk stratification and counseling, including specific pharmacologic and nonpharmacologic recommendations for patients with elevated VTE risk before they travel to HA.

Cardiovascular diseases, cold exposure and exercise

Both acute and prolonged cold exposure affect cardiovascular responses, which may be modified by an underlying cardiovascular disease. In addition, exercise in a cold environment increases cardiovascular strain further, but its effects among persons with cardiovascular diseases are not well known. Controlled studies employing whole-body or local cold exposure demonstrate comparable or augmented increase in cardiac workload, but aggravated cutaneous vasoconstriction in persons with mild hypertension. A strong sympathetic stimulation of a cold pressor test, increases cardiac workload in persons with coronary artery disease (CAD), but does not markedly differ from those with less severe disease or healthy. However, cold exposure reduces myocardial oxygen supply in CAD, which may lead to ischemia. Exercise in cold often augments cardiac workload in persons with CAD more than when performed in thermoneutral conditions. At the same time, reduced myocardial perfusion may lead to earlier ischemia, angina and impaired performance. Also having a heart failure deteriorates submaximal and maximal performance in the cold. Antianginal medication is beneficial in the cold in lowering blood pressure, but does not affect the magnitude of cold-related cardiovascular responses in hypertension. Similarly, the use of blood pressure lowering medication improves exercise performance in cold both among persons with CAD and heart failure. Both the acute and seasonal effects of cold and added with exercise may contribute to the higher morbidity and mortality of those with cardiovascular diseases. Yet, more controlled studies for understanding the pathophysiological mechanisms behind the adverse cold-related health effects are warranted.

Heat Generation in Axial and Centrifugal Flow Left Ventricular Assist Devices

Despite increasing use of left ventricular assist devices (LVADs) as a surgical treatment for advanced heart failure in an era of improved outcomes with LVAD support, the mechanical interactions between these pumps and the cardiovascular system are not completely understood. We utilized an in vitro mock circulatory loop to analyze the heat production incurred by operation of an axial flow and centrifugal flow LVAD. A HeartMate II and a HeartWare HVAD were connected to an abbreviated flow loop and were implanted in a viscoelastic gel. Temperature was measured at the surface of each LVAD. Device speed and fluid viscosity were altered and, in the HeartMate II, as artificial thrombi were attached to the inflow stator, impeller, and outflow stator. The surface temperatures of both LVADs increased in all trials and reached a plateau within 80 minutes of flow initiation. Rate of heat generation and maximum system temperature were greater when speed was increased, when viscosity was increased, and when artificial thrombi were attached to the HeartMate II impeller. Normal operation of these two widely utilized LVADs results in appreciable heat generation in vitro. Increased pump loading resulted in more rapid heat generation, which was particularly severe when a large thrombus was attached to the impeller of the HeartMate II. While heat accumulation in vivo is likely minimized by greater dissipation in the blood and soft tissues, focal temperature gains with the pump housing of these two devices during long-term operation may have negative hematological consequences.

Cerebral Venous Sinus Thrombosis during Everest Expedition: A Case Report and Review of the Literature

Cerebral venous sinus thrombosis (CVST) is a rare but serious disorder that is associated with a poor clinical outcome. We report a 35-year-old man who had a severe headache and diplopia while climbing Mount Everest. His MR venography showed right transverse and right sigmoid sinus thrombosis. He improved on anticoagulant and symptomatic measures. Cerebral venous sinus thrombosis at high altitude is discussed.

Venous Thromboembolism in Physically Active People: Considerations for Risk Assessment, Mainstream Awareness and Future Research

The global healthcare burden of venous thromboembolism (VTE) and associated comorbidities (e.g., obesity, heart disease and cancer) is significant. Physical activity-especially cardiovascular exercise-is popularly acclaimed for gold-standard prevention. Paradoxically, intensive training can expose athletes to several potentially thrombogenic risk factors (e.g., heat stress, dehydration, blood vessel injury and inflammation). However, awareness regarding the risk of VTE in physically active people is generally lacking. Given that the overall incidence of asymptomatic and/or occult blood clots that resolve spontaneously is uncharted, and because symptoms and sequelae are not always 'textbook', triage evaluation and diagnosis of VTE at large can be challenging. Front-line clinical evaluations, including the major Wells scoring criteria, are (versus the total number of possible factors and diagnoses) comparably reductionist, and the point at which a minor risk might be considered significant in one person-but not in another-is subjective. Considering the popular associations between VTE and inactivity, athletes might be at greater risk of a missed diagnosis quite simply because their cardiovascular conditioning presents as the polar opposite to standard assessment criteria. Undoubtedly, risk factors for VTE associated with exercise are not unique to cardiovascular training or athletes, but the extent to which they might increase the chances of blood clot precipitation in certain participants warrants attention. A multi-agency approach, including research to inform mainstream understanding and awareness about risk factors for VTE in patient groups across age, comorbidity and activity spectra, is required. In this article, the potential for pre-participatory thrombophilia screening, haemostatic monitoring and personalized prophylactic guidelines is discussed.

Deep Vein Thrombosis and Pulmonary Embolism in a Mountain Guide: Awareness, Diagnostic Challenges, and Management Considerations at Altitude

High intensity exercise is associated with several potentially thrombogenic risk factors, including dehydration and hemoconcentration, vascular trauma, musculoskeletal injuries, inflammation, long-distance travel, and contraceptive usage. These are well documented in case reports of venous thrombosis in track and field athletes. For mountaineers and those working at high altitude, additional risks exist. However, despite there being a high degree of vigilance for "classic" conditions encountered at altitude (eg, acute mountain sickness, high altitude pulmonary edema, and high altitude cerebral edema), mainstream awareness regarding thrombotic conditions and their complications in mountain athletes is relatively low. This is significant because thromboembolic events (including deep vein thrombosis, pulmonary embolism, and cerebral vascular thrombosis) are not uncommon at altitude. We describe a case of deep vein thrombosis and pulmonary embolism in a male mountain guide and discuss the diagnostic issues encountered by his medical practitioners. Potential risk factors affecting blood circulation (eg, seated car travel and compression of popliteal vein) and blood hypercoagulability (eg, hypoxia, environmental and psychological stressors [avalanche risk, extreme cold]) relevant to the subject of this report and mountain athletes in general are identified. Considerations for mitigating and managing thrombosis in addition to personalized care planning at altitude are discussed. The prevalence of thrombosis in mountain athletes is uncharted, but lowlanders increasingly go to high altitude to trek, ski, or climb. Blood clots can and do occur in physically active people, and thrombosis prevention and recognition will demand heightened awareness among participants, healthcare practitioners, and the altitude sport/leisure industry at large.

Impacts of hot and cold spells differ for acute and chronic ischaemic heart diseases

Background

Many studies have reported associations between temperature extremes and cardiovascular mortality but little has been understood about differences in the effects on acute and chronic diseases. The present study examines hot and cold spell effects on ischaemic heart disease (IHD) mortality in the Czech Republic during 1994–2009, with emphasis upon differences in the effects on acute myocardial infarction (AMI) and chronic IHD.

Methods

We use analogous definitions for hot and cold spells based on quantiles of daily average temperature anomalies, thus allowing for comparison of results for summer hot spells and winter cold spells. Daily mortality data were standardised to account for the long-term trend and the seasonal and weekly cycles. Periods when the data were affected by epidemics of influenza and other acute respiratory infections were removed from the analysis.

Results

Both hot and cold spells were associated with excess IHD mortality. For hot spells, chronic IHD was responsible for most IHD excess deaths in both male and female populations, and the impacts were much more pronounced in the 65+ years age group. The excess mortality from AMI was much lower compared to chronic IHD mortality during hot spells. For cold spells, by contrast, the relative excess IHD mortality was most pronounced in the younger age group (0–64 years), and we found different pattern for chronic IHD and AMI, with larger effects on AMI.

Conclusions

The findings show that while excess deaths due to IHD during hot spells are mainly of persons with chronic diseases whose health had already been compromised, cardiovascular changes induced by cold stress may result in deaths from acute coronary events rather than chronic IHD, and this effect is important also in the younger population. This suggests that the most vulnerable population groups as well as the most affected cardiovascular diseases differ between hot and cold spells, which needs to be taken into account when designing and implementing preventive actions.