Epidemiology and pathophysiology of vascular thrombosis in acclimatized lowlanders at high altitude: A prospective longitudinal study

JAK2 Mutation Assessment in Thrombotic Events at Unusual Anatomical Sites: Insights from a High-Altitude Cohort

Introduction

Thrombosis stands as a significant contributor to both morbidity and mortality in individuals afflicted with myeloproliferative neoplasms. This retrospective study investigated the association between JAK2 mutations and venous thrombosis at unusual sites, and in young individuals with ischemic stroke, residing at high altitudes in the Aseer region, Saudi Arabia.

Patients and Methods

Data were collected from two high-altitude referral hospitals over three years (2020-2022). Records of all JAK2 mutation tests were reviewed. Those requested as part of evaluation of thrombosis events, without known myeloproliferative neoplasms (MPNs) were analysed.

Results

Among the 208 JAK2 tests, 40 (19.2%) were linked to thrombotic event evaluations. The cohort, with a median age of 41, included 17 (42.7%) males and 23 females, with 57.5% having completely normal complete blood counts (CBC). Thrombotic events were divided between splanchnic vein thrombosis (36.6%) and cerebral thrombosis (34.1%), while the remaining cases involved unprovoked deep vein thromboses/pulmonary embolisms and portal vein thrombosis. Only 2 (5%) participants tested positive for JAK2 mutations: a 17-year-old male diagnosed concurrently with polycythemia vera after renal vein thrombosis and a 31-year-old woman with hepatic vein thrombosis and a normal CBC.

Conclusion

This study reveals that JAK2 mutations are infrequently found in high-altitude patients with unprovoked DVT, PE, or atypical thrombosis. While JAK2 testing is notably relevant for splanchnic vein thrombosis, its routine use for other thrombotic events, particularly with normal CBC results, remains uncertain. Given the study's limitations, further prospective research with larger cohorts is needed to refine guidelines for JAK2 mutation testing in various thrombotic contexts.

Cerebral venous thrombosis at high altitude: more severe symptoms and specific predisposing factors than plain areas

BACKGROUND

Exposure to a high-altitude environment is a risk factor for cerebral venous thrombosis (CVT) probably due to hypercoagulability. The study aims to explore the unique characteristics of CVT patients in high-altitude areas of China by comparing them with those in plain areas.

METHODS

We retrospectively included consecutive patients with CVT admitted to Tibet Autonomous Region People's Hospital (altitude 3650 m) and Peking Union Medical College Hospital (altitude 43.5 m) between January 2015 and December 2023. Patients from the plateau and the plain were considered two independent groups in this study. The risk factors, clinical and radiological presentations, treatment, and outcomes were analyzed and compared between the two groups.

RESULTS

A total of 169 patients with CVT were included in the study, 48 patients from plateau and 121 patients from plain. The median age was 27 and 34 years old, and women accounted for 66.7% and 54.5% respectively. Headache (91.7% vs. 71.1%, P = 0.004), altered consciousness (31.3% vs. 16.5%, P = 0.033), hemorrhage (41.7% vs. 19.0%, P = 0.002), and venous infarction (50.0% vs. 25.6%, P = 0.002) on imaging were more common in patients from plateau than those from plain. Pregnancy or puerperium was significantly more common in highland patients (25% vs. 5.8%, P < 0.001). The levels of D-Dimer (1.7 vs. 0.8 mg/L FEU, P = 0.01), fibrinogen (3.7 vs. 3.0 g/L, P < 0.001), hemoglobin (157 vs. 129 g/L, P = 0.01), white blood cells (9.6 vs. 7.5*1012/L, P < 0.001) and highly sensitive C-reactive protein (20.2 vs. 3.2 mg/L, P = 0.005) were remarkably higher in highland patients. The percentage of receiving anticoagulant therapy was lower in high-altitude patients (70.8% vs. 93.4%, P < 0.001). Favorable outcome at follow-up was observed in 81.4% of highland patients and 90.7% of lowland patients, with a median follow-up time of 330 days and 703 days respectively.

CONCLUSIONS

The more severe clinical and imaging manifestations along with prominent inflammatory and hypercoagulable states were observed in plateau CVT patients, probably due to exposure to the hypoxic environment at high altitude. Pregnancy or puerperium were more common in highland patients. The overall prognosis of CVT patients from both groups were favorable.

Recent advances in predicting acute mountain sickness: from multidimensional cohort studies to cutting-edge model applications

High-altitude illnesses, encompassing a spectrum of health threats including Acute Mountain Sickness (AMS), pose significant challenges to individuals exposed to high altitude environments, necessitating effective prophylaxis and immediate management. Given the variability in individual responses to these conditions, accurate prediction of high-altitude illnesses onset is of paramount importance. This review systematically consolidates recent advancements in research on predicting AMS by evaluating existing cohort data, predictive models, and methodologies, while also delving into the application of emerging technologies. Through a thorough analysis of scholarly literature, we discuss traditional prediction methods anchored in physiological parameters (e.g., heart rate, respiratory frequency, blood pressure) and biochemical markers, as well as the integration and utility of novel technologies such as biosensors, genetic testing, and artificial intelligence within high-altitude prediction research. While conventional pre-diction techniques have been extensively used, they are often constrained by limitations in accuracy, reliability, and multifactorial influences. The advent of these innovative technologies holds promise for more precise individual risk assessments and personalized preventive and therapeutic strategies across various forms of AMS. Future research endeavors must pivot decisively towards the meticulous identification and stringent validation of innovative predictive biomarkers and models. This strategic re-direction should catalyze intensified interdisciplinary cooperation to significantly deepen our mechanistic insights into the pathogenesis of AMS while refining existing prediction methodologies. These groundbreaking advancements harbor the potential to fundamentally transform preventive and therapeutic frameworks for high-altitude illnesses, ultimately securing augmented safety standards and wellbeing for individuals operating at elevated altitudes with far-reaching global implications.

Central Retinal Artery Occlusion in Young Adults at High Altitude: Thin Air, High Stakes

Rana, Vipin, Pradeep Kumar, Sandeepan Bandopadhyay, Vijay K. Sharma, Meenu Dangi, Dattakiran Joshi, Sanjay Kumar Mishra, Satyabrat Srikumar, and V.A. Arun. Central retinal artery occlusion in young adults at high altitude: thin air, high stakes. High Alt Med Biol. 00:000-000, 2024.-We present five cases of young security personnel who were posted at high altitude (HA) for a duration of at least 6 months and presented with a sudden decrease of vision in one eye. The diagnosis of central retinal artery occlusion (CRAO) was made in all patients. Fundus fluorescein angiography and optical coherence tomography of the macula supported the diagnosis. None of these cases had any preexisting comorbidities. Erythrocytosis was noticed in all patients, and two of them had hyperhomocysteinemia. Four out of five patients showed either middle cerebral artery or internal carotid artery (ICA) thrombosis on computed tomography angiography. The patients were managed by a team of ophthalmologist, hematologist, vascular surgeon, and neurologist. In cases of incomplete ICA occlusion, patients were managed surgically. However, in the case of complete ICA occlusion, management was conservative with antiplatelet drugs. This case series highlights HA-associated erythrocytosis and hyperhomocysteinemia as important risk factors for CRAO in young individuals stationed at HA.

Hormonal Contraception and Menstrual Cycle Control at High Altitude: A Scoping Review-UIAA Medical Commission Recommendations

Horakova, Lenka , Susi Kriemler, Vladimír Študent, Jacqueline Pichler Hefti, David Hillebrandt, Dominique Jean, Kastė Mateikaitė-Pipirienė, Peter Paal, Alison Rosier, Marija Andjelkovic, Beth Beidlemann, Mia Derstine, and Linda E. Keyes. Hormonal contraception and menstrual cycle control at high altitude: a scoping review-UIAA Medical Commission recommendations. High Alt Med Biol. 00:00-00, 2024. Background: Women who use hormonal contraception (HC) may have questions about their use during travel to high altitude. This scoping review summarizes current evidence on the efficacy and safety of HC and cycle control during high-altitude travel. Methods: We performed a scoping review for the International Climbing and Mountaineering Federation (UIAA) Medical Commission series on Women's Health in the Mountains. Pertinent literature from PubMed and Cochrane was identified by keyword search combinations (including contraception) with additional publications found by hand search. Results: We identified 17 studies from 7,165 potentially eligible articles. No articles assessed the efficacy of contraception during a short-term high-altitude sojourn. Current data show no advantage or disadvantage in HC users for acclimatization or acute mountain sickness (AMS). Use of HC during high-altitude travel is common and safe for menses suppression. A potential concern of estrogen-containing HC is the increased thrombotic risk, which theoretically could be compounded in hypobaric hypoxia. Conclusions: Evidence is limited for the interaction of HC and high altitude on performance, thrombosis, and contraceptive efficacy. HC does not affect the risk of AMS. The most efficacious and safest method at high altitude is generally the one women are most familiar with and already using.

Altitude-Related Venous Thrombosis With Heart Disease: An Updated Review

Altitude-related venous thrombosis (ARVT) is a condition of growing concern among individuals engaged in high-altitude travel and activities. This updated review explores the epidemiology, pathophysiological mechanisms, clinical presentations, and management of ARVT based on a thematic analysis and synthesis of the existing literature. ARVT's multifactorial etiology involves the interplay of hypobaric hypoxia and endothelial dysfunction, creating a procoagulant state and increasing the risk of thrombosis. Common clinical manifestations include pain, swelling, and redness in the extremities, necessitating accurate and timely diagnosis, particularly in remote settings. Thromboprophylaxis during high-altitude travel and activities plays a crucial role in reducing the risk of ARVT, while anticoagulation remains the mainstay of management. Further research is needed to optimize preventive and treatment strategies, enhancing patient outcomes and safety in high-altitude environments.

High-Altitude Exposure and Cerebral Venous Thrombosis: An Updated Systematic Review

Kharel, Sanjeev, Suraj Shrestha, Samriddha Raj Pant, Suman Acharya, Amit Sharma, Santosh Baniya, and Sanjeeb S. Bhandari. High-altitude exposure and cerebral venous thrombosis: an updated systematic review. High Alt Med Biol. 24:167-174, 2023. Background: High altitude (HA) may increase the risk of cerebral venous thrombosis (CVT). Differentiating it from other HA illnesses is crucial for prompt treatment and better outcomes. We aimed to summarize the clinical data, etiology, and risk factors of this poorly understood entity at an HA. Materials and Methods: A systematic literature search of various databases, including PubMed, Embase, and Google Scholar, was done using relevant keywords; cerebral venous thrombosis; HA, up to May 1, 2022. Results: A total of nine studies, including 75 cases of CVT at HA (3,000-8,848 m), with 66 males and 9 females, were included in this review. Headache and seizure were the most common clinical presentations. Smoking, drinking habits, and the use of oral contraceptive pills (OCP) were the most common risk factors for the development of CVT. Similarly, various underlying hypercoagulable states were also present among cases of CVT associated with HA exposure. Conclusion: Our review concludes that HA exposure can predispose individuals with risk factors such as preexisting hypercoagulable states, smoking, drinking habits, and use of OCP to an increased risk of CVT.