PAI-1 polymorphism as a cause of severe high altitude associated arteriovenous thrombosis

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.

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

BACKGROUND

Previous literature suggests that thrombosis is more common in lowlanders sojourning at high altitude (HA) compared to near-sea-level. Though the pathophysiology is partly understood, little is known of its epidemiology. To elucidate this, an observational prospective longitudinal study was conducted in healthy soldiers sojourning for months at HA.

METHODS

A total of 960 healthy male subjects were screened in the plains, of which 750 ascended, to altitudes above 15,000ft (4,472m). Clinical examination, haemogram, coagulogram, markers of inflammation and endothelial dysfunction, were studied at three time points during ascent and descent. The diagnosis of thrombosis was confirmed radiologically in all cases where a thrombotic event was suspected clinically. Subjects developing thrombosis at HA were labelled as Index Cases (ICs) and compared to a nested cohort of the healthy subjects (comparison group,(CG)) matched for altitude of stay.

FINDINGS

Twelve and three subjects, developed venous (incidence: 5,926/105 person-years) and arterial (incidence: 1,482/105 person-years) thrombosis at HA, respectively. The ICs had enhanced coagulation (FVIIa: p<0.001; FXa: p<0.001) and decreased levels of natural anticoagulants (thrombomodulin, p=0.016; tissue factor pathway inhibitor [TFPI]: p<0.001) and a trend to dampened fibrinolysis (tissue plasminogen activator tPA; p=0.078) compared to CG. ICs also exhibited statistically significant increase in the levels of endothelial dysfunction and inflammation markers (vascular cell adhesion molecule-1[VCAM-1], intercellular adhesion molecule-1 [ICAM-1], vascular endothelial growth factor receptor 3 [VEGFR-3], P-Selectin, CD40 ligand, soluble C-reactive protein and myeloperoxidase: p<0.001).

INTERPRETATION

The incidence of thrombosis in healthy subjects at HA was higher than that reported in literature at near sea-level. This was associated with inflammation, endothelial dysfunction, a prothrombotic state and dampened fibrinolysis.

FUNDING

Research grants from the Armed Forces Medical Research Committee, Office of the Director General of Armed Forces Medical Services (DGAFMS) & Defence Research and Development Organization (DRDO), Ministry of Defence, India.

Prevalence and Clinical Characteristics of Post-Thrombotic Syndrome in High-Altitude-Induced Deep Vein Thrombosis: Experience of a Single Tertiary Care Center from Real-World Settings

Uday, Yanamandra, Revanth Boddu, Suman Pramanik, Kundan Mishra, Rajan Kapoor, Ankur Ahuja, Tathagata Chatterjee, and Satyaranjan Das. Prevalence and clinical characteristics of post-thrombotic syndrome in high-altitude-induced deep vein thrombosis: experience of a single tertiary care center from real-world settings. High Alt Med Biol. 21:319-326, 2020. Background: Exposure to high altitude (HA) is a recognized predisposing factor for venous thrombosis. Post-thrombotic syndrome (PTS) is a significant late complication, occurring in ∼30%-50% of patients of deep vein thrombosis (DVT). There are not many studies about the characteristics of PTS in patients with HA-DVT. Aim: The aim was to study the epidemiology and clinical characteristics of PTS using a noninvasive Villalta score and identify the risk factors for its development in patients with HA-DVT. Methodology: This is a retrospective single-center observational study (n = 47). The diagnosis of HA-DVT was confirmed using color Doppler ultrasonography at HA. The patients were managed with low molecular weight heparin, followed by vitamin K antagonist therapy till normalization of D-dimer and imaging. The therapeutic target range of >80% was ensured. Villalta scale was used for PTS assessment. JMP 15.0 was used for statistical analysis. Results: All study participants were male with a median age of 34 years, of which 46.81% developed PTS with mean Villalta of 5.29 ± 4.25. The most common symptom was pain (87.23%; n = 41), whereas the most common sign was hyperpigmentation (42.5%; n = 20). On multivariate analysis, the time from onset of DVT and the extent of DVT were related to the development of PTS (degree of freedom [dF] = 5, χ² = 17.34, p = 0.0039) with a likelihood ratio of 4.95 (p = 0.026) and 4.96 (p = 0.026), respectively. The extent of DVT was associated with the severity of PTS (dF = 5, χ² = 12.6, p = 0.0273) with a likelihood ratio of 5.24 (p = 0.022). Conclusions: PTS develops in approximately half of the patients with HA-DVT. The extent of DVT is a significant risk factor for both development of PTS and its severity, whereas time to assessment of PTS from the onset of DVT was associated only with the occurrence of PTS.

Investigation of Plasminogen Activator Inhibitor-1 (PAI-1) 4G/5G promoter polymorphism in Indian venous thrombosis patients: A case-control study

BACKGROUND

The role of PAI-1 4G/5G polymorphism in venous thrombosis has been contradictory. PAI-1 4G/4G genotype is associated with elevated levels of PAI-1 resulting in a hypofibrinolytic state and a higher thrombotic risk.

OBJECTIVE

In this study, the distribution of genotypes and frequency of alleles of the 4G/5G polymorphism of PAI-1 gene in Indian patients with different types of venous thrombosis was investigated for its role in development of thrombosis.

METHOD

A total of 87 portal vein thrombosis (PVT), 71 Budd-Chiari syndrome (BCS), 156 cerebral vein thrombosis (CVT), and 163 deep vein thrombosis (DVT) patients were studied alongside 251 healthy controls for the PAI-1 4G/5G polymorphism by allele-specific PCR.

RESULTS

Frequency of 4G/4G genotype was higher in all groups in comparison with controls. 4G/4G was associated with PVT risk (OR=2.51, 95% CI=1.29-4.96, P=.0075), BCS risk (OR=5.98, 95% CI=2.68-13.42, P<.0001), and DVT risk (OR=1.75, 95% CI=0.98-3.02, P=.0225). This is the first case-control study from India establishing PAI-1 4G/4G as a strong risk factor for abdominal thrombosis (PVT and BCS). Statistically significant association was not found between 4G/4G genotype and CVT risk.

CONCLUSION

PAI-1 4G/4G is a strong risk factor for venous thrombosis in Indian patients and should be included in laboratory testing panel of thrombophilia.

Dysfunctional fibrinolysis and cerebral venous thrombosis

Cerebral venous thrombosis (CVT) is an uncommon neurological disease with high morbidity and mortality. Even after extensive thrombophilia screening, majority of the thrombosis cases remain with unknown etiology. Hypofibrinolysis due to acquired or congenital deficiencies or abnormalities in factors in the fibrinolytic cascade is a known cause of thrombosis at any site. In the present study 104 cases of radiologically confirmed CVT cases were investigated for the conventional thrombophilia along with factors in the fibrinolytic cascade to find a possible etiology for the clinical manifestation. Conventional thrombophilia markers which included PC, PS, AT and FVL mutation were detected in 16.3% of the patients. Approximately 19% cases had grossly elevated plasma PAI-1 levels. PAI-1 4G/4G genotype was found to be strongly associated with high PAI-1 levels. 2.9% cases had reduced tPA levels, 1.9% had plasminogen deficiency and 1.9% cases had increased alpha-2-antiplasmin levels. Along with conventional thrombophilia, dysfunctional fibrinolysis is found to be strongly associated with CVT. Understanding the role of risk factors is important for appropriate treatment of this serious disorder.