Why acute pulmonary embolism becomes chronic thromboembolic pulmonary hypertension: clinical and genetic insights

The significance of CD16+ monocytes in the occurrence and development of chronic thromboembolic pulmonary hypertension: insights from single-cell RNA sequencing

Background

Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious pulmonary vascular disease characterized by residual thrombi in the pulmonary arteries and distal pulmonary microvascular remodeling. The pathogenesis of CTEPH remains unclear, but many factors such as inflammation, immunity, coagulation and angiogenesis may be involved. Monocytes are important immune cells that can differentiate into macrophages and dendritic cells and play an important role in thrombus formation. However, the distribution, gene expression profile and differentiation trajectory of monocyte subsets in CTEPH patients have not been systematically studied. This study aims to reveal the characteristics and functions of monocytes in CTEPH patients using single-cell sequencing technology, and to provide new insights for the diagnosis and treatment of CTEPH.

Methods

Single-cell RNA sequencing (scRNA-seq) were performed to analyze the transcriptomic features of peripheral blood mononuclear cells (PBMCs) from healthy controls, CTEPH patients and the tissues from CTEPH patients after the pulmonary endarterectomy (PEA). We established a CTEPH rat model with chronic pulmonary embolism caused by repeated injection of autologous thrombi through a central venous catheter, and used flow cytometry to detect the proportion changes of monocyte subsets in CTEPH patients and CTEPH rat model. We also observed the infiltration degree of macrophage subsets in thrombus tissue and their differentiation relationship with peripheral blood monocyte subsets by immunofluorescence staining.

Results

The results showed that the monocyte subsets in peripheral blood of CTEPH patients changed significantly, especially the proportion of CD16+ monocyte subset increased. This monocyte subset had unique functional features at the transcriptomic level, involving processes such as cell adhesion, T cell activation, coagulation response and platelet activation, which may play an important role in pulmonary artery thrombus formation and pulmonary artery intimal remodeling. In addition, we also found that the macrophage subsets in pulmonary endarterectomy tissue of CTEPH patients showed pro-inflammatory and lipid metabolism reprogramming features, which may be related to the persistence and insolubility of pulmonary artery thrombi and the development of pulmonary hypertension. Finally, we also observed that CD16+ monocyte subset in peripheral blood of CTEPH patients may be recruited to pulmonary artery intimal tissue and differentiate into macrophage subset with high expression of IL-1β, participating in disease progression.

Conclusion

CD16+ monocytes subset had significant gene expression changes in CTEPH patients, related to platelet activation, coagulation response and inflammatory response. And we also found that these cells could migrate to the thrombus and differentiate into macrophages with high expression of IL-1β involved in CTEPH disease progression. We believe that CD16+ monocytes are important participants in CTEPH and potential therapeutic targets.

miR-221-3p is upregulated in acute pulmonary embolism complicated with pulmonary hypertension and promotes pulmonary arterial smooth muscle cells proliferation and migration by inhibiting PTEN

Pulmonary arterial smooth muscle cells (PASMCs) functions are associated with the pathogenesis of pulmonary hypertension (PH) which is a life-threatening complication of acute pulmonary embolism (APE). This study sought to explore the expression pattern of microRNA (miR)-221-3p in APE-PH patients and its role in PASMCs proliferation and migration. The clinical data and venous blood of APE-PH patients were collected. The expression levels of miR-221-3p and phosphatase and tensin homolog (PTEN) in serum were determined, followed by receiver operator characteristic curve analysis of miR-221-3p diagnostic efficacy. PASMCs were transfected with miR-221-3p mimics and PTEN-overexpressed vector, followed by assessment of cell viability, proliferation, and migration through cell counting kit-8, 5-ethynyl-2'-deoxyuridine, Transwell, and wound healing assays. The binding between miR-221-3p and PTEN 3'UTR region was testified by the dual-luciferase assay. miR-221 was upregulated in the serum of APE-PH patients and presented with good diagnostic efficacy with 1.155 cutoff value, 66.25% sensitivity, and 67.50% specificity. miR-221 was negatively correlated with PTEN in APE-PH patients. miR-221 overexpression facilitated PASMCs proliferation and migration in vitro. miR-221-3p bound to PTEN 3'UTR region to decrease PTEN protein levels. PTEN overexpression abolished the promotive role of miR-221-3p in PASMCs. Overall, miR-221-3p targeted PTEN to facilitate PASMC proliferation and migration.

Pulmonary hypertension in Behçet's disease: echocardiographic screening and multidisciplinary approach

BACKGROUND

Little is known about the prevalence and causes of pulmonary hypertension (PH) in Behçet's disease (BD). This study was conducted to determine the prevalence and causes of PH in BD.

METHODS

In this descriptive study, we screened 154 patients with BD for PH using transthoracic echocardiography between February 2017 and October 2017. An estimated systolic pulmonary arterial pressure (sPAP ≥ 40 mmHg) was used as the cutoff value to define PH. Patients with BD were categorized into 5 groups according to organ involvement including mucocutaneous/ articular, ocular, vascular, gastrointestinal, and neurologic involvement. Additional laboratory and imaging results were obtained from hospital file records to determine the causes of PH.

RESULTS

PH was detected in 17 (11%) patients. Nine (52.9%) of these patients had group II PH (due to left heart disease), 4 (23.5%) had IV PH (due to pulmonary arterial involvement), and 1 had III PH (due to chronic obstructive lung disease). The frequency of PH was higher in BD patients with vascular involvement than those without (52.9% vs 28.5%; p = 0.04). Among 10 patients with pulmonary artery involvement (PAI) 4 (40%) had PH. Although the vascular BD group had the highest rate of PH, we observed no statistically significant difference in the frequency of PH between the predefined BD subgroups.

DISCUSSION

: PH is not rare in patients with BD. The majority of BD patients with PH are in group II or IV PH. Patients with vascularinvolvement carry a higher risk for the development of PH. Monitoring BD patients with PAI should be considered for the development of group IV PH.

Clinical and imaging risk factors for the persistence of thromboembolism following acute pulmonary embolism

Background

Predicting the progression of acute pulmonary embolism to chronic pulmonary thromboembolism (CPTE) disease is essential to monitoring and improving the long-term prognosis of pulmonary embolism. We explored the risk factors for chronic persistence of thromboembolism after acute pulmonary embolism.

Methods

Cases with newly onset acute pulmonary embolism in the China-Japan Friendship Hospital from November 2016 to November 2019 were retrospectively analyzed. The clinical characteristics, serological examination results, and treatment strategies of acute pulmonary embolism patients were obtained through the electronic medical record system (Goodwill E-Health Info Co., Ltd.). Imaging parameters on computed tomography pulmonary angiography (CTPA) images at the onset of the acute pulmonary embolism were measured and counted. Notably, we propose a new parameter based on CTPA images: the ratio of S_d (sum of residual segmental pulmonary artery diameter) to MPA_d (the main pulmonary artery diameter) (S_d/MPA_d). After 3 months of regular treatment for acute pulmonary embolism, patients were classified into a CPTE group or a non-CPTE group based on the presence of residual embolus. All data were compared between the CPTE group and non-CPTE group. Furthermore, logistic regression analysis was used to investigate risk factors for the progression of acute pulmonary embolism to CPTE.

Results

A total of 77 cases (male:female = 1:1.26) were included in the study. There were 43 cases (55.84%) in the CPTE group and 34 cases in the non-CPTE group (44.16%). The results of univariate analysis showed that there were statistically significant differences between the 2 groups in risk stratification (χ²=8.043; P=0.005), protein S activity (χ²=5.551; P=0.018), the ratio of sum of residual segmental pulmonary artery diameter to the main pulmonary artery diameter (S_d/MPA_d; t=–2.103; P=0.039), Mastora score (U=362.500; P<0.001), and embolus location (χ²=16.969; P<0.001). However, there were no statistically significant differences between the 2 groups in treatment options (P=0.381). According to multivariate logistic-regression analysis, protein S activity <55% (P=0.025), S_d/MPA_d ≥1.97 (P=0.011), and an embolus being located in the central pulmonary artery (P<0.001) were independent risk factors for chronic persistence of thromboembolism following acute pulmonary embolism.

Conclusions

The protein S activity, location of the embolus, and S_d/MPA_d on CTPA at the onset of acute pulmonary embolism may suggest the progression of acute pulmonary embolism to CPTE.

Acute on Chronic Thromboembolic Pulmonary Hypertension: Case Series and Review of Management

Chronic thromboembolic pulmonary hypertension (CTEPH) is a distinct form of precapillary pulmonary hypertension classified as group 4 by the World Symposium on Pulmonary Hypertension (WSPH) and should be excluded during an episode of acute pulmonary embolism (PE). Patients presenting to emergency departments with sudden onset of signs and symptoms of acute PE may already have a pre-existing CTEPH condition decompensated by the new PE episode. Identifying an underlying and undiagnosed CTEPH during acute PE, while challenging, is an important consideration as it will alter the patients’ acute and long-term management. Differential diagnosis and evaluation require an interdisciplinary expert team. Analysis of the clinical condition, the CT angiogram, and the hemodynamic situation are important considerations; patients with CTEPH usually have significantly higher sPAP at the time of index PE, which is unusual and unattainable in the context of acute PE and a naïve right ventricle. The imaging may reveal signs of chronic disease such as right ventricle hypertrophy bronchial collaterals and atypical morphology of the thrombus. There is no standard for the management of acute on chronic CTEPH. Herein, we provide a diagnostic and management algorithm informed by several case descriptions and a review of the literature.

Hospitalizations for pulmonary embolism in Brazil (2008-2019): an ecological and time series study

Objective

To assess the temporal trends of hospitalizations for pulmonary embolism (PE) in Brazil, its regions, and states between 2008 and 2019.

Methods

An ecological and time series study was conducted. Data were obtained from the Hospital Information System (SIH) of the Brazilian Ministry of Health. The inflection point regression model was applied for temporal trend analyses. Trends were classified as increasing, decreasing, or stationary according to the slope of the regression line. The Annual Percent Charge (APC) and the Average Annual Percent Change (AAPC) were calculated considering a confidence interval of 95% and p-value <0.05. Furthermore, spatial distribution maps of epidemiological indicators related to PE in Brazil were elaborated.

Results

There was an increasing trend in the hospitalization rate for PE in Brazil, ranging from 2.57 in 2008 to 4.44/100,000 in 2019 (AAPC=5.6%; p<0.001). Total and average hospitalizations costs also showed increasing trend in the country (AAPC=9.2% and 3.0%, respectively). Still, there was a decrease in the in-hospital mortality rate (from 21.21% to 17.11%; AAPC=-1.9%; p<0.001). Similar trends were observed in most regions. The average hospitalization time in Brazil showed a stationary trend. The hospitalization rate has also increased in 18 states (66.67%). Seven states showed a decrease in the mortality rate (25.93%), except for Roraima, which showed an increasing trend.

Conclusion

Hospitalizations for PE represent a serious public health problem in Brazil and the temporal patterns observed herein demonstrate an increasing trend in all regions and states of the country.

Peripheral Arterial Stiffness in Acute Pulmonary Embolism and Pulmonary Hypertension at Short-Term Follow-Up

Chronic thromboembolic pulmonary hypertension (CTEPH) is a severe and under-recognized complication of acute pulmonary embolism (PE). Forty consecutive patients with acute PE (Group 1), predominantly female (22, 55%) with a mean age of 69 ± 15 years, were matched for demographic data with 40 healthy subjects (Group 2), 40 systemic hypertension patients (Group 3) and 45 prevalent idiopathic pulmonary arterial hypertension (IPAH) patients (Group 4). The baseline evaluation included physical examination, NYHA/WHO functional class, right heart catheterization (RHC) limited to IPAH patients, echocardiographic assessment and systemic arterial stiffness measurement by cardio-ankle vascular index (CAVI). Patients with PE underwent an echocardiographic evaluation within 1 month from hospital discharge (median 27 days; IQR 21–30) to assess the echo-derived probability of PH. The CAVI values were significantly higher in the PE and IPAH groups compared with the others (Group 1 vs. Group 2, p < 0.001; Group 1 vs. Group 3, p < 0.001; Group 1 vs. Group 4, p = ns; Group 4 vs. Group 2, p < 0.001; Group 4 vs. Group 3, p < 0.001; Group 2 vs. Group 3, p = ns). The predicted probability of echocardiography-derived high-risk criteria of PH increases for any unit increase of CAVI (OR 9.0; C.I.3.9–20.5; p = 0.0001). The PE patients with CAVI ≥ 9.0 at the time of hospital discharge presented an increased probability of PH. This study highlights a possible positive predictive role of CAVI as an early marker for the development of CTEPH.

Research progress on the pathogenesis of CTEPH

Chronic thromboembolic pulmonary hypertension (CTEPH) is an established long-term complication of pulmonary thromboembolism (PTE). However, studies have shown that many patients with a definitive CTEPH diagnosis have no history of symptomatic PTE, suggesting that PTE is not the only cause of CTEPH. Despite extensive progress in research on pulmonary hypertension in recent years, due to a lack of relevant studies on the pathophysiology of CTEPH, implementing pulmonary endarterectomy (PEA) in patients has many challenges, and the prognosis of patients with CTEPH is still not optimistic. Therefore, revealing the pathogenesis of CTEPH would be of great significance for understanding the occurrence and development of CTEPH, developing relevant drug treatment studies and formulating intervention strategies, and may provide new preventive measures. This article summarizes the current research progress in CTEPH pathogenesis from the perspective of risk factors related to medical history, abnormal coagulation and fibrinolytic mechanisms, inflammatory mechanisms, genetic susceptibility factors, angiogenesis, in situ thrombosis, vascular remodeling, and other aspects.

Imaging of Chronic Thromboembolic Disease

Acute pulmonary embolism (PE) is a leading cause of cardiovascular morbidity. The most common long-term complication of acute PE is chronic thromboembolic disease, a heterogenous entity which ranges from asymptomatic imaging sequelae to persistent symptoms. Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare disease that can develop in this population and represents the only treatable type of pulmonary hypertension. Recognition of the characteristic findings of chronic pulmonary embolism and CTEPH provides not only diagnostic information, but is also crucial for guiding therapy. The present state-of-the-art review focuses on the multimodality imaging features of chronic pulmonary embolism. Detailed description and illustrations of relevant imaging findings will be demonstrated for ventilation/perfusion (V/Q) scan, CT scan and Dual-Energy CT and MRI and features that distinguish chronic PE from common imaging mimics.

Differential effect of mild and severe pulmonary embolism on the rat lung transcriptome

BACKGROUND

Pulmonary thromboembolism (PTE) is a common diagnosis and a leading cause of cardiovascular morbidity and mortality. A growing literature has associated PE with systemic inflammation, and global hyper-coagulability, which contribute to lung remodeling and clot recurrence. The source and mechanism of inflammation remains unstudied. In humans, inhibition of cholesterol synthesis with statins decreases biomarkers of inflammation. We test the differential effect of pulmonary vascular occlusion during mild and severe pulmonary embolism on the lung transcriptome.

METHODS

Experimental PE was induced in adult male rats by injection of 25 micron polystyrene microspheres into the jugular vein. The effect of Mild PE, (2-h right ventricular systolic pressure [RVSP] normal, 18-h RVSP 44 mmHg) and Severe PE (2-h RVSP > 50 mmHg; 18-h RVSP 44 mmHg) on lungs was assessed by measuring transcriptome-wide changes in gene expression by DNA microarrays.

RESULTS

Severe PE was associated with a large change in lung gene expression and in the expression of KEGG pathways and other gene functional annotation groups. Mild PE was also associated with a large number of significant changes in gene expression and in the expression of KEGG pathways and gene functional annotation groups, even after only 2 h of PE. Up-regulated pathways included increased adipocytokine, chemokine and cytokine signaling as well as cholesterol synthesis.

CONCLUSIONS

Mild PE without acute pulmonary hypertension (PH) increased lung gene expression of inflammatory pathways, including increased cholesterol synthesis. These data indicate that even mild persistent pulmonary vascular occlusion is capable of inciting an inflammatory response from the lung. These data imply the detrimental effect of unresolved pulmonary obstruction from PE.

Current concepts in the pathogenesis of chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by fibrotic obstruction of the proximal pulmonary arteries, and it is believed to result from incomplete thrombus resolution after acute pulmonary embolism. While treatment for this condition with surgery and medical therapy has improved outcomes, our understanding of the molecular mechanisms underlying CTEPH is incomplete. Numerous risk factors have been associated with the development of CTEPH, including but not limited to acquired thrombophilias and chronic inflammatory states. A minority of patients with CTEPH have an abnormal fibrin structure that may delay thrombus resolution. Recently, examination of resected scar material in patients with CTEPH has suggested that deficient angiogenesis may play a role in thrombus nonresolution, and there is increasing interest in factors that drive intravascular scar formation. An additional challenge in CTEPH research is understanding the etiology and implications of the small-vessel disease present in many patients. Future work will likely be directed at understanding the pathways important to disease pathogenesis through further examinations of resected tissue material, continued work on animal models, and genomic approaches to identify alterations in gene expression or gene variants that may distinguish CTEPH from other forms of pulmonary hypertension.

Pulmonary vascular morphology as an imaging biomarker in chronic thromboembolic pulmonary hypertension

Patients with chronic thromboembolic pulmonary hypertension (CTEPH) have morphologic changes to the pulmonary vasculature. These include pruning of the distal vessels, dilation of the proximal vessels, and increased vascular tortuosity. Advances in image processing and computer vision enable objective detection and quantification of these processes in clinically acquired computed tomographic (CT) scans. Three-dimensional reconstructions of the pulmonary vasculature were created from the CT angiograms of 18 patients with CTEPH diagnosed using imaging and hemodynamics as well as 15 control patients referred to our Dyspnea Clinic and found to have no evidence of pulmonary vascular disease. Compared to controls, CTEPH patients exhibited greater pruning of the distal vasculature (median density of small-vessel volume: 2.7 [interquartile range (IQR): 2.5-3.0] vs. 3.2 [3.0-3.8]; P = 0.008), greater dilation of proximal arteries (median fraction of blood in large arteries: 0.35 [IQR: 0.30-0.41] vs. 0.23 [0.21-0.31]; P = 0.0005), and increased tortuosity in the pulmonary arterial tree (median: 4.92% [IQR: 4.85%-5.21%] vs. 4.63% [4.39%-4.92%]; P = 0.004). CTEPH was not associated with dilation of proximal veins or increased tortuosity in the venous system. Distal pruning of the vasculature was correlated with the cardiac index (R = 0.51, P = 0.04). Quantitative models derived from CT scans can be used to measure changes in vascular morphology previously described subjectively in CTEPH. These measurements are also correlated with invasive metrics of pulmonary hemodynamics, suggesting that they may be used to assess disease severity. Further work in a larger cohort may enable the use of such measures as a biomarker for diagnostic, phenotyping, and prognostic purposes.

Dual-energy CT for differentiating acute and chronic pulmonary thromboembolism: an initial experience

The purpose of this study was to prospectively evaluate the diagnostic capability of single-phase dual-energy CT (DECT) angiography to differentiate acute and chronic pulmonary thromboembolism (APTE, CPTE). We prospectively enrolled 26 patients (M:F = 9:17; mean age, 61 years old) with a filling defect in the pulmonary artery on DECT angiography. They were divided into two groups-APTE and CPTE-based on the clinical criteria. Two investigators quantitatively measured the following parameters at the embolism and main pulmonary artery: CT attenuation density [Hounsfield unit (HU) values], iodine-related HU value (IHU), and iodine concentration (IC, mg/ml). These parameters of the embolism and their ratio divided by those of the main pulmonary artery were compared between APTE and CPTE groups. Among 26 patients, 15 were categorized into the APTE group and 11 into the CPTE group. The mean HU, IHU, and IC values of emboli were significantly different between the APTE and CPTE groups (32.2 ± 17.0 vs. 52.1 ± 13.6 HU; P = 0.016, 7.2 ± 2.8 vs. 27.3 ± 12.7 HU; P < 0.001, and 0.57 ± 0.23 vs. 1.56 ± 0.67; P < 0.001). The mean HU, IHU, and IC ratios between emboli and main pulmonary arteries were also significantly different between the two groups (0.085 ± 0.046 vs. 0.156 ± 0.064 HU; P = 0.003, 0.023 ± 0.013 vs. 0.099 ± 0.053; P < 0.001, and 0.048 ± 0.035 vs. 0.130 ± 0.064; P = 0.001). DECT angiography using a quantitative analytic methodology can be used to differentiate between APTE and CPTE.

Risk marker associations with venous thrombotic events: a cross-sectional analysis

OBJECTIVE

To examine the interrelations among, and risk marker associations for, superficial and deep venous events-superficial venous thrombosis (SVT), deep venous thrombosis (DVT) and pulmonary embolism (PE).

DESIGN

Cross-sectional analysis.

SETTING

San Diego, California, USA.

PARTICIPANTS

2404 men and women aged 40-79 years from four ethnic groups: non-Hispanic White, Hispanic, African-American and Asian. The study sample was drawn from current and former staff and employees of the University of California, San Diego and their spouses/significant others.

OUTCOME MEASURES

Superficial and deep venous events, specifically SVT, DVT, PE and combined deep venous events (DVE) comprising DVT and PE.

RESULTS

Significant correlates on multivariable analysis were, for SVT: female sex, ethnicity (African-American=protective), lower educational attainment, immobility and family history of varicose veins. For DVT and DVE, significant correlates included: heavy smoking, immobility and family history of DVEs (borderline for DVE). For PE, significant predictors included immobility and, in contrast to DVT, blood pressure (BP, systolic or diastolic). In women, oestrogen use duration for hormone replacement therapy, in all and among oestrogen users, predicted PE and DVE, respectively.

CONCLUSIONS

These findings fortify evidence for known risk correlates/predictors for venous disease, such as family history, hormone use and immobility. New risk associations are shown. Striking among these is an association of PE, but not DVT, to elevated BP: we conjecture PE may serve as cause rather than consequence. Future studies should evaluate the temporal direction of this association. Oxidative stress and cell energy compromise are proposed to explain and predict many risk factors, operating through cell-death mediated triggering of coagulation activation.