Objective-Acute pulmonary emboli usually resolve within 6 months. However, in 0.1% to 3.8% of cases thrombus transforms into fibrous masses. If vascular obstruction is severe, the resulting condition is chronic thromboembolic pulmonary hypertension (CTEPH). Patients who carry ventriculo-atrial (VA-) shunts for the treatment of hydrocephalus and report a history of shunt infection are at an increased risk for CTEPH. Because CTEPH lacks traditional plasmatic risk factors for venous thromboembolism, we hypothesized that delayed thrombus resolution rather than abnormal coagulation is important, and that bacterial infection would be important for this misguidance. Methods and Results-Human CTEPH thromboemboli were harvested during pulmonary endarterectomy. The effects of Staphylococcal infection on thrombus organization were examined in a murine model of stagnant-flow venous thrombosis. Staphylococcal DNA, but not RNA, was detected in 6 of 7 thrombi from VA shunt carriers. In the mouse model, staphylococcal infection delayed thrombus resolution in parallel with upregulation of transforming growth factor (TGF) beta and connective tissue growth factor. Conclusions-In the present work, we propose a mechanism of disease demonstrating that infection with Staphylococci enhances fibrotic vascular remodeling after thrombosis, resulting in misguided thrombus resolution. Thrombus infection appears to be a trigger in the evolution of CTEPH.

BackgroundSplenectomy is a clinical risk factor for complicated thrombosis. We hypothesized that the loss of the mechanical filtering function of the spleen may enrich for thrombogenic phospholipids in the circulation, thereby affecting the vascular remodeling of thrombosis.Methods and ResultsWe investigated the effects of splenectomy both in chronic thromboembolic pulmonary hypertension (CTEPH), a human model disease for thrombus nonresolution, and in a mouse model of stagnant flow venous thrombosis mimicking deep vein thrombosis. Surgically excised thrombi from rare cases of CTEPH patients who had undergone previous splenectomy were enriched for anionic phospholipids like phosphatidylserine. Similar to human thrombi, phosphatidylserine accumulated in thrombi after splenectomy in the mouse model. A postsplenectomy state was associated with larger and more persistent thrombi. Higher counts of procoagulant platelet microparticles and increased leukocyte–platelet aggregates were observed in mice after splenectomy. Histological inspection revealed a decreased number of thrombus vessels. Phosphatidylserine‐enriched phospholipids specifically inhibited endothelial proliferation and sprouting.ConclusionsAfter splenectomy, an increase in circulating microparticles and negatively charged phospholipids is enhanced by experimental thrombus induction. The initial increase in thrombus volume after splenectomy is due to platelet activation, and the subsequent delay of thrombus resolution is due to inhibition of thrombus angiogenesis. The data illustrate a potential mechanism of disease in CTEPH.

Key Points• PECAM-1 deficiency misguides venous thrombus resolution.• PECAM-1 cell surface shedding occurs at the site of venous thrombosis.Platelet endothelial cell adhesion molecule 1 (PECAM-1) is involved in leukocyte migration and angiogenesis, which are key components of venous thrombus resolution. This study investigated the effect of PECAM-1 deficiency on thrombus resolution in FVB/n mice and the extent to which levels of soluble PECAM-1 (sPECAM-1) correlate with delayed thrombus resolution in humans after acute symptomatic deep vein thrombosis (DVT). In a mouse stagnant flow venous thrombosis model Pecam-1 2/2 thrombi were larger, persisted for longer periods of time, and displayed attenuated macrophage invasion and decreased vessel formation in the presence of increased fibrosis. In humans, higher levels of truncated plasma sPECAM-1 possibly cleaved from cell surfaces, were found in patients with delayed thrombus resolution (assessed via duplex-based thrombus scoring) relative to those whose thrombi resolved (median, 25th/75th percentile): 92.5 (87.7/103.4) ng/mL vs 71.5 (51.1/81.0) ng/mL; P < .001. Furthermore, unresolved human deep vein thrombus specimens stained positively with antibodies specific for the extracellular, but not the cytoplasmic domain of PECAM-1, consistent with accumulation of cleaved PECAM-1. Our data suggest a regulatory role of PECAM-1 in venous thrombus resolution and suggest a predictive value of sPECAM-1 for postthrombotic syndrome (PTS) after acute DVT. (Blood. 2013;122(19):3376-3384)

For intraoperative ECLS, different modes may be applied depending on the intended procedures and required mechanical ventilation. In our experience, different settings of veno-venous ECLS provide sufficient partial or complete lung support, avoiding possible complications associated with other forms of extracorporeal support such as CPB or v-a-ECMO.

Objective Restoration of patency is a natural target of vascular remodeling following venous thrombosis that involves vascular endothelial cells and smooth muscle cells as well as leukocytes. Acute pulmonary emboli usually resolve within six months. However, in some instances, thrombi transform into fibrous vascular obstructions, resulting in occlusion of the deep veins, or in chronic thromboembolic pulmonary hypertension (CTEPH). We proposed that dysregulated thrombus angiogenesis may contribute to thrombus persistence. Approach and Results Mice with an endothelial-cell-specific conditional deletion of vascular endothelial growth factor receptor 2/kinase insert domain protein receptor (VEGF-R2/Kdr) were utilized in a model of stagnant flow venous thrombosis closely resembling human deep vein thrombosis. Biochemical and functional analyses were performed on pulmonary endarterectomy specimens from patients with CTEPH, a human model of non-resolving venous thromboembolism. Endothelial cell-specific deletion of Kdr and subsequent ablation of thrombus vascularization delayed thrombus resolution. In accordance with these findings, organized human CTEPH thrombi were largely devoid of vascular structures. Several vessel-specific genes such as KDR, vascular endothelial cadherin and podoplanin were expressed at lower levels in white CTEPH thrombi than in organizing deep vein thrombi and organizing thrombi from aortic aneurysms. In addition, red CTEPH thrombi attenuated the angiogenic response induced by VEGF. Conclusions In the present work, we propose a mechanism of thrombus non-resolution demonstrating that endothelial cell-specific deletion of Kdr abates thrombus vessel formation, misguiding thrombus resolution. Medical conditions associated with the development of CTEPH may be compromising early thrombus angiogenesis.

Pulmonary arterial hypertension is a severe and progressive disease characterized by a pulmonary vascular remodeling process with expansion of collateral endothelial cells and total vessel occlusion. Endothelial cells are believed to be at the forefront of the disease process. Vascular endothelial growth factor (VEGF) and its tyrosine kinase receptor, VEGF receptor-2 (VEGFR-2), play a central role in angiogenesis, endothelial cell protection, but also in the destabilization of endothelial barrier function. Therefore, we investigated the consequences of altered VEGF signaling in an experimental model, and looked for translational correlates of this observation in patients. We performed an endothelial cell-specific conditional deletion of the kinase insert domain protein receptor (kdr) gene, coding for VEGFR-2, in C57/BL6 mice (Kdr ∆end) and held them in an environmental chamber with 10% FiO 2 or under normoxia for 6 weeks. Kdr knockout led to a mild PH phenotype under normoxia that worsened under hypoxia. Kdr ∆end mice exhibited a significant increase in pulmonary arterial wall thickness, muscularization, and VEGFR-3 + endothelial cells obliterating the pulmonary artery vessel lumen. We observed the same proliferative vasculopathy in our rodent model as seen in patients receiving anti-angiogenic therapy. Serum VEGF-a levels were elevated both in the experimental model and in humans receiving bevacizumab. Interrupted VEGF signaling leads to a pulmonary proliferative arteriopathy in rodents after direct ablative gene manipulation of Kdr. Histologically, similar vascular lesions can be observed in patients receiving anti-VEGF treatment. Our findings illustrate the importance of VEGF signaling for maintenance of pulmonary vascular patency.

Neutrophil accumulation at the coronary culprit lesion site is a strong and independent predictor of mortality in patients with ACS/AMI.

Administration of an ETA receptor blocker during primary PCI in patients with STE-ACS is safe and may improve tissue-level perfusion and LVEF.