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Objective To evaluate the incidence and clinical relevance of silent nontarget occlusion (NTO) of superficial and deep veins occurring after ultrasound-guided foam sclerotherapy (UGFS) that can be detected by serial duplex ultrasound scan (DUS). Methods This retrospective analysis evaluated the medical records of patients treated with UGFS at a private clinic in Moscow, Russia from 2015 to 2017. All patients underwent serial DUS at 1 to 2 weeks and 1, 3, 6, and 12 months after UGFS. Results During the observation period, 268 patients were treated with UGFS, using physician compounded polidocanol foam 257 lower limbs of 196 patients (73%) with varicose veins who underwent DUS at 1 to 2 weeks after the last session of UGFS (inclusion time-point): 139 women and 57 men (mean age: 44.2 ± 12.2 years) with the following CEAP clinical class distribution: C2, 74.0%; C3, 20.0%; C4, 4.5%; and C5, 1.5%. NTO at the inclusion time-point occurred in 60 limbs (23.3%) of 57 patients (28.5%) and was symptomatic only in three limbs (1.2%). Most occlusions were localized in the untreated great saphenous vein trunk ( n = 28) and the calf muscle veins ( n = 23). Overall, 72%, 44%, 29%, and 10% of all limbs and 77%, 45%, 28%, and 12% of limbs with NTO were followed up by DUS at 1, 3, 6, and 12 months, respectively. There were no cases of thrombus progression or symptomatic venous thromboembolism (VTE). At six months, no deep vein occlusions persisted. Conclusions The frequency of nontarget vein occlusion after UGFS revealed by serial DUS may be as high as 23.3%. These occlusions tend to resolve within six months and are not associated with symptomatic VTE.

According to a widespread theory, thrombotic masses are not formed in the pulmonary artery (PA) but result from migration of blood clots from the venous system. This concept has prevailed in clinical practice for more than a century. However, a new technologic era has brought forth more diagnostic possibilities, and it has been shown that thrombotic masses in the PA could, in many cases, be found without any obvious source of emboli. Chronic obstructive pulmonary disease, asthma, sickle cell anemia, emergency and elective surgery, viral pneumonia, and other conditions could be complicated by PA thrombosis development without concomitant deep vein thrombosis (DVT). Different pathologies have different causes for local PA thrombotic process. As evidenced by experimental results and clinical observations, endothelial and platelet activation are the crucial mechanisms of this process. Endothelial dysfunction can impair antithrombotic function of the arterial wall through downregulation of endothelial nitric oxide synthase (eNOS) or via stimulation of adhesion receptor expression. Hypoxia, proinflammatory cytokines, or genetic mutations may underlie the procoagulant phenotype of the PA endothelium. Both endotheliocytes and platelets could be activated by protease mediated receptor (PAR)- and receptors for advanced glycation end (RAGE)-dependent mechanisms. Hypoxia, in particular induced by high altitudes, could play a role in thrombotic complications as a trigger of platelet activity. In this review, we discuss potential mechanisms of PA thrombosis in situ.

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Background Venous thromboembolism (VTE) with the prevalence of pulmonary microcirculatory thrombosis is considered a common complication of novel coronavirus disease (COVID-19) that develops despite anticoagulation. Methods The clinical course of the disease and the autopsy findings of seven deceased patients with verified COVID-19 were analyzed. The chest computed tomography (CT) scan was routinely performed while CT pulmonary angiography and a duplex ultrasound scan (DUS) of the lower limbs were used in cases of suspected VTE. The VTE prophylaxis was administered to all patients with intermediate or therapeutic doses of low-molecular-weight heparin. The histological examination of the lung tissue and other organs was performed with particular attention paid to the pulmonary vasculature. Results Venous thromboembolism, including deep vein thrombosis in one patient and pulmonary artery thrombosis in two patients, was confirmed by imaging tests despite anticoagulation. Systemic thrombolysis was performed in two patients with putative and confirmed pulmonary embolism. An autopsy revealed the signs of acute respiratory distress syndrome in all seven patients. Abnormalities of lung vessels were found in all cases and were represented by dystrophy and necrosis in the endothelium and muscle fibers, and by infiltration by plasmatic cells, neutrophils, and lymphocytes. Multiple clots of variable maturity were observed. All those changes developed despite anticoagulation and were preserved after systemic thrombolysis. Conclusion Inflammatory and prothrombotic changes in the arterial wall in parallel with the lack of lung perfusion may cause diffuse arterial thrombosis in the lungs. This background may be responsible for the low response to systemic anticoagulation and thrombolysis in severe forms of COVID-19.