Introduction Venous thromboembolism (VTE) has been observed as a frequent complication in patients with severe novel coronavirus disease 2019 (COVID-19) infection requiring hospital admission. Aim This study was aimed to evaluate the epidemiology of VTE in hospitalized intensive care unit (ICU) and non-ICU patients. Materials and Methods PubMed was searched up to November 13, 2020, and updated in December 12, 2020. We included studies that evaluated the epidemiology of VTE, including pulmonary embolism (PE) and/or deep vein thrombosis (DVT), in patients with COVID-19. Results A total of 91 studies reporting on 35,017 patients with COVID-19 was included. The overall frequency of VTE in all patients, ICU and non-ICU, was 12.8% (95% confidence interval [CI]: 11.103–14.605), 24.1% (95% CI: 20.070–28.280), and 7.7% (95% CI: 5.956–9.700), respectively. PE occurred in 8.5% (95% CI: 6.911–10.208), and proximal DVT occurred in 8.2% (95% CI: 6.675–9.874) of all hospitalized patients. The relative risk for VTE associated with ICU admission was 2.99 (95% CI: 2.301–3.887, p <0.001). DVT and PE estimated in studies that adopted some form of systematic screening were higher compared with studies with symptom-triggered screening. Analysis restricted to studies in the 5th quintile of sample size reported significantly lower VTE estimates. Conclusion This study confirmed a high risk of VTE in hospitalized COVID-19 patients, especially those admitted to the ICU. Nevertheless, sensitivity analysis suggests that previously reported frequencies of VTE in COVID-19 might have been overestimated.

Introduction: Venous and arterial thrombosis are frequently observed complications in patients with severe novel coronavirus disease 2019 (COVID-19) infection who require hospital admission. In this study, we evaluate the epidemiology of venous and arterial thrombosis events in ambulatory and post- discharged patients with COVID-19 infection. Materials and Method: EMBASE and MEDLINE were searched up to July 21st, 2021, in addition to other sources. We included studies that assessed the epidemiology of venous and arterial thrombosis events in ambulatory and post dischargepost-discharged COVID-19 patients. Results: A total of 16 studies (102,779 patients) were identified. The overall proportion of venous thromboembolic events in all patients, ambulatory and post dischargepost-discharge, was 0.80% (95% confidence interval [CI]: 0.4437 to 1.278), 0.28% (95% CI 0.0703 to 0.640), and 1.16 % (95% CI: 0.694 to 1.7437), respectively. Arterial events occurred in 0.75% (95% CI: 0.274 to 1.471) of all patients, 1.45% (95% CI: 1.103 to 1.864) of post dischargepost-discharge patients, and 0.23% (95% CI: 0.01987 to 0.663) of ambulatory patients. The pooled incidence rate estimates per 1,000 patient-days for VTE events were 0.056 (95%CI 0.030 – 0.082) and 0.124 (0.067 – 0.1986) for outpatients and post-discharge, respectively, whereas for arterial events were 0.103 (95%CI 0 – 0.303) and 0.264 (95% CI 0.162 – 0.3766). Conclusion: This study found a low risk of venous and arterial thrombi in ambulatory and post-discharge COVID-19 patients, with a higher risk in post-discharged patients compared to ambulatory patients. This suggests that regular universal thromboprophylaxis in these patient populations is probably not necessary.

Introduction: Venous thromboembolism (VTE) is one of the leading causes of morbidity and mortality during pregnancy and the postpartum periods. Despite that, the prevention and management of VTEs in pregnant patients remains an area of great debate, particularly among those with a personal VTE history. There is no solid evidence behind the current practice guidelines on the prevention of VTE in pregnancy as most data comes from studies focusing on non-pregnant patients or from small studies. It has been suggested that without low molecular weight heparin (LMWH) thromboprophylaxis, women with a personal history of VTE may have a 2% to 10% absolute risk of developing recurrent VTE during a subsequent pregnancy. We conducted a systematic review to evaluate the risk of VTE recurrence during pregnancy for pregnant patients with prior personal history of VTE and the effect of LMWH on such risk. Materials and Methods: MEDLINE and EMBASE were searched between January 2000 to December 2020. We included studies that evaluated pregnant patients with previous personal VTE history (deep vein thrombosis (DVT) and pulmonary embolism (PE) only) that assessed venous thromboembolism recurrence and/or bleeding complication and/or pregnancy outcomes. Study selection and data extraction was conducted by 3 reviewers and discrepancies resolved by consensus. A meta-analysis of proportions was done through a Freeman-Tukey transformation using random effect models. Groups were analyzed according to prophylaxis strategy. Heterogeneity between studies was assessed by Cochrane Q and Higgins I 2 analyses. Publication bias was assessed using Eggers' tests and funnel plot. Results. Of 6934 potential studies, 27 were included in this systematic review. The studies included 3631 pregnant patients with a previous history of DVT or PE, regardless of the presence of thrombophilia. We found a wide variability in thromboprophylaxis practices which included mostly low molecular weight heparin using weight-based, risk category-based, anti-Xa based, fixed, or trimester-adjusted doses . In studies that categorized patients into provoked, estrogen associated and unprovoked, most patients had an estrogen-associated previous VTE. The estimated pooled proportions of VTE recurrence were 2.7% (95% CI 1.8-3.7; I 2 55.5%) in patients who were consistently on anticoagulation during pregnancy (pre- and post-partum), 2.6% (95% CI 0.6-5.9; I 2 not estimable) in patients who received anticoagulation in the postpartum period only, and 25.3% (95% CI 8.9-46.6; I 2 93.2%) in patients who were not on anticoagulation. No comparison could be done on the different dosage strategies due to the limited number of studies and wide variety of strategies. Due to limited data available, bleeding complications and pregnancy outcomes could not be assessed. Conclusion. In patients with a previous VTE history receiving prophylactic anticoagulation (either both pre- and post-partum or post-partum only), the estimates of VTE recurrence were significantly lower than that for patients who did not receive prophylaxis, however, a direct comparison was not possible. The optimal thromboprophylaxis strategy remains unknown. Disclosures No relevant conflicts of interest to declare.